North Carolina Dairy Nutrition Management Conference ... conf... · 2 Conference Supporters and Exhibitors Primary financial support for the North Carolina Dairy Nutrition Management

February 20-21, 2002Holiday Inn

Salisbury, North Carolina

An Educational Program For NorthCarolina’s Dairy Herd Managers And

Dairy Industry Personnel

North CarolinaDairy Nutrition

ManagementConference

Proceedings

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Conference Supporters and ExhibitorsPrimary financial support for the North Carolina Dairy NutritionManagement Conference is provided by the businesses listed below.Their generous assistance is greatly appreciated.

Supporters:Carolina Farm CreditElanco Animal HealthMonsanto Dairy BusinessPurina MillsRenaissance Nutrition, Inc.Southern States Cooperative, Inc.

Exhibitors:Automated Farm Systems, Inc.Bartlett Milling Co.Biovance Technologies, Inc.Carolina Farm CreditElanco Animal HealthFort Dodge Animal HealthGenex CooperativeHarper Financial ServicesLallemandMD & VA Milk Producers Association, Inc.Mid-Atlantic Agri SystemsMonsanto Dairy BusinessPiedmont Agri-Systems, Inc.Prince Agri Products, Inc.Purina MillsRenaissance Nutrition, Inc.R.S. Braswell Co., Inc.Select Sires PowerSouthern States Cooperative, Inc.SoyPlusSUDIA/ADA of North CarolinaSunset FeedsWestfalia-Surge LLCZinpro Corporation

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The North Carolina Dairy NutritionManagement Conference is sponsored by theNorth Carolina Dairy Producers Association.

The program was planned by Dr. Lon Whitlow, Dr. Brinton Hopkins,and Dr. Don Pritchard, Dairy Extension Specialists in the Department

of Animal Science at North Carolina State University.

Permission to reprint material contained in this proceedings isgranted, provided the meaning is not changed. Please give credit to

the author and this publication as the source.

Edited by Dr. Donald E. Pritchard, Dairy Extension SpecialistDepartment of Animal Science, North Carolina State University

Box 7621, Raleigh, NC 27695-7621

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Table of ContentsPage

Welcome Letter from Norman Jordan, Jr., ................................................................................5President of the North Carolina Dairy Producers Association

Welcome Letter by Dr. Roger McCraw ......................................................................................6Interim Head, Department of Animal Science NC State University

An Overview of the 2001 NRC Dairy Cattle Requirements .......................................................7Dr. Bill Weiss, The Ohio State University

Potential to Improve Rumen Function .......................................................................................18Dr. Vivek Fellner, North Carolina State University

The 100-Day Contract With The Dairy Cow ...............................................................................23Dr. James Spain and Wendy A. Scheer, University of Missouri

Protein and Carbohydrate Utilization by Lactating Dairy Cows ................................................44Dr. Bill Weiss, The Ohio State University

Practical Considerations for Feeding Fat to Dairy Cattle ..........................................................52Dr. Jon Goodson, Southern States Cooperative

Dairy Feed Additives .................................................................................................................57Dr. R. Randy Lyle, Purina Mills

Silage Management ...................................................................................................................65Dr. Lon Whitlow, North Carolina State University

Utilizing Selected By-Product Feeds for Dairy Cattle ................................................................69Dr. Brinton A. Hopkins and Dr. Lon W. Whitlow, North Carolina State University

Mineral Needs of Dairy Cattle ....................................................................................................75Dr. Jerry Spears, North Carolina State University

Vitamin Nutrition of Dairy Cattle: circa 2002 .....................................................................81Dr. Will Seymour, Roache Vitamins, Inc.

Nutrition Management for Tomorrow’s Dairy Herds ..................................................................103Dr. Lane Ely, University of Georgia

Conference Summary and Evaluation Comments ....................................................................109Dr. Lon Whitlow, North Carolina State University

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An Overview of the 2001 NRC Dairy Cattle Requirements

Dr. William P. WeissDepartment of Animal Sciences

Ohio Agricultural Research and Development CenterThe Ohio State University

About every 10 years, the National Research Council (NRC) appoints a subcommitteeto review the scientific literature and use the new information to revise the nutrientrequirements of dairy cattle. In 2001, the NRC published the Seventh Revised Editionof the Nutrient Requirements of Dairy Cattle. The new revision includes requirementsfor energy, protein, minerals, and vitamins of calves, growing heifers, dry cows, andlactating cows. The book also presents recommendations for carbohydrate fractions(adult cows only), equations to estimate dry matter intake (growing heifers, dry cows,and lactating cows), and information on health disorders related to improper nutrition. Amajor component of the new edition is a computer program that can be used to evaluatethe ability of a diet to meet the nutrient requirements of a specific animal. A detaileddiscussion of all nutrients for all classes of dairy cattle is beyond the scope of this paper.Rather, this paper will discuss only adult lactating and non-lactating cows and willpresent general concepts using a few nutrients to illustrate the principles followed in thenew edition. The NRC book is an excellent resource for people involved with dairycattle nutrition and readers are referred to the book for the details.

NEL RequirementsThe daily NEL requirements for a lactating cow is a function of body weight (BW), milkyield, milk composition (fat, protein, and lactose), stage of gestation, and whether thecow is grazing (Table 1). Body weight is used to calculate the maintenance requirement(increasing BW increases maintenance requirement). The maintenance requirementincludes the NEL needed to maintain the cow plus the NEL expended for normalactivity. Grazing cows (and perhaps cows confined in large pens that have to walk along distance to the parlor) expend more energy walking and eating than cows in typicalconfinement systems. For grazing cattle, the new NRC calculates the NEL required forwalking as a function of BW, the distance the cows walk from the paddock to the milkingcenter (i.e., distance times number of one-way trips), and topography. The NEL energyrequired for gathering food was calculated as a function of BW. The assessment oftopography is qualitative, the user can choose flat or hilly. Depending on distance andtopography the grazing activity requirement can range from a relatively modest to asubstantial amount of NEL (Table 2). Daily yields of milk fat, milk protein, and lactoseare used to calculate lactation requirements. If users have milk fat and milk proteinconcentration, milk lactose concentration can be estimated quite accurately with anequation. For most cows the lactation requirement will be the largest component of totalNEL requirements. For lactating cows, stage of gestation has only a small effect onNEL requirements (usually less than 10% of total requirements). No gestationrequirement is calculated until a cow has been pregnant for 190 days. At 220 days ofgestation (the time when most cows are dried-off) gestation requirement will range from

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about 1.9 (1000 lb cow) to 2.9 (1400 lb cow) Mcal/day. The total NEL requirement ismaintenance + lactation + gestation + grazing (if any).

Table 1. Daily NEL requirements of non-grazing cow calculated using NRC (2001)1.

Body weight. bs Milk yield, lbs Milk fat, % NEL, Mcal

1000 35 4.0 20.2

1000 65 4.0 30.7

1000 35 4.5 20.9

1000 65 4.5 32.1

1400 55 3.4 28.1

1400 85 3.4 37.8

1400 55 3.9 29.2

1400 85 3.9 39.61Milk true protein was assumed to be 3.6% for the 1000 lbs. cow and 3.2% for the 1400lb cow.

Table 2. Net energy for lactation (Mcal/day) required for activity associated with grazingas calculated by NRC (2001).

Flat Terrain Hilly Terrain

Body weight = 1000 lbs

Distance from paddock to parlor (4 one-way trips per day)

500 ft (total distance = 2000 ft/day) 0.6 3.4


Body weight = 1400 lbs

Distance from paddock to parlor (4 one-way trips per day)



NEL SupplyIn previous versions of the NRC, feed NEL values were static; they were calculateddirectly from reference total digestible nutrient (TDN) values. The TDN values weredetermined using sheep and cattle fed at or near maintenance and an 8% discount wasincluded to account for the higher dry matter intake of lactating dairy cows. Thisapproach did not account for the effects of variation in feed composition, dry matterintake, and diet composition on energy values. Furthermore, the previous NRC (1989)

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system overestimated the NEL content of feeds by an average of 7%. Because ofthese problems, the new NRC developed an entirely different method to estimate NELconcentrations of feeds.

Digestible energy (DE) and TDN concentration of feeds when fed at maintenance intakeis calculated from feed composition data. A discount factor is calculated based on drymatter intake and TDN of the total diet to estimate DE at productive levels of intake.The discounted DE is converted to metabolizable energy (ME) which is then convertedto NEL. The DE and TDN (at maintenance) concentrations of feeds are calculated(Conrad et al., 1984; Weiss et al., 1992) using concentrations of neutral detergent fiber(NDF), crude protein (CP), ash, lignin, crude fat (or fatty acids), acid detergent insolubleCP (ADICP), and neutral detergent insoluble CP (NDICP). For most feeds, actualvalues should be used for NDF, CP, ash, and lignin, and table values can be used forfat, ADICP, and NDICP. If a feed has an appreciable concentration of fat (e.g.,cottonseeds), a fat analysis is recommended. Concentrations of ADICP and NDICPshould be measured in heat-damaged forages and in byproducts that have highconcentrations of NDF and CP (e.g., brewers grains). The TDN values obtained areonly used to calculate the discount factor; TDN is not used to directly calculate otherexpressions of energy.

Because feed processing can affect digestibility, but not necessarily feed composition, amethod was needed to account for processing effects. Starch digestibility (measuredusing lactating cows) of different feeds relative to the value for ground dry corn wasused to develop a Processing Adjustment Factor (PAF). The estimated digestibility ofthe nonfiber carbohydrate (NFC) fraction is multiplied by the PAF to account forprocessing effects. Ground dry corn was given a PAF of 1.0. Feeds that had starchdigestibility greater than ground dry corn were give PAF values greater than 1 and feedwith starch digestibility less than dry ground corn were given values less than 1. ThePAF can be altered by users which will change the NEL content of feeds, especiallyfeeds with high concentrations of NFC. Based on a review of the literature a reasonablerange for PAF is about 0.8 to 1.1. The PAF of feeds in the 2001 NRC are means and incertain situations are not correct. For example, high moisture ground corn (mean DM of75%) has a PAF of 1.04. Starch digestibility increases as DM content of high moisturecorn decreases. If high moisture corn has 70% DM a higher PAF probably should beused (maybe 1.05 or 1.06). Normal corn silage has a PAF of 0.94 but kernelprocessing usually increases starch digestibility about 5%. Therefore for processedcorn silage an appropriate PAF would be 0.98 or 0.99.

Digestibility decreases as feed intake increases therefore DE calculated formaintenance intake is not appropriate when feeds are fed at higher intakes and inmixed diets. The NRC (2001) developed an equation based on intake and digestibilityof the total diet (diet digestibility is estimated as total diet TDN) to estimate the discountfactor. The discount increases as intake and diet digestibility increases (Figure 1). TheDE (at maintenance) is multiplied by (1 - Discount) to obtain DE at productive levels ofintake. Feed ME concentrations are calculated from discounted DE concentrations andNEL values are calculated from the ME concentration.

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On average, NEL concentrations will be about 5% lower than those in the 1989 version.Actual differences will depend on the feedstuff (Table 3), intake, and diet composition.The NRC (2001) compiled published data from lactation trials to compare calculatedNEL use with calculated NEL concentrations in the diet. On average, NEL intake wasabout 1.02 times NEL expenditures suggesting that either the new NRC slightlyunderestimates NEL requirements or slightly overestimates diet NEL values. Comparedto the 1.05 to 1.07 bias using the 1989 system, the new energy system is a substantialimprovement and should result in more accurate estimates of energy balance.

Figure 1. Discount factor calculated using the 2001 NRC. Feed DE values estimatedat maintenance are multiplied by (1 - Discount) to estimate DE values at energy intakesof 3, 4, and 5 times maintenance energy intake.

Table 3. Comparison of NEL concentrations (Mcal/lb of dry matter) estimated using the2001 NRC system and 1989 table values. To eliminate effects of dry matter intake, the2001 values assume an 8% discount (identical to that used in the 1989 NRC).

Feedstuff NRC, 1989 NRC, 20011

1989 Composition 2001 Composition

Orchardgrass, full head 0.55 0.40 0.51

Alfalfa, immature 0.68 0.68 0.63

Alfalfa, midbloom 0.59 0.53 0.58

Corn silage, normal 0.73 0.62 0.66

Corn, ground 0.89 0.94 0.91

Citrus pulp 0.80 0.74 0.80

Wheat middlings 0.71 0.77 0.76

Whole cottonseed 1.01 0.98 0.88

Soybean meal, 44% CP 0.88 0.99 0.971 The column identified as 1989 Composition used the 2001 NRC equations with thedata from the 1989 NRC feed composition table. The column identified as 2001Composition used the 2001 NRC equations and data from the 2001 feed compositiontable.

Protein RequirementsProtein requirements are on a metabolizable protein (MP) basis. Metabolizable proteinis defined as the total component of amino acids (on a crude protein equivalent basis)that have been absorbed by the intestine and are used for productive purposes.Although some equations were substantially changed, the total MP requirement formaintenance calculated using the 2001 NRC will be similar but generally lower thanmaintenance requirements in the previous version (NRC, 1989). The MP requirement

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for lactation was changed to reflect experimental data showing that efficiency is higherthan previously assumed. This change will mean that the lactation requirements for MPusing the 2001 system will be 2 to 3 percent lower than the 1989 system. The MPrequirement for pregnancy is a function of BW and day of gestation (no requirement isestimated until gestation day is greater than 190). For a 1400 lb cow, the pregnancyrequirement for MP is about 240 g/day at 220 days of gestation. Overall, total MPrequirements calculated using 2001 NRC will be about 3 percent lower than valuescalculated using the 1989 system.

Protein SupplyThe 2001 NRC uses a completely different method of calculating MP supply than usedpreviously. The amount of crude protein broken down in the rumen (rumen degradedprotein, RDP) is calculated from in situ data and software-estimated rates of passage.To estimate RDP, feed crude protein is partitioned into three fractions using in situtechniques. The A fraction is readily soluble in water and is measured as the amount ofcrude protein washed from the bag before ruminal incubation. The C fraction is thecrude protein that will not be degraded in the rumen after at least 48 hour of incubation.The B fraction is the remaining crude protein and it will be degraded in the rumen at agiven rate. The A fraction is considered all RDP and the C fraction is all RUP. Theproportion of B that is RDP depends on the rates of degradation and passage. Feedswith a rapid rate of degradation will have more RDP derived from the B fraction thanfeeds with slow rates of degradation. The amount of microbial protein synthesized isthen calculated from RDP supply and energy intake The amount of rumen undegradedprotein (RUP) is simply CP minus RDP. The amount of MP provided by RUP iscalculated using an efficiency of 0.67 and variable digestibility constants. Digestibilityconstants are a function of feedstuff and range from 0.5 to 1.0. Estimated RUPdigestibility for the more common feedstuffs range from about 0.65 to 0.9. The 1989system used constant rumen degradability estimates (determined using intestinallycannulated animals) and a constant digestibility of RUP (0.80). The approach adoptedby NRC means that RDP and RUP of feeds will not be constant; they will vary with feedcomposition, dry matter intake, and to a lesser extent, diet formulation. Compared tothe 1989 version, the RUP concentrations in hay crop forages are much lower, andoilseed meals tend to be higher using the 2001 method (Table 4).

When RDP is limiting, microbial protein (g/day) = 0.85 x RDP intake (g/d). When RDPis not limiting microbial protein is calculated from intake of discounted TDN. Becausediscounted TDN is used, the marginal increase in microbial protein usually decreasesas dry matter intake increases. The practical consequence of this is that as milkproduction increases resulting in increased feed intake, the marginal increase in RDPrequirement is reduced and the marginal increase in RUP requirement is increased.High producing cows at high intakes will require a higher proportion of the crude proteinas RUP than cows at lower intakes. However, supply of RUP will also increase athigher intakes because of increased rate of passage and reduced degradation in therumen.

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Table 4. Estimated (NRC, 2001) rumen degraded protein (% of total crude protein)from different feedstuffs. Feed composition data are from the NRC (2001) feed library.

Feedstuff Dry matter intake

40 lbs/day 50 lbs/day

Alfalfa hay, immature 84 83

Grass hay, midmaturity 73 72

Grass silage, immature 80 79

Grass silage, mature 66 66

Corn silage 66 65

Corn grain, ground 57 55

Corn gluten feed 74 71

Corn gluten meal 30 27

Soybean meal, solven extracted 63 60

On average, the 2001 NRC protein system will result in higher RUP supply and higherRUP requirements than the 1989 system. In general total crude protein requirementswere reduced slightly. With respect to ration formulation, the most noticeabledifferences between the 2001 and 1989 versions will be observed with diets containinga large proportion of high protein hay crop forages and with diets containing a largeproportion of oilseed meals (i.e., corn silage based diets). Hay crop forages providerelatively little MP so that total dietary crude protein for these diets will have to be high.Oilseed meals provide relatively high amounts of MP so that diets with oilseed mealscan contain lower amounts of crude protein.

MineralsThe 2001 NRC includes an extensive review of mineral nutrition of dairy cattle. The2001 NRC contains no �safety factors�; the calculated requirements assume normal,healthy cows fed diets with few mineral antagonists. The text discusses situations whenmineral absorption may be compromised but the model does not include equations toadjust bioavailability for the presence of antagonists. Users must be aware of thesesituations and make appropriate adjustments in mineral supplementation.

Macromineral RequirementsFor all macrominerals except S, requirements were established for maintenance, milkproduction, and pregnancy. The maintenance requirements for P and K are functions ofdry matter intake (requirement increases as intake increases); for all other minerals it isa function of BW. The requirement for lactation is the amount of mineral secreted innormal milk per day. For example, average milk contains 0.4 g of P/lb, therefore theabsorbable P requirement for lactation is 0.4 g x milk yield (lbs./d). Pregnancyrequirements are a function of the BW and day of gestation. No pregnancy requirement

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is calculated when cows are less than 190 days pregnant. The pregnancy requirementfor most minerals increase exponentially with increasing day of gestation greater than190 days up to 280 days. Compared to the 1989 version, on an absorbed basis, themaintenance requirements for Ca and P were approximately doubled for lactating cows.Lactation requirements are similar between the 1989 and 2001 versions. For lategestation (>260 days), pregnancy requirements for Ca and P were increased, butpregnancy requirements are similar between 1989 and 2001 for cows at approximately60 days before calving.

A different approach was used for S because data are extremely limited and ruminalmicroorganisms require S. Adequate S must be provided for good rumen fermentationin addition to the S required by the cow. The 2001 NRC stated that diets (DM basis)with 0.2% S should be adequate for lactating cows.

Macromineral AbsorptionAn important change in the 2001 NRC was the adaptation of feedstuff-specificabsorption coefficients. In the 1989 version a single absorption coefficient for a mineralwas used regardless of mineral source, but bioavailability varies among sources. Forexample, the Ca in alfalfa is less absorbable by cows than is the Ca provided bylimestone. Because of inadequate data, specific absorption coefficients could not bederived for all feedstuffs. An absorption coefficient of 0.16 for Mg and 0.90 for Na, K,and Cl was used for all feedstuffs (excluding minerals supplements). For P and Ca, theabsorption coefficients were set at 0.64 and 0.30, respectively, for hay crop forages,and 0.70 and 0.60, respectively, for concentrates and corn silage. Mineralssupplements were assigned variable absorption coefficients (Table 5).

Dietary Supply of MacromineralsMost previous nutrient standards for dairy cattle provided minerals requirements as aconcentration of diet dry matter. However, dry matter intake is not constant amongcows, even at similar milk yields, therefore, minerals requirements should be expressedas g/day as done in the 2001 NRC. The software calculates the grams of absorbablemineral provided per day based on the ration entered by the user and compares thatvalue to the requirement. If the total absorbable supply is equal or greater than totalabsorbed requirement, the diet is adequate. If supply is less than requirement, anegative value will be shown and the user should modify the diet. Because differentabsorption coefficients are used for different ingredients, two diets with the sameconcentration of a mineral may not provide the same amount of absorbed nutrient. Forexample, a 1400 lb cow producing 70 lb/day of milk with a dry matter intake of 50 lbs/dwill need to absorb 59 g/day of Ca to meet her Ca requirement. If the diet was basedon alfalfa and contained no supplemental sources of Ca, the diet would need about0.78% Ca to provide 59 g of absorbable Ca. If the diet was based on corn silage withlimestone as the source of supplemental Ca, the diet would need about 0.42% Ca toprovide 59 g of absorbable Ca. The difference between the two diets reflects the higherCa absorption coefficient for limestone compared with alfalfa.

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Because the necessary dietary concentration of a given mineral depends on dietcomposition, specific requirements cannot be presented. Assuming a typical diet andtypical dry matter intakes relative to milk yield, a diet with about 0.6 to 0.8% Ca, 0.32 to0.38% P, 0.18 to 0.2% Mg, 1.0 to 1.1% K, 0.22 to 0.24% Na, and 0.24 to 0.30% Cl willmeet the requirements for a Holstein cow (1400 lbs) producing 50 to 110 lbs of milk/day. As stated previously these values are based on the assumption that antagonists toabsorption are minimal and do not include any safety margin.

Table 5. Absorption coefficients (NRC, 2001) for calcium, phosphorous, andmagnesium from common supplemental sources.

Absorption coefficient of primarymineral

Calcium sources

Calcium carbonate 0.75

Calcium chloride 0.95

Calcium sulfate 0.70

Dicalcium phosphate 0.83

Limestone 0.70

Phosphorous sources

Deflourinated rock phosphate 0.65

Dicalcium phosphate 0.75

Monosodium phosphate 0.90

Magnesium sources

Magnesium carbonate 0.30

Magesnium chloride 0.70

Magnesium oxide 0.70

Magnesium sulfate 0.70

Trace Mineral Requirements

Trace Mineral AbsorptionDifferent absorption coefficients for each trace minerals were given to differentingredients. The absorption coefficients used for Cu (0.04), Fe (0.10), Mn (0.01), andZn (0.15) do not vary among feedstuffs (except mineral supplements) because datawere not available. The absorption coefficients for trace mineral supplements variedamong the different sources. In general, the absorption coefficient was lowest for oxidesources, intermediate for carbonate sources, and highest for sulfate and chloridesources (Table 6).

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Table 6. Absorption coefficients (NRC, 2001) for copper, iron, manganese, and zincfrom common supplemental sources.

Absorption coefficient of primarymineral

Copper sources

Copper chloride 0.05

Copper oxide 0.01

Copper sulfate 0.05

Iron sources

Iron carbonate 0.10

Iron oxide 0.01

Iron sulfate 0.20

Manganese sources

Manganese chloride 0.01

Manganese oxide 0.00

Manganese sulfate 0.01

Zinc sources

Zinc carbonate 0.20

Zinc chloride 0.20

Zinc oxide 0.12

Zinc sulfate 0.20

Dietary Supply of Trace MineralsRequirements for trace minerals should be expressed as mg/day. General guidelineswith respect to dietary concentrations can be derived assuming dry matter intake istypical for a given milk yield (Table 7). In general, recommended dietaryconcentrations of Cu are similar to 1989 recommendations. Recommendedconcentrations of Fe and Mn are substantially lower, and the recommendedconcentration for Zn is higher than 1989 recommendations. Many factors affect tracemineral absorption. The values derived using the 2001 NRC model assume normalabsorption of trace minerals. The text contains a very thorough discussion of factorsknown to reduce trace minerals absorption and diet formulation may have to bemodified in many cases to ensure adequate trace mineral nutrition.

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Table 7. Requirements (NRC, 2001) and approximate concentrations needed in dietdry matter (DM) to meet requirements for copper, iron, manganese, and zinc fornonlactating pregnant cows (250 days of gestation and 1450 lbs body weight) and forlactating cows (1350 lbs body weight).

Nonlactating Lactating

45 lbs of milk/day 90 lbs of milk/day

mg/day ppm mg/day ppm mg/day ppm

Copper 152 13 201 11 271 12

Iron 186 15 200 11 400 17

Manganese 206 17 236 13 320 14

Zinc 262 22 647 36 1045 44

VitaminsThe 2001 NRC presents requirements for vitamins A, D, and E. In general, data onvitamin requirements of dairy cattle is extremely limited. The factorial approach couldnot be used for vitamins because data were not available. Milk production studies, invitro rumen studies, and clinical (health) studies were used to evaluate and modifyvitamin requirements. An important change made in 2001 was that requirements forvitamins A, D and E are expressed as the amount of supplemental vitamin needed.Vitamins provided by basal feedstuffs are generally not considered. This approach wasfollowed because the concentrations of vitamins in feedstuffs are extremely variable andare rarely measured in field situations.

Vitamin A requirements were increased substantially from the 1989 version. Therequirement was increased primarily because in vitro data show substantial ruminaldestruction of vitamin A when concentrate feeds make up about one-half of the diet drymatter. The vitamin A requirement for lactating cows was set at 50 IU/lb of BW or70,000 IU/day for a 1400 lb cow. The vitamin D requirement was not changed and wasset at 14 IU/lb BW or 19,000 IU/day for a 1400 lb cow. The vitamin E requirement wasincreased substantially. Several clinical studies have been published in the last 10years that examined vitamin E supplementation and cow health (mostly mastitis andreproductive disorders). Based on those data, the committee concluded that the 1989requirement did not promote optimal health of dairy cows and therefore, did not meetthe vitamin E requirement. Because titration studies have not been conducted, thecommittee based the vitamin E requirement on supplementation rates of publishedstudies. The vitamin E requirement was set at 0.36/lb BW for lactating cows (510 IU/dayfor a 1400 lb cow) and 0.72 IU/lb BW for late gestation, nonlactating cows (1020 IU/dayfor a 1400 lb cow). Green pasture usually contains substantially more vitamin E thanhay or silage. Based on average vitamin E concentrations of pasture relative toconserved forages, the requirement for supplemental vitamin E was reduced by two-

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thirds for grazing cows (170 IU/day for 1400 lb lactating cow and 340 IU/day for a 1400lb dry cow).

SummarySubstantial modifications in the methods used to calculate nutrient requirements andnutrient supply were incorporated into the 2001 NRC. The approaches taken accountfor more sources of variation than previous versions and in many cases are clearlymore biologically sound. Actual differences in requirements between the 2001 NRCand 1989 NRC depend on many factors. In general, NEL requirements did not changeappreciably but the NEL concentrations of feeds are lower using the 2001 NRCapproach. Requirements for RUP and dietary supply of RUP are generally higher in the2001 version, but requirements for total crude protein tend to be lower. On average,dietary Ca requirements were increased, dietary P requirements were reduced slightlyand requirements for the other macrominerals are similar between the 2001 and 1989versions. Requirements for Fe and Mn are substantially lower in the 2001 version,requirements for Co, Cu, and Se are similar, and requirement for Zn is higher.Requirements for vitamins A and E were increased substantially but the requirement forvitamin D was not changed.

ReferencesConrad, H.R., W.P. Weiss, W.O. Odwongo, and W.L. Shockey.1984. Estimating net

energy lactation from components of cell solubles and cell walls. J. Dairy Sci. 67:427-436.

National Research Council. 1989. Nutrient Requirements for Dairy Cattle. 6th RevisedEdition, National. Academy Press, Washington DC.

National Research Council. 2001. Nutrient Requirements of Dairy Cattle, 7th RevisedEdition. National. Academy Press, Washington DC.

Stangl, G.I., Schwarz, F.J., Muller, H. and Kirchgessner, M. 2000. Evaluation of thecobalt requirement of beef cattle based on vitamin B-12, folate, homocysteineand methylmalonic acid. Brit. J. Nutr. 84:645-653.

Weiss, W.P., H.R. Conrad, and N.R. St. Pierre 1992. A theoretically-based model forpredicting TDN values of forages and concentrates. Anim. Feed Sci. Tech.39:95-110.

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Potential to Improve Rumen Function

Dr. Vivek FellnerNorth Carolina State University

IntroductionThe dairy industry is going through a period of dramatic changes that will impact thefuture direction of the U.S. dairy business. The number of dairy farms, with grade A andB permits, fell 37 percent between 1992 and 2000 and during this same period, milkproduction rose 11.5 percent (American Farm Bureau Federation). The decline in totalfarm numbers did not translate into less milk. On the contrary, dairy farmers whoremained in the business produced more milk from more cows compared to those wholeft the industry. The current dynamics of a global economy and the incessantintroduction of new technology have resulted in the development of adaptiveapproaches to increase efficiency of milk production for a volatile and highly competitivemarket.

