Managing pastures - Department of Primary Industries...suggest practical ways of getting the best from your cows and pastures. The DairyLink series is a result of collaboration between

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D A I R Y L I N K — M A N A G I N G P A S T U R E S

ManagingPastures

Bill Fulkerson, NSW Agriculture, Wollongbar

Mike Blacklock, Australian Prodairy Ltd, Nowra

Neil Nelson, Neil Nelson Agvice Pty Ltd, Singleton

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The author appreciate the contribution made by Megan Reevesand Danny Donaghy, who provided much of the knowledge inthe area of grazing management through their studies for Ph.D.degrees. Thanks also to Ian Johnson, Heritage Seeds, Brisbane.

Acknowledgments

Edited, designed and desktop published by Matthew Stevens,ScienceScape Editing, Sydney, and Ann Munroe, Sydney

Line drawings by Matthew Stevens (except figure 23)

Series coordinator Alex Ashwood, NSW Agriculture,Wollongbar

© NSW Agriculture 1997

This publication is copyright. Except as permitted under theCopyright Act 1968 (Cth), no part of this publication may beproduced by any process, electronic or otherwise, without thespecific written permission of the copyright owner. Neithermay information be stored electronically in any form whateverwithout such permission.

NSW Agriculture does not accept any form of liability, be itcontractual, tortious or otherwise, for the contents of thispublication or for any consequences arising from its use or anyreliance placed upon it. The information, opinions and advicecontained in this publication are of a general nature only andmay not relate or be relevant to your particular circumstances.

Pesticides Act 1978

Under the Pesticides Act you must use only a registeredchemical. It must not be used for any purpose or in any waycontrary to the directions on the label unless a permit has beenobtained under the Act.

ISBN 0 7310 9816 1 (Dairylink monographic series)ISBN 0 7310 9818 8 (Managing Pastures)Agdex 410/51

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Foreword

Dairying is one of the most progressive rural industries in NSW.This is evidenced by substantial changes in herd sizes andincreases in production by cows and from farms.

An outcome of these increases is that management has becomemore complex, requiring greater knowledge and technical skills.

As farmers become more competitive through increases inboth production and productivity, they will require even bettertechnical information and management skills. Most important,they will need to know how to use the information in improvingwhole-farm performance and profits. This statement is supportedby results of various Dairy Research and DevelopmentCorporation workshops and NSW Dairy Farmers’ Associationsurveys, which have clearly indicated that farmers requiretechnical packages that are current and relevant.

DairyLink is a series of integrated information packages thatlook at aspects of pasture, herd and feed management, andsuggest practical ways of getting the best from your cows andpastures. The DairyLink series is a result of collaborationbetween NSW Agriculture officers, agribusiness and farmers.

The packages will be the basis of workshops and meetings forNSW dairy farmers.

DairyLink has much to offer the NSW dairy industry inhelping improve farm productivity and profitability. Weencourage farmers to attend and participate in the DairyLinkworkshops and meetings.

John Craven, ProgramManager, FarmProduction, DRDC

Kevin Sheridan,Director-General,NSW Agriculture

Reg Smith, President,NSW Dairy Farmers’Association

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Preface

DairyLink is an innovative concept that introduces you to someimportant technical areas to help improve farm productivity andprofits.

The modules in the series are of value to farmers, students,consultants and extension service providers.

DairyLink consists of the following information packages:

Establishing PasturesManaging PasturesGrowing HeifersRealistic RationsConserving Feed

The modules have been developed as technical manuals andfarmer-friendly booklets, and are linked to the Tocal Dairy HomeStudy course.

I would like to take this opportunity to acknowledge and thankthe various technical teams for doing an excellent job. I alsoappreciate the funding and support provided by DRDC.

Alex AshwoodDairyLink Series Coordinator

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Contents

Introduction 1

Pasture utilisation 2

Calculating pasture utilised 3

Limitations to pasture production 4Grazing management—ryegrass 4Regrowth of the ryegrass plant 6When to graze? 8How hard to graze? 8How long to graze? 9Managing ryegrass for persistence 10Rust in ryegrass and oats 11

Grazing management—white clover 12Ryegrass – white clover 12Kikuyu – white clover 12

Grazing management—kikuyu 14Kikuyu yellows 15

Grazing management—lucerne 16When to graze 16Lucerne in a mixed pasture 18Yield 18

What production per cow can we get from well managed pasture alone? 19Ryegrass and white clover 19Kikuyu 19

Which nutrients in pasture limit milk production? 20Protein to carbohydrate ratio 20Stage of regrowth 20Time of day 21Seasonal variation in nutrients 22

Efficient supplementation of cows on pasture 25

Setting up an effective grazing management system 27Feed planning 28

Allocating pasture and feed 29Step 1. Measure pasture on offer 29Step 2. Calculate pasture available per cow per day 30Step 3. Calculate DM supplements per cow per day 31

Budgeting and monitoring pasture 32

References 34Questions 34

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1


Introduction

The objective of this manual is to help dairy farmers understandthe principles behind good pasture management practice. Theemphasis is on grazing management.

Pasture should be managed to balance maximum pasturegrowth against maximum animal production. To do this, you needa good understanding of how pasture grows.

Under a pasture-based system of farming, the key toprofitability is high levels of utilisation of the pasture feed base,through the adoption of an effective grazing management system.The manual concentrates on the four most commonly grownpasture species: ryegrass, white clover, lucerne and kikuyu.

Bill Fulkerson

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Pasture utilisation

The main goal of good pasturemanagement practice is to achieve highquality pasture that is efficiently utilisedby stock over the long term. The keywords are therefore production of topquality, utilisation and persistence ofpasture. (In this setting utilisation is usedto mean the consumption of pasture bycows and its conversion into milk.)

In most grazing systems there is amassive amount of waste through foragedecay; small changes in grazing intensityor frequency can dramatically improvepasture productivity. The potential forimprovement varies with the region.

The cost of growing 1 ha of ryegrass–clover pasture is more than $500 a year (ifgrown under irrigation)—this is moneywasted if some of the pasture is notutilised.

On the average dairy farm, 5–6 t drymatter (DM) per hectare per year ofryegrass or white clover pastures isutilised, but under good management upto 16tDM can be utilised. However , onthe typical North Coast dairy farm, lessthan 3 t DM/ha/year is utilised (allpastures on the farm being considered;assuming 0.8 milkers/ha; each cowreceiving 0.75 t of concentrates andproducing 4400 L of milk per lactation).By contrast, on the South Coast, anaverage of 8–10tDM/ha/year is utilised.

Table 1 shows the potential productionachievable on commercial dairy farmswith present technology for the mostcommon pasture types. (Obviously one ofthe greatest limitations is irrigationavailability, particularly the further northyou are.)

Table 1. Potential pasture production achievable on commercial dairy farms.

Pasture type Yield(t DM/ha

/year)

Notes

Perennial ryegrass + white clover 15

Perennial ryegrass + nitrogen 16 At 200–250 kg N/ha/year

Annual ryegrass + nitrogen 14 On a kikuyu-based pasture but does notinclude the kikuyu

Kikuyu + white clover 18 If nematodes are not a problem

Kikuyu + nitrogen 9 Quality is the limiting factor

Lucerne 15

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Calculating pasture utilised

To be convinced of the benefits ofadopting better grazing management, youneed to be able to compare your presentlevel of utilisation with the potential.

Accurate determination of pastureutilised is very time-consuming, but anacceptable estimate can be made fromdata readily found on-farm. For thisestimate, assume 1kgDM gives 1L ofmilk. This estimate is based on the methoddeveloped in Victoria as part of the Target10 extension project(1).

Step 1: Convert feed brought ontoproperty during past 12 months into‘pasture DM’ equivalence:

t hay* × 0.77

t pasture silage (as fed) × 0.28

t maize silage (as fed) × 0.26

t grain or pellets × 1.1

Total brought-in feed (tDM)* or tropical grass pasture; 40 square bales pertonne or 4.5 round bales (1.2 m) per tonne

Step 2: Calculate milk production frompasture:

Your annual milk prodn (L) ÷ 1000

Brought-in feed (B from step 1)

Total feed consumed on farm (A – B)

Pasture utilised/ha (C ÷milking ha)

= t DM consumed per ha

This estimate tends to lose its accuracyif milk production per cow is much above6000L, as maintenance requirementsdecline relative to milk production.

You can now compare the value fortonnes DM utilised with previous years’production and with production on otherfarms. As a rough guide:

• < 2 t DM/ha consumed—read thismanual

• 2–5tDM/ha consumed—average

• 5–8tDM/ha consumed—excellent

• > 8 t DM/ha consumed—we’ll do acase study!

B:

A:

B:

C:

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Limitations to pasture production

Pasture growth sets the potential forpasture utilisation, which has been shownmany times to be related to profitability.This is because home-grown forage is stillthe cheapest source of feed. To increasepasture utilisation, you need to identifythe aspects of your management that limitproduction.

The various components of pasturemanagement that can limit the potential ofpasture growth and influence utilisationare shown in Figure 1.

For example, a comprehensiveirrigation system is useless if growth is

restricted by poor fertility. Declining soilfertility, caused by removal of nutrients bya high yielding pasture, can suppressyield.

This manual concentrates on grazingmanagement, and discusses other aspectsof management, such as supplementationof stock and pests and diseases ofpastures, which affect or are affected bygrazing management. See the otherDairyLink manuals on EstablishingPastures and Conserving Fodder fordiscussion of these topics.

Grazing management—ryegrass

The ryegrass plant is actually a series ofindependent tillers clumped together. Inthe vegetative state (Figure 2), each tillerregrows after grazing until about 3 livegreen leaves have expanded. This numberof leaves is then maintained by theemergence of new leaves matching thedeath of the oldest leaves.

The growing point of the vegetativetiller is near the soil surface; therefore it ishard to kill a ryegrass plant by hardgrazing. In contrast, in its reproductivestate (Figure 3), the tiller’s growing point

moves up the stem as the uppermost node.If the tiller is cut below this point, it willdie.

The cue to begin reproductive growthis increasing daylength in spring, but aperiod of chilling is required before seedcan set. This poses a problem forperennial ryegrass varieties (except theKangaroo Valley types) on the NSWNorth Coast, as chilling is inadequate, andfewer than 10% of tillers produce a seedhead. In contrast, 100% of annual ryegrasstillers set seed.

Figure 1. Pasture management practices that influence growth potential andutilisation of pasture.

Management practice

Increasingly sets pasture growth potential

Increasingly sets pasture utilisation

Soil fertility

Pest and disease control

Pasture species

Drainage

Grazing management

Fodder conservation

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The poor seed set, and the fact that thefew seeds that do set have little chance ofsurviving the harsh subtropical summer,means that swards need to be thickened upby oversowing. The continual decline inplant population from establishment isshown in Figure 4.

On the other hand, the lack of seed set

reduces the need to ‘top’ perennialryegrass pastures in spring to keep themleafy, as is common in temperate regions.Topping by slashing or grazing annualryegrass hard after stem elongationbegins, however, is still useful to let lightin to the pasture to encourage newvegetative tillers.

Figure 4. Ryegrass plant density declines from sowing in April–May to the autumn ofthe second year.

Figure 2. The vegetative ryegrass tiller.

leaf 1

leaf 2

leaf 3

leaf 4growingpoint

Figure 3. The reproductive ryegrasstiller.

leaf 5

seed head

leaf 1leaf 2

leaf 3

leaf 4

growingpointatnode

April July September November May

300

200

100

0

ryegrass sown at 20 kg/ha

ryegrass sown at 8 kg/haRye

gras

s pl

ants

per

m2

(sowing)

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Regrowth of the ryegrassplant

The drawings in Figure 5 show theregrowth of a tiller from grazing until 4leaves have expanded.

In well grazed pasture, where most leafis removed, the ryegrass tiller relies oncarbohydrate reserves to initiate growthbefore the plant has sufficient leaf area tophotosynthesise again and produce morecarbohydrates. The changes in plantcarbohydrate reserves during regrowth areshown in Figure 6.

The time taken for 1 leaf to expand isknown as the leaf appearance interval.This is determined primarily bytemperature. For example, leaf appearance

Figure 5a. In well grazed pasture, mostryegrass leaves are removed and only thestubble remains. The roots stop growingafter grazing.

roots stop growing

carbohydratesin stubble

grazingheight

carbohydrates

Figure 5c. When the ryegrass tiller hasregrown about 3⁄

4 of a new leaf, it starts

to replenish its carbohydrate reserves,which were used up to expand the newleaf. The plant is most vulnerable tograzing at this stage because of the lowreserves. The roots begin to regrow.

Figure 5d. When the tiller has regrown 2new leaves, the carbohydrate reserves areadequately replenished, and the plantcan again cope with grazing. Thus, thetime it takes the plant to regrow 2 leavesis the minimum interval betweengrazings.

carbohydrates

interval of ryegrass is 20+ days in colderinland regions of NSW in winter, 12–14days on the North Coast in winter, and asshort as 6 days on the North Coast inspring.

Figure 5b. The remnant of the youngestleaf expanding before grazing mustextend quickly in order to catch thesunlight to produce its owncarbohydrates, otherwise the tiller willdie. It relies at first on carbohydratereserves in the stubble.

first newleaf

roots begin growing again

carbohydrates

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0 3 6 9 12 15 18 21 24 27

30

20

10

0

% d

ry m

atte

r

Days of regrowth

1 le

af

2 le

aves

3 le

aves

solublecarbohydrates %

starch %

graz

ed

Figure 6. Soluble carbohydrates and starch in leaves decrease from grazing untilregrowth of 1 leaf per tiller, and then increase to 3 leaves per tiller.

oldestleaf

carbohydrates

Figure 5e. At 3 leaves per tiller,carbohydrate reserves have increasedfurther. Net growth is probably at amaximum.

Figure 5f. After 3 leaves per tiller haveexpanded, the oldest leaf starts to die as anew leaf appears. A total of 3 greenleaves is thus usually present at any time.As a consequence, pasture quality beginsto decline beyond this stage and pastureis wasted. The 3–31⁄

2-leaf stage is gener-

ally the maximum grazing interval.

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When to graze?

It is always best to use leaf appearanceintervals to decide when to graze.

The best time for regrazing is from theminimum grazing interval (2 leaves) tothe maximum grazing interval (31⁄

2

leaves). This stage often coincides withthe attainment of the 2400kgDM ofregrowth per hectare recommended byTarget 10(1). This amount is generally themaximum that stock can graze withoutunacceptable wastage.