The past several decades have seen a major shift in the direction of research in dairyscience. Much of the research focus had been on altering different aspects of dairyproduction systems to increase the production efficiency of dairy cows. Such anintegrated approach has its merits however, the main thrust of dairy research today is inimproving efficiency of milk production by manipulating fundamental biologicalprocesses that regulate milk production. The past 20 years have seen tremendousprogress in the field of rumen microbiology enabling us to better understand thecomplex microbial interactions governing efficient nutrient utilization by ruminants.

Renewed pressure, in part, due to regulation of nutrient output from farms has resultedin considerable research on minimizing nutrient wastage and maximizing nutrient use bythe animal. A large proportion of dietary nutrients are made available to ruminants in theform of end-products of rumen fermentation, primarily short chain fatty acids (SCFA)and microbial protein. The removal of fermentation products from the rumen and theoutflow of microbial biomass have a direct impact on the nutritional status of ruminants.Short chain fatty acids, are used by the host as a major source of metabolizable energy.Microbial protein is the major source of metabolizable amino acids for maintenance andmilk synthesis. The efficiency with which dairy cows convert dietary energy and proteininto nutrients for milk synthesis varies considerably. Much of this variation is due toinefficiency that occurs in the rumen and appears to be related to the ruminalenvironment. Consequently, the ability to characterize and modulate SCFA andmicrobial protein synthesis is essential if we want to increase nutrient use towardsdesirable products such as milk, and decrease waste in the form of nitrogen excretionand methane. A key issue being addressed currently is the need to obtain more data onfermentation products including microbial protein synthesis to include in model systemsdesigned to predict overall nutrient requirements of ruminants.

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Ruminants — A Nutritional ChallengeUnlike non-ruminants, formulating for precise nutrient requirements in ruminant rationsis difficult. Both ruminants and non-ruminants utilize nutrients in tissues but the formerhave another metabolic system - microbial metabolism in the rumen. This poses anutritional challenge because nutrient requirements of the two systems are distinctlydifferent. Maximizing ruminant productivity involves meeting the requirements for bothsystems. Inherent losses in energy and nitrogen associated with pre-gastricfermentation by microbes in the rumen make the digestion and subsequent absorptionof dietary nutrients less complete in ruminants. The rumen is a complex microbialecosystem and not easy to manipulate like an industrial fermentation. The primaryresearch focus, from an evolutionary standpoint has been on making rumen microbesdegrade grasses quicker and more extensively. In that respect, attempts have beenmade to modify feeds to make the cell wall more accessible to microbial enzymes.Rumen microorganisms are interdependent for supplies of carbon and nitrogen;improving the availability of carbon sources to increase digestibility would providemaximum benefit to overall fermentation if it were synchronized with the availability ofnitrogen. New strains of genetically engineered bacteria that are more effective fiberdigesters have been introduced into the rumen. Although temporal variations occur, the'dynamic steady-state' of the flora seems highly resistant to changes. As a result theintroduction and subsequent growth of exogenous bacterial strains with desirablebiochemical properties is difficult if not impossible to sustain over long periods in thehostile rumen environment. Perhaps the greatest potential to manipulate ruminalfermentation has been realized with the use of dietary additives that alter microbialphysiology to either enhance beneficial processes like fiber digestion, lactatefermentation and non-protein nitrogen use or minimize inefficient processes likemethane production and ammonia absorption. Biochemical reactions in the rumen arehighly interactive and intervening one reaction almost always results in a cascade ofinterrelated reactions, some of which may not necessarily be beneficial. For instance,reducing methane production invariably increases ruminal propionate, both of which aredesirable from the whole animal perspective but lowering methane and increasingpropionate at the cost of reduced acetate can limit the supply of ATP (energy), which isundesirable from a microbial perspective.

Rumen Environment — Life without OxygenRumen microorganisms require strict anaerobic conditions for normal function.Consequently, a key feature of fermentation is the partial oxidation of substrates withinthe rumen. To better understand the energetics of microbial metabolism, ruminalfermentation can be characterized into three main processes: (1) amount of organicmatter fermented; (2) concentration of relative proportions of fermentation productsproduced and (3) amount and efficiency of microbial protein synthesis.

Anaerobes conserve ATP in the form of a transmembrane electrochemical gradientcommonly referred to as the Proton Motive Force (PMF). The PMF is however, notdirectly responsible for driving many biosynthetic processes and bacterial cell growthdepends largely upon a membrane bound ATPase for the transfer of ATP from PMF.The rumen is a highly reduced environment and energy is often limiting. The survival of

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rumen microorganisms is dependent upon the efficiency with which ATP is produced,transferred and utilized during bacterial growth. Maintenance of normal fermentationwithin the rumen requires that the large amounts of reducing equivalents produced inthe form of NADH must be re-oxidized. Microbial populations have evolved fermentationpathways that effectively lower the concentration of reducing equivalents in the rumen.The main products of these fermentation reactions are SCFA, CO2 and CH4. Acetate isthe predominant SCFA found in the rumen and its formation is largely a function of theproduction of hydrogen from reduced cofactors. However, a high concentration ofhydrogen gas is thermodynamically unfavorable and will inhibit further fermentation.Low hydrogen levels are maintained by methanogens resulting in greater hydrogen andconsequently acetate production. Anaerobic conditions within the rumen result in mostof the energy (ATP) in the fermented organic matter being retained in the products(SCFA and microbes) with some losses occurring in the form of CH4 and heat. Theavailability of ATP is determined by the route with which reducing equivalents aredisposed. If the removal of hydrogen is coupled to acetate production ATP yield ishighest compared to ATP yields for butyrate and lactate. It is now believed that ATPyield from propionate can be comparable to that from acetate. If ATP production isuncoupled with microbial growth, excess SCFA production will be inversely related tomicrobial cell synthesis. This will have a major impact on the supply of the two mostimportant sources of nutrients i.e. SCFA (energy source) and microbial biomass (proteinsupply).

Approach to Manipulating Ruminal Dynamics - Carbohydrate fermentationCarbohydrates are the major components of ruminant diets and they differ widely in therate and extent of fermentability in the rumen. In forage based diets the cell wallpolysaccharides (structural carbohydrates) are the primary source of energy whereas incereal based diets the storage polysaccharides (starch and fructosans) provide most ofthe energy requirements. In the rumen both the cell wall, and storage polysaccharides,are converted by microbes to five and six carbon sugars. These sugars are rapidlyfermented into SCFA and can provide up to 70% of the energy requirements of the cow.Dietary ingredients have a significant impact on the proportion of acetate, propionateand butyrate produced in the rumen. Storage polysaccharides are more highlyfermentable and diets of dairy cattle are often supplemented with grains to meet theenergy demands associated with higher milk production. Starch may be digested byeither microbial or host enzymes and shifting the site of starch digestion has been thefocus of intense research. The efficiency with which the three main SCFA are utilizedhas been suggested to be similar but theoretic estimations indicate starch digestion inthe small intestine to be energetically more efficient. In contrast, performance data fromseveral experiments show that starch fermented extensively in the rumen resulted in ahigher production supporting the theory that increasing ruminal propionate is morebeneficial since it increases the capture of fermentation energy by reducing carbons thatwould otherwise be lost in methane. There may be limits to the use of starch in thelower tract and its fermentation in the rumen and maximizing starch use requires a clearunderstanding of those parameters. There is increasing evidence to suggest that thesource of starch may result in a variable response. Feeding corn over barley has shownto alter ruminal fermentation. Barley is more rapidly fermented in the rumen and

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supports a higher SCFA production compared to corn. This implies that a greaterproportion of carbon from barley would be made available to the cow in the form ofpropionate in contrast to reduced fermentation of corn in the rumen and greater captureof corn carbon as glucose in the lower tract. We know very little about how thesefermentation schemes impact the energy status in the rumen and subsequent outflow ofmicrobial protein.

Nitrogen metabolismMicrobial cells and dietary nitrogen that escapes ruminal degradation are the majorsources of protein and amino acid requirements of ruminants. Although plant materialsthat comprise the bulk of ruminant feeds are composed of a vast array of nitrogenouscompounds, most of the nitrogen contained in the forages and cereals fed to ruminantsis protein. Compounds that are not true protein but contain nitrogen are non-proteinnitrogen (NPN) and include nucleic acids, nitrates and supplemental urea. Enzymaticactivity in the rumen converts dietary protein into amino acids, which are in turndeaminated to ammonia and various carbon skeleton compounds (organic acids). Thisaffects the composition of dietary protein that escapes the rumen as well as themicrobial protein fraction. This process appears to be wasteful since the animal requiressome amino acids for its own use. However, some plant proteins may be veryindigestible by the host enzymes and these proteins often have a low content of theessential amino acids. Since the microbes synthesize protein from the ammonia andother suitable carbon skeletons they contribute to the nutritional metabolism of theanimal. Nucleic acids (5 to 10% of dietary N) are fermented rapidly and the nitrates areconverted to nitrite, which is fermented to ammonia. The most common strategy is toincrease the escape of high quality dietary protein by minimizing proteolysis,peptidolysis and deamination. It is well accepted however, that increasing theundegradable intake protein fraction must not be at the expense of lowering thedegradable intake protein in the diet. Optimal protein supply to the animal depends onadequate degradable protein to maximize capture of organic matter in microbialbiomass. Synchronizing the rate of nitrogen hydrolysis with the rate of energy releasewill increase the rate of assimilation of ammonia by microbes and maximize nitrogenuse by the animal.

Lipid metabolismBasal rations fed to high producing lactating cows typically contain 2 to 3% fat. It iscommon to increase the energy density of diets fed to early lactating cows by includingadditional fat. However, fats tend to have a negative effect on microbial metabolism andit is recommended not to include supplemental fat in amounts greater than 3 to 4% ofthe diet dry matter. Lipids in natural feeds consist primarily of triglycerides andglycolipids. Supplemental fats can be either of vegetable origin (oils and oil seeds) oranimal origin (tallow, grease and fish oils) or they can be a blend of the two (blendedfats). Microbial lipases rapidly hydrolyze the acyl ester bonds of lipids releasing theglycerol from the fatty acids. Glycerol is fermented but the unesterified fatty acids areadsorbed onto particulate matter (feed or microbial cells) and are not fermented ordegraded any further. Anaerobic conditions in the rumen are unfavourable for oxidation

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of fatty acids. Consequently, unesterified fatty acids are either incorporated intomicrobial lipids or are hydrogenated by the microbes.

Given the caloric benefits of additional fat and the limitations on intake during peakproduction, the inclusion of higher levels of fat in the diet are extremely beneficial. Muchof the research is aimed at manipulation of lipid metabolism in the rumen to minimizethe anti-microbial effects of fatty acids and to ameliorate disruption of ruminalfermentation.

Efforts to increase flow of unsaturated fatty acids stimulated by human health concernsabout saturated fat have resulted in another aspect of manipulation of dietary lipidmetabolism by rumen microbes. Controlling biohydrogenation to affect absorption ofselected fatty acids has been shown to improve the nutritional qualities of milk.

Since unsaturated fatty acids are more inhibitory to fermentation than the saturated fats,biohydrogenation seems to be a defense mechanism of the microbes. The process ofbiohydrogenation also competes for metabolic hydrogen, which is used as mentionedearlier, in the reduction of CO2 and production of propionate. Lipolysis is a prerequisitefor biohydrogenation to proceed because the isomerase that catalyzes the initial step toform the trans-11 isomer is not functional unless the fatty acid has a free carboxylgroup. Therefore, the main objective in manipulating lipid metabolism is to minimizelipolysis. In that respect, the feeding of protected lipids is a common practice.

Modifiers of ruminal microbial activityØ BuffersØ Ionophore antibioticsØ Inhibitors of proteolysis, peptide degradation and deaminationØ Fat supplementationØ Methane inhibitorsØ Growth factors (vitamins, fatty acids, minerals)Ø Microbial feed additives and enzymes

ConclusionsWe have made tremendous progress in the area of rumen microbiology in the past severalyears. There is still much that we do not know about the microbial ecology that exists withinthe rumen. Molecular techniques to identify specific bacterial strains will undoubtedlycontribute to our knowledge on the complex network of interrelated biochemical reactions inthe rumen. With the current interest in this area across several scientific disciplines it is onlya matter of time before we will have reliable models that will allow us to predict bacterialresponses to dietary manipulations. Increasing awareness of the public to productionagriculture, growing environmental concerns resulting in strict guidelines on nutrientdisposal and the changing nature of the dairy business are factors that will continue tochallenge ruminant nutritionists and microbiologists to better understand the biochemicalprocesses that underlie rumen energetics. We know that biological reactions have built-ininefficiencies. With the state of current knowledge and the direction of future research in thearea of microbial physiology the potential to lower inherent inefficient pathways and improverumen function is enormous.

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The 100-Day Contract With The Dairy Cow:30 Days Prepartum To 70 Days Postpartum

Dr. James N. Spain1 and Wendy A. ScheerDepartment of Animal Sciences, University of Missouri-Columbia

AbstractDuring the transition period, the dairy cow is undergoing numerous changes inendocrine, nutritional, metabolic, and physiological status as she prepares for calvingand initiation of lactation. These changes result in a dramatic decrease in dry matterintake that worsens the negative energy balance already present after calving. If thenegative energy balance during transition becomes excessive, metabolic diseases suchas fatty liver and ketosis can result. Disruption of mineral balance during theperiparturient period leads to mineral balance disorders, especially milk fever. Thesediseases are costly in terms of their affect on milk production, reproduction, and thecow’s susceptibility to other periparturient disorders. Intensive management of thenutrition, feeding system, and environment of the periparturient dairy cow reduces theodds of disease and increases the odds of success.

The ‘100 day contract’ is a series of delicate negotiations that encompass the full impactof the transition cow. Unsuccessful negotiations at any point increase the risk of overallfailure. Getting the details right and ensuring adequate intake of all nutrients are thekey elements of the ‘100-day contract’.

IntroductionIn evaluating the production cycle of the dairy herd, a 100-day period of criticalimportance exists. The ‘100-day contract’ with the dairy cow begins 30 days beforecalving and continues through first breeding at 70 days postpartum. The terms of thecontract include the birth of a live calf with the cow remaining healthy during thetransition period, high peak milk production, controlled loss of body condition, and highfertility at first breeding (Figure 1). The momentum toward successful achievementbegins in the close-up dry cow group and builds through calving to first breeding.Getting the cow off the track at any point disrupts the momentum and can lead to‘wrecks’. Wrecks include metabolic disorders during the periparturient period that canhave long-term impact on production and reproduction. This paper will focus on aphase-by-phase look at the negotiations required to successfully fulfill the ‘contract’ aswell as the long-term consequences of cows getting off track.

The Transition PeriodGoff and Horst (1997) defined the transition period of a dairy cow’s productive cycle asthe change from the pregnant, lactating state to the nonpregnant, lactating state duringthe interval from three weeks prepartum until three weeks postpartum. The transitionperiod is characterized by numerous changes in physiological, metabolic, and endocrine

1 Contact to: 116 Animal Sciences Research Center, University of Missouri, Columbia, MO 65211, (573)882-6452, FAX (573) 882-6640, Email: [email protected].

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status to accommodate parturition and lactogenesis (Grummer, 1995; Drackley, 1999).If nutritional management does not meet these challenges, the transition cow is at riskof developing a wide range of health problems soon after parturition (Bell, 1995). Theseproblems include milk fever, fatty liver, ketosis, retained placenta, displaced abomasum,and severely suppressed immune function (Goff and Horst, 1997). Proper managementduring the transition period affects the well being of the dairy cow by decreasing theincidence of metabolic and infectious diseases, increasing production, and improvingreproductive performance during the subsequent lactation. Achieving successfultransition should have a positive impact on the profitability of a successful dairy.

To successfully manage the transition cow, we must first understand the changes thecow is experiencing and the impact of a poor transition. Then we must implementstrategies that address the challenges of the transition cow.

The Transition Cow: Understanding the ChallengeDuring the dry period, the cow must be prepared for calving and initiation of lactation.The concept of preparing the dry cow is different from the traditional view of the dryperiod as a ‘rest’ phase (Gerloff, 1988). Goff and Horst (1997) concluded that theperiparturient period should adapt the rumen while maintaining normal energy andcalcium metabolism as well as supporting a strong immune system.

Changes in Endocrine StatusAs parturition approaches, the transition cow undergoes a variety of changes inendocrine status (Figure 2). Plasma prolactin levels increase sharply the day prior tocalving, resulting in initiation of lactation and increased colostrum synthesis.Progesterone concentration, which is elevated during gestation for maintenance ofpregnancy, drops to nearly undetectable levels on the day before calving. Plasmaestrogen concentration rises sharply at the same time in response to secretion of fetalcortisol. Prostaglandin F2α (PGF2α) concentration begins to rise and peaks atparturition, causing luteolysis and further inhibition of progesterone synthesis (Goff andHorst, 1997). High levels of estrogen are thought to contribute to the decline in drymatter intake (DMI) that occurs around parturition (Bell, 1995; Grummer, 1995). Goffand Horst (1997) reported that dry matter intake declines by as much as 30 to 40%, orfrom 2% to less than 1.5% of the animal’s body weight. Severe decreases in intake putthe animal at risk for a number of metabolic disorders.

Changes in Nutritional and Metabolic StatusAlthough not producing milk, the prepartum cow is undergoing numerous changes thatresult in significantly higher nutrient requirements. Bell et al. (1995) measured energyand protein deposition in the uterus and fetus. Their research clearly illustrated theincreased nutrient requirements during the final 30 days of gestation (Table 1).However, as shown in Figure 3, the increased nutrient requirements occur concurrentlywith declining appetite and nutrient intake.

To compensate for the negative energy balance caused by decreased DMI aroundparturition (Figure 4), the stress of calving, increased energy demands resulting from

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fetal growth and lactogenesis, and other unknown endocrine-related factors,mobilization of adipose tissue increases. Adipose tissue provides energy in the form ofnon-esterified fatty acids (NEFA) (Grummer, 1995). Plasma NEFA concentrationincreases approximately two-fold during the last 17 days of gestation, peaks aroundparturition, and remains higher than prepartum levels until about two weeks postpartum(Figure 5). The liver oxidizes NEFA to ketone bodies and carbon dioxide via thetricarboxylic acid cycle or esterifies them to triacylglycerols (TG), which are exportedfrom the liver as very low density lipoproteins (VLDL) (Rukkwamsuk et al., 1998). Ifthese changes become too dramatic, they can lead to ketosis and fatty liver disease.

In short, there is a significant increase in the cow’s nutrient requirements during the final30 days of gestation and therefore a critical need to maintain intake and support properplane of nutrition. A key to successful transition cow management is a nutritionalmanagement system (diet and feeding system) that provides nutrients in the properbalance and maximizes intake.

Changes in Physiological Status of the ReticulorumenSignificant physiological changes also occur during the transition period. Because ofsignificant fetal growth during the last 60 days of gestation, ruminal capacity decreasesby as much as 20%, then increases again within 8 days after calving. Ruminal drymatter and fluid fill also decrease just before calving and remain low until about 20 dayspostpartum (Table 2). Decreased capacity of the rumen limits the amount of feed thecow can consume, however, it does not account for the magnitude of the decrease indry matter intake that occurs around calving (Stanley et al., 1993).

Absorptive capacity of the rumen also changes during the dry and transition periods.Beginning at dry-off, cows are most often fed a high-forage, low-concentrate diet that ishigher in neutral detergent fiber (NDF) and less energy dense than the lactation diet.The lower energy diet causes a decrease in length and surface area of rumen papillae(Figure 6). This physiological change in rumen papillae corresponds to a 50% loss ofabsorptive capacity of VFA during the first 7 weeks of the dry period (Dirksen et al.,1985).

Postpartum, the papillae must increase in length and surface area to achieve maximumabsorption of VFA. Feeding a diet higher in fermentable organic matter stimulatesdevelopment of the papillae. However, this growth process requires 4 to 6 weeks afterchanging to a high-energy diet (Dirksen et al., 1985). If the amount of fermentableorganic matter is increased too rapidly after parturition and before the papillae havereached adequate surface area, the cow cannot absorb VFA efficiently. Volatile fattyacids can build up in the rumen, causing pH to fall, and resulting in rumen acidosis.Protozoa and some bacteria in the rumen are killed, releasing endotoxins that areabsorbed into the bloodstream (Goff and Horst, 1997). These endotoxins causesystemic changes in blood flow and affect the growth and health of the hooves. Thesechanges can result in the painful condition of laminitis. Cows with laminitis have limitedmobility and therefore limited intake. Lameness, combined with the rumen papillae’slimited ability to absorb VFA from the rumen, may worsen the transition cow’s negative

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energy balance, increasing the risk of metabolic disorders. Successful transition cowprograms are designed to accommodate the endocrine and physiological changes inthe cow while minimizing costly metabolic diseases.

Metabolic DisordersThe transition from late gestation, non-lactating to nonpregnant, lactating presentssignificant challenges to the cow’s system. When nutrition management does not meetthese challenges, a wide range of health problems can result. Metabolic diseases aredisorders that are nutritional in origin and often result in acute symptoms requiringtreatment. Incidence is highest during the period just prior to calving through peaklactation (Shearer and Van Horn, 1992). As shown in Table 3, most of the periparturientdiseases, such as milk fever, ketosis, retained placenta, and displaced abomasum,occur within the first 2 weeks postpartum. Many infectious diseases, such as mastitis,also become clinically apparent at this time as a result of the animal’s depressedimmune function. Other health disorders that become evident later in lactation, such aslaminitis, can be traced back to complications during the first two weeks after parturition(Goff and Horst, 1997). The majority of metabolic diseases are related to either energybalance or mineral balance. The diseases commonly associated with severe negativeenergy balance include fatty liver and ketosis. Milk fever is the most common mineralbalance disorder (Shearer and Van Horn, 1992).

Energy Balance DisordersDuring late gestation and early lactation, the cow becomes anorexic. This conditionseverely limits consumption of energy in amounts necessary to meet demands formaintenance and milk production. Fatty acids are mobilized from adipose tissue as anadditional energy source, however, the bovine liver has limited capacity for the amountof fatty acids that can be oxidized or exported as VLDL. When this limit is reached,triglycerides (TG) accumulate in the liver and acetyl coenzyme-A (from oxidation of fattyacids) that is not utilized in the tricarboxylic acid (TCA) cycle is converted to ketonebodies, such as acetone, acetoacetate, and β-hydroxybutyrate. These ketones appearin the blood, milk and urine. (Goff and Horst, 1997).

Fatty liver occurs when the rate of TG synthesis exceeds the rate of TG hydrolysis andTG export as VLDL (Grummer et al., 1993). Excessive accumulation of TG in the liverimpairs its normal function and, in severe cases, can result in liver failure (Shearer andVan Horn, 1992). Because rate of TG synthesis is proportional to plasma NEFAconcentration, fatty liver is likely to develop during periods of high plasma NEFA, suchas the periparturient period. As shown in Figure 5, NEFA concentration increasesapproximately two-fold between 17 days prepartum and two days prepartum andincreases two-fold again, reaching peak concentration by calving (Grummer et al.,1993). Because the accumulation of fat in the liver impairs its function, the liver of anoverconditioned cow has a more limited ability to oxidize fatty acids than that of athinner cow (Goff and Horst, 1997). As a result, excessive body weight gain during latelactation or the dry period predisposes cows to the development of fatty liver followingparturition (Rukkwamsuk et al., 1998).

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Another major factor contributing to the formation of fatty liver is the inherently slow rateof VLDL secretion by the liver in ruminant animals compared to other species (Bertics etal., 1992). The elevated estrogen levels around parturition can also enhance TGdeposition in the liver, escalating the problem even more (Grummer et al., 1993; Goffand Horst, 1997). Fatty liver is best prevented by nutritional management during the dryperiod that minimizes TG deposition in the liver and maximizes liver glycogen stores(Grummer et al., 1993). This balance can be accomplished by monitoring andmanaging body condition through the late lactation and dry period diets so cowsapproach calving in proper body condition (Shearer and Van Horn, 1992). There is alsoevidence that propylene glycol administration prevents fatty liver by improving energybalance during the last days of gestation and first few weeks of lactation (Formigoni,1996). Data from work done by Grummer et al. (1994) show that 296 ml of propyleneglycol given as an oral drench once daily was effective for reducing plasma NEFAconcentrations.

Fatty liver is thought to precede spontaneous clinical ketosis. Fatty liver is mostcommon by the first day after calving, but cows are most susceptible to ketosis at 3weeks postpartum. In addition, development of fatty liver may have a direct effect oncarbohydrate metabolism and influence susceptibility to ketosis. Gluconeogenic activityof liver tissue has been found to be impaired under conditions conducive to fatty liverdevelopment. Reduction in gluconeogenesis by the liver may lower blood glucose levelsand decrease insulin secretion, which would support greater lipid mobilization andincreased rate of fatty acid uptake by the liver and increased ketogenesis (Grummer etal., 1993).

Ketosis results from impaired metabolism of carbohydrates and volatile fatty acids(VFA) leading to hypoglycemia. Formation of ketones is the result of incompletemetabolism of mobilized fat. Fatty acids accumulate in the liver as acetyl-CoA becausethe liver has reduced ability to utilize them. Excess acetyl-CoA is converted to ketonesthat can be metabolized by peripheral body tissues. When ketones are produced inexcess of peripheral tissue’s capacity to use them, they accumulate in the bloodstream,resulting in ketosis. Cows with clinical ketosis exhibit reduced feed intake, reduced milkyield, loss of body weight, central nervous system involvement (staggering, lack ofcoordination, and appearance of staring or blindness), and, in severe cases, acetoneodor on the cow’s breath (Shearer and Van Horn, 1992). Implementing the samenutritional management strategies used to prevent fatty liver can prevent ketosis.Additional prevention strategies include avoidance of fermented feeds, such as certainsilages containing ketogenic precursors, increased frequency of concentrate feeding,and use of specific additives during the dry and transition periods (Kronfeld, 1982;Grummer et al., 1993). Additives include daily niacin supplementation, which has beenshown to reduce plasma concentration of the ketone β-hydroxybutyrate (Duffield, 1998),and daily oral administration of propylene glycol, which provides glucose precursors(Shearer and Van Horn, 1992; Grummer et al., 1994).

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Mineral Balance DisordersA second major cause of metabolic disease is a disruption of mineral balance, primarilycalcium balance, around parturition. Lactogenesis and colostrum synthesis place alarge demand on calcium homeostasis mechanisms so that almost all cows developsome degree of hypocalcemia at parturition (Beede and Pilbeam, 1998). When plasmacalcium concentration drops too low to support nerve and muscle function, parturientparesis, or milk fever, develops (Goff and Horst, 1997).

Milk fever affects up to 9% of dairy cows around calving (Joyce et al., 1997). Risk ofmilk fever increases with age and parity. Cows of third or greater parity are at thehighest risk, while milk fever is rare in first-calf heifers. Increased risk is also likelyrelated to higher milk yield (Shearer and Van Horn, 1992; Rajala-Schultz et al., 1999;Horst et al., 1997).

The most widely used treatment for milk fever is intravenous infusion of 23% calciumborogluconate solution. However, this treatment can cause cardiac arrest by raisingplasma calcium concentrations to dangerous levels. Also, approximately 25% of cowstreated for milk fever relapse and require additional treatment (Horst et al., 1997).Prevention can be a more cost-effective alternative in managing milk fever.

Traditionally, limiting calcium intake during the dry period was used to prevent milkfever. The goal of this strategy is keep dietary calcium low enough so that calciummobilization mechanisms move calcium from body stores and are functional at calvingwhen calcium demand for milk synthesis suddenly increases. Dietary calcium intakeshould be limited to less than 50 g/day, however, diets containing such a low calciumconcentration are often difficult to formulate because many forages commonly used indairy diets, especially legumes, contain a substantial amount of calcium (Shearer andVan Horn, 1992).