Table 2 shows that cutting ryegrass atthe 3-leaf stage gives a higher total yieldthan cutting it at a set interval of 2 or 4weeks throughout the year. It also resultsin more tillers per plant, more roots perplant, greater plant survival duringsummer, and less invasion by summergrasses and weeds.

Pasture height is a better indicator ofwhen to graze than set time intervals, butit is influenced by soil fertility and airtemperature, and hence is not solelyrelated to the plant’s development.

In late autumn, the oldest leaf begins todie when the newest leaf is only about halfgrown, at the 21⁄

2-leaf stage, because new

growth slows down. Therefore, exercisecaution if you are going to delay grazing

* The bigger % increases in year 2 are because ofgreater increases in summer grasses and weeds inthe more frequently cut pastures.

Yieldkg DM/ha (% increase)*

Harvestinginterval

Year 1 Year 2

2 weeks 9 260 3 0844 weeks 10 927.(+18%) 4 384.(+41%)3-leaf stage 12 223.(+32%) 4 904.(+59%)

Table 2. Cutting ryegrass at the 3-leafstage of regrowth gives a higher totalyield than cutting it at regular intervalsof 2 or 4 weeks.

to save pasture for winter: if you wait untilthe 31⁄

2-leaf stage you will waste pasture

and it will be unpalatable.In late spring, as ryegrass turns

reproductive, up to 6 live green leaves canbe supported. This allows more bulk to bebuilt up for hay or silage. However, thisstill promotes reproductive growth and adecline in pasture quality. If this bulk issubsequently grazed, there will be greaterwastage as cows will trample it or simplynot eat it.

If moisture stress becomes severe, newgrowth slows, leaf appearance intervalincreases, and death of older leaves beginsbefore the 3-leaf stage. This is a survivalmechanism designed to reduce the numberof leaves exposed to evaporation.Therefore in this case grazing shouldbegin earlier.

If shading of pasture limits growth (forexample, plants lodge), also graze earlier.This could happen at the second or thirdgrazing after establishment of short-termryegrass, such as Concord, sown at highrates or fertilised with high rates of N.

If ryegrass becomes infected with leafrust, you must graze more frequently orslash to remove badly infected leaves.

Grazing at the 3–31⁄2-leaf stage has

been shown to improve persistence ofryegrass. The plant appears to build upcarbohydrate reserves to allow it to copebetter with summer stress(2). Most nutri-ents in pasture are also at the optimum forstock at this stage (see ‘Which nutrients inpasture limit milk production?’, later).

How hard to graze?

The harder you graze, the higher theutilisation at any one grazing. However, ifpasture is grazed too hard (below 5cmstubble height), production per cowdeclines; and as more stubble is grazed,more of the plants’ reserves are removed

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and less leaf remains to photosynthesise,and so regrowth declines. On the otherhand, although leaving a few leavesspeeds regrowth, it does not outweigh theconsequent reduced utilisation, as theseolder leaves are photosyntheticallyinefficient.

Achieving a desirable residue of 5cmoften conflicts with achieving a highproduction per cow. Figure 7 shows thatresidues increase as pasture on offerincreases in an attempt by the dairy farmerto increase intake. Management practicescan reduce this conflict:

• Train cows. Giving cows daily breaksor strips of adequate amounts ofpasture trains them to graze harder at agiven level of DM. The effect can bedramatic. Cows should be trained fromcalves to graze behind wires, as cowstransferred from a herd grazing laxly toa herd under controlled grazing cantake up to 3 months to adjust and maylose several condition scores.

• Providing new pasture at each milkingis a common way of improving intakeand reducing selection of pasture bycows. Some producers have taken thisa step further and give a new strip ofpasture 4–6 times a day to enticefurther increases in pasture intake.

• Sometimes pasture is cut beforegrazing and left to wilt 12–24 hours.After 4–5 days of adaptation, cows

increase their intake, perhaps as aresult of reduced water intake or thereduced energy required to graze. Thispractice is most common when the aimis to control bloat. The energy cost andtime spent mowing should beconsidered.

• With a leader–follower system you canget high production per cow as well ashigh rates of pasture utilisation: theleaders (milkers) take the lower fibre,higher protein tops, and the followers(dry stock) take the higher fibre, lowerprotein stubble.

Although following milkers with drycows has proved valuable, followinghigher with lower producing cows has notbeen shown to increase total milkproduced.

How long to graze?

After grazing, carbohydrate reserves in thestubble are moved to the youngestexpanding leaf remaining. If thisexpanding leaf is regrazed there will belittle carbohydrate reserve left to initiateregrowth. Figure 8 shows a dramatic fallin DM yield after a full regrowth cycleand an increase in plant death when plants

1.6

1.2

0.8

00 0.8 1.2 1.6 2.0 2.4 2.8 3.2

Pasture on offer (t DM/ha)

Pas

ture

res

idue

(t D

M/h

a)

Figure 7. As pasture on offer increases,pasture residues also increase. (Cowsgrazing ryegrass – white clover pasturesat Wollongbar.)

Figure 8. Glasshouse studies atWollongbar showed a dramatic effect ofreduction in regrowth by ryegrass plantsrecut at 3, 6, or 3 and 6 days afterharvest(3). More plants died too.

6

5

4

3

2

1

00 3 6 3 + 6

Recut (days after initial cut)

Reg

row

th (

g D

M/p

lant

)

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were recut at 3, 6, or 3 and 6 days afterinitial harvest. Studies in Tasmania(4)

showed a 40% decline in DM regrowth ofpastures grazed continuously for 6 dayscompared with pastures grazed for 1 or 3days.

The greater the pasture growth rate, theshorter should be the duration of grazing(and the grazing interval). Generally, ifregrown shoots are long enough to beregrazed by cows—say 8cm—duration istoo long. Use a back fence to keep thecows off the regrowth.

Similarly, if followers are used or thearea is mulched or slashed, it must bedone within 3 days of the start of the firstgrazing or it will do more harm than good.

Managing ryegrass forpersistence

Perennial ryegrass pastures are not verypersistent on the east coast of NSW, buttheir rate of survival can be improved byappropriate management. The key topersistence is to maximise survival ofryegrass plants through the first summer,thus providing the least bare space forinvasion by summer grasses (kikuyu,paspalum, couch and weeds).Management must focus on this goal.

Fortunately, grazing managementpractices that maximise forage quality andutilisation by stock also maximise persist-ence of pasture (see above), althoughother factors also affect it, including fert-iliser and grazing in spring and summer.

Fertiliser requirements

Fertiliser requirements should be based onsoil tests and the DM yields expected. Forexample, common soil test targets forhighly productive dairy farms are

>100ppm phosphorus (Colwell test)(perhaps lower on sands and loams) and>0.4meq of potassium per 100g of soil.Consult your local agronomist for localinformation.

A major cause of deterioration ofperennial ryegrass pastures is often soilnutrient drain. Ryegrass contains about3% potassium and 0.35% phosphorus. Tominimise soil nutrient drain:

• grazing management must ensure thatmost dung and urine is returned topasture—no night paddocks; use shortgrazing breaks (no cattle camps, etc.);reduce time on the laneway, yards anddairy

• nutrients lost in milk, calves sold,laneways and yards, and leached fromor bound to soil must be replaced

• replacement rates of 400–600kg/ha/year of a 2:1 mix of superphosphateand muriate of potash must beconsidered.