Another concept in milk fever prevention is utilization of dietary cation-anion difference(DCAD). When the amount of calcium in the blood drops below normal, parathyroidhormone (PTH) is secreted to stimulate release of calcium from body tissues into theblood pool. Cows that have a relatively high blood pH are less or non-responsive tosecretion of PTH, but cows that have relatively low blood pH are more responsive toPTH. The number of equivalents of cations and anions present ultimately determinesblood pH. Blood pH decreases when more anions than cations enter the blood from thediet and digestive tract. The goal in utilizing DCAD in diet formulation and anionsupplementation should be to reduce blood pH enough to effect calcium mobilization inresponse to hypocalcemia. An appropriate DCAD can be achieved by reducing thenumber of cations or increasing the number of anions in the diet. The number of cationsin the diet can be controlled by selecting feeds, especially forages, that are as low inpotassium and other cations as practically possible (Beede and Pilbeam, 1998). Goffand Horst (1997) have provided evidence that increasing potassium in the prepartumdiet increases the incidence of milk fever. However, current guidelines for forageproduction are inadequate for providing dairy producers with low potassium forages.

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Sources of anions include Cl- and SO4-2 salts of calcium, ammonium, and magnesium.

Phosphate salts are weakly acidifying and are not commonly used. However, only alimited amount of anionic salts can be added to the diet because of palatability problemsthat can affect intake (Horst et al., 1997). When DCAD is sufficiently reduced, increasedcalcium content of 180 to 210 g per cow per day does not cause milk fever and appearsto have some benefit to the cow (Beede and Pilbeam, 1998).

Diets containing anions must be properly mixed in order for each cow to receive thecorrect amount of anions to affect blood pH. Anions are ineffective in componentfeeding situations because the cow’s DCAD cannot be controlled. For the DCADapproach to be most effective, anion/cation content of feedstuffs, intake of the diet, andurine pH (an indicator of blood pH and acid-base status) of cows must be closelymonitored (Beede and Pilbeam, 1998). If management requirements cannot be met,other options for preventing milk fever are available. These include feeding a prepartumdiet low in calcium (less than 50 g/day) and administration of readily available calciumsources at calving to increase plasma calcium (Horst et al., 1997). Sources of calciuminclude commercially available oral supplements, such as gels and pastes.

Parturition Disease ComplexSevere losses of body stores or a more general lack of properly balanced nutrientsincrease the risk of the cow experiencing a number of metabolic diseases. Markusfield(1993) describes these as a parturition disease complex. It is important to understandthat these disorders are not independent but are related. For example, milk fever is asignificant risk factor for several other transition cow problems, including dystocia,ketosis, retained placenta, mastitis, and displaced abomasum.

Grohn et al. (1995) reported the incidence of these diseases for Holstein cows in NewYork (Table 3). As the median day of occurrence indicates, these diseases are mostlikely to occur during the period immediately after calving. However, these disordershave an impact on production and reproduction during the entire lactation. Cowsexperiencing any one of these disorders are at much greater risk of suffering from anumber of the other periparturient dysfunctions. Furthermore, these periparturientdisorders disrupt the cow’s metabolic momentum toward high peak milk yields and alsohave negative carryover effects on reproductive performance.

Effects of Metabolic DiseasesThe culmination of periparturient disorders is lost milk production and decreasedreproductive efficiency, both of which reduce income. Cows with fatty liver exhibitdepression, loss of appetite, rapid loss of body weight in severe cases, and markeddecrease in milk production. Fatty liver is frequently associated with most of the otherperiparturient disorders, including ketosis, milk fever, displaced abomasum, retainedplacenta, and metritis. Fatty liver cases do not respond well to treatment, with mortalityrates of up to 50% (Shearer and Van Horn, 1992) Cows that do recover have alengthened interval to first estrus and days to first service (Morrow, 1975).

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Ketosis also causes appetite depression, decreased milk yields, and weight loss(Shearer and Van Horn, 1992). Deluyker et al. (1991) reported that clinical ketosiscaused losses in milk production of 557 lbs. during the first 119 days in milk for cowsthat were diagnosed within the first 21 days postpartum. These cows also had peakmilk production of nearly 6 lbs. less than healthy animals. Clinical ketosis has beenassociated with increased risk of metritis, displaced abomasum, and mastitis.Subclinical ketosis has been associated with decreased milk yield, increased risk ofclinical ketosis, metritis, and cystic ovarian disease, and impaired reproductiveperformance (Duffield, 1998).

Energy balance disorders, such as fatty liver and ketosis, indicate that the parturientcow is in a state of severe negative energy balance. During this period of negativeenergy balance, luteinizing hormone pulse frequency and growth rate and size of thedominant follicle are decreased. As a result, cows have a longer interval to firstovulation, which causes an increase in days to first service, days open, and services perconception, as well as decreased first service conception rate (Table 4). Achieving highenergy intake during the transition period is critical to normal resumption of ovulationand normal corpus luteum development and therefore high reproductive efficiency(Roche et al., 2000).

Milk fever is another important periparturient disorder. Rajala-Schultz et al. (1999)found that milk fever alone caused a milk loss of between 2.42 and 6.38 lb/d during thefirst 4 to 6 weeks following parturition. It can also reduce the productive life of the cowby as much as 3.4 years. The average cost per case of milk fever has been estimatedat $334, based on direct treatment cost and estimated production losses (Horst et al.,1997).

Milk fever also increases the risk of other metabolic diseases, primarily because it has adetrimental affect on smooth muscle function. Muscle tone decreases in most bodysystems, particularly in the cardiovascular, reproductive, and digestive systems, andpossibly in the mammary system. Blood flow to the extremities is reduced, causing thecharacteristic cold ears of a cow suffering from milk fever. Jonsson and Daniel (1997)found that there was also a significant reduction in blood flow to the ovaries of sheepwith induced hypocalcemia. This would result in suppressed ovarian function, includingprogesterone synthesis and follicular development. Unfortunately, the highest incidenceof hypocalcemia is during the first 6 weeks after calving, a critical time for resumption ofovarian activity.

As shown in Table 5, hypocalcemia also predisposes the cow to calving disorders,including retained placenta, dystocia, and metritis, as well as other periparturientdisorders. Calving disorders are detrimental to postpartum reproductive functionbecause they slow the rate of uterine involution and resumption of a normal estrouscycle (Risco, 1992). Reproductive efficiency is decreased as a result of a longerinterval to first service and first conception and a lengthened calving interval.

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Hypocalcemia affects the digestive system by reducing rumen contractility andincreasing the risk of displaced abomasum. As a result, feed intake may besuppressed, worsening the negative energy balance already present around parturitionand putting the cow at greater risk for ketosis (Goff and Horst, 1997). Hypocalcemiamay also put the cow at greater risk for mastitis by affecting the teat end sphincter. Ifthe teat end cannot close sufficiently following milking, the cow is more susceptible tobacterial invasion that causes mastitis. In addition, hypocalcemic cows have increasedplasma cortisol concentrations that may worsen the immunosuppression normallypresent at parturition. This leaves the cow with decreased ability to fight infectiousdiseases, including mastitis (Goff and Horst, 1997).

Transition Cow ManagementDry Cow NutritionThe decreases in milk production and reduced reproductive efficiency associated withthe periparturient diseases indicate that incidence of these diseases must be closelymonitored. Retained placenta and related reproductive tract infections are oftenassumed to be caused by nutritional deficiencies. More specifically, since researchersreported the relationship between vitamin E, selenium, and retained placenta, manyproducers first react to cows calving with retained placenta by increasing vitamin andmineral supplementation of the dry cow diet. Vitamin E and selenium are antioxidantsubstances that aid in the removal of reactive oxygen metabolites (ROM), or freeradicals, that are generated during normal metabolism. When ROM are not effectivelyremoved, they can impair the health and productivity of the cow by damaging cells andtissues, altering metabolism, and inducing changes in steroidogenesis. Membranepermeability, enzyme function, and muscle tone can be affected by reactions involvingROM. In addition, ROM alter metabolism by reducing the supply of essential cofactors,such as NADPH, and diverting glucose from the important metabolic pathways. ROMalso cause inactivation of steroidogenic enzymes that are necessary for the synthesis ofreproductive hormones such as progesterone and estrogen. Vitamin E is chain-breakingantioxidant that terminates reactions involving ROM by reacting directly with the radicalsafter they have been formed. Glutathione peroxidase, an enzyme containing selenium,prevents the formation of ROM by removing the reactants O2

- and H2O2 . Research hasshown that the levels of antioxidants in the blood are higher for cows that shed theplacenta within 12 hours of parturition (Figure 7). Several other studies have shownthat supplementation of vitamin E and selenium reduced the incidence of retainedplacenta. In addition, supplementation seems to be more effective when vitamin E andselenium are both added to the diet than when one or the other is lacking (Table 6)(Miller et al., 1993).

Correct vitamin and mineral supplementation to enhance immunity is certainly a goal ofproper transition cow management. However, French researchers more completelydescribed retained placenta as an under-nutrition disease. Chassagne and Chacornac(1994) reported that cows that retained the placenta were on a lower plane of nutritionprior to calving. Blood metabolite measurements showed higher fat mobilization andlower blood glucose, as well as lower blood calcium and amino acids (Table 7). Theseresults show the importance of the overall nutritional balance of the transition cow and

32

indicate the importance of focusing attention first to feed intake and energy balancebefore balancing the “smaller inclusion” nutrients like vitamins and minerals.

Several studies have been conducted to develop feeding strategies that would increaseenergy intake during the transition period. The concern is the dramatic decrease in feedintake 5 to 7 days before the animal calves. Dann and co-workers (1999) replacedcracked corn with steam-flaked corn in the diets fed to dairy cows during the transitionperiod. Inclusion of steam-flaked corn increased energy intake during the pre-partumphase of the study. The increased energy intake decreased the release of NEFA intothe blood as the cows achieved a less negative (more positive) energy balance. In asimilar study Rabelo et al. (2001) replaced forage in the prepartum diet with crackedcorn or a cracked corn-corn starch combination. The corn-enriched diets containedlower NDF and higher NFC. The higher NFC diets increased DMI almost 2.0 kg percow per day. The diets with the higher corn/starch levels also supported the highestconcentration of Volatile Fatty Acids in the rumen with these animals having the lowestruminal pH.

A concern with feeding large amounts of starch is the risk of ruminal acidosis. Thisconcern is especially relevant given the once daily feeding and component feedingsystems still used for the dry cows on most dairy farms. Halcomb and others (2001)used fiberous by-product feeds soy hulls and hominy to replace forage in diets fedduring the prepartum transition period. The diet containing the by-product feedsincreased DMI during the pre-partum phase 3.4 kilograms per cow per day (p<0.07).The increased energy intake caused the cows to have a lower blood NEFA and higherblood insulin levels. In unpublished data from our laboratory also found that the partialreplacement of hay with soy hulls increased feed intake and decreased NEFA. Thelong-term impact of these changes during the transition phase was a decrease to daysfirst service.

Levels of crude protein and amino acids in the dry cow diet also affect performance inthe subsequent lactation. During pregnancy, the cow requires protein for maintenance,fetal growth, and, in the case of a primiparous heifer, growth of the dam. The NationalResearch Council (NRC, 2001) recommends feeding 12.4% crude protein in the late dryperiod, or 2.8 lbs of crude protein for a mature 1500-lb (without conceptus) cowconsuming 22.2 lbs of dry matter per day. Approximately 9.6% of the diet should be inthe form of rumen degradable protein (RDP). Levels above or below theserecommendations can have detrimental effects. Greenfield et al. (2000) found thatcows fed 12% crude protein for 28 days prepartum had a higher dry matter intake andproduced more milk during the first 56 days in milk when compared to cows fed 16%crude protein. On the other hand, lower protein levels in the dry cow diet can restrictthe growth of the fetus, resulting in low calf birth weight. In addition, amino acids fromprotein can be oxidized for energy during the late dry period, when energy demands forfetal growth are high, and dry matter intake is depressed (Greenfield et al., 2000).Without this additional energy source, the transition cow’s negative energy balance mayworsen. More recent reports have further investigated the role of protein concentrationin the pre-partum diet on animal performance. Santos and others (2001) concluded that

33

12.7% crude protein was sufficient for multiparous cows. Increasing dietary crudeprotein concentration using RUP protein sources did improve the lactation performanceof first lactation animals. Diets containing the higher protein content increased 120-daymilk yield, lactation daily average, and 305-d ME yields for the younger animals.Robinson and coworkers (2001) reported similar results when feeding diets containing11.7% versus 14.7% crude protein with primiparous cow response increasing as dayseating the protein supplement increased to 9 to 12 days pre-partum.

There are also a variety of feed additives available to help make the transition periodmore successful (Hutjens and Tomlinson, 2001). Anionic salts and oral calciumsupplements can be given to alleviate milk fever problems. Daily oral doses ofpropylene and/or daily niacin supplementation during the transition period helpdecrease the severity of negative energy balance. Other feed additives such as yeastculture and probiotics have been used to aid cattle in the transition from low starch drycow diets to high starch diets fed to lactating cows.Feeding Management

The environment in which cows are fed is important when evaluating the transitionprogram and ability to successfully achieve the 100-day contract. Much has beenwritten pertaining to the feeding environment of lactating cows; but comparatively littleinformation is available relative to the periparturient cow. Adequate bunk space to allowall cows equal access at feeding time is important, as is the availability of water relativeto distance from feed (less than 50 feet) and the number of animal spaces. Inmanaging the transition cow group, there can be large fluctuations in the number ofcows on a day-to-day basis. The amount of feed delivered must be carefully monitoredas group size changes when fresh cows are moved out after calving and late gestationcows are added. Age and body weight of the cows entering and leaving the transitiongroup will also affect the amount fed. These details of where and how feed is offered tothe transition cow group can determine the success or failure of the early lactation cow.

EnvironmentAnother factor critical to a successful transition cow contract is housing. The dry cowexperiences significant stress with calving and initiation of lactation. The housingsystem is key to minimizing exposure to environmental stress. Housing should protectthe animal from injury and disease. This is especially important for the dry cow in lategestation. Harmon and Crist (1994) reported that the incidence of environmentalmastitis is highest in the first two weeks and the last two weeks of the dry period.Voermans (1997) recommended evaluating the housing system in terms of ability toreduce exposure of the animals to pathogens. Furthermore, Voermans concluded thatthe important benefits of good housing in minimizing animal stress were manifested inimproved immune function and increased resistance to challenge by pathogenicmicroorganisms. Clean, dry bedding is essential to improved animal health, especiallyin the periparturient transition phase.

High environmental temperatures result in significant thermal stress for the transitioncow. Exposure to heat during the third trimester of gestation shifts blood flow to the

34

extremities and away from the uterus, compromising placental and fetal growth. Calvesoften have lower than normal birth weights, putting them at higher risk for mortality(Shearer and Beede, 1990). In addition, researchers in Georgia found that theincidence of retained placenta increased from 12% during the warm, humid months ofMay through September to 24% during the cooler months (Dubois and Williams, 1980).Hormone alterations due to heat stress affect mammary development and lactogenesis,reducing milk yield in the subsequent lactation (Table 7) (Shearer and Beede, 1990).Strategies to keep cows cool and comfortable during the transition period includeproviding shade for cows on pasture or utilizing sprinklers, misters, and/or fans in free-stall structures. Cows should also be provided with an easily accessible source of cleandrinking water.

SummaryDuring the transition period, the dairy cow is undergoing numerous changes inendocrine, nutritional, metabolic, and physiological status as she prepares for calvingand initiation of lactation. These changes result in a dramatic decrease in dry matterintake that worsens the negative energy balance already present after calving. If thenegative energy balance during transition becomes excessive, metabolic diseases suchas fatty liver and ketosis can result. Disruption of mineral balance during theperiparturient period leads to mineral balance disorders, especially milk fever. Thesediseases are costly in terms of their affect on milk production, reproduction, and thecow’s susceptibility to other periparturient disorders. Intensive management of thenutrition, feeding system, and environment of the periparturient dairy cow reduces theodds of disease and increases the odds of success.

The ‘100 day contract’ is a series of delicate negotiations that encompass the full impactof the transition cow. Unsuccessful negotiations at any point increase the risk of overallfailure. Getting the details right and ensuring adequate intake of all nutrients are thekey elements of the ‘100-day contract’.

ReferencesBeede, D.K., and T.E. Pilbeam. 1998. Anion, vitamin E, and Se supplementation ofdiets for close-up dairy cows. Proc. 1998 West. Can. Dairy Sem., Edmonton, Alberta.

Bell, A.W. 1995. Regulation of organic nutrient metabolism during transition from latepregnancy to early lactation. J. Anim. Sci. 73:2804-2819.

Bell, A.W., R. Slepetio, and R.A. Ehrhardt. 1995. Growth and accretion of energy andprotein in the gravid uterus during late pregnancy in Holstein cows. J. Dairy Sci.78:1954-1961.

Bertics, S.J., R.R. Grummer, C. Cadorniga-Valino, and E.E. Stoddard. 1992. Effect ofprepartum dry matter intake on liver triglyceride concentration and early lactation. J.Dairy Sci. 75:1914-1922.

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Chassagne, M., and J.P. Chacornac. 1994. Blood metabolites as indicators of nutritionalrisk factors for retained placenta in the dairy cow. Vet. Res. 25:2.

Curtis, C.R., H. Erb, C. Sniffen, R. Smith, P. Powers, M. Smith, M. White, R. Hillman,and E. Pearson. 1983. Association of periparturient hypolcalcemia with eightperiparturient disorders in Holstein cows. J. Am. Vet. Med. Assoc. 5:559.

Dann, H.M. G.A. Varga, and D.E. Putnam. 1999. Improving energy supply to lategestation and early post partum dairy cows. J. Dairy Sci. 82:1765-1778.

Deluyker, H.A., J.M. Gay, L.D. Weaver, and A.S. Azari. 1991. Change of milk yield withclinical diseases for a high producing dairy herd. J. Dairy Sci. 74:436-445.

Dirksen, G.U., H.G. Liebich, and E. Mayer. 1985. Adaptive changes of the ruminalmucosa and their functional and clinical significance. Bovine Pract. 20:116-120.

Drakely, James K. 1999. Biology of dairy cows during the transition period: the finalfrontier? J. Dairy Sci. 82:2259-2273.

Dubois, P.R. and D.J. Williams. 1980. Increased incidence of retained placentaassociated with heat stress in dairy cows. Theriogenology. 13(2):115-121.

Duffield, T.F., D. Sandals, K.E. Leslie, K. Lissemore, B.W. McBride, J.H. Lumsden, P.Dick, and R,. Bagg. 1998. Effficacy of monensin for the prevention of subclinical

ketosis in lactating dairy cows. J. Dairy Sci. 81:2866-2873.

Formigoni, A., M.C. Cornil, A. Prandi, A. Mordenti, A. Rossi, D. Portetelle, and R.Renaville. 1996. Effect of propylene glycol supplementation around parturition on milkyield, reproduction performance and some hormonal and metabolic characteristics indairy cows. J. Dairy Res. 63:11-24.

Gerloff, B.J. 1988. Feeding the dry cow to avoid metabolic disease. Vet. Clinics of N.America: Food An. Pract. 4(2):379.

Goff, J.P. and R.L. Horst. 1997. Physiological changes at parturition and theirrelationship to metabolic disorders. J. Dairy Sci. 80:1260-1268.

Goff, J.P. and R.L. Horst. 1997. Effects of the addition of potassium or sodium, but notcalcium, to prepartum rations on milk fever in dairy cows. J. Dairy Sci. 80:176-186.

Greenfield, R.B., M.J. Cecava, T.R. Johnson, and S.S. Donkin. 2000. Impact of dietaryprotein amount and rumen undegradability on intake, peripartum liver triglyceride,plasma metabolites, and milk production in transition dairy cattle. J. Dairy Sci. 83:703-710.

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Gröhn, Y.T., S.W. Eicken, and J.A. Herth. 1995. The association between previous 305day milk yield and disease in New York state dairy cows. J. Dairy Sci. 78:1693-1702.

Grummer, R.R. 1995. Impact of changes in organic nutrient metabolism on feeding thetransition dairy cow. J. Anim. Sci. 73:2820-2833.

Grummer, Ric. 1996. Close-up dry period: feeding management for a smoothtransition. Proceedings of the Western Canadian Dairy Seminar. Pages 23-38.

Grummer, R.R., J.C. Winlker, S.J. Bertics, and V.A. Studer. 1994. Effect of propyleneglycol dosage during feed restriction on metabolites in blood of prepartum Holsteinheifers. J. Dairy Sci. 77:3618-3623.

Grummer, R.R.. 1993. Etiology of lipid-related metabolic disorders in periparturient dairycows. J. Dairy Sci. 73:3882-3896.

Harmon, R.J., and W.L. Crist. 1994. Environmental mastitis in lactating and dry cowsand prepartum heifers. Proc. National Mastitis Council. pp. 241-249.

Horst, R. L., J.P. Goff, T.A. Reinhardt, and T.R. Buxton. 1997. Strategies for preventingmilk fever in dairy cattle. J. Dairy Sci. 80:1269-1280.

Hutjens, Michael F. and Dana J. Tomlinson. 2001. Nutrition is important in transitionfeeding programs. Feedstuffs &3(54):9-11, 18.

Jonsson, N.N. and R.C.W. Daniel. 1997. Effects of hypocalcaemia on blood flow to theovaries of sheep. J. Vet. Med. A44:281-287.

Joyce, P.W., W.K. Sanchez, and J.P. Goff. 1997. Effect of anionic salts in prepartumdiets based on alfalfa. J. Dairy Sci. 80:2866-2875.

Kronfeld, D.S. 1982. Major metaboic determinants of milk volume, mammary efficiency,and spontaneous ketosis in dairy cows. J. Dairy Sci. 65:2204-2212.

Markusfeld, O. 1993. Parturition disease complex of the high-yielding dairy cow. ActaVet. Scand. Suppl. 89:9.

Miettinen, P.V.A. 1990. Metabolic balance and reproductive performance in Finnishdairy cows. J. Vet. Med. A37:417.

Miller, J.K., E. Brzezinska-Slebodzinska, and F.C. Madsen. 1993. Oxidative stress,antidoxidants, and animal function. J. Dairy Sci. 76:2812-2823.

Morrow, D.A. 1975. Fat cow syndrome. J. Dairy Sci. 59:1625-1629.

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National Research Council. 2001. Nutrient requirements of dairy cattle. 7th rev. ed. Natl.Acad. Sci., Washington, DC.

Rabelo, E. S.J. Bertrics, J. Mackovic, and R.R. Grummer. 2001. Strategies forincreasing energy density of dry cow diets. J. Dairy Sci. 84:2240-2249.

Rajala-Schultz, P.J., Y.T. Gröhn, and C.E. McColloch. 1999. Effects of milk fever,ketosis, and lameness on milk yields in dairy cows. J. Dairy Sci. 82:288-294.

Risco, C.A. 1992. Calving related disorders. In Large Dairy Herd Management,192-198,eds. H.H. Van Horn and C.J. Wilcox. Champaign, IL:ADSA.

Robinson, P.H., J.M. Moorby, M. Acura, R. Hinders, T. Graham, L. Castelanelli, N.Barney. 2001. Influence of close-up period protein supplementation of Holstein cows intheir subsequent lactation. J. Dairy Sci. 84:2273-2284.

Roche, J.F., D. Mackey, and M. D. Diskin. 2000. Reproductive management ofpostpartum cows. Anim. Reprod. Sci. 60-61:703-712.

Rukkwamsuk, T.T., T. Wensing, and M.J.H. Geelen. 1998. Effect of overfeeding duringthe dry period on regulation of adipose tissue metabolism in dairy cows during theperipartuient period. J. Dairy Sci. 81:2904-2911.

Shearer, J.K. and H.H. Van Horn. 1992. Metabolic diseases of dairy cattle. In. LargeDairy Herd Management, 358-372, eds. H.H. Van Horn and C.J. Wilcox, Champaign,IL:ADSA.

Shearer, J.K., and D.K. Beede. 1990. Effects of high environmental temperature onproduction, reproduction, and health of dairy cattle. Agri-Practice. 11(5):6-17.

Stallings, Charles C. 1998. Feeding management during the transition phase.Proceedings of the Western Canadian Dairy Seminar.

Stanley, T.A., R.C. Cochran, E.S. Vanzant, D.L. Harmon, and L.R. Corah. 1993.Periparturient changes in intake, ruminal capacity, and digestive characteristics in

beef cows consuming alfalfa hay. J. Anim. Sci. 71:788-795.

Underwood, J.P. 1998. Effects of feeding palatability enhancer in transition cow diet onperformance of Holstein dairy cows. M.S. Thesis. University of Missouri-Columbia.

Voermans, J.A.M. 1997. Health and disease perspectives. In: Proc. 5th Int. Symposiumon Livestock Environment, Bloomington, MN. p. 1-6.

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Table 1. Energy and protein deposition in the uterus and fetus duringpregnancy in Holsteins.1

Energy (kcal/d) Protein (g/d)

Gestation (days) Uterus Fetus Uterus Fetus

210 631 500 76 54230 694 601 90 73250 757 703 103 91270 821 805 117 1101Adapted from Bell et al., 1995.

Table 2. Periparturient changes in ruminal water-holding capacity and fill.1

Average days from calving2

-61 -48 -34 -20 -6 +8 +22

Rumen Capacity,gal. 33.5 31.4 28.5 28.0 26.9 37.5 35.1

Total fill/capacity, % 46.5 51.9 57.3 55.5 53.1 51.0 58.9

DM fill/capacity, % 6.7 6.2 6.6 6.0 6.2 6.4 7.4

Fluid fill/capacity, % 39.9 45.7 50.7 49.5 47.0 44.6 51.51Adapted from Stanley et al., 1993.2Negative values indicate days prior to calving; positive values indicate days aftercalving.

Table 3. Lactational incidence risks and median days postpartum ofdisorders in 8070 multiparous Holstein cows in New York state.1

Lactational IncidenceDisorder Risk (%) Median day of

occurrenceRetained placenta 7.4 1Metritis 7.6 11Milk fever 1.6 1Ketosis 4.6 8Displaced abomasum 6.3 11Mastitis 9.7 591Adapted from Grohn et al., 1995.

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Table 4. The effects of early postpartum energy status on reproductiveperformance.1

Days tofirst

serviceDays open

Servicesper

conception

First serviceconception rate

(%)Normal 70.5 80 1.2 75

Subclinical ketosis 75.8 102 2.0 44

Ketotic 78.0 100 1.9 401Adapted from Miettinen, 1990.

Table 5. Influence of hypocalcemia on risk of other periparturientdisorders.1

Disease Odds ratio P-valueDystocia 2.8 <0.0001Retained placenta 6.5 <0.0001Left displacedabomasum 3.4 0.06

Ketosis 8.9 <0.0001Mastitis 8.1 <0.00011Adapted from Curtis et al., 1983.

Table 6. Incidence of placental retention in dairy cows fed diets containing>0.12 ppm of Se with or without 1000 IU of supplemental vitamin E duringthe last 40 days of gestation.1

TreatmentYear Reference Control Vitamin E

(% of group)1988 Mueller et al., 1988 26.7 6.9*1989 Mueller et al., 1989 34.4 10.8**1990 Thomas et al., 1990 52.9 22.0*1991 Brzezinska-

Slebodzinska andMiller, 1992

32.3 21.9

*P<0.05**P<0.011Adapted from Miller and Brzezinska-Slebodzinska, 1993.

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Table 7. Measurements of blood metabolites and nutrients between normalcows and cows with retained placenta.1

Item Retained NormalGlucose, ng/dl 59.6 61.8NEFA, meq/dl 0.494 0.340*Amino acids, moles/dl 2.34 2.48*Calcium, mg/dl 96.3 98.5*Monocytes, 103/ml 225 310*

*P<0.051Adapted from Chassagne and Chacornac (1994).

Table 8. Effect of prepartum heat stress on postpartum milk yield.1

Production Cooled Heat stressed Difference (%)

305-d milk yield, lbs.2 14,867.6 13,085.6 1782.0 (12)150-d milk yield,lbs./d

89.5 81.8 7.7 (8.5)

Peak milk yield,lbs./d3 91.0 87.4 3.6 (4)1Adapted from Shearer and Beede, 1990.2305-d predicted yield adjusted for age, month of calving, and Estimated RelativeProducing Ability (ERPA).3Means of peak milk production taken from three herds.

Figure 1. Terms of the 100-Day Contract

1. Birth of a live calf

2. Healthy cow during the transition period3. High peak milk production4. Controlled loss of body condition

5. High fertility at first breeding

41

Figure 2. Changes in serum concentrations of hormones in cows during theperiparturient period.1

1Adapted from Bell, 1995.