Grazing in spring

Infrequent grazing in winter–spring allowsthe ryegrass plant to build up carbohydratereserves to cope with the stress ofsummer. In trials at Casino(2), plantsgrazed in spring at the 3-leaf stage ofregrowth had nearly twice as muchsoluble carbohydrates in early summer asplants grazed at the 1-leaf stage ofregrowth. The carbohydrate levels alsodeclined less after grazing; this left 3times more carbohydrate per plant inFebruary. The more frequently grazedplants also had a smaller root mass, whichallowed 6 times as many plants to be lostthrough sod-pulling.

Any practice that reduces carbohydrateconcentrations in plants seems to reducethe plants’ persistence. This includesgrazing for too long and grazing too hard.

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Grazing in summer

Trial results and farmer experienceindicate that perennial ryegrass must begrazed hard but infrequently (every 4–6weeks) in summer. A follow-up mulchingor slashing is vital if there are any summergrass weeds present, or the less palatableweeds will smother the ryegrass.

The worst practice is continuousgrazing. This punishes the more palatableryegrass and gives the weeds an evengreater advantage.

Rust in ryegrass and oats

Rust is a fungal disease commonly foundon ryegrass and oats under humidconditions. The problem is greatest in latespring in the more subtropical dairy

regions of Australia. Lack of moisture andnutrients (particularly N) predisposesplants to it. A typical symptom is yellowblotches on the leaves. The growth ofinfected plants can be severely reduced.Utilisation by cattle is also affectedbecause of reduced palatability.

There is no commercially viablechemical control of rust. Fortunately, plantbreeders are continually breeding for rustresistance in grasses. Appropriatemanagement specifies removal of theinfected leaves by grazing or cutting andremoval of the moisture or nutrient stressif possible. Apart from minimising plantstress, it may be necessary to grazeinfected pastures earlier than normal, asthe denser the canopy, the more severe theeffect of the rust will be.

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Grazing management—white clover

If white clover is the sole pasture species,the general recommendation is to graze ithard and infrequently. Graze when theoldest, lowest leaves in the canopy arestarting to turn yellow. This could varyfrom 50 days in winter to 18 days inspring.

White clover ‘breaks up’ in summer.That is, the stolons (see Figure 9) breakbetween the nodes and form new plants,which initiate roots from the nodes. Theroots of these plantlets are much shallowerthan the taproot of the parent plant, andthis makes the plants vulnerable to stressat this time and probably into the secondyear(2). We are still not certain of the bestway to graze white clover in summer toimprove its survival.

Ryegrass – white clover

White clover is more sensitive to lowtemperatures than ryegrass. As a result,growth in winter is slower, and thus plantsare easily shaded by the more rapidlygrowing ryegrass. With its wide leaves,annual ryegrass is particularly quick to

shade clover. Sow annual ryegrass at lessthan 10kg/ha to retain a worthwhileclover component in the pasture.

Within limits, the grazing intervalsmost appropriate for ryegrass also suitlarge-leafed white clover varieties such asHaifa, Osceolo and El Lucero.

Kikuyu – white clover

The incorporation of white clover into akikuyu pasture in autumn by judiciousmanagement can be very productive. Thepasture is more sustainable than ryegrass,there is less need for N fertiliser, and thepasture quality is excellent. Yields of morethan 15tDM/ha/year (9 of white cloverand 7 of kikuyu) can be achieved.However, the clover does not persist afterthe third year; the problem appears to be asevere build-up of root-knot nematodes.The system is not recommended until wecan either select resistant varieties (not yetcommercially available), or find amanagement practice that minimises theeffect of nematodes. It should be triedonly if adequate irrigation is available.

13


Figure 9. The growing point of the white clover plant is at its tip. The oldest leaves,furthest from the growing point, die if they are not grazed. The plant relies oncarbohydrate reserves in its stolons to recover after grazing.

flower

taproot

node

node

leaves

growingpoint

petiole

nodal rootsoldestleavesdying

stolon

nodal roots

nodal roots

14


Grazing management—kikuyu

Management of kikuyu pastures shouldaim at getting the best forage quality andutilisation. To achieve this, as much leafas possible should be presented to stock.This is because the leaf has much moreprotein and metabolisable energy (ME)than the stem. Unlike ryegrass, whichdevelops a true stem only when it isreproductive, kikuyu has a stem in itsvegetative state. Kikuyu is also lessdigestible than temperate grasses at thesame stage of development.

Recent studies have led to thedevelopment of a system of managementthat achieves this aim:

1. After grazing, preferably mulch orslash back to 5cm of stubble ifmoisture status is adequate (less than6 days since rain of at least 18mm)and if residues exceed about 15cm.Followers (dry or young stock) canalso be used to reduce stubble if this isfeasible. This operation removes thelow quality kikuyu and allows light into stimulate new growth. It is normallyrestricted to once in early summer totop weeds, perhaps 2 or 3 times at thepeak of the season, and then once inlater summer if the kikuyu is to beoversown with ryegrass or clover.

2. Apply N fertiliser after each grazing. Arate of 100kg of urea or 120kg ofammonium nitrate (nitram) per hectare(if rainfall or irrigation is not assured)seems ideal for productive and qualitygrowth. Higher rates tend to cause abuild-up of nitrates in kikuyu. Thisbuild-up could reduce digestibility inthe rumen or, in extreme cases, causenitrate poisoning. Higher rates of Nalso lead to lower efficiency ofutilisation, resulting in higher costs perunit of growth and potential loss of N

to the environment.

3. Graze at the appropriate interval.Studies at Wollongbar have shown thatbest quality coincides with the 41⁄

2 new

leaves per tiller stage of regrowth.After this the proportion of stem beginsto increase and the number of deadleaves also increases markedly,resulting in a marked decline in quality(Figure 10). The mineral levels alsochange to be more in line with dairycows’ requirements. The time taken toreach 41⁄

2 leaves depends on

temperature, from as short as 12 daysin mid summer to 35 days in autumn.The use of leaf number as an indicatorof when to graze is relevant only inwell-grazed or mulched pasture.

4. Provide a new strip of kikuyu pastureafter each milking—this reducesselection and contamination of pastureby stock.

0 5 10 15 20 25 30 35 40Days of regrowth

% o

f DM

abo

ve 5

cm

100

90

80

70

60

50

40

30

20

10

0

protein dead

stem

4.5

leav

es

leaf

Figure 10. At the 41⁄2-leaf stage ofregrowth, kikuyu protein content is stillhigh. After this stage, the proportion ofstem and dead leaves increases markedly.

15


Kikuyu yellows (Verru-

calvus flavofaciens)

Kikuyu yellows is a fungal diseasespecific to kikuyu. It causes great concernto farmers north of Taree who rely onkikuyu for a major part of their pasturefeed. The fungus spreads by waterbornespores, which is why infestations movefrom laneways and gateways and downgullies through movement of surfacewater or on cows’ hooves.

Typical symptoms are circular patchesof yellowing kikuyu swards. In advancedcases, weeds invade the centre of thecircle as the kikuyu is progressivelydestroyed.

The yellowing, as such, is as much theresult of stress caused by weakened rootslacking moisture and fertility. In fact,infected plants are reasonably productiveunder irrigation and high fertility.

At present there are no fungicidesavailable to control kikuyu yellows, butwork at Wollongbar is looking at using the

antifungal agents in brassica species forcontrol.

The fungus becomes inactive whenminimum temperatures fall below 15°C.Benefit can be gained from applying Nand other fertilisers once minimum dailyautumn temperatures fall below 15°C sothat the kikuyu plant can be repairedbefore next spring.

Spray small patches of kikuyu yellowswith glyphosate to 50cm into the healthykikuyu to starve the fungus and stopfurther spread—cows’ hooves can spreadit far and wide. These patches can be sownto ryegrass or rhodes grass until they arere-covered with healthy kikuyu. If entirepaddocks are affected, a spell of 1–2 yearswithout kikuyu may be sufficient toremove infection potential.

The kikuyu variety Noonan is slightlytolerant to yellows, but in view of itslower production (about 25% lower thanWhittet), it is not commonly used.Breeders are currently selecting cultivarsof kikuyu resistant to yellows.

16


Grazing management—lucerne

Lucerne is a perennial legume capable ofproducing feed throughout the year, but itsmain production period is from spring toautumn. It is a high-quality feed with norequirement for nitrogen fertiliser.Varieties fall into 4 growth types: highlywinter-active, winter-active, semi-winter-dormant and winter-dormant (Figure 11shows 2 of these).

Lucerne’s biggest asset is its welldeveloped taproot, which can extend towell over a metre in well drained, fertilesoils. The taproot enables the plant toreach nutrients and soil moisture muchdeeper than most other pasture plants canreach, giving it a well deserved record ofdrought resistance.

Carbohydrate reserves are held in themain taproot. Lucerne is often quicker torecover after cutting or grazing thangrasses because its taproot has moreenergy for regrowth and does not die aftergrazing or cutting, unlike many grassroots.

After the plant is grazed or cut, freshshoots grow from either the remaininggreen stems or, most commonly, buds inthe crown. The crown is the part of thetaproot at or just above ground level.Heavy grazing can damage the new buds,but in most varieties these are rapidlyreplaced. Lucerne can live for 10 years ormore, although the life of an averageirrigated stand is closer to 4–5 years. Aslucerne paddocks age, grazing damage,weed invasion, disease and insects taketheir toll, and the stand thins out.

Table 3 shows optimum plant densitiesfor lucerne. Lucerne stands with lowerplant densities than those will havereduced yield and will tend to be invadedby weeds; this will result in lower-qualityfeed. Direct drilling of other pasturespecies (for example, ryegrass and clover)

Figure 11. Highly winter-active lucerneyields more in summer, autumn andwinter than semi-dormant lucerne, butyields less in spring.

summer autumn winter spring

Dry

mat

ter

yiel

d (k

g/ha

)

3000

2000

1000

0

highly winter-active

semi-dormant

into thinning lucerne stands can helpmaintain the productivity and quality offeed in the paddock.

When to graze

The optimum grazing interval depends onthe growing conditions in your area.

To promote good productivity andpersistence of lucerne, root reserves haveto be allowed to build up. Lucerne is welladapted to cutting or grazing, provided anadequate recovery period is given to allowessential root reserves to be replenished.Without these reserves, rapid regrowthafter grazing is not possible, and survival,

Table 3. Optimum plant density inlucerne stands for maximum yield.

Age of stand Optimum plant density/m2

Seeding year >1801 year 1002 years 70

3 years and after 50

17


particularly through stress periods, isthreatened. Frequent removal of newshoots from lucerne plants depletes theessential carbohydrate reserves. Figure 12shows the changes in carbohydrate rootreserves in lucerne from harvest to fullseed set.

By the time full flowering is reached,the stem is thick and the plant has alreadybegun to drop leaves; this reduces bothquality and yield. The maximum yield ofdigestible nutrients is obtained before fullflowering (Figure 13). Cutting or grazing

Figure 12. When growth begins, rootreserves are mobilised and are used bynew shoot growth for about 15 days afterdefoliation. This process continuesbeyond the time when new leaves beginsending reserves back to the roots (about5 days after defoliation). Root reservesreach a minimum at about 3 weeks afterharvest and reach maximum at fullflowering.

40

30

20

10

0stage of growth

% c

arbo

hydr

ates

in r

oots

growthinitiated

20–25 cmtall

bud

fullbloom

matureseed

Figure 13. Digestibility of lucernedecreases as the plant matures.

80

75

70

65

60

% d

iges

tibili

ty too latefor goodquality orregrowth

max.yield ofdigestiblenutrients

fullbloom

10%bloombud

vegetative0

management is often based on the 10%flowering stage, which is considered aneasily identifiable growth stage; this givesthe best compromise for achieving highyields, adequate quality and persistence.

New varieties, including winter-activeand highly winter-active lucerne, regrowfaster after cutting and reach harvestmaturity earlier than the more dormanttypes.

During winter in warmer climates, themore winter-active lucerne types cancontinue growth with very little or noflowering. Studies by K. Lowe at the DPIin Queensland showed that in spray-irrigated lucerne stands, the fixed cuttingintervals shown in Table 4 achieved highyields, good quality and adequate rootreserves. The same studies showed thatcutting intervals were more important thancultivar type in determining yield. Grazingor cutting intervals more frequent thanthese substantially depleted root reserves.

Season Variety types

Winter-dormant Semi-dormant Winter-active Highly winter-active

Summer 5 4 4 4Winter 8 8 7 7

Table 4. Fixed cutting intervals (in weeks) for lucerne types in spray-irrigated standsin Queensland to achieve the optimum balance of yield, quality and root reserves.

18


Longer intervals reduced forage andnutrient yield.

Root reserves are lowest in latesummer. This reduces autumn – earlywinter production. Delaying cutting orgrazing in late autumn allows lucerne toflower, which helps prevent run-down ofroot reserves.

Trampling and grazing damage crownshoots and allow disease entry. Thereforeyou should cut lucerne for hay or silage(not graze it) for as long as possible(particularly in the first 12 months) tomaintain the plant population. Strip-grazing with back-fencing is necessary toprevent excessive crown damage. Thenarrower crowns and higher basal buds ofthe more winter-active lucerne varietiespredispose them to greater crown damage.

Lucerne is more susceptible to puggingand trampling in wet weather than manyother pastures. Grazing lucerne paddocksshould be the last option in wetconditions.

Pest and disease incidence willinfluence grazing management. Earlygrazing can be justified to control bothaphids and leaf diseases.

Cows grazing lucerne are susceptibleto bloat. Lucerne can contain highamounts of plant oestrogens (which cancause animal reproductive disorders) if

leaves are stressed by disease or insectdamage.

Lucerne in a mixedpasture

Lucerne is sown mostly as a sole species,because of its use as a specialist hay cropand its specific grazing or cutting regimes,which do not suit other companionspecies. There are 2 alternatives: to favourthe lucerne with long grazing intervals,which allows the companion species togrow past its best; or to graze the lucernetoo frequently, causing a progressive run-down of root reserves and reducing itspersistence. When lucerne stands ofdeclining vigour are oversown withryegrass, grazing management should aimto maximise utilisation and persistence ofthe ryegrass at the expense of the lucerne.

Yield

The maximum potential yield of wellmanaged lucerne stands has beenestimated at more than 25tDM/ha.Commercial yields are generally 12–18tDM/ha from 5–7 grazings betweenearly October and late April.

19


What production per cow can we getfrom well managed pasture alone?