Figure 3. Dry matter intake of transition cows.1

1Adapted from Underwood, 1998.

0

2

4

6

8

10

-9 -7 -5 -3 -1 1 3 5 7 9Pro

gest

eron

e co

ncen

trat

ion

(ng/

ml s

erum

)

0

0.05

0.1

0.15

0.2

0.25

-9 -7 -5 -3 -1 1 3 5 7 9Days from parturition

Est

radi

ol

Con

cent

ratio

n (p

g/m

l ser

um)

0

5

10

15

20

25

30

35

40

-3 to -2 -2 to -1 -1 to 0 0 to 1 1 to 2 2 to 3 3 to 4

Weeks from parturition

DM

I (lb

s./d

)

42

Figure 4. Estimated prepartum energy balance of transition cows.1

1Adapted from Grummer, 1995.

Figure 5. Serum non-esterified fatty acid concentration of transition cows.1

1Adapted from Underwood, 1998.

-20

-15

-10

-5

0

5

-21 -14 -7 -4 -1 0 1 4 7 14 21

Days from parturition

Mca

l NE

L/d

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

-21 -14 -7 -3 0 3 7 14 21

Days from parturition

NE

FA

con

cent

ratio

n (m

Eq/

l)

43

Figure 6. Changes in the area of cross sections of rumen papillae of cows fedlow-energy diets prepartum and high-energy diets postpartum.1

1Adapted from Dirksen et al., 1985.

Figure 7. Total antioxidants in bovine plasma as measured by their protection ofphycoerythrin fluorescence in vitro.1

4142434445464748495051

0123456Time before calving (weeks)

Flu

ore

scen

ce (

% o

f in

itia

l)

Not Retained Retained

1Adapted from Miller et al., 1993.

0

0.2

0.4

0.6

0.8

1

1.2

1.4

-7 -5 -3 -1 0 1 3 5 7

Weeks from parturition

Are

a of

cro

ss s

ectio

n (m

m2 )

44

Protein and Carbohydrate Utilization by Lactating Dairy Cows

Dr. William P. WeissDepartment of Animal Sciences

Ohio Agricultural Research and Development CenterThe Ohio State University, Wooster 44691

Milk production requires large amounts of protein and energy, and these two nutrientsmake up about 80% of total feed costs. About 70% of the energy consumed by a cow isderived from carbohydrates, therefore, energy nutrition is largely a function ofcarbohydrate utilization. Because protein and energy have a substantial impact on milkproduction and production costs, diets must be formulated properly for these twonutrients.

CarbohydratesCarbohydrates are divided into two main classes by dairy nutritionists: neutral detergentfiber (NDF) and nonfiber carbohydrate (NFC). Feeds are analyzed directly for NDF butNFC is usually calculated as 100 - NDF - crude protein - fat - ash. The NDF fraction iscomprised mostly of cellulose, hemicellulose, and lignin, and the NFC fraction is mostlystarch, simple sugars, soluble fiber, and organic acids (acids are not carbohydrate butbecause NFC is calculated by difference, acids are included). The major nutritionaldifferences between NDF and NFC are their site, rate, and extent of digestion. Usuallymore than 90% of the digestion of NDF occurs in the rumen. Depending on the feed,between 60 and 80% of digestible NFC is digested in the rumen and 20 to 40% isdigested in the small intestine. The rate of digestion in the rumen is usually rapid forNFC and slow to moderate for NDF. Total tract digestibility of NFC is usually greaterthan 90% and 30 to 60% for NDF. These differences between NDF and NFC must beconsidered when formulating diets.

Nonfiber carbohydratesCows do not have a requirement for NFC, but because NFC is highly digestible it is aprimary energy source for cows. Because NFC is digested rapidly, increasing NFCusually increases dry matter (DM) intake. The same properties (rate and extent ofdigestion) that make NFC desirable can be detrimental to the health and long termproductivity of cows. Excess dietary NFC causes ruminal acidosis which is related todepressed milk fat, metabolic disorders, reduced DM intake, and laminitis. Therelationship between NFC concentration and energy intake is not linear. Increasingdietary NFC increases energy intake to a point and then further increases in NFCgenerally decreases energy intake (Figure 1). A good diet should provide enough NFCto promote high energy intake without adversely affecting the health of the cow.

Neutral detergent fiberBecause NDF is usually digested slowly and not very extensively, it often limits energyintake. Conversely, adequate NDF is needed to maintain proper rumen pH and preventacidosis related problems. The slow rate of digestion of NDF in the rumen reduces acid

45

production preventing a large drop in rumen pH. In addition, forage is usually a primarysource of NDF and the physical characteristics of most forages stimulate chewing whichincreases saliva flow helping to buffer the rumen. The NDF in feed that promoteschewing is called effective NDF. Although effective NDF is used in some rationsoftware, no uniform method of measuring effective NDF has been adopted, thereforeconcentrations of effective NDF cannot be measured. To overcome this problem theNRC (2001) adopted a simple approach of dividing NDF into NDF provided by foragesand NDF provided by other feedstuffs. This is the approach that will be discussed.

Figure 1. Relationship between dry matter intake and dietary NFC concentrations(calculated as 100 - NDF - CP - ash - fat). The equation was DM intake (% of BW) =1.07 + 0.147 X - 0.00179X2. Maximum intake occurred at 41% NFC. Source of data:Triangles = Valadares Filho et al., 2000; Cirlces = Batajoo and Shaver, 1994; Squares =Weiss and Shockey, 1991.

Carbohydrate RecommendationsDietary recommendations for NDF and NFC are closely related; the concentration ofone influences the needed concentration of the other. One reason for this relationshipis simply mathematical. The concentration of NFC is calculated by difference thereforediets with higher concentrations of NDF usually have lower NFC and vice versa.Because protein, fat, and ash concentrations vary between diets, the relationshipbetween NDF and NFC is not perfect. The second reason for the relationship isbiological; NDF and NFC have essentially opposite effects on rumen pH and energyintake. Other factors influencing the recommended concentrations of NDF and NFCinclude the source of NDF (forage, vs. nonforage), effectiveness of the feed inpromoting chewing, the source of NFC, use of supplemental buffers, and feeding

2

2.5

3

3.5

4

4.5

15 20 25 30 35 40 45 50

NFC, % of DM

DM

inta

ke, %

of

BW

46

management. The NRC (2001) guidelines (Table 1) are a good starting point in rationformulation. The dietary concentration of forage NDF (% of DM) determines therecommended concentrations of total NDF and NFC. As the amount of forage NDF in adiet decreases, the amount of total NDF needed increases and the maximumconcentration of NFC decreases. In general NDF from forage is about twice aseffective at maintaining rumen pH than NDF from nonforage sources. Therefore, a 1-unit decrease in forage NDF results in a 2-unit increase in recommended NDFconcentration and a 2-unit decrease in maximum NFC. The recommendations in Table1 are based on the following assumptions: 1) forages have adequate particle size, 2)dry ground corn is the primary starch source, and 3) the diet is fed as a TMR. If theseassumptions are not true for a particular situation, modifications to Table 1 are needed.

Table 1. Recommended (NRC, 2001) concentrations of NDF and NFC in lactation diets(% of diet DM). The values in this table assume that forage particle size is adequate,the primary starch source is dry ground corn, and the diet is fed as a TMR. See text forappropriate modifications when these assumptions are not met. Diets should neverexceed 44% NFC or contain less than 25% total NDF or less than 15% forage NDF.

Minimum forageNDF

Minimum diet NDF Maximum diet NFC

19 25 44

18 27 42

17 29 40

16 31 38

15 33 36

Particle size of forage. Finely-chopped forages promote less chewing than morecoarse forages, therefore when forages are finely chopped, concentrations of forageNDF and total NDF should be higher and NFC concentrations should be lower than thevalues in Table 1. Unfortunately we do not yet have an adequate method of evaluatingadequate particle size. Particle size distribution using the Penn State Particle Separatorhas not been related to chewing or rumen pH. Diets with very little material on the topscreen of the Penn State Separator maintained rumen pH as well as diets withsubstantial amounts of material on the top screen. Differences in the amount ofmaterial in the pan also are not related to rumen pH. Rather than givingrecommendations for particle size that are not supported by any scientific data, Isuggest that nutritionists closely monitor the herd. If the diet appears adequate onpaper, but milk fat is lower than expected or if day-to-day variation in DM intake isexcessive, particle size of the forage may not be adequate and modifications should bemade to the diet.

Source of starch. The starch in dry ground corn is less digestible in the rumen thanmany other starch sources, therefore, ruminal acid production is lower with dry corn

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than some other feeds. The starch in high moisture corn, steam-flaked corn, and smallgrains (wheat, barley, oats) is more digestible in the rumen and produces more acidsthan dry ground corn. Because acid production is higher with those ingredients,concentrations of total NDF should be higher and NFC concentrations should be lowerthan values in Table 1. A good general rule is to increase NDF by 2-units and decreaseNFC by 2-units when those grains are fed. Very wet high moisture corn and very thinlyflaked steam-flaked corn may require an increase of 3 or 4 units in NDF (and a similardecrease in NFC) to maintain rumen pH.

Other factors. When diets are fed as a TMR, intake of NFC and NDF are more or lessconcurrent. When forage and concentrate are fed separately, cows can consume largequantities of NFC from the concentrate in a relatively short period of time. This canresult in a large increase in ruminal acids and low pH. Quantitative data are notavailable, however, when forage and concentrate are fed separately and when theconcentrate is made primarily of starchy ingredients diets should have higher NDF andlower NFC concentrations than shown in Table 1. Feeding supplemental buffers canreduce the minimum concentration of total NDF by about 1-unit and increase themaximum concentration of NFC by about 1-unit. Whole-linted cottonseed stimulateschewing about as well as forage. When cottonseeds are fed the NDF provided by thecottonseed can be considered as forage NDF.

ProteinProtein nutrition of dairy cows is complex, and simply balancing diets for crude protein isnot adequate for high production or for efficient use of protein. Diets should bebalanced for rumen degradable protein (RDP) and rumen undegradable protein (RUP).Overfeeding RDP does not affect RUP requirement and results in increased excretion ofnitrogen via the urine and may reduce reproductive efficiency. When RDP is deficient,overfeeding RUP can make up for that deficiency but when adequate RDP is fedoverfeeding RUP has the same effects as overfeeding RDP.

Rumen degradable proteinCows do not require RDP but rumen microorganism do. The amount of RDP neededdepends on the metabolic activity of rumen microbes which ultimately depends on theamount of energy available to the microbes. As energy intake increases, microbialprotein production increases and the requirement for RDP increases. When diets aredeficient in RDP microbial growth and microbial protein production are reduced. Thiscan reduce fiber digestion, DM intake, and ultimately milk production. The RDPrequirement is based solely on energy intake; increased milk production does not effectRDP requirement unless energy intake is increased (Table 2).

Rumen undegradable proteinAssuming adequate RDP is fed, microbial protein production ranges from about 3.5 to 5lbs/day. Although this is a large amount, microbial protein alone can usually onlymaintain the cow and provide adequate protein for 25 to 30 lbs of milk. High milkproduction requires a substantial amount of RUP. This does not necessarily mean thatfeeds with high concentrations of RUP are always needed. A simple diet of high quality

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alfalfa, corn silage, corn grain, and soybean meal can support about 85 lbs of milkproduction by midlactation cows. In very early lactation (<30 days in milk), when DMintake is depressed, that same diet can only support about 60 lbs of milk. Diets for earlylactation cows and high producing cows usually require special attention to proteinsupplementation. In those cases, ingredients with high concentrations of RUP usuallywill be needed in the diet.

Table 2. Effect of milk production and intake on rumen degradable protein (RDP)requirements of an average Holstein cow (calculated using NRC, 2001). Note thecomparison between 75 and 100 lbs of milk when intake is the same (RDP requirementdoes not change but RUP increases with increasing milk production).

Milklbs/day

DM intakelbs/day

RDP RUP

% of DM lbs/day % of DM lbs/day

50 44 10.0 4.4 3.6 1.6

75 52 10.0 5.2 5.2 2.7

100 52 10.0 5.2 7.7 4.0

100 61 9.7 5.9 6.2 3.8

Concentrations of RDP and RUP in feedsThe degradability of protein depends mostly on the feedstuff and DM intake. Hay cropforages have high protein degradability, conventional oilseeds have high to moderateprotein degradability, most corn products have moderate to low protein degradability,and heat-treated products and animal protein meals have low protein degradability. Theeffect intake has on degradability depends on the feed (Table 3). The protein inhaycrop forages has a very rapid rate of digestion and intake has little effect on RDPconcentrations. The protein in animal protein meals (e.g., blood meal) is digested veryslow and again intake has little effect on concentrations of RDP. Oilseed meals andsome byproducts have an intermediate rate of protein degradation and increased intakereduces protein degradability (i.e., increases the RUP concentration).

Protein RecommendationsAlthough variation exists, the RDP requirement for most cows will be met if diets containabout 10% RDP (DM basis). Because the cost of under feeding RDP (reduced intakecausing reduced milk production) is greater than the cost of slightly overfeeding RDP(slightly increased feed costs, small increase in excretion of nitrogen via urine, andslightly increased risk of reduced reproductive performance) a small excess of RUP (5to 10%) should be fed (approximately 10.5 to 11% of DM). If additional RDP is needed,hay crop forages, urea, or oilseed meals are good sources. Once the RDP requirementis met, RUP supply must be evaluated. The supply of RUP can be increased byincreasing the total CP content of a diet or by selecting feeds with high RUPconcentrations. In many cases, providing slightly more CP than required to meet RUP

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requirements is the most economical alternative. However, this option increasesexcretion of nitrogen via manure, and environmental regulations may make this optionless economically feasible.

Table 3. Effect of DM intake on RUP concentrations (% of total CP) in some commonfeeds.

Feedstuff Daily DM intake

40 lbs 50 lbs

Alfalfa hay, immature 15.3 16.4

Alfalfa silage, midbloom 17.2 18.2

Blood meal, ring-dried 74.5 77.1

Brewers grains, wet 32.5 35.3

Corn silage 34.2 35.1

Corn grain, ground 42.9 46.8

Cottonseed meal, 50% CP 44.4 47.4

Cottonseed, whole 20.4 22.6

Distillers grains 47.1 50.3

Fish meal 63.1 65.5

Soybean meal, 48% CP 37.4 41.9

Soybean meal, heat-treated 64.3 68.2

When microbial protein and standard protein supplements are not adequate, judicioussupplementation with specific feeds can be used to meet the RUP requirement of highproducing and early lactation cows without excessive loss of nitrogen to theenvironment. When choosing an RUP source, the digestibility of the RUP must beconsidered (Table 4). For example, about 73% of the DM in batch-dried blood meal isRUP, but the average digestibility of the RUP is only 65%, therefore digestible RUP is73 x 0.65 = 47.5% of the DM. Heat-treated soybean meal averages 39% RUP (DMbasis) that is 93% digestible equaling 36% digestible RUP. The difference in digestibleRUP between those two sources is much less than the difference in RUP. Pricecomparisons must be made on a digestible RUP basis, not on an RUP basis. If thebatch-dried blood meal cost more than about 1.25 times the price of the heat-treatedsoybean meal, it would not be a wise purchasing decision. The second factor toconsider when choosing a source of RUP is amino acids. Cows (as do all animals)require amino acids, not protein. The best method of ensuring an adequate balance ofamino acids is to evaluate the diet using a nutrition model such as the NRC (2001) orthe Cornell program. These programs estimate amino acid supply; the Cornell modelalso estimates requirements. Because of limited data we are less certain about amino

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acid requirements than amino acid supply. Lysine or methionine is generally the firstlimiting amino acid for milk protein production. If the model you are using suggests thediet is limited in methionine then RUP sources that are good sources of methionineshould be used (Table 4). Conversely if lysine is limiting, use lysine sources. Diets withlarge amounts of corn products (corn silage, corn grain, distillers grains) will be lysine-limited, and diets with high amounts of alfalfa protein usually are limited in methionine.

Table 4. Average RUP digestibility of some common feeds Amino acid classdesignates whether a given feed contains above average concentrations of lysine ormethionine. When diets are limited by lysine, feeds classified as lysine should be used,and when diets are limited by methionine, feeds classified as methionine should beused. To estimate RUP (% of DM), dry matter intake was set at 50 lbs/day.

Feedstuff RUP, % of DM

RUPDigestibility,

%

DigestibleRUP, % of

DM

AminoAcid

ClassBlood meal, batch dried 73 65 47.5 Lysine

Blood meal, ring-dried 73 80 58.4 Lysine

Brewers grains, dried 16 80 12.8 Neither

Corn gluten meal 47 92 43.2 Methionine

Distillers grains 15 80 12.0 Neither

Fish meal 44 88 38.7 Lys/met

Soybean meal, heattreated

31 93 28.8 Lysine

Soybean meal, 48% CP 22 93 20.5 Lysine

Cottonseed meal, 50%CP

21 92 19.3 Neither

SummaryCarbohydrate balance affects production and health of cows. Most diets should contain27 to 32% NDF and 35 to 40% NFC, but specific situations may require concentrationsoutside this range. Diets that contain excessive amounts of NDF (usually means NFCis low) will usually reduce energy intake and diets with excessive amounts of NFC (i.e.,NDF is low) can reduce energy intake and are related to rumen health problems. Dietsshould be formulated for RDP and RUP rather than CP. This will increase utilizationefficiency of nitrogen (reduced excretion of N) and allow for high milk production. Mostdiets will need to contain about 10% RDP (% of DM) and varying amounts of RUPdepending on intake and milk production. Cows in early lactation and high producingcows usually require substantial amounts of RUP. The RUP supplement used shouldbe highly digestible and provide the proper balance of amino acids.

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References

Batajoo, K. K., and R. D. Shaver. 1994. Impact of nonfiber carbohydrate on intake,digestion, and milk production by dairy cows. J. Dairy Sci. 77:1580-1588.

National Research Council. 2001. Nutrient Requirements of Dairy Cattle. Natl. Acad.Press, Washington DC.

Valadares Filho, S. C., G. A. Broderick, R. F. D. Valadares, and M. K. Clayton. 2000.Effect of replacing alfalfa silage with high moisture corn on nutrient utilization andmilk production. J. Dairy Sci. 83:106-114.

Weiss, W. P., and W. L. Shockey. 1991. Value of orchardgrass and alfalfa silages fedwith varying amounts of concentrates to dairy cows. J. Dairy Sci. 74:1933-1943.

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Practical Considerations for Feeding Fat to Dairy Cattle

Jonathan Goodson, Ph.D. PASSouthern States Inc.

PO Box 767487Roswell, Georgia 30076

The use of fat as a supplemental energy source in the diets of lactating dairy cows hasbecome commonplace in the last ten years. It may be used at higher levels in dairies inthe southeastern part of the United States due to the lower quality forages fed in thisarea. Forages such as alfalfa, which can provide substantial energy to the lactating cow,are frequently fed in high amounts in the northeast, the Midwest, as well as in the FarWestern dairy areas. Here in the southeast, corn silage, which of course is also high-energy forage, is used in large amounts. However, the grass type forages that we feedtend contribute a much lower amount of energy to the diet on a per weight basis. Thesecalories must be made up for. Although we also tend to feed higher grain levels in thisarea than in other parts of the US, again, due to lower quality forages, grain feeding hasdefinite upper limits. Since fat has an energy density that is about 2.25 times that ofcarbohydrates, which are found in high levels in many grains, it is an obvious choice tomake up this energy deficit since it is higher in energy and free of starch. An additionalconsideration in regard to the use of fat is that it allows us to feed higher levels offorage, so that adequate fiber intake can be maintained. The objective of thispresentation is to discuss some practical measures that can be taken to feed fat in thediet of milking cows.

One of the most difficult aspects of dairy nutrition is estimating the energy density offorages. The new 2001 Dairy NRC (7th Revised Edition) includes methods for estimatingenergy available in forages, that are probably a lot closer to the real values than anytool we have had previously. One important difference is due to the fact that the newsystem includes the impact of intake on digestibility. To put this more simply, as a cowconsumes more feed, the amount of energy available in any given amount of feed,whether it is corn or hay, decreases. This is due to the fact that as intake goes up, rateof passage through the gut increases and the length of time that material is exposed tothe digestive process decreases. The shorter the period of time feed is in the gut, theless of it will be digested. An example of this is seen on most dairies every day. If oneinspects recently expelled fecal material from a high producing cow being fed cornsilage, generally, corn particles can be seen. These particles did not get digestedbecause the silage moved through the intestinal tract so fast that total digestion did notoccur. If this same material were fed to a dry cow, consuming feed at a much lowerintake level, very little if any corn grain would be seen in the manure. The dry cow rateof passage is substantially lower than the cow milking at a high level, because she iseating so much less feed. This allows more complete digestion.

So what does this have to do with feeding fat? Lets start by briefly discussing energy.Getting a good estimate of energy densities in all other portions of the diet leads us todetermination of how much fat to feed. Fat tends to be an expensive source of calories

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and this alone is reason enough not to use it frivolously. Thus the best way to determinehow much fat to feed is to back into the number by figuring out much energy is neededfor the production level you are interested in achieving, then determining whatcontribution is being made by all the other diet components. By difference you knowhow many calories you need to make up from fat. All of this is predicated on the factthat we have a reasonably good estimate of dry matter intake, which is a whole othertopic.

There are rather specific upper limits on the amount of fat that can be added to cowdiets and most nutritionists agree that 6% of the diet dry matter is the upper limit. Whenfat is fed above this level to milking cows, the rate of passage is so high, that the fat fedabove 6% or so of the dry matter will pass through the gut and not be digested. Inaddition to this problem, fat has some properties that are not favorable to the cow,which will be discussed shortly. It should be pointed out that this 6% level includes thenaturally occurring fat in forages and feeds

One of the major drawbacks to feeding high fat levels to cows is the fact that fat cannegatively effect fiber digestion in the rumen. The exact mechanism of this effect doesnot seem be extremely clear at this point. Research done at Ohio State has shown thatunsaturated fats can be quite toxic to some important fiber-digesting bacteria. Otherworkers have thought that high levels of fat may actually coat fibrous material in therumen, thus preventing rumen microorganisms from attaching and breaking down theforage fiber. If ruminal fiber digestion is depressed by excessive fat feeding, the totalamount of energy available to the cow can decrease which can result in productiondecreases or excessive mobilization of body reserves. Some researchers havesuggested that the reason fat feeding may depress dry matter intake is due to the factthat fat depresses fiber breakdown, causing forage material to stay in the rumen longer,thereby reducing intake.

In addition to its potential influence on fiber digestion, high levels of fat may depress drymatter intake. It has long been know that fat has a high “satiety” value. That is, fatconsumption followed by digestion leads to some hormonal changes in the brain thatdramatically slow down or shut off feed intake. It is possible to feed enough fat such thatthe total caloric intake may actually be less than if fat was not fed, since lower fat dietsdo not have as high a satiety value. For these reasons and perhaps some others, fatfeeding must be undertaking with some caution.

There are several major fat sources that are generally used in our part of the country.The first one that comes to mind is whole cottonseed. Thousands of tons of wholeseeds are fed in dairies throughout the U.S. This product has achieved almost mysticalproperties in the minds of many dairymen. No doubt they are a wonderful ingredient,containing protein, fat as well as fiber, but they are not an end all. There have beenseveral years here in the southeast when cottonseed was priced such that it did notmake economic sense to use them. Even in those years, many of my producers insistedon continuing to feed whole cottonseed. They do a good job of supplying energy in theform of fat as well as protein. The fact that they also have high levels of fiber makes

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them quite attractive since they will cover up a lot of “sins”. That is the physical makeupof a whole seed contributes to the “effective fiber” intake of a cow, while being part ofthe grain intake. My experience has shown that 4 to 6 pounds per day of wholecottonseed is about right. Higher amounts than this make it difficult to achieve the non-structural carbohydrate levels that I want to reach. Whole cottonseeds probably averagearound 15 to 17% fat on an as fed basis but it is worthwhile to have seed checked fromtime to time for fat and protein level since there can be a bit of variation.

Probably the next most important type of fat fed to dairy cows is that fat used by feedmanufacturers. For the most part the feed industry uses either tallow oranimal/vegetable blend, called A/V blend in the industry. A lot of people think that tallowimplies that the fat comes strictly for beef rendering operations, but this is not the case.Tallow is fat that meets certain industry specifications mostly for hardness. Withoutgetting too technical lets us just say that tallow tends to be one of the harder fats usedin the feed industry, and like most other fats as well, must be held in a heated tank tokeep it liquid so that it can be pumped. In general hardness is a function of fatty acidchain length as well as degree of unsaturation, or the number of double bonds in thefatty acid chains. A/V blend, which is probably the most widely used fat, as you mightexpect, is a blend of animal and vegetable fats. The vegetable portion is generally usedfryer fat picked up from restaurants, although it should be noted that many fryer oilsused in human food cooking also contain animal fats. A/V blend tends to be a bit softerthan tallow, but also must be held in a heated tank to keep it in liquid form so that it canbe pumped. In my career and even today, I use both tallow and A/V blend and havenever been able to see any performance differences on the farm. My feeling, which isgained mostly by experience as well as careful perusal of research data shows that wecan use up to about one pound of added fat per cow per day. If we go higher than thiswe may see reduced fiber digestion, which is most easily observed as depressedbutterfat. If you are feeding higher levels of fat and are having trouble maintaining anacceptable butterfat, it may be that fat intake is excessive. Reducing fat intake mayallow the rumen organisms to more effectively breakdown fiber, thus increasingproduction of acetic acid the precursor to butterfat.

The final major fat source used would encompass the by-pass fats. These range fromprilled dry fats to calcium salts of fatty acids as well as several other lesser-usedproducts. These are the fats of last resort as it were. They are fats that are inert in therumen, that is when these products are fed, the rumen bugs do not even know they arethere. Inert fats have little or no effect on the rumen microflora, thus they do not tend todepress butterfat. A significant drawback with calcium salts is that they appear todepress dry matter intake. Recently Mike Allen from Michigan State, summarized 24published studies in which calcium salts of fatty acids were fed (J.Dairy Sci. 83:1598). In22 of the 24 trials, dry matter intake was numerically less when calcium salts were fed.Of these 22 trials, 11 were statistically significant. Other sources of added fats did notappear to have a consistent dry matter intake depressing effect. My experience wouldtend to support this report. I have used calcium salts but have tried to keep them thelowest levels possible to minimize their effects on dry matter intake. Prilled fats do notseem to depress intake in my experience. The rations that I prepare tend to use little if

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any inert fat of any source however. Most of these products tend to cost about 40 centsper pound or there about. In many cases manufacturers of these products like torecommend around a pound per cow per day, so you can quickly see that the cost percow is right at 40 cents. Most farmers tend to choke a bit when they are told their feedcost is going to go up say $30 dollars a ton if we add a pound per cow of a 40 centproduct to a grain mix that is fed at about 25 pounds per cow. This is not to say theseproducts do not have value in the right place however. There have been times when Ihave felt strongly that a by-pass fat would be appropriate to use and have beendisappointed to have my producer veto the idea simply over cost. There are also caseswhere these products are being fed and they are not justified. It is a matter of doingsome careful cost benefit calculations and trying to determine if the added cost willresult in a return. I have used these products in herds that have been poorly fed forsome period of time resulting in extremely thin cows that will not breed. I do not expecta milk production response in most cases though. I use by-pass fats as tools to keepvery high producing cows from losing excessive amounts of weight. One must be verycareful though, not to depress dry matter intake with inert fats when the goal is toincrease total caloric intake. When comparing inert fat sources on a price basis it isimportant to take into account the percent of fat in the product. The amount of fat canrange from around 83% to near 100%. It is interesting to note that over the years theseproducts have tended to be priced very close to each other on a per calorie basis. Thecost per pound will vary, but the cost per calorie will usually be very close.

At this point it is worth mentioning some recent work by Charlie Staples and co-workersat the University of Florida. This group has reported several times in the last few yearsthat certain fatty acids may have a profound influence on reproductive efficiency in dairycows. In a 1998 publication (J.Dairy Sci. 81:556) they suggest that linoleic acid, one ofthe fatty acids long known to be essential, supplementation may result in enhancedembryo survival. As recently as January of this year, they reported that cows fed aproduct high in linoleic acid, resulted in a significant (P<.05) shortening of the periodfrom calving to first ovulation, 26.8 days vs. 42.4 days for unsupplemented cows. Whiletheir numbers were low, it appears to me that these efforts bear close attention.

In conclusion, fat can be a useful addition to the ration of high producing cows. It can beused to help increase energy density in the ration so that fewer pounds of grain may befed in an effort to keep forage fiber intake up. It can result in milk fat depression if overused. When used properly it can help high producing cows not lose excessive weight.Added fat can be a useful tool in an effort to regain body condition on a whole herdbasis in herds that have lost excessive body condition for one reason or another. Inmost years, whole cottonseed will provide an inexpensive source of fat. Fat added bythe feed manufacturer to a grain mix can be very economical as well. Currently (January02) AV/Blend is about $200 per ton. So a cow can be fed a pound of fat for about 10cents. Handling fat on most farms is not a reasonable thing for a farmer to consider,due to the cost of the inventory as well as the equipment it takes to handle the material.It should be left to manufacturers who use fat rapidly enough that it is fresh and notrancid as it goes into a grain mix. Cattle do not consume rancid fat well at all. Evenstabilized fat will become unpalatable to cattle in a fairly short time. Calcium salts seem

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to have important depressing effects on dry matter intake and should be used withcaution. By-pass or inert fats can play an important role, but they should be used as alast resort, due to cost. They are like any tool used on a dairy farm, there is a place forthem but it is not everywhere.

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Dairy Feed Additives

R. Randy Lyle, Ph.D.Purina Mills, Dairy Business Manager, Statesville, NC

I. Introduction:• Why use feed additives in dairy rations? The main reason should be to obtain

an improvement in performance and/or health of dairy cattle (calves, heifers,dry cows, milk cows). Logically, increased profitability should occur, as well.

• What is a “feed additive”? A feed additive is an ingredient that is supposedto have a positive impact on an animal, but is usually not considered anutrient (i.e., there is not a scientifically recognized nutrient requirement forthe ingredient/additive). This delineation is clear for most additives, but thereare some additives that do not clearly fall into the above definition (e.g., thereis a requirement for zinc in dairy rations, and there is zinc in zinc methionine,so is zinc methionine an additive or a nutrient?). “One person’s feed additivecould be another persons essential nutrient” - anonymous quote

• Like anything else, feed additives do not have 100% probability of showing apositive, measurable response. Establishing a tangible, positive benefit fromuse of a feed additive is the responsibility of the user. Controlled research isessential to establish efficacy before market release. Very few dairy farmscan conduct controlled research, so dairy producers must, therefore, rely onpublished research (not necessarily testimonials) to demonstrate likelybenefits from use of feed additives.

II. Industry Adoption - Use of Dairy Feed Additives Feed additives are widely used by dairy producers. Most rations contain atleast one, and perhaps several, feed additives. Results of two dairy producersurveys are provided:• Jordan and Fourdraine, Texas A&M University, 1993, sent surveys to 128

top producing dairy herds in the U.S. (identified by nine DHI processcenters). Sixty-one surveys were returned.

• Hoard’s Dairyman Research Department, 2000, tabulated survey resultsfrom 508 dairy respondents

Table 1. Survey results from Texas A&M and Hoard’s Dairyman studies. Percent ofproducers using feed additives. Additive Texas A&M Study Hoard’s Dairyman Study Bicarb/buffers 75 47 Bypass protein 69 38 Yeast/yeast culture 51 32 Zinc methionine 48 27 Niacin 38 12

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Probiotics - 8 Anion salts - 8 Mycotoxin binder - 8 Amino acids/methionine - 11 Use no additives - 11 (additives with no number in the Texas A&M study were not evaluated)

Only 11% of respondents in the Hoard’s survey used no feed additives. Bufferswere the most widely used additives in both surveys. Results of these two studiesshow that use of feed additives is high, but variable.

III. Conditions desired before using a feed additive Additives cannot overcome the effects of mismanagement or unbalanced rations.When considering use of an additive, dairy producers can go through the followingchecklist:

• The ration first should be balanced for all major nutrients• Water should be clean and available• There should be good herd health, and animals should be comfortable• Cost of the additive must be reasonable• Is there a real need? Will there be a measurable response?• Are there well documented, controlled research studies?

IV. Categories of feed additives:• Trace minerals (chelates, proteinates)• Mycotoxin binders (mineral, organic adsorbants)• Water-soluble, B-vitamins (niacin, choline, biotin)• Growth promotants for heifers and steers (lasalocid, monensin,

bambermycins)• Buffers (sodium bicarbonate, sodium sesquicarbonate)• Fats• Sugars (mono- and di-saccharides)• Protein or amino acids {aa} (bypass proteins, encapsulated aa’s, aa

analogues, crystalline aa’s)• Probiotics (live bacteria)• Yeast/Fungi (live or cultures)• Anion salts or chloride products (for pre-fresh dry cows)• Mold inhibitors (propionic acid, other organic acids)• Flavors• Antibiotics (none allowed in milk cow; calf and heifer use only)

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V. Evaluation

It is not the intent of this report to evaluate efficacy of dairy feed additives.Rather, this report describes a process by which the producer, or those to whomhe looks for advice, can better evaluate whether a feed additive provides abenefit to the animal and its owner.

Many producers rely on advisors to help make nutritional and managementdecisions. Also, producers read popular dairy publications, dairy extensionreports, or company promotional literature, and then try to draw conclusions onwhether a feed additive would provide a benefit on their farm. But many times, itis not possible to collect enough published information to allow a producer tofirmly conclude whether a feed additive will benefit his dairy herd. This leads to“trial” tests on farms, under uncontrolled conditions, and the outcomes of suchtrial tests are often difficult to evaluate. So evaluation of feed additives oftenbecomes a subjective (produced by state of mind or feelings), rather than anobjective (independent of the mind, real) exercise.

Here is a list of questions that might help you evaluate whether a feed additive is worthyof use:

1. What is the mode of action by which a feed additive exerts a positive effect onperformance or health of the animal? Any reputable ingredient supplier shouldbe able to explain how a feed additive works. This often requires knowledge ofbasic animal physiology and metabolism, and may even require deepunderstanding of biochemistry, before a mode of action can be explained. But amode of action certainly needs to be established, before there is any reasonablechance of expecting a tangible benefit. Most producers rely on their technicaladvisors to sort through scientific information. This is another good reason tohave technical advisors to help make decisions.

2. How widespread is the use of an additive? If an additive is advertised and usedin only one small geographic area, and has not been adopted across a widearea, its benefit should be questioned.

3. How many years has the additive been marketed? Additives tried by earlyadopters might be beneficial, but most producers do not want to use their herdsas “test herds”. So if an additive is new to the market, you should be morecautious, compared with using an additive that has been marketed for manyyears. The “marketplace” has an unparalleled ability to eventually eliminateproducts that bring no real value to the consumer. But this elimination processsometimes requires several years to come about. So new products should besuspect, simply because they have not gone through sufficient marketplacescrutiny, whereas mature products (marketed for several years) have gonethrough marketplace scrutiny (i.e., mature products are survivors of marketplacecost-value assessments).

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4. Am I likely to realize an economic benefit if I use a feed additive? Let’s use milkproduction as an example. Suppose the recommended amount of a feedadditive costs $.15/cow/day to use. Many producers require an economic returnof 2:1 before they will even consider use of a feed additive. Given this 2:1relationship, a feed additive that costs $.15/cow/day needs to provide anincrease in milk production worth at least $.30/cow/day (about 2 lb milk).Compare this example with another feed additive that costs only $.05/cow/day.In the latter case, an additional milk yield worth $.10/cow/day would provide thedesired 2:1 economic return. So one big factor is cost /cow/day of the feedadditive, compared with the milk increase needed to see a 2:1 economic benefit.This judgment criterion is not easy to use with feed additives that impact animalhealth, reproduction, or hoof health, because these variables are much moredifficult to measure, compared with milk production.

5. Are advertised testimonials, such as those in popular dairy magazines, backedup by good research? Ask your advisors for their opinions. Ask to see theresearch.

6. Have your dairy farm neighbors had experience with the additive? See if you cantalk with another dairy producer who has tried the additive. What were theresults?

If a feed additive can meet most, or all, of these considerations (known mode ofaction, widespread use, history of market acceptance, likely economic return,research, and local references) then a dairy producer should consider its use.

A partial listing of commonly used dairy feed additives, their normalrecommended amounts, and approximate cost per head per day, is in Table 2.

Table 2. Examples of commonly used feed additives, recommended amounts, andapproximate cost per head per day.

Recommended ApproximateAdditive amount/head/day cost/head/day, $Sodium bicarbonate .3 to .6lb .03-.06Yeast (Diamond V XP®) 2 ounces .05Zinpro 100® 3.6 gm .02Niacin 6 gm .03Clay binder .25 -.5 lb .025-.05MTB100 ® 10-20 gm .04-.08Encapsulated methionine 15 gm .22Biotin 20 mg .074-Plex ® 14 gm .04anion salts .5 lb .20Rumensin® 60-200 mg .005-.017Probios® 5 gm .04

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VI. Basic rationale for use of select classes of feed additives:

• Trace minerals – 7 trace minerals (Se, Mn, Zn, Fe, I, Co, Cu) are routinelyadded to dairy rations. Conventional forms of trace minerals are broadlyclassified as “inorganic salts”. Examples would be iron sulfate, cobaltcarbonate, and copper sulfate. Inorganic forms of trace minerals are notattached to a carrier molecule. Trace mineral feed additives, such as Zinpro®,4-Plex®, ZnMet®, AvailaMins®, and Optimin® are trace minerals that havebeen chemically attached to a relatively large, organic molecule, such asmethionine (metal–amino acid complex), or protein peptides (proteinate), inan attempt to increase efficiency of absorption (bioavailability) of the tracemineral across the cells of the intestine. It should be noted that organic formsof trace minerals are more expensive than inorganic forms.

• Mycotoxin binders – mycotoxins are biological compounds produced by

molds. But presence of molds does not necessarily confirm the presence ofmycotoxins. Mycotoxins can have effects in animals ranging from relativelyinnocuous, to very toxic. Compared with simple stomach animals, ruminants(cattle) are more resistant to mycotoxins, but at high levels, some mycotoxinscan be toxic to cattle, or can be excreted in milk. Mycotoxins in feedstuffs arevery difficult to remove or degrade. Moldy feedstuffs must often be feed tocattle, even if mold and mycotoxins are known to be present. In an attempt toreduce the chance of negative effects of mycotoxins on cattle, mycotoxin“binders” are often fed, in an attempt to prevent absorption of mycotoxinsacross the gut wall. Examples of binders are activated charcoal, mineral/claybinders (sodium bentonite, hydrated sodium calcium aluminosilicate) ormicrobial cell material (mannan oligosaccharides, MTB100®). These productsare fed with the purpose of physically binding (adsorbing) mycotoxins, therebypreventing absorption from the gut, with subsequent excretion in feces. Itshould be noted that the author is not aware that any of these compoundshas received FDA approval for control of mycotoxicosis in cattle.

• B-vitamins – most water-soluble vitamins (choline is an exception) are

normally synthesized by rumen microorganisms and ruminant tissues insufficient quantities to meet animal requirements. B-vitamins are not stored inbody tissues, so ongoing synthesis is required to meet requirements. Non-ruminating calves require supplemental B-vitamins. Research indicates,however, that even mature, lactating, dairy cows, might require dietarysupplementation with B-vitamins, if milk production is very high, or if rationscontain high levels of grain. Normal ruminal synthesis of B-vitamins might notoccur with high grain rations, because of pH-induced shifts in microbialpopulations. Addition of B-vitamins to dairy rations has been to control andprevent ketosis (niacin), improve hoof health and increase milk production(biotin), and improve fat metabolism and reduce fatty liver (choline).

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• Growth promotants – growth promotants have been used in heifer rations toincrease rate of growth. These products alter rumen fermentation andincrease efficiency of energy and protein utilization. Examples of theseproducts are the ionophore antibiotics Rumensin® (monensin), and Bovatec®(lasalocid), and the murein-inhibiting antibiotic Gainpro® (bambermycins).These products alter the population of rumen microorganisms andsubsequently shift the amount and ratios of the main volatile fatty acids (loweracetic and butyric acids, and higher propionic acid) produced in the rumen.Increased rates of weight gain have been reported in dairy heifers fed theseproducts. Their use is also widespread in the cattle feedlot industry. They arenot approved for use in lactating or dry dairy cows.

• Buffers – sodium bicarbonate, sodium sesquicarbonate, and sodium

carbonate, have multiple effects on metabolism, but the main positive effect ofthese products is thought to be on rumen pH, rumen metabolism, and rumendilution rate (osmotic effect). Rumen microorganisms degrade mostfeedstuffs to organic acids. High levels of organic acids, particularly lacticacid, can cause large reductions in pH of rumen contents. Low rumen pH(high acidity) has been shown to de deleterious to dairy cattle, and can alsocontribute to low milk fat content. Addition of buffers to rations helps toprevent severe,prolonged decreases in pH of rumen fluid. Rumen function(fiber digestion, rumen motility) is optimized when pH is between 6.5 to 6.8.Note that ruminant saliva contains bicarbonate and phosphate buffers, and issecreted in very large amounts when rumination and chewing activity arehigh. But dietary addition of buffer is often beneficial to dairy cows.

• Fats – supplemental fats are discussed in another section of the proceedings. • Sugars – Carbohydrates are the main source of energy in dairy rations.

Examples of carbohydrates are starches, cellulose, hemicellulose, pectin, andsugars. Addition of sugars to dairy rations has been done in an attempt toprovide a rapidly available source of energy to rumen microorganisms. Someresearch indicated that a species of rumen bacteria might show stimulatoryeffects from specific monosaccharides (malate and fumarate). Sources ofsupplemental sugars have varied, ranging from commercial products (RuMin8®) to molasses blends. Results have been variable.

• Bypass proteins and amino acids – Bypass proteins are proteins that are notreadily degraded in the rumen. Proteins are composed of many amino acids,linked together. It is known that high levels of milk production require a highflow of proteins, peptides, and amino acids into the intestines, to meet animalrequirements for maintenance and milk production. The most importantsource of protein and amino acids, at intestinal absorption sites, is microbialprotein. Microbial protein is the protein found in the cell wall of rumenbacteria and protozoa. Even with conventional sources of protein (e.g.,soybean meal), only a portion of the protein is degraded in the rumen, with

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some protein “bypassing” into the intestine, for subsequent digestion andabsorption. So under most all conditions, there is a large flow of microbialprotein, and undigested feed protein into the intestine. With high levels ofmilk production, this normal flow of microbial and undigested plant proteinmight need to be “augmented” with a special type of dietary protein (by-pass,UIP, undegraded) that is more resistant to ruminal degradation. Examples ofthese types of “special” proteins are extruded/expeller soy, animal proteins(fish, blood meal), corn distiller’s grains, and roasted soybeans. Withinrecent years, specific amino acids (lysine and methionine) have beenprotected from ruminal degradation by “encapsulation”, a process thatphysically prevents ruminal bacteria from destroying (digesting) these aminoacids. Results have been variable. Improvements in modeling of mammaryrequirements for maximum milk production will eventually lead to refinement in our understanding of the needs for specific amino acids in the highproducing dairy cow.

• Probiotics/Yeast/Fungi – there are many products that fall into this category.Nomenclature is variable, but the term “direct-fed microbial” has beenaccepted to describe the different classes of products. Categories of direct-fed microbial products are: 1) bacterial products, such as lactobacillusacidophilus and streptococcus species; 2) live yeast products, typically fromvarious strains of Saccharomyces cerevisiae; 3) yeast culture, which is theresidue (by-product) from active yeast cultures; 4) enzymes, which areproteins of microbial origin that degrade dietary protein and carbohydrate; and5) fungal-based products, typically derived from yeast or from fungalpreparations. These products are reported to stimulate microbial activity inthe rumen and to sometimes modulate functions of the intestinal tract (post-ruminal effect), leading to improved digestibility of feeds. In the non-ruminating animal (calves), lactobacillus species reportedly improve intestinalfunction, by suppressing growth of undesirable gut microbes. Responses tothese products have been variable.

• Anion salts and chloride products – these products are intended only for

feeding to pre-fresh dry cows, for 14 to 21 days before calving, when rationshave a high level of “cations”. Cations are minerals that carry a positivecharge. The most significant cation in a dry cow ration is potassium. Anionproducts, therefore, are used when forages fed to pre-fresh dry cows are highin potassium. If the total ration of a pre-fresh dry cow is at or above 1.5 to2.0% potassium, the anion:cation ratio (DCAB) is likely high, which can leadto problems with calcium homeostasis, at or shortly after calving. Whendietary potassium cannot be reduced (usually when high potassium foragesmust be fed) in rations of pre-fresh dry cows, anions (negatively chargedminerals) can be fed, in order to reduce the anion:cation ratio. Mostfrequently used are ingredients that are high in chloride and sulfur (anions).Examples are ammonium chloride, magnesium sulfate, calcium sulfate,fermentation by-products high in chloride (BioChlor®), and soy products that

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contain chloride from hydrochloric acid (SoyChlor®). These products cause aslight decrease in pH of blood, which has a stimulatory effect on calciummobilization at calving. High levels of anion products, or feeding anionproducts when not needed, can create metabolic problems in cows. Usecautiously.

• Mold inhibitors – these products can be applied to forage, before ensiling.But this paper deals with mold inhibitors that are used as feed additives (e.g.,incorporated into total mixed rations {TMRs} or added to grains). Moldinhibitors contain organic acids, such as propionic, sorbic, acetic, andbenzoic. Ammonium propionate is the most widely used acid product. Theseorganic acids (or salts of acids) act as preservatives, by lowering the pH offeeds. Feeds at near-neutral pH exposed to oxygen can support growth ofyeasts, molds and fungi. These organisms oxidize nutrients in feeds, withsubsequent reduction of nutrient content, and production of heat (aerobicspoilage). Reduction of pH, by application of mold inhibitor products, cansometimes extend bunk life, reduce heating of wet feeds, and extend thestorage life of dry grains. Typical inclusion rates have been 1-3 lb per ton ofTMR (wet basis). Research has shown that mold inhibitors added to TMRscan reduce heating (extend bunk life), but effects on milk yield and dry matterintake have been highly variable.

• Feed flavors – feed flavors have been added to grain products for dairy cattle,with the intention of increasing grain intake and performance. Responsesfrom addition of flavors to grains have been more predictable, and positive, inbaby calves, than with mature cattle. Feed flavors, added to grains fed inparlors or computer feeders to mature milk cows, have shown highly variableeffects on rates of intake. Addition of flavors to total mixed rations has shownno benefit. It should be noted that, compared with cattle, humans areprobably more positively affected by feed flavors, because of the pleasantaroma of these products.

• Antibiotics – these additives have long been used in the livestock industry, at

subtherapeutic levels, to promote performance. Use of antibiotics in dairycalves and non-lactating heifers still occurs. In baby calves, antibiotics (oxy-neo, decoquinate) are used to improve performance and health. In dairyheifers, antibiotics (ionophores) are used to increase rate of weight gain.Antibiotics cannot legally be added to lactating cow rations.

Author’s note – use of a trademark should not be interpreted as anendorsement for that product.

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Silage Management

Dr. Lon WhitlowExtension Dairy Nutrition

North Carolina State University, Raleigh

Corn silage is the primary forage fed to lactating dairy cattle in North Carolina.Sorghum, small grain and alfalfa silages contribute less than 20% of the total silage fed.Small amounts of hay, other roughages and pasture provide the remaining amounts ofroughage fed to lactating cows.

Silage, properly made, is superior to the same crop made as hay and is less dependenton weather conditions. Corn is recognized as a silage superior to sorghum and smallgrain crops and is replacing alfalfa silage in some areas of the country. Being moredrought tolerant, sorghum is preferred for silage in areas of the country where rainfallhas proven to be unreliable for a good corn crop. Small grains produce excellent silagethat can contribute to the roughage value of the ration. Small grains can replace hay inthose rations where additional roughage value is desirable.

Silage Types:

Corn SilageMaking a high quality silage is important, but along with quality, the silage we producemust be compatible with the needs and constraints set forth by the overall farmoperation. For example, it may be advantageous for some dairymen to produce a higherfiber "forage-type" corn silage and get a greater tonnage yield while other dairymen maywant to produce a lower fiber silage that is higher in energy content. Therefore choosingthe appropriate variety may be the first management step in production of silage.

High Grain or High-Forage VarietiesThe choice of a high grain vs. a high forage variety should be based on the need forproducing adequate forage on the available land base and secondly on the cost ofpurchased corn versus the cost of producing that corn as a part of the silage. Availabilityof sufficient high-quality fiber for dairy cattle production is a limiting factor on manyNorth Carolina dairy farms. If corn land is limited, then the type of silage that is mostappropriate may be a high-fiber, forage type silage. On the other hand, if land isunlimited then silage with a higher grain content may be more desirable. Normally it ischeaper to produce the corn grain as a part of the silage, but if forage is limited, it canalso be costly to purchase a quality forage. There will be regional differences about thisdecision based on the cost of grain and forage and the availability of other forages. InNorth Carolina corn silage is often fed as the only forage, and must therefore haveadequate effective fiber.

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High Fiber DigestibilityDigestible fiber is a key for high producing dairy cattle. Silage as the primary fibercomponent of the ration must also have digestible fiber. There is a limit on the amountof grain that can be added to a ration to increase ration energy. The upper limit of grainis limited by dilution of fiber to low levels that can result in poor rumen function. Highlydigestible - high quality fiber provides energy without the addition of high levels of grain.This is because the fiber itself is digestible and yet provides the roughage value neededby the cow. Silage fits the same example. We can choose high grain varieties thatproduce a high energy silage, but this energy comes from grain and not digestible fiber.While the digestibility of grain is not very different among corn varieties, there aredifferences in fiber digestibility. Selection of these varieties can result in a high qualitysilage that still has good levels of fiber and therefore provides good roughage value.

Some corn varieties have higher fiber digestibility primarily because they contain lowerlevels of lignin. A low lignin content not only increases digestibility but decreasesstandibility. Low lignin content can increase lodging and thus reduce tonnage yield.Currently silages with high digestibility due to low lignin content yield less tonnage thanother varieties.

Other FactorsSome of the genetic factors in corn that may be of interest and value are: "Waxy Corn","High-Fat Corn", "Leafy Corn", "Brown Midrib Corn" and "Bt Corn".

Maturity Affects Quality:

Small Grains and "Hay Crop" SilagesIt is well understood that as these forages mature, dry matter yield increases and fiberdigestibility decreases. Protein content also declines. Harvest decisions must be madebased on the need for quality versus quantity. For rye silage, palatability greatlydecreases as the plant reaches the heading stage and therefore must be harvestedmore immature. Barley, wheat. oats and triticale may be best harvested at the boot toheading stage, but can be harvested later if quantity is most needed.

Corn SilageCorn silage similar to other forages increases in dry matter yield as the plant matures.However, fiber digestibility decreases with increasing maturity and grain digestibilitydecreases as the grain increases in starch and becomes hard. It appears that the idealtime for corn silage harvest to maximize digestibility is when the corn kernel containshalf milk and half starch. The whole plant moisture content will be near 65% when thekernel is 1/2 milk.

Sorghum SilageSorghum is somewhere between small grains and corn in its relationship of maturity toquality silage. There is a rapid decline in digestibility associated with grain maturitybecause the formation of a hard seed coat of the mature grain reduces digestibility.There is also an increase in lignin that reduces fiber digestion. Sorghum harvest is

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generally recommended to be at the milk stage and definitely by the soft dough stage.Early harvest prior to heading has been successful if the silage is wilted to reducemoisture content to support a good silage fermentation. When immature, sorghum maycontain more tannins that can reduce intake.

Other Management Factors:

Kernel Processing Improves Corn SilageKernel processing or simply silage processing or rolling can increase the digestibility ofcorn silage. Processing breaks almost all the kernels increasing digestibility of the grainmeasured by increased starch digestibility. Processing also macerates the fibrous partsof the plant, potentially increasing fiber digestibility. Feeding studies have shown thatdairy cattle produce approximately two pounds more milk when fed processed silage,compared with normal silage. Some of this increase in milk production is because ofimproved digestibility but better production is also related to increased feed intake.Processing can improve corn silage at any stage of maturity, but the potential forimprovement is greatest when silage is mature, drier than normal and contains hardmore indigestible kernels.

Length of Chop for Corn SilageA short length of chop helps silage to pack well, but the chop must be of sufficientlength to provide "roughage value" for the cow. Normally a 3/8 inch theoretical length ofchop (TLC) is recommended, but if silage is processed, the chop length should beincreased to 3/4 to 1 inch.

Moisture ContentProper moisture content of silage is critical for good silage fermentation and keepingqualities. Air is the enemy on silage. Proper moisture content limits air in the silage toensure a proper aerobic environment. A dry silage allows air to infiltrate the silagemass, resulting in growth of aerobic spoilage bacteria, molds and yeast. A wet silageencourages the growth of clostridium bacteria which can produce putrid smelling fattyacids such as butyric acid, odiferous amines from the destruction of protein and toxins.

For most silages is the optimal moisture content is 60 to 70 percent. Silage put intoupright silos may need to be somewhat dryer than put into horizontal silos.

Managing the SiloSilo management is critical in producing a high quality silage. The silo must be in goodworking order and its size should match the size of the herd. The critical managementfactors are fast filling, good packing, use of an effective additive, proper sealing, andgood feeding face management.

Silage AdditivesThere is a good probability that additives can improve the value of silage by reducingspoilage. For best results additives should be applied as a liquid during harvest.

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Selection of the appropriate additive should be based on reliable research and otherproduct information.

Filling, Packing and CoveringThe silo should be filled rapidly but with enough time between loads to allow foradequate packing. Packing compresses the silage and excludes air to ensure a goodfermentation and keeping qualities. The easiest way to accomplish a good pack is tospread the silage into a thin layer and fill the silo layer my layer.

Once filled, the silo should be sealed with plastic and covered with tires touching eachother.

Managing the Silo Feeding Face and Feed BunkThe silo should be sized so that six inches of silage can be removed from the entirefeeding face on a daily basis. Therefore, the size of the silo is dependent on the numberof cows in the herd and the amount of silage fed per cow daily. Silage should beremoved immediately prior to feeding. The silage feeding face should maintain itsintegrity. No piles of silage should remain on the silo floor. Any spoiled silage should bediscarded. If spoilage or secondary fermentation of silage is a problem, the feeding facecan be treated daily with a spray of propionic acid or other effective preservative. Thepreservative may also be added to the TMR blend.

Silage should be fed so that cows refuse approximately 10 percent of that fed. Silagebunks should be cleaned routinely. In some herds, silage bunks must be cleaned daily,while in others weekly cleaning appears to be adequate. More frequent cleaning isusually required during the summer. Flat feeding floors and a slick surface makecleaning easier.

Problem Silages:

A number of problems can occur with a corn silage based feeding program. Some ofthese include, lack of effective fiber (roughage value) because there is too much grainor because it is too finely chopped, dry silages that can mold and deteriorate, drysilages that can heat and destroy the protein content, wet silages that produce putridunpalatable feed, wet silages that loose their protein through seepage and bacterialbreakdown, silages that produce too much acid and become unpalatable, silages thatare unstable on feed out and heat in the feed bunk, weather damaged silage andinsufficient quantities of silage.

Summary:

Silage, and most importantly corn silage, provides the most suitable forage base fordairy production in North Carolina. Proper management can help insure a high qualityforage that supports excellent milk production with a minimum of problems.

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Utilizing Selected By-Product Feeds for Dairy Cattle

Dr. Brinton A. Hopkins and Dr. Lon W. Whitlow Dairy Nutrition Extension Specialists

Department of Animal ScienceNC State University

IntroductionBy-product feeds can be defined as commodity feedstuffs obtained from plant andanimal processing or from the food processing industry. Each of the commodity or by-product feeds have a unique nutrient composition and may be used to cut feed costs. Inaddition, some of these feeds can be used to increase the nutrient density of the dietand also provide a source of rumen undegradable protein (RUP) and the amino acidsmethionine and lysine. Some may serve as a substitute for roughage, and increase thefiber level in the diet. Because of their unique nutrient composition, by-product feedsmust be used as a component of a nutritionally balanced ration.