There is a remarkable divergence ofopinion on how good pasture is for milkproduction—some people believe it is theperfect food, others believe onlyconcentrates will give high production percow. Both are probably right!

Ryegrass and whiteclover

Good ryegrass pasture should produce 20–22L of milk per cow per day. Thisassumes normal genetic merit and no live-weight change of stock and an acceptablelevel of pasture utilisation. Another 4–5La day from body reserve loss brings totalpeak production to 26–28L a day (5500–6000L per cow per lactation).

Although most herds have a few cowsproducing 30–35L of milk a day onpasture, these cows ‘strip’ 11–12L ofmilk a day off their back. Such cows canlose 2 condition scores in 6 weeks. Thesecows end up in poor condition at matingand can therefore be difficult to get backinto calf.

Production of up to 28L a day can alsobe achieved with energy-basedconcentrates, which are also fed toimprove the protein to carbohydrate ratioof the total ration (see ‘Which nutrients inpasture limit milk production?’, below,and the DairyLink manual RealisticRations). For example, on well manageddairy farms in Tasmania, an average of20L of milk a day over the wholelactation is produced from pasture andpasture silage. In Western Australia, topherds produce 28–30L per cow per day,of which 18–20L is estimated to come

from pasture and the rest fromapproximately 5kg of concentrates a day .Above this level of production thesituation becomes more complex and thenutrient composition becomes critical.Higher production can be obtained frompure swards of clover, but work atEllinbank in Victoria(5) has shown that thissystem is not stable.

Kikuyu

Even when best management practice hasachieved the best quality pasture possible,kikuyu is still of lower quality thanryegrass. Daily yields of 15L of milk percow (without bidyweight change) havebeen achieved with supplements ofsodium (as salt), phosphorus and calcium.Although calcium levels seem reasonable,a high proportion may be bound to achemical called oxalate and is notavailable. In addition, the level of sugars,a readily available energy source, is verylow in kikuyu.

With well managed kikuyu as the feedbase, delivering about 15Lof milk percow per day, there is a useful role forenergy supplements—barley fed at 3kgper cow per day lifts production to about19L/day .

Higher milk production requires aprotein supplement in addition to theenergy concentrate. A trial at Wollongbarused canola meal that had been treatedwith formaldehyde to protect it fromdegradation in the rumen. Production of21.5L/day was achieved by feeding4.8kg barley and 1.2kg of treated canolameal. This supplement produced the larg-est response in milk produced per kg fed.

20


Which nutrients in pasture limitmilk production?

Some dairy farmers want more productionper cow than pasture alone can provideand must therefore supplement. The firststep in deciding how much and what is todetermine which nutrients in pasture limitmilk production.

In all pasture species, phosphorus andmagnesium are marginal and potassium istoo high. In kikuyu, sodium and availablecalcium are also too low.

The nutrient levels in pastures dependon the pasture species, stage of growth,season and even time of day. The nutrientlevel desired depends on the level of milkproduction.

The commonly used nutrients and theirabbreviations are listed here:

• ME (metabolisable energy) is theenergy available to the animal forgrowth and production.

• ADF (acid detergent fibre) consists ofcellulose, insoluble ash, indigestibleprotein and lignin. It is a goodindicator of digestibility. Fibre is aprecursor for milk fat synthesis and isimportant for rumen motility.

• NDF (neutral detergent fibre) is ADF +hemicellulose and is the plant cell wall.

• CP (crude protein) is estimated as totalnitrogen % × 6.25.

• NPN (non-protein nitrogen) is the Nlevel after the N in true protein hasbeen subtracted.

• WSC (water-soluble carbohydrate) isthe plant sugars. It is immediately solu-ble in the rumen and is readily avail-able to rumen microflora as energy.

• Ca (calcium), Cu (copper), Zn (zinc),Mg (magnesium), K (potassium), P(phosphorus), Na (sodium), Fe (iron)and Mn (manganese).

Protein to carbohydrateratio

One major limitation to production percow is believed to be the high protein tocarbohydrate ratio of most pastures. As ageneral rule, protein levels are too high,and energy levels, as readily fermentablecarbohydrates, are too low for optimumdigestion of feed by the microorganismsin the rumen.

If the protein to carbohydrate ratiois too high, the excess protein isconverted to ammonium in the rumen, andthe ammonium is detoxified to urea,which is secreted into the milk and urine.The excess protein is not only wasted, itcosts energy to detoxify and excrete asurea. Cows often lose weight as they try tobalance the high protein intake withenergy from body reserves. Surprisingly,farmers still feed high protein pellets tocows on lush green pasture.

If the protein to carbohydrate ratiois too low (too much carbohydrate), forexample from feeding silage low inprotein (such as maize), protein deficiencylimits growth of the rumenmicroorganisms, and carbohydrate iswasted. As a consequence, nutrients go tolive weight rather than to milk.

Stage of regrowth

In spring, at the 3–31⁄2-leaf stage of

regrowth, ryegrass has a protein tocarbohydrate ratio (Figure 14) of 1.8:1.This is much better than the 4:1 ratio atthe 1-leaf stage of regrowth. The changesin the ratio are even more dramatic in

21


winter, going from 3:1 at the 1-leaf stageto 1:1.7 at the 3-leaf stage. This is becauseloss of carbohydrates is low during thecool nights, but clear skies during the dayensure ample accumulation. In spring, thecarbohydrate levels are lower because thehigher night temperatures allow higherrespiration. In both ryegrass and kikuyu,magnesium and calcium levels increaseand potassium levels decreases as theplant regrows (Figures 15 and 16). This iswhy older grass is better for stock thanyounger grass. The phosphorus levels,however, decrease.

Time of day

In the plant, the immediate product ofphotosynthesis is sugar, a ready source ofenergy for plants (and animals). As aconsequence, the carbohydrate content ofthe plant increases during the day (in the

0.6

0.5

0.4

0.3

0.2

0.1

00 10 20 30 40

Days after defoliation

% o

f dr

y m

atte

r

3.0

3.5

2.0

2.5

1.0

4.5-

leaf

sta

ge

potassium

calciumphosphorus

magnesium

0.6

0.5

0.4

0.3

0.2

0.1

0

4.0

3.5

3.0

2.5

2.0

0 10 20 30 40 50

% o

f dry

mat

ter


potassium

calcium

magnesium

phosphorus

3-le

af s

tage

Figure 14. Levels of carbohydratesincrease and levels of protein decreaseduring regrowth in spring (a) and, moredramatically, in winter (b).

30

25

20

15

10

5

0

30

25

20

15

10

5

0

% o

f dry

mat

ter


a. spring

b. winter

protein

soluble carbohydrate

protein

soluble carbohydrate

% o

f dry

mat

ter

0 10 20 30 40 50

0 5 10 15 20 25

1-le

af

2-le

af

3-le

af

Figures 15 (left) and 16 (right). Calcium and magnesium levels increase andpotassium and phosphorus levels decrease in ryegrass–clover pasture (left) andkikuyu pasture (right) during regrowth.

22


Figure 17. Changes in solublecarbohydrate from 6 a.m. to 6 p.m. forannual ryegrass, perennial ryegrass andkikuyu. The actual levels in ryegrass arefrom samples taken in early autumn andhence are low.

Figure 18. Seasonal variation innutrients in annual ryegrass pasture. Thedotted lines are the minimum requiredfor cows producing 20L of milk a day.

4 6 8 10 12 14 16 18 20Time of day (24 h clock)

% w

ater

-sol

uble

car

bohy

drat

es

kikuyu

annualryegrass

perennialryegrass

121110

9876543210

ME

protein

carbohydrate

NDF

ADF

calcium

phosphorus

protein

M J J A S O N D

M J J A S O N D

% o

f dry

mat

ter

% o

f dry

mat

ter

% o

f dry

mat

ter

MJ/

kg D

M 12

11

10

3025201510

5

50

40

30

20

1.0

0.8

0.6

0.4

0.2

0

month

The ADF level is well below optimumfrom first grazing to the end of August.ADF is needed to keep the rumenfunctional and for fat synthesis. Thisperiod coincides with time of ‘low fat’problems in many herds.

ME is adequate but declines rapidlyfrom October. This coincides with stemelongation and seed set.

Protein, NDF and calcium are alwaysadequate. Phosphorus is marginal.

sun) and decreases at night (as the plantrespires) (Figure 17).

The level of carbohydrates increases atabout 0.5% per hour from sunrise. Thus acow eating, say, 15kgDM of pasture at4 p.m. (13% sugars) would eat 0.75kgmore carbohydrate than a cow grazingpasture at dawn (8% sugars). This is whysome farmers cut silage late in theafternoon.

Perhaps it is worthwhile giving cowstheir largest pasture allocation after theafternoon milking, particularly withpastures low in carbohydrates, such askikuyu. This proposition is being evalu-ated by NSW Agriculture at Wollongbar.

Seasonal variation innutrients

Figures 18, 19 and 20 show the seasonalvariation in nutrients in annual ryegrasspasture (Figure 18), perennial ryegrass –white clover pasture (Figure 19) andkikuyu pasture (Figure 20), and theminimum values required for cowsproducing 20L of milk a day(6). Table 5

shows the average values of minerals withno seasonal variation for these 3 pastures.

23


Figure 19. Seasonal variation innutrients in perennial ryegrass – whiteclover pasture. The dotted lines are theminimum required for cows producing20L of milk a day.

Figure 20. Seasonal variation innutrients in kikuyu pasture. The dottedlines are the minimum required for cowsproducing 20L of milk a day.

ME

protein

carbohydrate

NDF

ADF

calcium

phosphorus

protein

J F M A M J J A S O N D


% o

f DM

% o

f DM

% o

f DM

MJ/

kg D

M 121110

3025201510

5

50403020

1.00.80.60.40.2

0

month

ME

protein

carbohydrate

NDF

ADF

calcium

phosphorus

protein



% o

f DM

% o

f DM

% o

f DM

MJ/

kg D

M 1110

98

3025201510

5

6050403020

0.80.60.40.2

0

month

ADF is adequate, but NDF levels arefar too high. This is believed to be themain reason why the daily DM intake ofcows grazing kikuyu is only 12–13kg.

The ME values are always low, buthighest in winter, when there are no hightemperatures to increase fibre content.The problem with such a low ME is tofind a sufficiently energy-densesupplement to raise the total ration MEto 11.5MJ/kg DM. This is dif ficult toachieve with grain at an ME of 12MJ/kgDM, and more energy-densesupplements based on oil may be needed.

Protein levels, surprisingly, areadequate, but carbohydrate levels arevery low. Calcium and phosphorus levelsare marginal to inadequate.

ADF and NDF are adequate. ME isadequate except from late spring to earlyautumn.

Protein levels are always high. Theprotein to carbohydrate ratio is worst inautumn (4:1) and best in spring (3:1).This supports farmers’ observations ofquality differences between autumn andspring pasture.

Phosphorus levels are marginal,particularly in spring, but calcium isalways adequate. This is probably due tothe high levels of calcium in clover.

24


Table 5. Average values of nutrients with no seasonal variation. Most are adequate ormore than adequate. Kikuyu is low in sodium and zinc.

Minerals Minimum requiredfor 20 L milk per cow

per day(6)

Annual ryegrass Perennialryegrass – white

clover

Kikuyu

Magnesium (%) 0.25 0.27 0.30 0.29Sodium (%) 0.18 0.37 0.47 0.10

Potassium (%) 1 3.43 3.00 2.89Copper (ppm) 10 11 14 14.5Zinc (ppm) 40 38 37 29Manganese (ppm) 40 112 119 88Iron (ppm) 50 188 386 210

25


Efficient supplementation of cowson pasture

This section discusses the factors thatdetermine response to supplementation.

Concentrates can be given:

• to fill seasonal feed gaps

• to allow pasture growth and utilisationto be optimised

• to ensure that cows are on a risingplane of nutrition at mating.

The concentrate should be balanced fornutrients that limit production.

Concentrates are expensive, and whenthey are fed to cows also grazing pasture,the response is lower than under feedlot

conditions. This is because cowsinvariably reduce their pasture intake asthey are less hungry. This is called thesubstitution effect. Therefore,concentrates should be fed underconditions that minimise substitution.

The potential response to 1kg ofconcentrate is predictable—1kg of, say ,barley contains 90% DM and has an MEvalue of about 13MJ/kg DM. To producemilk with 4.7MJ/L energy (at 3.6% milkfat), 1kg of barley should produce 13 ×0.9 ÷ 4.7 = 2.5L milk (if all othernutrients are adequate).

The actual response to an additional1kg of concentrates varies from nil to1.5L of milk, depending on the rate ofsubstitution (of grass for concentrates) andon the effect of feeding concentrates ondigestion of pasture in the rumen. Inpractice, very low responses can beexpected from medium- to low-genetic-merit cows, in late lactation, on lushpasture, fed high amounts of concentrate.High responses can be expected fromhigh-genetic-merit cows, in peak lactation,on poor quality pasture, and to the firstfew kg of concentrate a day.

Table 6 and Figure 21 show the effectof both genetic merit and level ofconcentrate feeding on productionresponse.

Table 6. The amount of milk produced per kg of concentrate fed decreases as moreconcentrate is given. High-genetic-merit cows do better than low-genetic-merit cows.The response in each case is relative to that of a group fed no concentrate.

Genetic merit kg concentrate fed per cowper day

L of milk produced perkg DM fed

Total L produced onconcentrate

Medium 2.9 1.24 3.66.3 0.68 4.3

High 2.9 1.46 4.26.3 0.97 6.1

1.2

1.0

0.8

0.6

0.4

0.2

00 2 4 6 8

L of

milk

per

kg

conc

entr

ate

fed pasture taken reduced as

concentrates increased

pasture takenunchanged asconcentrates increased

Concentrates fed (kg/day)

Figure 21. If pasture availability isreduced as concentrates are increased,response to feeding should not change.On the other hand, if concentrates areincreased but pasture availability staysthe same and is high, response toconcentrate fed decreases markedly(5).

26


On average, dairy farmers cannotexpect more than 1L of milk per kg DMof concentrate fed. With the cost of 1kgof concentrate near that of 1L ofmanufacturing milk, concentrates must befed cautiously. Feeding concentratesmerely to increase production per cow,and constant feeding throughout the year,can only be wasteful as it must beassociated with a high level of substitutionfor at least part of the year.

To gain a far greater benefit from

feeding concentrates to cows on pasture,feed concentrates in order to achieveincreased stocking rates and thereby toachieve greater utilisation when pasturesare in surplus (Figure 22). In thissituation, the direct benefits of feedingconcentrates are minor but there is anoverall increase in farm productivity. Thusthe direct effect on milk response is notthe dollar value of feeding concentratesbut the dollars gained from higherstocking rate.