Using By-Product Feeds to Increase Nutrient DensityWhole cottonseed is an example of a by-product feed that is often fed to increase thenutrient density of the diet. The fat in whole cottonseed increases the energy density ofthe ration while providing a good source of crude protein and acid-detergent fiber. Thisallows the energy level in the diet to be increased without feeding excessive grain andcausing problems with acidosis or low milk fat tests. Feeding fat in the form of wholecottonseed to increase energy density in the diet is also important during hot weatherwhen dry matter intake decreases. The fat from whole cottonseed appears to be utilizedas well as other fats with little affect on rumen fermentation.

Using By-Product Feeds to Increase Rumen Undegradable Protein (RUP)By-product feeds are often included in the ration to increase the level of rumenundegradable protein. Dried brewers grains and distillers grains with solubles are goodsources of RUP. Blood meal is a good source of the amino acid lysine while corn glutenmeal is a good source of the amino acid methionine. Lysine and methionine are oftenlimiting or co-limiting for milk protein synthesis. The ratio of lysine:methionine in the totaldiet should be about 3:1. It is important to take into account amino acid content whenformulating the diet to insure that the by-product feed provides the proper amino acidprofile. Sometimes a combination of protein sources is needed to provide the properprofile of amino acids.

Using By-Product Feeds to Serve as a Substitute for Forage or to Increase theFiber LevelCottonseed hulls are an example of a by-product feed that functions as an excellentforage substitute and increases the fiber level in the diet. Five pounds of cottonseedhulls plus 5 pounds of corn grain will replace about 25 pounds of corn silage in theration. An increase in dry matter intake (associative effect) is another benefit fromfeeding cottonseed hulls. As dry matter intake increases, milk production increases. Theroughage value of cottonseed hulls appears to be nearly as good as that of forages and

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yet diets formulated with cottonseed hulls can contain more fiber without a negativeeffect on feed intake or milk production.

Consider Using Cottonseed Hulls in a Heifer TMRConsider feeding cottonseed hulls as a forage substitute in a heifer TMR. We have hadgreat success feeding a complete TMR that uses cottonseed hulls to our 2 to 6 monthold heifers at the Piedmont Research Station (see table below). This TMR is fed free-choice through gravity flow self feeders.

Self-fed TMR for heifers 2 to 6 months of age.Nutrient analysis on a dry matter basis:16% crude protein; 76% TDN; .66% calcium; .42% phosphorous; Ca:P ratio 1.6:1Ingredient Pounds per Ton

Ground corn grain 986

Cottonseed hulls 600

Soybean meal - 48% 369

Calcitic limestone 18

Tricalcium phosphate 10

Plain white salt 10

Bovatec® or Rumensin® Add according to manufacturersdirections

Vitamin- trace mineral premix Add according to manufacturersdirections

How to Determine the Nutritional Value of a By-Product Feed In Your RationThere are tables of factors available that allow you to compare the protein and energyvalue of a by-product feed with corn grain and soybean meal. However, these factors donot take into account fiber value or any associative effects from feeding the by-productfeed.

The best way to determine the value of a by-product feed and whether it will fit in theration is to include it as a possible feed source, using its farm delivered price, along withall of the other feed sources available to your herd when doing a computer rationformulation. For example, the DART ration program will formulate the best ration,considering all available feed sources and use the by-product feed if it fits in the ration,or list the calculated nutritional value for the by-product feed if it is not used in the ration.

Feeding Management Decisions to Make When Considering By-Product FeedPurchases• What nutrients or dietary components may be limiting in the current ration?• Will the nutrients in the by-product feed complement the other ration ingredients?• Is there a limit on the use of certain feeds (because of fat or gossypol content)?

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• Is the by-product feed palatable?• What is the availability of the by-product feed?• Is there a consistent supply at an attractive price?• What is the market price for the by-product feed? Is this price below the nutrient

value?• What could be the effects of using the by-product feeds on cow health, milk

production, milk fat test, or milk protein content?• Are there any beneficial associative effects from using the by-product feed (such as

when feeding cottonseed hulls increases dry matter intake)?• What are the procurement and transportation costs?• Is there good quality control from your feed supplier?• What is the consistency of the by-product? Is the product the same from lot to lot? Is

the nutrient content consistent?• Do you have enough storage capacity for the by-product feed?• How much feed shrinkage can you expect in your storage facilities?• Can you handle the by-product without excessive additional expenses?• Will you have to do additional feed processing or purchase additional equipment to

feed the by-product feed?• Can you take advantage of seasonal availability and price fluctuations?• Taking all of the above into consideration, will it be profitable for you to use the by-

product feed in your feeding program?

Characteristics of Selected By-Product Feeds for Dairy Cattle(2001 NRC feed composition values on a dry basis are shown in parentheses.CP=crude protein; TDN=total digestible nutrients, a measure of energy; andADF=acid-detergent fiber).

NOTE: The feeding recommendations shown for each by-product feed in thispaper are general and may vary by diet or herd. They are subject to changedepending on the number of other by-products used and the nutrient levels in thediet.

Whole cottonseed (23.5% CP, 77.2% TDN, 40.1% ADF) contains moderate levels ofcrude protein, but is high in energy and fiber. Upper limits on feeding are dictated bytotal fat in the diet and total gossypol from cottonseed and other cotton products.Because of gossypol content, the amount of whole cottonseed fed to calves and bullsshould limited. In herds where a bull runs with the herd for breeding, the bull should notbe fed the regular herd ration if it contains whole cottonseed because gossypol canimpair fertility in the bull. Feeding recommendation: 5 to 10 pounds per cow perday.Cottonseed hulls (6.2% CP, 34.3% TDN, 64.9% ADF) are an excellent source of fiberand have the associative effect of increasing dry matter intake. They can be used as themain fiber component in a total mixed ration or to replace part of the forage. Feedingrecommendation: No limit but often included at 3 to 6 pounds per cow daily.

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Corn gluten feed (23.8% CP, 74.1% TDN, 12.1% ADF) can be used to provide bothcrude protein and energy in a ration. However, the protein found in corn gluten feed isvery degradable in the rumen, so a source of rumen undegradable protein may need tobe fed. In addition, the calcium level (0.07%) in corn gluten feed is low while thephosphorous level (1.0%) is high. Therefore, be sure to include limestone or calciumcarbonate in the diet when feeding corn gluten feed and balance the ration to maintainthe calcium:phosphorous ratio above 1.5:1. Palatability can be a problem, so include itgradually in the ration. The highly degradable protein content in corn gluten feed willlimit its use for high producing cows unless RUP is supplied from other feed sources.Feeding recommendation: 5 to 10 pounds per cow per day.

Corn gluten meal (65.0% CP, 84.4% TDN, 8.2% ADF) is an excellent source of bypassmethionine, an amino acid that is often limiting for milk protein synthesis. Feedingrecommendation: Include in the ration as a source of rumen undegradablemethionine to provide a ratio of about 3:1 lysine:methionine in the total diet.

Blood meal (batch dried) (95.5% CP, 65.9% TDN) is an excellent source of bypasslysine, an amino acid that is often limiting for milk protein synthesis. Palatability can be aproblem. Feeding recommendation: Include in the ration as a source of rumenundegradable lysine to provide a ratio of about 3:1 lysine:methionine in the totaldiet. Generally limit fed at 1 to 1.25 pounds per cow per day.

Hominy feed (11.9% CP, 83.1% TDN, 6.2% ADF) can be fed to replace the corn grainin the ration. Hominy is a nondescript feed ingredient and can be inconsistent inappearance and nutrient content. Hominy feed can vary in fat content. Price and use willdepend on the fat level. Check the fat level in the hominy feed since high fat hominyfeed can turn rancid in storage during hot weather. Feeding recommendation: Nolimit when fed as part of a balanced ration.

Soybean hulls (13.9% CP, 67.3% TDN, 44.6% ADF*) can be fed as a source of energyand protein in the diet. * However, when formulating rations using soybean hulls,discount the ADF value to 10% or lower because the fiber is not effective fiber and willnot help maintain proper rumen function or milk fat tests. Feeding recommendation: 6to 8 pounds per cow per day.

Cottonseed meal (solvent, 41% CP) (44.9% CP, 66.4% TDN, 19.9% ADF) can be fedas a source of crude protein in the diet. The protein in cottonseed meal is also lessdegradable in the rumen than the protein in soybean meal. Research has shown thatcottonseed meal can be fed in limited amounts along with whole cottonseed withoutproblems from gossypol toxicity. Total gossypol in the diet must be limited. Feedingrecommendation: Use to replace soybean meal as a source of protein in theration as economics dictate.

Dried brewers grains (29.2% CP, 71.3% TDN, 22.2% ADF) can be fed as a source ofprotein and energy. Dried brewers grains are also a good source of rumen

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undegradable protein but energy value is somewhat low. Feeding recommendation: 8to 10 pounds per cow per day.

Wet brewers grains (28.4% CP, 71.6% TDN, 23.1% ADF) can be fed as a source ofprotein and energy. Watch ration moisture level since wet brewers grains are only about21.8 % dry matter. Some brewers grains are pressed to remove water and those have ahigher dry matter content. Feeding recommendation: Up to 30 pounds per cow perday.

Distillers dried grains with solubles (29.7% CP, 79.5% TDN, 19.7% ADF) can be fedas a source of protein and energy in the diet. They are also a good source of rumenundegradable protein. Palatability can be a problem. Because of the high level of fat,be sure that dietary fat limits are not exceeded. Feeding recommendation: 12 to 16pounds per cow per day.

Wheat middlings (18.5% CP, 73.3% TDN, 12.1% ADF) are palatable and are a goodsource of crude protein and energy and are high in phosphorous (1.02%). Feedingrecommendation: 6 to 10 pounds per cow per day.

Dried citrus pulp (6.9% CP, 79.8% TDN, 22.2% ADF) is a palatable feed that is high incalcium (1.92%) and energy but low in crude protein. Feeding recommendation: 5 to8 pounds per cow per day.

Possible Nutritional Problems from Using By-Product FeedsThe unique nutritional value of by-product feeds may create nutritional problems if suchfeeds are misused in a ration. Some possible problems include:

•palatability problems when using certain feeds (such as blood meal and corn glutenfeed)

•mineral imbalances (such as when corn gluten feed is fed without making adjustmentsfor its high phosphorous content)

•high moisture levels in the ration (such as when large amounts of wet brewers grainare fed along with silage)

•lack of enough effective fiber in the ration (such as when soybean hulls are fed and theADF level is not discounted because of their low effective fiber)

•fat level in the total ration dry matter (should not exceed about 7% in order not tocompromise fiber digestibility and rumen function)

•possible mycotoxin contamination

•availability and consistency of the commodity feeds

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•handling and storage problems

•quality control

SummaryCommodity or by-product feeds are very different feedstuffs that can be used to lowerfeed costs, increase the nutrient density of the diet, increase the level of RUP, serve asa substitute for forage, or increase the fiber level in the ration. Determine the nutritionalvalue of a by-product feed for your herd by evaluating it as a feed choice in a computerration formulation program. Evaluate your feeding management and determine if it willbe profitable for you to use the by-product feed in your feeding program.

Note: Reference to commercial products or trade names is made with theunderstanding that no endorsement is implied or criticism of other products notmentioned.

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Mineral Needs Of Dairy Cattle

Dr. Jerry W. SpearsDepartment of Animal ScienceNorth Carolina State University

IntroductionMinerals are required for normal functioning of basically all metabolic processes in thebody. A number of macro and microminerals have been shown to be required byanimals. Providing adequate amounts of essential minerals to meet animalrequirements is critical to maximizing milk production, reproduction and health of dairycattle.

Requirements for most minerals are not constant, but are affected by a number ofdietary and physiological factors that affect either absorption or metabolic demand forthe mineral. Physiological factors, that affect requirements of certain minerals, includegenetics, age, sex, type of production (maintenance, growth, reproduction, andlactation), and level of production. Dietary factors usually affect mineral requirementsby altering absorption of minerals from the gut. Mineral requirements in NRC and otherpublications are actually estimates of requirements. Precise requirements for aparticular mineral under a given set of conditions may be lower or higher than valuesshown in NRC publications.

In the recent dairy cattle NRC (2001) requirements for most minerals were estimatedusing a factorial modeling approach. In contrast, previous dairy NRC reports (1989)have estimated requirements for most minerals based on results from experimentswhere different minerals concentrations were fed to animals.

Mineral Requirements in the Dairy NRCThe new dairy cattle NRC (2001) estimates the requirements for absorbed mineralbased on needs for maintenance and production (growth, lactation pregnancy). Dietaryrequirements were estimated by dividing the absorbed or net mineral requirements for agiven mineral by an absorption coefficient. Maintenance requirements in the modelwere comprised of endogenous fecal and insensible urinary and sweat losses. Thelactation requirement was determined from the concentration of mineral in milkmultiplied by 4% fat-corrected milk yield. The requirement for growth was derived fromthe amount of mineral retained per kg body weight gain. The pregnancy requirementwas defined as the amount of mineral retained within the reproductive tract (fetus,uterine contents, and uterus) at each day of gestation. Mineral requirements of femalespregnant less then 190 days was considered small and not considered in modelingrequirements.

The major advantage of the factorial approach is that requirements can be estimated fora wide range of production levels and stages. For example, in the dairy NRC (2001)

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estimated requirements of most minerals, when expressed as percent or mg/kg diet,vary with stage of pregnancy and level of milk production (Table 1).

Accuracy of mineral requirements derived from the factorial approach is dependent onthe data used in the model. It is possible to determine the amount of a mineral presentin milk and body gain with a high degree of accuracy. Maintenance requirements andabsorption coefficients used in the model, potentially, are major sources of error. Bothof these are difficult to accurately measure and as a result, studies estimatingmaintenance requirements and absorption coefficients are scarce for most minerals.Endogenous fecal losses comprise the major component of the maintenancerequirement for most minerals. The endogenous fecal component consist of mineralssecreted into the gut that are not reabsorbed. Mineral secretions into the gut includethose in saliva, bile, digestive juices, and sloughed off intestinal cells. Measurement ofendogenous fecal mineral generally requires the use of radioisotopes and valuesobtained can be affected by dietary level and body stores of mineral (Thompson, 1965).

Quantitative measurement of true absorption coefficients, especially for trace minerals,is difficult and research data are limited for many minerals. Absorption coefficients arealso affected by dietary (antagonist, level of mineral, etc.) as well as animal relatedfactors such as age and physiological state (nonlactating vs lactating). Absorptioncoefficients for minerals such as zinc, iron and calcium are most meaningful when theyare measured at levels at or below the animal's requirement. When dietary levels ofthese minerals exceed requirements, homeostatic control mechanisms, within theanimals, reduce percent absorption to maintain tissue mineral concentrations within anarrow range (Miller, 1975).

Mineral requirements for lactating cows, dry pregnant cows and growing heifers in the2001 and 1989 dairy cattle NRC are compared in Table 2. Primarily because of thedifferent approach used to arrive at requirements, estimated requirements in the 2001NRC are slightly and in some instances substantially different from those published inthe 1989 NRC. The most striking changes occurred for magnesium, iron, andmanganese. Requirements for these minerals are considerably lower in the new dairyNRC. Calcium and phosphorus requirements were estimated using the factorial methodin both the 1989 and 2001 NRC. Differences in estimated requirements for calcium andphosphorus between the two relate largely to different absorption coefficients andmaintenance values being used in the models.

Calcium and PhosphorusFrom an environmental perspective, phosphorus excretion in animal waste has becomea major concern. Feeding phosphorus in concentrations that greatly exceedrequirements of dairy cattle dramatically increases phosphorus excretion in waste.Phytate phosphorus found in plant feedstuffs is poorly available to nonruminants.Rumen microorganisms in ruminants produce phytase that hydrolyzes phytate releasingthe phosphorus in an available form.

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Phosphorus requirements of dairy cattle can often be met without any phosphorus beingsupplemented to the diet. Recent research (Valk and Sebek, 1999;, Wu and Satter,2000; Wu et al., 2000) has clearly indicated that phosphorus requirements of dairy cowsdo not exceed .40% of the diet. Results of a study (Wu et al., 2000) where Holsteincows were fed diets containing .31, .40 or .49% phosphorus throughout a completelactation are shown in Table 3. The low level of phosphorus did not have an adverseeffect on milk production or reproduction. In a two-year study, milk production andreproductive performance did not differ between cows fed .38 and those receiving .48%phosphorus (Wu and Satter, 2000).

Forages are generally high in calcium while concentrates are low. However, availabilityof calcium in some forages may be low due to the presence of calcium oxalate. Inalfalfa, 20 to 33% of the calcium is present as insoluble calcium oxalate and apparentlyunavailable to the animal (Ward et al., 1979). Martz et al. (1990) found that trueabsorption of calcium in alfalfa hay was only 25% in lactating dairy cows. In the dairyNRC (2001) forages were assigned a calcium absorption coefficient of 30% while avalue of 60% was used for other feedstuffs.

References

Martz, F. A., A. T. Belo, M. F. Weiss, R. L. Belyea, and J. P. Goff. 1990. Trueabsorption of calcium and phosphorus from alfalfa and corn silage when fed tolactating cows. J. Dairy Sci. 73:1288-1295.

Miller, W. J. 1975. New concepts and developments in metabolism and homeostasis ofinorganic elements in dairy cattle. A review. J. Dairy Sci. 58:1549-1560.

NRC. 1989. Nutrient Requirements of Dairy Cattle. 6th Rev. Ed. National ResearchCouncil. Nat. Acad. Sci., Washington, DC.

NRC. 2001. Nutrient Requirements of Dairy Cattle. 7th Rev. Ed. National ResearchCouncil. Nat. Acad. Sci., Washington, DC.

Valk, H., and L.B.J. Sebek. 1999. Influence of long-term feeding of limited amounts ofphosphorus on dry matter intake, milk production, and body weight of dairy cows.J. Dairy Sci. 82:2157-2163.

Wu, Z., and L. D. Satter. 2000. Milk production and reproductive performance of dairycows fed two concentrations of phosphorus for two years. J. Dairy Sci. 83:1052-1063.

Wu, Z., L. D. Satter, and R. Sojo. 2000. Milk production, reproductive performance,and fecal excretion of phosphorus by dairy cows fed three amounts ofphosphorus. J. Dairy Sci. 83:1028-1041.

Ward, G., L. H. Harbers, and J. J. Blaha. 1979. Calcium-containing crystals in alfalfa:Their fate in cattle. J. Dairy Sci. 62:715-722.

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Table 1. Mineral requirements for Dairy Cows in the 2001 Nutrient Requirement ofDairy Cattlea

Dry Pregnant Cowb Lactating Cowb

Days pregnant 240 270 279 --- ---Milk Production, kg/d --- --- --- 25 54Calcium, % 0.44 0.45 0.48 0.62 0.60Phosphorus, % 0.22 0.23 0.26 0.32 0.38Magnesium, % 0.11 0.12 0.16 0.18 0.21Chlorine, % 0.13 0.15 0.20 0.24 0.29Potassium, % 0.51 0.52 0.62 1.00 1.07Sodium, % 0.10 0.10 0.14 0.22 0.22Sulfur, % 0.20 0.20 0.20 0.20 0.20Cobalt, mg/kg 0.11 0.11 0.11 0.11 0.11Copper, mg/kg 12 13 18 11 11Iodine, mg/kg 0.4 0.4 0.5 0.6 0.4Iron, mg/kg 13 13 18 12 18Manganese, mg/kg 16 18 24 14 13Selenium, mg/kg 0.3 0.3 0.3 0.3 0.3Zinc, mg/kg 21 22 30 43 55

aFrom NRC (2001).

bHolstein cow with mature body weight of 680 kg.

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Table 2. Comparison of Mineral Requirements in the 1989 and 2001 NutrientRequirements of Dairy Cattle

Lactating Cow Dry Pregnant Cow Growing Heiferd

1989d 2001b 1989 2001c 1989 2001Calcium, % 0.64 0.67 0.39 0.44 0.41 0.41Phosphorus, % 0.41 0.36 0.24 0.22 0.30 0.28Magnesium, % 0.25 0.20 0.16 0.11 01.6 0.11Chlorine, % 0.25 0.28 0.20 0.13 0.20 0.11Potassium, % 1.00 1.06 0.65 0.51 0.65 0.47Sodium, % 0.18 0.22 0.10 0.10 0.10 0.08Sulfur, % 0.20 0.20 0.16 0.20 0.26 0.20Cobalt, mg/kg 0.10 0.11 0.10 0.11 0.10 0.11Copper, mg/kg 10 11 10 12 10 10Iodine, mg/kg 0.60 0.44 0.25 0.40 0.25 0.27Iron, mg/kg 50 17 50 13 50 43Manganese, mg/kg 40 13 40 16 40 22Selenium, mg/kg 0.30 0.30 0.30 0.30 0.30 0.30Zinc, mg/kg 40 52 40 21 40 32

a700 kg cow producing 48 kg/d of milk (3.5% fat).

b680 kg cow producing 45 kg/d of milk (3.5% fat).

cDry cow 240 days pregnant.

d6 months of age.

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Table 3. Effects of dietary phosphorus on milk production and reproductiveperformance of Holstein cowsa

Dietary P0.31% 0.40% 0.49%

Number of cows 8 9 9Dry matter intake, kg/d 23.0 22.4 23.4Milk ,kg/308-d 10,790 11,226 11,134Days openb 78 106 112Cows conceived at first AI 7 4 3 Before 206 DIM 8 8 8Services per conception 1.4 1.6 2.3

aFrom Wu et al., (2000).

bIncludes only cows that became pregnant before 206 DIM.

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Vitamin Nutrition of Dairy Cattle: circa 2002Dr. Will Seymour, Roche Vitamins Inc.

IntroductionVitamins are essential for health and productivity of dairy cattle and other livestock.Optimal vitamin nutrition is required in order for dairy cattle to express their full geneticpotential for growth and milk production. Vitamin status affects the function of theimmune system and the ability of the animal to protect itself from bacteria, viruses andother pathogens in its environment. Other physiological functions that depend onvitamin status include: reproduction; calcium and phosphorus metabolism; and hoofgrowth and integrity.

Vitamins are essential nutrients, not drugs or additives. Terminology such as “dose”and “efficacy” do not apply to vitamin nutrition any more than to mineral or amino acidnutrition. “Additive” implies something non-nutritive or non-essential. Each vitamin hasits own unique and essential functions in the natural physiology and biochemistry of theanimal that cannot be replaced by any other nutrient.

Vitamin nutrition is a component of, and not a substitute for, good managementpractices. Optimum vitamin nutrition (Figure 1) provides the assurance that bodysystems and processes of the cow, such as immunity, reproduction and milk production,are not limited by the availability of any vitamin(s) and are thus more able to operate atfull capacity and efficiency. Although some vitamins can have pharmacological effects,e.g. niacin in reducing serum LDL in humans, optimum vitamin nutrition involvessupplementing to the point where normal physiological processes are fully functioningunder all conditions, and not to produce a pharmacological effect. This seems to be apoint of confusion in the livestock industry.

Vitamin supplementation of dairy cattle begins shortly after birth. Colostrum is a rich,natural source of vitamins for the calf. Vitamin concentrations vary with colostrumquality and nutritional status of the cow, and decline with subsequent milkings (Table1.).

Table 1. Vitamin concentrations in colostrum and milk of dairy cows*Colostrum1st Milking

Colostrum5th Milking

MilkSaleable

Vitamin A, IU/lb 4,455 1,116 512Beta-carotene,mg/lb

40 (~16,000 IUvitamin A)

17.5 (~7000 IUvitamin A)

0.03 (~12 IUvitamin A)

Vitamin E, IU/lb 4.1 1.7 0.5*(McDowell, 2001; Zanker et al., 2000; Kume and Toharmat, 2001; Weiss et al., 1997)

Calves deprived of good quality colostrum during the first 24 hours after birth have lowserum vitamin levels and also lack the normal capacity to absorb vitamins during the

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first 7-14 days of life (Blum et al., 1997 Zanker et al., 2000). Serum vitamin levelsremain depressed up to one month of age in calves deprived of colostrum (Zanker etal., 2000). Furthermore, serum vitamin levels are higher in calves fed colostrum in thefirst 12 hours after birth than in calves not fed colostrum until 24 hours after birth(Zanker et al., 2000). This “avitaminosis” may partly explain the reduction in immunefunction and disease resistance seen in calves deprived of adequate, good qualitycolostrum. These facts reinforce the importance of good nutrition, including vitaminnutrition, for the gestating cow during the dry period and transition period, and of the calfduring the first few hours, days and weeks of life.

In the years just after their discovery most vitamin experiments were aimed atdetermining the minimum dietary requirements that would prevent outright deficiencysymptoms. Originally the National Research Council nutrient requirements for livestockhad a built-in 20 percent safety margin for vitamins that provided insurance against lowand variable levels of vitamins in feeds. That margin of safety is no longer used, and isleft up to the nutritionist doing the formulation. More recently the approach to researchin vitamin nutrition has changed to defining the optimum level of vitamin intake thatresults in the best overall health and performance of livestock and the health andlongevity of humans and companion animals. In livestock the optimum level ofsupplementation for a vitamin is that level that results in the greatest overall efficiencyand economic return to the livestock producer (Figure 1).

Figure 1:

Optimum Vitamin Nutrition Concept

A

B

C

Nutrient Supply

Response D

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Fat-soluble Vitamins: A, D, E, K and beta-carotene

Sources and Stability:Sources and deficiency symptoms of the fat-soluble vitamins are summarized in Table 2(see appendix). Vitamins A, E and beta-carotene are abundant in fresh, green pasture.Vitamin D is derived from green forage and from exposure of the animal to sunlight.Sun-cured, green legume hay is a source of vitamin A and D activity. Rumen bacteriasynthesize vitamin K. Vitamins A, D and E are commonly supplemented in dairy rationsusing stabilized, commercial product forms that resist breakdown in feed processing,storage and in the rumen.

Vitamin A is the least stable of the fat-soluble vitamins. Rumen degradation can reach70% when rations of 60% grain or higher are fed (Weiss, 1998). Vitamins E, D andbeta-carotene are generally more stable in the rumen than vitamin A, in that order. Thevitamin A (beta-carotene) and vitamin E content of forages and grains is variable anddeclines during weathering and storage. Vitamin K is synthesized in large quantities byrumen bacteria. Commercial forms of vitamin K (menadione, K3) are converted to activevitamin K in pre-ruminant dairy calves (Nestor, Jr. and Conrad, 1990) as they arehumans and other animals (McDowell, 2000).

Vitamins A and E and beta-carotene are natural antioxidants. In their native forms theyreact with oxidation products in feeds and their vitamin activity is lost. Unsaturated fattyacids as found in pasture, oilseeds and some commercial fat sources, are the mostcommon and problematic source of oxygen radicals, through the process ofrancidification. Stabilized commercial forms of the vitamins are resistant to oxidation.

Moisture is another enemy of vitamins in feeds and forages during storage. Wateraccelerates many of the reactions leading to breakdown of the vitamins. Trace mineralsalso tend to increase the rate of vitamin degradation. Correct premix formulation usingadequate amounts of an appropriate organic carrier, such as rice hulls or wheatmiddlings, can help reduce vitamin-mineral interactions by producing uniformdistribution of the vitamins in the premix and by reducing physical contact betweenvitamins and minerals via dilution. Inorganic mineral sources such as limestone andmagnesium oxide are not suitable carriers for vitamin premixes. Vitamin product formsdo not adhere evenly to inorganic mineral sources, and mineral sources generatefriction and abrasion during mixing. Limestone and magnesium oxide increase the pHof the premix, which is detrimental to stability of many vitamins. Organic carrier shouldcomprise 40% or more of the premix for optimum vitamin stability and mixingcharacteristics.

AbsorptionIntestinal absorption of vitamins A, D, E, K and beta-carotene takes places inconjunction with fat digestion and absorption. While this is not normally a barrier toutilization it is possible that very low fat diets (<2% fat) may limit absorption, as wouldany defect in liver or gall bladder function. In calves cryptosporidia infection has beenshown to reduce the absorption of vitamin A (Holland et al.,1992). Others have shown

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that in dairy calves infected with coccidia, supplemental vitamin E acts synergisticallywith the anti-coccidial lasalocid to restore growth rate (Goodier, 2001).

Vitamin A DeficiencyVitamin A is the most extensively stored and tightly regulated of the vitamins inmammals and therefore very unlikely to be deficient except in animals that have beenfed a virtually vitamin A-free diet for a number of months (Appendix Table 2A).Ruminants consuming adequate quantities of beta-carotene from plants orsupplemental vitamin A in feed normally have a 3-4 month supply of vitamin A stored intheir liver. This adaptation enables wild ruminants to survive long periods without greenforage, such as the dry season in arid climates and winter in northern climates. Cattleentering feedlots from good quality pastures have been maintained for several monthswithout vitamin A supplementation before any vitamin A deficiency symptoms wereobserved (McDowell, 2000).

Vitamin A deficiency symptoms include night blindness, lesions of the eye mucosa,coughing or respiratory distress, diarrhea and edema of the brisket or extremities (Fryeet al., 1991). Reduced immunity and impaired reproduction are also symptoms ofvitamin A deficiency (Bruns and Webb, 1990). Calves may be born dead or inweakened condition. Serum vitamin A levels are maintained until liver vitamin A storesare exhausted (<20ug/g wet weight). Therefore liver biopsy is the only reliable methodof confirming a vitamin A deficiency. However other conditions can result in low valuesof serum vitamin A, most notably zinc or phosphorus deficiency or liver disease(McDowell, 2000; Frye et al., 1991).

Dairy cows have depressed serum vitamin A (retinol) levels (<150 ng/ml) during the firstfew weeks after calving and during clinical illness (Dr. Tom Herdt, personalcommunication). Blood samples taken from cows at these times for vitamin A analysismay be erroneously interpreted as vitamin A deficiency. The reduced levels are likelydue to a reduction in the synthesis or export of retinol binding protein by the liver duringtimes of stress or disease. All in all, the likelihood of true, primary vitamin A deficiencyin modern dairy cows, consuming typical industry levels of supplemental vitamin A orsignificant amounts of green forage is quite low. Dairy calves are more likely to bemarginally deficient in vitamin A due to inadequate intake of colostrum or poorcolostrum quality (Zanker et al., 2000; Blum and Hammon, 2000). Intestinal disease,Cryptosporidium for example, also reduces vitamin A absorption in calves (Holland etal., 1992).

Vitamin D DeficiencyVitamin D is derived both from the diet and from ultraviolet irradiation of the skin bysunlight. In either case the vitamin D compounds formed or absorbed must be activatedby enzyme reactions in the liver and kidney in order to produce the active form ofvitamin D (1,25 hydroxy-vitamin D). Vitamin D deficiency is manifested as loss of boneintegrity and skeletal deformations (rickets), especially in young, growing animals (Fryeet al., 1991). In mature animals vitamin D deficiency reduces the utilization of calciumand phosphorus, can result in bone fragility (osteoperosis) and can contribute to milk

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fever. Vitamin D also plays a role in the immune system (McDowell, 2000). Thelikelihood of outright vitamin D deficiency in dairy cattle is low, although marginaldeficiency could occur in animals having little or no exposure to sunlight and receivinglittle or no supplemental vitamin D. Secondary vitamin D deficiency might result fromimpaired liver or kidney function due to other diseases. Concentrations of 1,25 hydroxy-vitamin D are related to the incidence of milk fever and are increased by feeding anionicdiets (Horst et al., 1994).

Vitamin E DeficiencySymptoms of vitamin E deficiency (Frye et al., 1991) include impaired reproduction andimmunity. In young, growing ruminants, vitamin E deficiency appears as white muscledisease (nutritional muscular dystrophy). This is related to oxidative damage to themuscles and is also related to the selenium status of the animal. Beef cattle exhibit a“buckling syndrome” characterized by physical collapse and muscle atrophy oftentriggered by shipping stress (McDowell, 2000). In dairy cattle marginal rather thanoutright deficiency is more likely and can result in reduced pregnancy rates, poor calfvigor and immunity and increased susceptibility to mastitis or other infections in cows.Bulls exhibit reduced fertility. Exposure to environmental or disease stress tends toreduce blood vitamin E levels. Blood levels reach minimal values at calving and theperipartum period, similar to vitamin A. Unsaturated fats undergoing oxidation destroyvitamin E and increase the dietary requirement (McDowell, 2000). Several traceminerals, including selenium, zinc, copper and manganese function synergistically withvitamin E as components of the body’s antioxidant system (Miller et al., 1997).

Fortification Guidelines for Fat Soluble VitaminsDry cow fortification guidelines for the fat-soluble vitamins are summarized in Table 3.The values shown for the National Research Council, Nutrient Requirements of DairyCattle (NRC) are summary table values and apply to a 1500 lb cow during the last twomonths of gestation. The 2001 NRC calculates fat-soluble vitamin requirements directlyfrom body weight and has reduced the expected contribution of stored forages andfeeds to vitamin needs of dairy cattle, due to high variability and potentially low values ofvitamins in common feedstuffs. The 2001 NRC also makes greater allowances forfactors such as reduced dry matter intake of dry cows nearing calving. Rocheguidelines are aimed toward optimum levels of supplementation based on availableresearch and consensus among global areas. Ranges are provided for use bynutritionists and others. Some recent studies that support these levels will be discussedbelow.

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Table 3. Fortification guidelines for fat-soluble vitamins in dry and transition dairy cows(1500 lb mature cow, last 2 months gestation)

1989 NRC Dairy* 2001 NRC Dairy** Roche Global**Vitamin A, IU/h/d 52,000 100,000 75,000-100,000Vitamin D, IU/h/d 20,000 25,000 25,000-35,000Vitamin E, IU/h/d 210 1200-1800 1000-3000Beta-carotene,mg/h/d

NA NA 200-300

* total vitamin E requirement** supplemental vitamin E requirement

Fat-soluble vitamin recommendations for lactating dairy cows are shown in Table 4.Similar comments to those made with reference to the dry cow recommendations apply.

Table 4. Fortification guidelines for fat-soluble vitamins in lactating dairy cows (1500 lbmature cow, 85 lbs milk, 70 days in milk)

1989 NRC Dairy* 2001 NRC Dairy** Roche Global**Vitamin A, IU/h/d 72,500 75,000 100,000-150,000Vitamin D, IU/h/d 22,500 21,000 30,000-50,000Vitamin E, IU/h/d 350 545 500-1000Beta-carotene,mg/h/d

NA NA 200-300

* total vitamin E requirement** supplemental vitamin E requirement

Fat-soluble vitamin recommendations for calves and growing heifers are shown in Table5. The 2001 NRC bases requirements on body weight and so mid-point values wereselected for the two heifer growth stages.

Table 5. Fortification guidelines for fat-soluble vitamins in dairy calves and heifers (bodyweights of 120 lb, 440 lb and 990 lb with intake of 2% body weight)

1989 NRC Dairy* 2001 NRC Dairy** Roche Global**Vitamin A, IU/h/d,Calves, < 3 mo. 2,200 6,050 20,000-32,000Heifers, < 12 mo. 8,462 16,000 20,000-40,000Heifers, > 12 mo. 19,038 36,000 50,000-70,000Vitamin D, IU/h/dCalves, < 3 mo. 392 392 1,400-1,800Heifers, < 12 mo. 1232 1154 2,500-4,000Heifers, > 12 mo. 2772 1195 5,000-7,000Vitamin E, IU/h/dCalves, < 3 mo. 25 33 100-150Heifers, < 12 mo. 97 160 200-300Heifers, > 12 mo. 218 360 300-500* total vitamin E requirement** supplemental vitamin E requirement

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Rationale for Current RecommendationsThis section will highlight selected research studies that support recent changes in fat-soluble vitamin recommendations for dairy cattle, primarily vitamin E. Vitamins A and Dare generally supplemented at levels at or above levels shown in the tables.

Vitamin E in Transition CowsVitamin E recommendations for transition cows have been increased based on theresults of recent studies (Weiss et al., 1997; Politis et al., 1995, 1996; Baldi et al., 2000)showing that cows supplemented with 2000 to 4000 IU vitamin E per day during the last3-4 weeks prior to calving and 2000 to 3000 IU vitamin E during the first 2 to 4 weeksafter calving had significant reductions in new mastitis infections or somatic cell countand an increase in the bacteria killing ability of white blood cells (Tables 6 and 7).These results are consistent with the observation that plasma vitamin levels reachminimum levels at or near the time of calving and that immune function of dairy cows issuppressed around the time of calving. Parturition is the time when dairy cows are mostsusceptible to contracting new mastitis infections. The threshold value of 3.5 ug/mlplasma vitamin E calculated by Weiss et al. (1997) for cows at calving appearsconsistent with changes in plasma vitamin E observed in the other studies. Cows withplasma vitamin E below 3.5 µg/ml were nine times more likely to have new clinicalmastitis infections (Weiss et al., 1997). Although Weiss et al. (1997) fed dietssupplemented with 0.1 ppm selenium, plasma selenium values were within normalranges. The other two studies supplemented cows with 0.3 ppm selenium andexhibited normal plasma selenium values. Vitamin E and selenium work in conjunctionwith each other and optimal levels of both nutrients need to be supplied. Vitamin Esupplementation of transition cows should be viewed as another management tool foroptimizing udder health and milk quality.

Table 6. Effects of Supplemental Vitamin E on Mammary Gland Health in Dairy Cows(representative studies)

ItemSmith et al.,

(61)Smith et al.,

(60)Batra et al.,

(7)Weiss et al.,

(65)Baldi et al.,

(5)Time Interval

Levels, IU/d

Mammaryresponse

Dry period

0, 1000

Reducedincidence,duration ofmastitis

Dry andlactation

0, 10000, 880

Reducedincidence,duration ofmastitis andmilk SCC

Dry andlactation

0, 10000, 500

No effect onclinical disease,reduced SCC

Dry and 1st 28dlactation

100, 1000, 4000100, 500, 2000

Clinical mastitisreduced 30%and 80% by1000/500 and4000/2000 IU/d

-14 days pre- to7 days post-calving

1000 vs 2000

Somatic cellcount (SCC)reduced by 2000IU vs 1000 IU/d

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Table 7. Effect of Supplemental Vitamin E on Neutrophil Function in Dairy Cows

Item Hogan et al., (32) Politis et al., (52) Politis et al., (53)Time Interval

Level, IU/d

Responses

Dry and lactation

0, 10000, 500

Increased killing ofS. aureus andE. coli byneutrophils

4 wk pre- and8 wk post-calving

0, 3000; plus1 injection 5000 IU

Improved functionof neutrophils; inc.,superoxideproduction

4 wk pre- and8 wk post-calving

0, 3000; plus1 injection 5000 IU

Improvedneutrophilchemotaxis

Vitamin E in Calves and HeifersCertain research studies have indicated benefits to supplementing young pre-weanedand weaned calves with 100 to 125 IU vitamin E per day (Reddy et al., 1987; Luhman etal., 1990). Another recent study found that supplementing vitamin E at 150 IU per dayin combination with an anti-coccidial (lasalocid) to calves infected with coccidiosisresulted in greater average daily gains compared to either treatment alone (Goodier,2001). These studies support the concept of supplementing 100 to 150 IU vitamin E perday to young calves to support rapid growth rates especially under exposure topathogens.

A Florida study found that the toxic effects of gossypol from cottonseed meal werecounteracted by supplemental vitamin E (Table 8) (Valasquez-Peirra et al., 1999). Thesame authors found that vitamin supplementation restored semen quality and fertility indairy bulls consuming gossypol from cottonseed meal (Table 9) (Valesquez-Peirra etal., 1998). The level of vitamin E fed in these studies was 3000 or 4000 IU per day.

Table 8. Effect of gossypol (390 ppm) and vitamin E on growth and mortality of dairycalves

SBM + 30 IUVitamin E/kg

Gossypol(CSM) + 30 IUVitamin E/kg

Gossypol(CSM) + 2000

IU VitaminE/hd/day

Gossypol(CSM) + 4000

IU VitaminE/hd/day

ADG, 43days, kg/day

0.7b 1.0a 1.1a 1.1a

Mortality, # 0 6 2 2Mortality, % 0 43 18 18

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Table 9. Effect of gossypol and vitamin E intake on semen quality of dairy bullsSBM + 135 IU

Vitamin EGossypol (CSM) +135 IU Vitamin E

Gossypol (CSM) +4000 IU Vitamin E

Normal, % 64.7a 31.4b 54.6a

Daily spermproduction (x109)

3.2a 2.2b 4.1a

The Dairy NRC 2001 has increased the level of vitamin E supplementationrecommended for calves and growing heifers. In particular dairy replacement heifershave received low or sporadic vitamin E supplementation under commercial conditions.The new guidelines emphasize the need to provide supplemental vitamin E throughoutdevelopment. For example, the 2001 Dairy NRC recommends 160, 240 and 360 IUsupplemental vitamin E per day for confined Holstein heifers at 6, 12 and 18 months ofage.

Beta-caroteneBeta-carotene is the most abundant and active natural precursor to vitamin A inanimals. Some studies have reported that supplemental beta-carotene has functionsunique from vitamin A, while others have not demonstrated any benefits fromsupplementation (NRC, 2001; Michal et al., 1994; Oldham et al., 1991; Rakes et al.,1985). A recent study from the University of Florida found that cows supplemented withbeta carotene for 60 to 90 days postpartum produced significantly more milk thancontrols (Arechiga et al., 1998). In this study the diet contained little green forage andplasma carotene levels were marginal (< 3 µg/ml). The study was designed to testeffects of beta carotene on reproduction, which were limited and found to occur duringheat stress in cows bred on estrus, but not in cows bred using a timed inseminationprotocol. Breed differences exist in beta-carotene metabolism and this has not beenfully examined. Cows fed low carotene rations may benefit from supplemental beta-carotene, but current evidence is not adequate to make a clear recommendation.

Table 10. Effect of Supplemental Beta-Carotene (400 mg/d) Fed for 60-90 DaysPostpartum on Milk Yield of Holstein Cows (Arechiga et al., 1998)Experiments, 1-3 n Milk yield (kg) per cow for experimental period1

ControlTreatment

ControlTreatment

ControlTreatment

6293

7458

112106

5,7986,452**

4,1854,445*

7,5778,106***

1Cumulative milk yield to the last DHIA test day after trial completion.*P<0.10; ** P<0.05; *** P<0.01

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Beta-carotene is abundant in colostrum and plasma concentrations are in calves arereported to be inversely related to the incidence of scours (Kume et al. 2000). Theremay be benefits from supplementing beta-carotene to young calves during the first fewweeks of life, but this remains speculation.

Water-soluble, B-vitaminsThe water-soluble (B) vitamins include thiamin (B1), riboflavin (B2), niacin (B3),pyridoxine (B6), vitamin B12 (cyanocobalamine), folic acid, pantothenic acid, biotin andvitamin C (ascorbic acid). Carnitine, choline and several other compounds aresometimes grouped with the B-vitamins, but do not meet the complete definition of avitamin (McDowell, 2000). These substances are not enzyme cofactors but influencemetabolic processes through roles as carriers and structural components, and are alsosynthesized in significant quantities by the body. The roles of the B-vitamins aresummarized in Table 6 (see appendix). The B-vitamins vary in chemical structures andfunctions, but all are required as co-factors for specific enzyme catalyzed reactions.

Rumen bacteria are a large and diverse population. A number of rumen organismsrequire certain of the B-vitamins, while other species are capable of synthesizing B-vitamins. The major fiber-digesting bacteria of the rumen require biotin and para-aminobenzoic acid, a precursor of folic acid (Baldwin and Allison, 1983). An anotherpredominant rumen bacterium (Butyrivibrio fibrisolvens) requires biotin, folic acid andvitamin B6 (Baldwin and Allison, 1983). Rumen protozoa are known to be sensitive tosupply of niacin (Erickson et al., 1990). This may be of nutritional importance in that therumen protozoa are the primary source of choline in ruminants.

The National Research Council 2001 publication for dairy cattle contains a gooddiscussion of the B-vitamins with respect to the older literature on B-vitamin deficienciesin calves and much of the recent research with B-vitamins in dairy cattle. This paper willreview some of the more recent studies with biotin, niacin, folic acid, thiamin and vitaminC.

BiotinBiotin is not as well known as some of the other B-vitamins, but its role as specificnutrient was discovered in 1936 (McDowell, 2000). Biotin is also called “vitamin H” after“haut” the German for “skin”, due to the distinctive skin lesions observed during biotindeficiency. Rumen bacteria synthesize biotin and the rate of biotin synthesis is reducedas the grain content of the ration is increased (Da Costa Gomez et al., 1998).

Common feed sources of biotin include alfalfa meal, molasses, distiller’s solubles,yeast, peanut meal and soybean meal. The typical daily intake of biotin by dairy cattleis 4 to 6 milligrams. Rancidity of fat reduces the biotin content of feed. Biotinantagonists exist, most notably avidin of egg white, and streptavidin produced by certainbacteria and molds (McDowell, 2000). Biotin is stable to pelleting.

Biotin is an enzyme co-factor required for synthesis of propionic acid by rumen bacteriaand by the fiber-digesting (cellulolytic) bacteria of the rumen. Biotin is synthesized in

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rumen by as yet unidentified bacteria. In the host animal biotin is a co-factor in fourenzymes that occupy pathways involved in the conversion of propionic acid to glucose,general gluconeogenesis, the initiating step of fatty acid synthesis and in amino acidmetabolism (Girard, 1998, McDowell, 2000). Biotin has also been shown to be requiredfor production of normal keratinized tissues, including skin, hair, hooves and fingernails.Biotin is required for the complete differentiation of keratin producing cells in the bovinehoof and for the production of the intra-cellular cementing substance that bondstogether the horn cells that make up the hoof structure (Mulling et al. 1999). Biotindeficiency in calves leads to the production of soft, brittle hooves and degeneration ofthe micro-structure of hoof horn due to irregular keratinization and loss of intra-cellularcementing substance (Mulling et al. 1999). Other nutrients such as vitamin A and D,zinc, copper and calcium are required for normal production of hoof horn and need to beprovided in the diet.

Biotin and Hoof HealthBiotin status has been shown to affect the production and integrity of hoof horn in swine,horses and ruminants (McDowell, 2000). Similarly biotin status affects foot pad integrityin poultry. In the last 5 to 10 years a series of controlled studies have examined the roleof biotin nutrition on hoof integrity and hoof health in dairy cattle, including studiesconducted in university research herds and on commercial dairy farms. The hoof of thecow grows slowly at the rate of 1/16 to 1/8 of an inch per month. The hoof wall turnsover completely every 12 to 15 months, the heel in 6-8 months and white line region in3-4 months. The thinnest area of the hoof sole may grow out in 2-3 months dependingon rate of wear and original thickness. Therefore hoof lesions take varying periods oftime to emerge and heal, and this must be kept in mind when discussing hoof studies.

Recent studies of supplemental biotin and hoof health in dairy cattle have been largerscale and conducted on commercial dairy farms. Researchers at the Ohio StateUniversity (Midla et al., 1998) conducted a study using first lactation cows in whichbiotin was supplemented at 20 mg per day starting at calving and through 305 days oflactation. Hooves were examined at 30, 120 and 305 days of lactation. After 120 daysof supplementation the incidence of white line lesions was significantly reduced by biotinsupplementation while 305 day ME milk production was increased compared to control.

Fitzgerald et al. (2000) used 20 commercial dairy herds calving seasonally in a pasture-based region of Australia. Ten herds were supplemented with 20 mg/day biotin, starting4 months prior to the calving season and continuing through the lactation. Investigatorsand farmers were blind to the treatments. Herds supplemented with biotin had asignificant reduction in lameness as reported by the dairy producers, fewer treatmentsrequired and an improvement in locomotion score compared to controls. There were nosignificant differences in milk production, although somatic cell count was reduced bybiotin.

A controlled field study in Britain (Hedges et al., 2001) used five commercial dairy herdsequipped to individually supplement cows with biotin or placebo over an 18 monthperiod. In this study lameness was detected by the dairy producer and confirmed by a

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participating group of bovine veterinarians. Supplementation with 20 mg/day biotinsignificantly reduced the incidence (risk) of lameness due to white line lesionscompared to control, and also reduced the number of treatments needed to correctwhite line lesions that did occur. The effect was detectable after 130 days ofsupplementation, which was in excellent agreement with the study of Midla et al. (1998).

Figure 2. Average (%) Response of Hoof Lesions to Supplemental Biotin (9 studies)

Two other studies have reported that supplemental biotin increased milk production inhigh producing dairy cows. Bergsten et al. (1999) conducted a study with 180 cows in acommercial dairy farm equipped with a computer feeding system over a one-yearperiod. Cows supplemented with 20 mg per day biotin had a significant increase in 305adjusted milk yield compared to unsupplemented controls. Cows supplemented withbiotin also had reductions in sole hemorrhage and hoof wall ridging, but the extent ofhoof lesions in the herd was limited and not likely to completely explain the difference inmilk production which averaged 6.2 lbs per day. A controlled study in early lactationwith 45 cows of mixed parity was conducted by Ohio State researchers (Zimmerly et al.,2001) in which biotin was supplemented at 0, 10 or 20 mg per cow per day starting 14days before calving through 100 days of lactation. Milk production increased linearlywith level of biotin fed. Cows fed 20 mg biotin per day produced 6.1 lbs more milk thancontrols. These studies provide evidence that supplemental biotin may increase milkproduction through metabolic pathways, possibly by allowing full activity of keyenzymes.

NiacinNiacin is a co-enzyme for a large number of metabolic reactions as a component ofNAD (nicotinamide adenine dinucleotide). Niacin is required by and has been shown toincrease the numbers of certain rumen protozoa (Girard, 1998). Rumenmicroorganisms synthesize niacin, however, there is also significant rumendisappearance of niacin, in contrast to the other B-vitamins and similar to vitamin C.

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Common sources of niacin include animal and fish byproducts, distillers grains, yeastsand some oilseed meals.

Niacin is the most studied of the B-vitamins in ruminants. Several authors havesummarized data from research trials involving niacin (Girard, 1998). Supplementalniacin has resulted in a significant increase in milk yield in roughly half the publishedstudies. A recent example is the case of two studies published in the same issue of theJournal of Dairy Science in 1998. The two studies were very similar, long term lactationstudies, both supplementing 12 grams of niacin per day. In one study (Drackley et al.,1998) a significant increase in milk production (+6.2%) was found in response to niacin,while no response was found in the other study (Minor et al., 1998). The average milkincrease to supplemental niacin fed at 6 or 12 grams per day has been ~1 kg (2.2 lbs)per day and responses, primarily in early lactation.

Niacin differs from the other B-vitamins in that there can be significant rumendegradation of supplemental niacin. Furthermore, niacin can be synthesized by cattle inlimited quantities from the amino acid tryptophan (McDowell, 2000). Therefore in thecase of niacin, partial rumen protection may be an advantage and amino acid statusmay come into play.

Niacin has been associated with a reduction in lipolysis in over-conditioned cows duringthe time around calving (Girard, 1998). There have been mixed results with respect toniacin’s effect on plasma ketone or free-fatty acid concentrations. Niacin has beenfound to increase the population of rumen protozoa (Erickson et al., 1990). Under someconditions increases in feed intake have been observed in lactating dairy cows andfeedlot cattle. Supplemental niacin may have benefits during heat stress in ruminants interms of milk or fat yield, feed intake or skin temperature (Muller et al., 1986; DiCostanzo et al., 1997; Belibasakis and Tsirgogianni, 1996; El-Barody et al., 2001).

Niacin is currently supplemented in dairy rations, primarily during the transition periodand early lactation in high producing cows. The current recommendation is 6-12 gramsper cow per day. Evidence suggests that cows in higher body condition or exhibitingsub-clinical ketosis will benefit most from niacin supplementation.

Folic AcidFolic acid was officially discovered in 1945. Folic acid is essential for aspects of aminoacid metabolism, including synthesis of methionine and the initiation of protein synthesis(Girard, 1998). Folic acid is necessary for the synthesis of DNA and RNA, which alsorequires vitamin B12 and relates to the deficiency symptom of anemia observed foreither of these vitamins (McDowell, 2000). Folic acid plays an important role in fetaldevelopment and supplementation has been found to reduce neural tube defects inhumans (McDowell, 2000). Brewer’s grains, alfalfa meal and whole soybeans aresources of folic acid. In contrast to biotin, folic acid synthesis in the rumen increaseswith increasing grain content of the ration (Girard et al., 1994).

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Folic acid has been studied as a supplemental vitamin in dairy cattle in several studiesconducted by Dr. Christine Girard and coworkers in Canada. Initial studies found thatplasma folates are decreased during pregnancy in dairy cows, being 40% lower fromtwo months after calving until the next calving (Girard, 1998). In the first experimentcows were injected with 160 mg folic acid each week starting from 45 days ofpregnancy through 6 weeks after calving. No effects on calf birth weight or growth werefound, but folic acid increased milk folates and increased milk protein from 3.2 to 3.5%during the first six weeks of lactation (Girard et al., 1995). In a subsequent study dairycows were fed supplemental folic acid at the rate of 0, 2 or 4 mg per kg body weightfrom 28 days pre-partum through 305 days of lactation (Girard and Matte, 1998). In thisstudy milk production of multiparous cows was increased (2.3 kg/d) by supplementalfolic acid, especially in the first 200 days of lactation. Current studies are focusing onthe interaction of folic acid with vitamin B12 and methionine in lactating dairy cows(Girard et al., 1999). Folic acid is linked to vitamin B12 and B6 in terms of biochemicalfunctions.

Thiamin (B1)Thiamin was the first of the vitamins to be identified, by C. Funk in 1911. Funk was oneof many scientists searching for a nutritional “anti-beri-beri factor” and isolated thiaminfrom rice bran. Thiamin deficiency in humans (beri-beri) was a major health problem atthe time, in part due to the use of new rice milling processes that removed the bran fromthe human diet. Funk coined the term “vitamin” derived from “vital amine” (McDowell,2000). Thiamin deficiency still occurs today in underdeveloped nations (McGready etal., 2001).

Thiamin is required as a co-enzyme (thiamin pyrophosphate) for several biochemicalreactions that are central in metabolism, including glycolysis and the Krebs cycle. Thusthiamin deficiency produces a wide range of symptoms in cattle, the most specific ofwhich are aberrations of the central nervous system (McDowell, 2000). The disorder isreferred to as polioencephelomalacia or PEM, although thiamin deficiency is not thesole cause and other nutritional imbalances are involved. Symptoms in young calvesincluding loss of coordination and mobility, heart arrhythmia, cramps, paralysis,trembling, diarrhea, gnashing of teeth, head retraction (star-gazing) and visualdisturbances. This may occur in calves shortly after weaning due to inadequate rumendevelopment and thiamin synthesis. In older cattle, usually feedlot cattle, the symptomsare similar and include general dullness, head pressing, circling, trembling, gnashing ofteeth, convulsions, collapse and sudden death. This often occurs in cattle shortly afterintroduction of a very high grain ration, or introduced suddenly to lush, high proteinpasture. This condition is normally treatable with injectible thiamin at the rate of 10-15mg per kg body weight. Vitamin A deficiency, magnesium tetany, sulfate toxicity (rumenproduction of hydrogen sulfide gas) and several infectious diseases can cause similarsymptoms (McDowell, 2000). Feeding 250 to 500 mg per day thiamin has been used toprevent relapses in feedlot cattle.

Thiamin deficiency (PEM) in ruminants has been linked to other nutritional and feedquality factors. These include the production of thiaminase enzyme by molds or

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bacteria in feeds or in the rumen, the production of anti-thiamin metabolites in thefermented feeds or the rumen, excess levels of sulfate in the feed or water and copperdeficiency.

Researchers at the University of Wisconsin studied the effect of supplemental thiamin inlactating cows fed corn byproducts known to contain significant levels of sulfates, whichcould reduce thiamin status (Shaver and Bal, 2000). Three experiments were carriedout using diets with and without corn byproduct and varying forage sources. Cows werein mid-lactation and producing 35 to 40 kg milk per day. The studies were rotationaldesign with four week periods.

Trial 1 used 16 primiparous and 12 multiparous cows supplemented with 0 or 150 mgper day thiamin. The rations contained 55% alfalfa silage and 45% concentrate. Milkproduction was significantly increased (+2.7 kg/day) by supplemental thiamin, with atrend for increased fat and protein yield. Trial two used 20 multiparous Holstein cowsfed either 0 or 300 mg supplemental thiamin per day. Rations contained 50% foragewith a 66:33 ratio of corn silage to alfalfa haylage. Milk production tended to increase(+.7 kg/day) with supplemental thiamin and protein yield was increased by 3.25% (.04kg/d). In Trial 3 sixteen multiparous cows were fed either 0 or 300 mg thiamin per dayin rations containing 60% alfalfa silage and 40% concentrate. In this studysupplemental thiamin decreased fat percentage (3.7 vs. 3.6%) and yield (1.51 vs. 143kg/d). Milk yield was not affected by treatment. Dry matter intake unaffected bytreatment in trials 1 and 2 and tended to be decreased by thiamin supplementation intrial 3. These studies suggest that thiamin status of dairy cows may be limiting to milkproduction under some conditions. The stage of lactation of the cows used, 120-195days in milk may have limited some of the responses.

Vitamin CVitamin C (ascorbic acid) is synthesized by most animals with the exception of humans,other primates, guinea pigs and some species of bats and birds (McDowell, 2000).Dairy cattle are capable of synthesizing vitamin C by 7 days of age (Toutain et al.,1997). The same authors reported that vitamin C is sequestered in lung (19% of bodypool), muscle (40%) and liver (30%). The lung appears to be a rapidly mobilized pool ofascorbic acid while muscle and liver are larger but more slowly mobilized pools (Toutainet al., 1997).

Vitamin C is required for hydroxylation reactions in the body, most notably thehydroxylation of lysine and proline as part of the synthesis of collagen. Many of theoutward symptoms of vitamin C deficiency in humans (scurvy) are related to disruptionof collagen synthesis (McDowell, 2000). These include inflammation and bleeding ofthe gums, loss of teeth, large hematomas and skin lesions. Vitamin C also serves awide antioxidant functions, analogous to those of vitamin E but in the aqueous phase.Vitamin C plays a role in regenerating vitamin E after oxidation by free radicalcompounds. As a result of its antioxidant role vitamin C participates in protectingcellular structures from oxidation reactions and specifically in the function of white blood

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cells. Vitamin C also plays a role in adrenal gland function with respect to corticosteroidsecretion and is therefore related to the stress response (McDowell, 2000).

Weiss (2001) studied the effects of supplemental vitamin C in stabilized form on plasmaand milk vitamin C and the oxidative stability of milk. A phosphate ester of vitamin Cwas used because previous research showed that this form was more stable in therumen than native vitamin C. Cows were supplemented with 0, 3, 16.5 or 30 gramsvitamin C per day in the feed. Plasma vitamin C was increased linearly bysupplementation, while milk vitamin C was not significantly increased bysupplementation. Vitamin C concentrations in milk were 4.5 times higher than inplasma. These findings support the concept that vitamin C uptake by the mammarygland is an active and saturatable process. No effects on milk flavor as evaluated by atrained test panel were found. The results do indicate that plasma vitamin C can beincreased by feeding stabilized vitamin C and that may have application if studies areundertaken around the time of calving.

Most of the interest in vitamin C supplementation of dairy cattle has focused on calves.Some studies (Cummins and Brunner, 1989) have found that supplemental vitamin Creduced scouring or enhanced immune function of calves, while others have not.Colostrum is quite high in vitamin C and inadequate intake of colostrum or poor qualitycolostrum may reduce vitamin C status of calves for the first 7 days of life.

A recent study at Purdue University (McKee et al., 2000) studied the effects ofsupplementing young calves fed milk replacer with either 0 or 250 mg vitamin C (asphosphate ester) with or without a beta-glucan derived from yeast cell wall. The studyperiod started 3 days after birth and continued through 6 weeks using 48 Holsteincalves. An interaction between the treatments resulted such that calves fed bothvitamin C and beta-glucan had significantly higher rate of gain than controls (2.32 vs.1.81 kg per week). Beta-glucans have been implicated as stimulants of certainelements of the immune system and vitamin C plays a role in normal immune function.This may explain the interaction of treatments. A similar study was conducted withearly-weaned pigs with similar results (S. D. Eicher, personal communication).

Summary B-VitaminsWater-soluble vitamins are not necessarily absorbed in optimal quantities by highproducing dairy cows or young calves. B-vitamin status may be a limiting nutritionalfactor in modern dairy production systems. B-vitamins may be co-limiting for milkproduction or other functions in dairy cattle because they act as essential co-enzymes ina wide array of interrelated metabolic pathways. Therefore co-supplementation of B-vitamins may be found to be economically beneficial in future research with dairy cows.

Overall SummaryVitamins are essential organic nutrients that are required for a wide range of metabolicand physiological processes. Vitamin supplementation at optimal levels based onresults of controlled research, using high quality, commercial vitamin sources, is a costeffective nutritional management practice for dairy producers.

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For more information on vitamins and vitamin nutrition of dairy cattle, visit our web siteat: www.rochenutrafacts.com

Appendix

Table 2. Common feed sources and vitamin deficiency symptoms in ruminants1

Vitamin Feed Sources Deficiency SymptomsA (retinol) Green pasture and forage

(beta-carotene)Night blindness, corneallesions, lacrimation,impaired reproduction andimmunity, diarrhea, edema,pneumonia, paresis

D (cholecalciferol, D3) Sunlight (UV) of skin, sun-cured legume hay

Osteoperosis, swelling ofjoints, stiff gait, milk fever-hypocalcemia, rickets incalves

E (alpha-tocopherol) Green pasture and forage,oilseeds, vegetable oils

Impaired reproduction andimmunity, white muscledisease in calves

K (menaquinone, K2) Bacterial synthesis Slow blood clotting,impaired bone growth

C (L-ascorbic acid) Endogenous synthesis Inflammation of mucosaltissues, impaired immunity,calf diarrhea (?)

B-complex Bacterial synthesis,pasture, fermentationbyproducts, grain products

Various: poor feedconversion, reducedimmunity, poor skin, hoofintegrity, “polio” in calves

1Summarized from McDowell, 2000 and Frye et al., 1991.

Table 2A. Likelihood of clinical or marginal vitamin deficiencies in dairy cattleClinical deficiency Sub-optimal intake Contributing factors

Vitamin A Very low Low Poor quality forage,high grain rations

Vitamin D Very low Low(?) Low sun exposure,poor quality forage

Vitamin E Low (calves) Moderate Poor quality forage,high PUFA in diet

Beta-carotene Low Moderate(?) Poor quality forage,high grain ration (?),seasonal effects

B-complex Low Moderate(?) High grain rations,poorly fermentedfeeds, stress (?)

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McKee, C.A., S.D. Eicher and T.R. Johnson. 2000. Ascorbic acid and a beta-glucanproduct from Saccharomyces cerevisiae influence on dairy calf well-being. J. Dairy Sci.83(Suppl.1):134 (abstr.).

Michal, J.J., L.R.Heirman, T.S. Wong, B.P. Chew, M. Frigg and L. Volker. 1994.Modulatory effects of dietary beta-carotene on blood and mammary leukocyte functionin periparturient dairy cows. J. Dairy Sci. 77:1408-1421.

Midla, L.T., K.H. Hoblet, W.P. Weiss and M.L. Moeschberger. 1998. Supplementaldietary biotin for prevention of lesions associated with aseptic subclinical laminitis(pododermatitis aseptica diffusa) in primiparous cows. Am. J. Vet. Res. 59:733-738.

Miller, J.K., M.H. Campbell, L. Motjope and P.F. Cunningham. 1997. Antioxidantnutrients and reproduction in dairy cattle. Proc. Minnesota Nutr. Conf. p.1.

Minor, D.J., S.L. Trower, B.D. Strang, R.D. Shaver and R.R. Grummer. 1998. Effects ofnonfiber carbohydrate and niacin on periparturient metabolic status and lactation ofdairy cows. J. Dairy Sci. 81:189-200.

Mudron, P., J. Rehage, K. Qualmann, H.P. Sallmann and H. Scholz. 1999. A study oflipid peroxidation and vitamin E in dairy cows with hepatic insufficiency. Zentralbl.Veterinarmed A 46:219-224.

Muller, L.D., A.J. Heinrichs, J.B. Cooper and Y.H. Atkin. 1986. Supplemental niacin forlactating cows during summer feeding. J. Dairy Sci. 69:1416-1420.

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Mulling, C.K.W., H.H. Bragula, S. Reese, K.-D. Budras and W. Steinberg. 1999. Howstructures in the bovine hoof epidermis are influenced by nutritional factors. Anat. Histol.Embryol. 28:103-108.

National Research Council. 2001. Nutrient Requirements of Dairy Cattle. 7th RevisedEd. National Academy Press, Washington, D.C.

Nestor, K.E., Jr. and H.R. Conrad. 1990. Metabolism of vitamin K and influence onprothrombin time in milk-fed preruminant calves. J. Dairy Sci. 73:3291-3296.

Oldham, E.R., R.J. Eberhart and L.D. Muller. 1991. Effects of supplemental vitamin A orbeta-carotene during the dry period and early lactation on udder health. J. Dairy Sci.74:3775-3781.

Politis, I., N. Hidiroglou, T.R. Batra, J.A. Gilmore, R.C. Gorewit and H. Scherf. 1995.Effects of vitamin E on immune function of dairy cows. Am. J. Vet. Res. 56:179-184.

Politis, I., N. Hidiroglou, J.H. White, J.A. Gilmore, S.N. Williams, H. Scherf and M. Frigg.1996. Effects of vitamin E on mammary and blood leukocyte function with emphasis onchemotaxis in periparturient dairy cows. Am. J. Vet. Res. 57:468-471.

Rakes, A.H., M.P. Owens, J.H. Britt and L.W. Whitlow. 1985. Effects of adding beta-carotene to rations of lactating cows consuming different forages. J. Dairy Sci. 68:1732-1737.

Reddy, P.G., J.L. Morrill and R.A. Frey. 1987. Vitamin E requirements of dairy calves. J.Dairy Sci. 70:123-129.

Seifi, H.A., M.R.M. Dezfuly and M. Bolurchi, 1996. The effectiveness of ascorbic acid inthe prevention of calf neonatal diarrhea. J. Vet. Med. B, 43:189-191.

Seymour, W. 2001. Review: Update on vitamin nutrition and fortification in dairy cattle.Prof. Anim. Sci. 17:227-237.

Shaver, R.D. and M.A. Bal. 2000. Effect of dietary thiamin supplementation on milkproduction by dairy cows. J. Dairy Sci. 83:2335-2340.

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Tsunoda, G., H. Hironori, K. Suzuki and H. Hanazumi, 1999. Vitamin E concentration incolostrum and neonatal calf serum from dams administered vitamin E daily orintermittently. J. Jpn. Vet. Med. Assoc., 52:699-701.

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Weiss, W.P. 2001. Effect of dietary vitamin C on concentrations of ascorbic acid inplasma and milk. J. Dairy Sci. 84:2302-2307.

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Zanker, I.A., H.M. Hammon and J.W. Blum, 2000. Beta-carotene, retinol and alpha-tocopherol status in calves fed the first colostrum at 0-2, 6-7, 12-13 or 24-25 hours afterbirth. Int. J. Vitam. Nutr. Res.70:305-310

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Nutrient Management for Tomorrow’s Dairy Herds

Dr. Lane ElyUniversity of Georgia

A tremendous amount of information on dairy production is available today. Herds areaveraging over 30,000 pounds of milk per cow. In this paper, I want to focus not on howto produce 30,000 pounds of milk per cow but focus on if the available knowledge isbeing used correctly. Also, it is important to try to identify potential problems beforethey become major problems. It is much easier to apply preventive maintenance thanto correct a serious problem.

There are two quotes that serve as the guiding principles. The first is AIf you can=tmeasure it, you can=t manage it.@ One has to be able to quantify change if one is toaffect the process.

The second quote is by Bliss Crandall, ADairy cows must be managed as individuals ona daily basis.@ As herds have gotten larger, this becomes more difficult but still shouldbe a guiding principle.

DataThere are two types of data which we will use to guide us in our evaluation. The firsttype of data are >rules of thumb= or guidelines. These usually have been establishedover time and have been proven true by experience. Many of these have beendeveloped from the underlying biology of the dairy cow. Some examples are: minimumforage content of the ration should be 40%, half of the cows should be chewing theircud, and maximum intake occurs at 100-120 days in milk. It is important to rememberthat these are guidelines and not absolutes. If these guidelines are not met, they shouldbe viewed as indicators of potential problems.

The second type of data used are benchmarks. Benchmarks are usually established byanalyzing a data set and creating standards of performance. At the University ofGeorgia, we have evaluated several large data sets to establish benchmarks forproduction parameters. Significant differences have been found in the parameters forherd size, production levels and region of the country. We have establishedbenchmarks so that herds can be compared to their contemporaries. Benchmarks areuseful to see where your herd lies in the population. For example, is it at the 50% levelor 90% level. Also, benchmarks provide goals if you want to improve or advance to thenext level.

Cows TalkAs one tries to evaluate the performance of the dairy farm, it is important to let the cowstalk to you. Observe your cows and how they act. They can tell us a lot about how thedairy is performing. The other thing is that cows don=t lie. As far as I know, there is noreward to the cow that tells you what you want to hear.

When I look at a group of cows, I like to see cows that are interested in what is goingon. They are not frightened and trying to escape through the back fence. Observe thegroup dynamics and flow of animals.

Cows should be eating, drinking, chewing their cud, milking and moving freely betweenthese activities. As we examine the herd, we need to note if these activities are noteasily performed.

Exceptions and DistributionThe exceptions in the herd and the distribution of the individuals within the herd need tobe examined as the data is evaluated. The cows that are exceptions may need specialtreatment or may have problems that are effecting them. An example is Body ConditionScore (BCS). For the herd, the desired BSC is 2.5 at peak lactation. If one has 100cows in this group and the average BCS is 2.5, things seem fine. A little closerexamination shows that 97 of the 100 cows fall between 2.0 and 3.0 BCS. Again theherd seems fine, but the other three cows are at 1.5 BCS. They are the exceptions oroutliers of the group. A closer look needs to be taken at those three individuals. Whyare they low? Do they have Johnes=, hardware disease or lameness? A decision mustbe made about those individuals, but not the group as a whole.

The distribution of the group can also be important. If the bulk tank fat test is 3.62%, itwould seem that things are fine. When the individual cow=s fat test are examined forherd A, they range from 3.45% to 3.75%. This herd has no outliers and most cows arewithin a very small range. When herd B is examined, the fat test ranges from 2.0% to3.9% and the cows are fairly evenly distributed across the range. Something is notworking in Herd B as a significant portion of the cows are in the low 2% fat test. Furtherexamination is required to determine the cause.

Areas of ConcernIn the next paragraphs, I am going to list several topics and outline some of thequestions you need to ask and evaluate.

RationAn old saying on the dairy farm is that there are 3 rations: 1) the ration calculated onpaper, 2) the ration that is mixed and 3) the ration the cow eats. Ideally these would allbe the same but one needs to check. Samples should be taken of the feed ingredientsto determine their nutrient composition so rations can be accurately calculated. Nutrientcomposition of feed ingredients can vary by 15% or more from book values. A sampleshould be taken of the mixed ration that is offered to the cows to insure that properweighing and mixing are happening. Third, a sample of the weighback should beanalyzed to see what the cows are actually consuming. These samples should betaken on a regular basis especially when ingredient changes are made. The rationshould be balanced for the cow=s requirements. As we move into the area of nutrientmanagement plans for the total farm this will be critical as excess nutrients in the rationwill have to be accounted for in the total plan.

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Dry Matter IntakeCows eat pounds not percentages. Balanced ration usually are quoted as having 16%crude protein or 18% crude protein. It is then assumed that cows will consume so manypounds of dry matter. For example, if cow A eats 50 pounds of a 16% crude proteinration, she is consuming 8.00 pounds of protein, but if she eats only 44 pounds then sheisl consuming 7.04 pounds of protein. How much difference in milk production occurs?

Determining the dry matter intake is critical in evaluating the nutrition program. Firstdetermine how much is offered and then determine the weighback on feed left after 24hours. Combine this information with the nutrient composition analysis of the ration andthe weighback to calculate the nutrient intake of the cows. This can also be used todetermine if the cows are eating the feed. Try to calculate the amount of feed wastedby the cow as she eats. How much feed is dragged onto the ground?

Dry Matter PercentOne of the easiest tests to run is the ration dry matter content. If the dry matter intake isimportant, then the dry matter percent must be calculated. It should remain fairlyconstant. If several wet feeds (silages or by-products) are being fed, the individualfeeds as well as total ration should be checked. For example, if the ration calls for 1000pounds of 33% DM silage then 330 pounds of silage DM is in the ration. If the drymatter drops to 28% the ration would contain 50 pounds less silage DM. This willreduce the nutrient content of the ration and make it unbalanced. If the DM% increases,extra nutrients will be fed and the ration will be unbalanced. Either of these situationscould have negative effects on milk production and the pocketbook. Dry matter percentcan be calculated using commercial units or a microwave. It is time well spent.

Delivery SystemHow the feed is delivered to the cow will influence what she eats. Probably the idealsystem would be to hand feed every part of the ration. This would insure that the properamounts are given to the cow and any sorting could be accurately monitored.

In theory the Total Mixed Ration (TMR) system closely follows this philosophy. Allingredients are mixed together in the proper amounts and given to the cow, AAbalanced ration in every bite.@ If the cow eats more than calculated amount, the rationis still balanced. Problems occur when the ration is not mixed well or over mixed. Also,cows may be able to sort the different ingredients and consume an unbalanced ration.

I have come to the conclusion that the partial TMR is the worst possible system. In thissystem, long stem hay (usually round bales) is offered free-choice and all the rest of theingredients are mixed together and fed. The cow is supposed to choose three poundsof hay throughout the day to balance her diet. For over 100 years, experiments haveshown that cows do not choose their diet to balance their requirements in a cafeteriastyle feeding system. Why would we expect her to eat only three pounds of hay everyday from the round bale?

Bunk ManagementThe first step in bunk management is to insure that adequate space is available. Aminimum of two feet per cow is desired. Besides minimum space, good cow flow isrequired. Do the first five cows block the alley way so the other cows have to wait for

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them to move? Does the water trough in the middle of the feed bunk cause a blockagewhen several cows want to drink? Is the last 15 feet of the feed bunk in the sun for partof the day? Is the feed bunk covered for shade? Are there fans and water for cooling?Both of these will entice cows to eat during our hot summers.

How much feed is in the feed bunk? For high producing cows and cows in the first halfof lactation, feed should always be available. It is recommended that 5% weighback beallowed everyday. This old feed should not be allowed to build up and become moldy.It can rapidly infect the fresh feed.

The other situation that causes problems is feeding the high herd ration to the latelactation group by limiting the amount of feed offered. In theory, the requirements of theindividual cows will be met if they consume the proper amount of feed. The problem isthat the more aggressive cows over-eat the ration and the less aggressive cows areshort of nutrients. If the cows are fed at 8:00 AM and the bunk is clean at 10:00 AM,either not enough feed is being fed or individual cows are not getting their proper shareof the ration.

Pattern of EatingIn general, dairy cows are meal eaters. They will consume a large amount of feed,drink water and ruminate. All cows typically want to eat a big meal after milking.Ideally, fresh feed should be available to the cow when she finishes milking. Cows willeat a large meal for 30 minutes, go to get a drink (fairy large), return to eat, drink again,return to eat, drink and then go to chew their cud for 2 to 4 hours. She will return to eatand drink again and resume rumination. Can your cows accomplish this easily? If thereare blocked feed alleys, too few waterers or a long distance to water, she may decidenot to eat again. The system should encourage the cow to return to the feed bunk.

WaterWater is the most essential nutrient, especially for milk production. A cow will consume4 to 5 pounds of water for every pound of milk produced. A 100 pound milk cow willdrink 60 gallons of water a day. Will your system fill the tank fast enough? Clean freshwater should be readily available at all times. Often times there are adequate watertanks available for the herd, but one cow standing at the water tank can block a dozencows who want a drink. Research has shown that cooler water is more appealing thanhotter water. Are waterers in the shade? Cows that have access to water 24 hours aday will drink more than cows that can only drink two or three times a day.

Balance RationMany problems occur when the system gets out of balance. Everyone wants to pushtheir cows. The easiest way to get a few more pounds of milk is by adding a fewpounds of grain. Get a good response from two pounds of additional grain andproducers will keep pushing the grain and problems occur.

One of the main lessons from the diversion program in the mid-1980's was that therewere several herds that tried to reduce milk production by reducing the amount of grainfed. Instead milk production increased because the ration was now balanced. Otherherds tried to reduce milk production by selling cows. Instead they had increased milk

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production because the cows left had more bunk access and got more feed. The entiresystem must be in balance.

It is critical to remember that a dairy cow is a ruminant who is designed to digest forage.Much effort in ration balancing is designed to maintain a minimum forage content in theration. The dairy cow needs not only forage but the forage needs to be of adequatephysical size. Dave Mertens has termed this effective fiber. This effective fiber causes(1) rumenmat formation to trap small particles for rumen digestion, (2) a physicalstimulus to the rumen wall to cause contractions (the strach factor) and (3) a largeamount of time spent by cowchewing her cud which produces salvia to balance rumenpH. Requirements have been set over the years to accomplish this. Minimum 17%crude fiber, minimum 22% Acid Detergent fiber, minimum 33% Neutral Detergent fiber,minimum 40% of ration dry matter from forage, 3/4 of ration NDF from forage are allattempts to provide minimum roughage to the dairy cow. The Penn State particle sizebox with two sizes of screens look at the distribution of particles and indicates the levelof effective fiber in the ration. The TMR should have 5-15% on the top screen and cornsilage should have 10-20% on the top screen. Testing the ration and weighback willindicate how much sorting the cows are doing. If the ration is at the minimum fiberlevel, then sorting could put the cow in an critical situation.

ManureThe consistency of the manure is an indicator of the balance of the ration. Firmermanure piles indicate adequate fiber in the ration. Excessive grain and acidosis canresult in diarrhea. Low manure pH indicates excessive acid from hindgut fermentationresulting from inadequate rumen fermentation. This may be a result of low effectivefiber, fineness of grind or excessive starch. The manure can also be screened todetermine the fiber size.

AdviceGet all the advice that you can. Get people to take a look at your farm, rations, cowsand records. Listen to what they have to say and evaluate their advice. Recognize thatyour advisors may have biases that will influence their decisions.

Risk ManagementAs one evaluates a farm more than likely several areas for improvement will behighlighted. Priorities need to be set for each of these areas. What is the risk forpotential losses? What is the cost of correcting the problem? What is the return for thechange? Cost-benefit ratios can be calculated and a plan can be developed to addressthe different areas.

ConclusionsAs you have reached this point, I hope you say AI know all of that.@ There is plenty ofknowledge available to us. The problem is the proper and timely application of thatinformation.

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References

Ely, L. O., D. W. Webb and M. J. Hoekema. 2001. Dairy Business Analysis Project:1999 Summary for Florida and Georgia Dairies. Bulletin 1205. University of GeorgiaCooperative Extension Service. October 2001.

Smith, J. W., A. M. Chapa, W. D. Gilson and L. O. Ely. 2001. Dairy GeneticsBenchmarks. Bulletin 1203, December 2001. University of Georgia CooperativeExtension Service.

Smith, J. W., A. M. Chapa, L. O. Ely and W. D. Gilson. 2001. Dairy Production andManagement Benchmarks, Bulletin 1193, Revised, December 2001. University ofGeorgia Cooperative Extension Service.

Smith, J. W., A. M. Chapa, W. D. Gilson, and L. O. Ely. 2001. Somatic Cell CountyBenchmarks, Bulletin 1194, Revised, December 2001. University of GeorgiaCooperative Extension Service.

Smith, J. W., W. D. Gilson and L. O. Ely. 2001. Dairy Reproduction Benchmarks,Bulletin 1204, December 2001. University of Georgia Cooperative Extension Service.

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Dairy Nutrition Management Conference Summary Points

Dr. Lon WhitlowExtension Dairy Nutrition

North Carolina State University, Raleigh

Milk production levels continue to increase yearly. It is my opinion that most of thisincrease is in response to improvements in genetic ability. As milk production increases,we learn more about the relationships of nutrition with production and health, and wehave been able to meet the nutritional needs of the genetically improved dairy cow. Astime goes on, nutritionists reevaluate the requirements of the higher producing cowsand make new recommendations. In 2001 the National Research Council published the"Seventh Revised Edition of the Nutrient Requirements of Dairy Cattle."

Nutrition of the dairy cow includes feeds and feeding management, and is not completewithout economic considerations. We must also be aware of the effects of nutrition onwaste management and the environment.

We are learning more about rumen function and the importance of transformations ofnutrients during rumen fermentation. We have learned more about protein andcarbohydrates, their interrelationship, about meeting the needs for rumen undegradableprotein and we are beginning to understand the requirements for individual amino acids.

The special aspects of fat feeding have been explored and current recommendationsare more accurate.

Recommendations have been fine tuned for minerals and vitamins. We have alsolearned more about the effective use of feed additives.

Important information about nutrition and waste management has been studied.Adjustments made in protein and phosphorus nutrition can greatly reduce nutrientexcretion to the environment without detrimental effects on the animal or milkproduction.

Nutritionists have made excellent improvements in understanding the special needs ofthe dry cow and the needs of the transition cow as she moves from the dry period tolactation. This knowledge is being used to help avoid metabolic and other healthdisorders.

There are certainly some gaps in our understanding of dairy cattle nutrition and feedingmanagement. In the past we have met the needs of the genetically superior cow, but wemust continue our search for new information to best meet the nutritional needs of thedairy herds of the future.

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North Carolina Dairy Nutrition Management Conference Agenda

February 20, 2002 (Wednesday)

Afternoon Program: - Steele RoomChair: Dr. Lon Whitlow, NC State University

4:15 p.m. Opening Comments, Dr. Lon Whitlow, North Carolina State University

4:30 p.m. An Overview of the 2001 NRC Dairy Cattle Requirements- Dr. Bill Weiss, The Ohio State University

5:15 p.m. Potential to Improve Rumen Function, Dr. Vivek Fellner, North Carolina State University

5:45 p.m. Attitude Adjustment Time, and View Exhibits

Evening Program: - Jackson and Overman RoomsChair: Dr. Brinton Hopkins, NC State University

6:30 p.m. Dinner

7:15 p.m. The Joys? of Managing Large Dairies - or Those Days I Just Pull Out My Hair- Mr. David Sumrall, Aurora Dairy Group, Bell, Florida

Time for Socializing

February 21, 2002 (Thursday) - Steele Room

7:30 a.m. Buffet Breakfast - Overman Room

Morning Program: - Steele RoomChair: Dr. Brinton Hopkins, NC State University

8:30 a.m. 100-Day Contract, Dr. James Spain, University of Missouri

9:15 a.m. Protein and Carbohydrate Utilization by Lactating Dairy Cows- Dr.Bill Weiss,The Ohio State University

10:00 a.m. Break for Refreshments and View Exhibits

10:30 a.m. Adding Fat to Cow Rations, Dr. Jon Goodson, Southern States Cooperative

11:00 a.m. Dairy Feed Additives, Dr. R. Randy Lyle, Purina Mills

11:30 a.m. Silage Management, Dr. Lon Whitlow, North Carolina State University

12:00 p.m. Buffet Lunch and View Exhibits - Jackson and Overman Rooms

Afternoon Program - Steele RoomChair: Dr. Lon Whitlow, NC State University

1:00 p.m. Utilizing Selected By-Product Feeds for Dairy Cattle, Dr. Brinton Hopkins, NCSU

1:30 p.m. Mineral Needs of Dairy Cattle, Dr. Jerry Spears, North Carolina State University

2:15 p.m. Vitamin Nutrition of Dairy Cattle: circa 2002, Dr. Will Seymour, Roche Vitamins, Inc.

3:00 p.m. Nutrition Management for Tomorrow’’s Dairy Herds, Dr. Lane Ely, University of Georgia

3:45 p.m. Conference Evaluation and Summary Comments - Dr. Lon Whitlow, NC State University

4:00 p.m. Conference Adjourns

Planning Committee:North Carolina State University Dairy Extension Specialists Dr. Lon Whitlow, Dr. Brinton Hopkins, and Dr. Don Pritchard

North Carolina Dairy Nutrition Management Conference ... conf... · 2 Conference Supporters and Exhibitors Primary financial support for the North Carolina Dairy Nutrition Management

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