Figure 22. Surplus and deficit before and after suppplementation when this isassociated with an increase in stocking rate to soak up the greater pasture surplus.

pasturedeficit

pasturesurplus

winter spring summer winter spring summer

pasturedeficit

pasturesurplus

Before supplements After supplements

t DM

of p

astu

re

requirementsnewrequirements

= supplement

27


Setting up an effective grazingmanagement system

These next sections discuss what isneeded to put the grazing managementoptions discusses previously into practice.

Setting up your farm for controlledgrazing can be as sophisticated or asinexpensive as you wish. The principle isto be able to control grazing, and thattakes only a few ‘hot’ wires.

Establish semi-permanent blocks smallenough to allow no more than 2 days’grazing in winter. Otherwise, use a backfence. These blocks can be further splitinto halves to give daily strips of pastureor into quarters to give a strip eachmilking. The fences need be only a singleelectric wire, which you can easily drop orroll up for cultivation, for example, or gounder when shifting sprinklers.

The number of blocks depends on theoptimum grazing interval, which is thetime taken for ryegrass to reach 21⁄

2–3

leaves per tiller. For example, if it takesryegrass 40 days to grow 3 new leaves pertiller, then you split your ryegrass areainto 20 two-day blocks. Note: the area of

each block is not an issue. If each blockhas insufficient pasture, either yourstocking rate is too high or you need togive more supplements.

To estimate the time to reach the 3-leafstage in the coldest month of the year(usually July), either look at a few leavesor use the average temperature for yourdistrict as follows:

3 leaf-appearance intervals = 3 × (20 –0.55 × (max. temp. + min. temp.) ÷ 2)

= 3 × (20 – 0.55 × average temperature)

To achieve correct timing and intensityof grazing and provide adequate feed foryour cows, you need to give supplementsif pasture on offer is inadequate, or closeup blocks for silage (or other stock) ifpasture on offer is too much.

Even if you have good irrigationpotential, you should store 3t of silage(1t DM) per cow per year . In a normalyear only 2⁄

3 of this will be used; the rest

can be ‘rolled over’ to be used in a pooreryear.

28


Feed planning

Feed planning is planning your feedsupply to meet your target levels of milkproduction and the nutritionalrequirements of the herd.

The level of feeding and the continuityof feed supply account for the biggestdifferences in productivity and incomebetween dairy farms. Feed planning canhelp you achieve maximum farmproductivity and profits by balancing feedquality and quantity.

For most dairy farmers the cheapestway to feed dairy cows is with pastures,which comprise 60%–100% of the cows’feed intake. For profits on pasture-baseddairy farms to be increased, it is vital thatthese pastures be well managed. Feedplanning is essential to achieving this.

Feed for dairy cows accounts for 50%–80% of total variable costs. Feed planningallows you to reduce costs and increaseprofits by:

• reducing feed shortages andunderfeeding of cows

• maximising the use of surplus feed

• examining management alternativesand options

• using farm equipment effectively

• optimising the use of pastures andsupplements

• increasing pasture production

• increasing milk production

• optimising the use of fertilisers

• using irrigation more effectively

• optimising the use of supplements percow

• maximising levels of profitableproduction for your farm.

Feed planing needs to take into accountfarm plans, feed budgets and grazingplans:

• Farm plans are long-term plans thatset targets for pasture and milkproduction for the whole farm. Theyconsider herd size, calving patterns,patterns of production and farmdevelopment.

• Feed budgets are medium-term plansthat examine management alternativesto overcome feed imbalances and makethe best use of pastures, supplementsand conserved feed.

• Grazing plans are short-term plansthat maximise pasture production anduse through various pasture andgrazing management strategies.

29


Allocating pasture and feed

Step 1. Measure pastureon offer

To calculate what quantity and quality ofsupplements to give, you need to measurethe available pasture. Pasture DM can beestimated by eye, or more accurately witha rising plate meter (Figure 23). The metermeasures the density of pasture bymeasuring how much the pasture holds upa standard plate (4kg/m 2).

Total DM (on offer) per ha can be workedout from the basic equation:

kg DM/ha = (final reading –initial reading) ÷ no. readings ÷ 2 (to

convert to cm) × pasture factor

Pasture factors:

• Ryegrass or ryegrass – white clover:195 (not valid after stem elongation)

• Oats: 185 (not valid after stemelongation)

• Kikuyu: 200; for before grazingsubtract 1200; for after grazing subtract1400. (This equation gives DMconsidered to be available to theanimal. It is valid only for hard-grazedpastures or for pastures mulched orslashed after grazing.)

• Lucerne: Estimating lucerne DM withthe rising plate meter is too inaccuratebecause of lucerne’s stalky nature. DMneeds to be estimated from the actualcrop height and density. Table 7 (over)shows DM estimates at different plantdensities and actual heights for lucerne,and conversions of pasture meterheights to kgDM/ha for the otherspecies discussed.

Available DM, which is always less thantotal DM (‘on offer’), is calculated in step 2.

When using the pasture meter:

• take 60–80 readings per block so thatthe estimate is accurate

• take these readings at set intervals (2–3paces) across the block

• place the plate of the meterhorizontally on the pasture. Do notthump the plate or use it as a walkingstick

• treat the meter carefully; bent rods givewrong readings. Use a wire brushevery 2–3 weeks to clean the stem andrachet

• remember that the normal Ellinbankrising plate meter is graduated in 1⁄

2cm,

not 1cm, graduations on the digitalreadout.

Figure 23. A rising plate meter in use.

30


Pastureheight(cm)

Ryegrass, orryegrass–

clover

Oats Kikuyu Lucerne

before grazing after grazing thin dense

4 780 740 0 – – –

6 1170 1110 0 – – –

8 1560 1480 400 200 – –

10 1950 1850 800 600 200 400

12 2340 2220 1200 1000 240 490

14 2730 2570 1600 1400 280 580

16 3120 2960 2000 1800 320 670

18 3510 3330 2400 2200 360 760

20 3900 3700 2800 2600 400 850

25 4875 4625 3800 3600 500 1150

30 5850 5550 4800 4600 650 1425

35 6825 6475 5800 – 800 1700

40 7800 7400 6800 – 1000 2000

45 – – – – 1200 2400

Table 7. Conversion between rising plate meter values (cm) for ryegrass, oats andkikuyu, or actual height (cm) for lucerne, and DM yields (kg/ha).

Step 2. Calculate pastureavailable per cow per day

In step 1, we calculated pasture on offer;that is, the total offered to cows. Forryegrass, this is to ground level, but forkikuyu, it is to 5cm stubble height. (Themat below this is considered to beinedible.)

In this step, we now calculate pastureavailable; that is, pasture on offer minusresidues left after grazing. Thus, pastureavailable depends on the residue, whichin turn depends on stocking intensity, typeof stock and actual amount on offer.

For ryegrass, aim to achieve 1000–1200kg DM/ha, or about 5cm, post-

grazing residue. However, it is probablymore relevant to determine pastureresidues in your situation from the mostrecently grazed blocks with similarpasture on offer.

In well utilised kikuyu or kikuyuslashed or mulched after grazing, work onutilising 2⁄

3 of the DM on offer above

5cm stubble height. For example, if800kg DM is on offer above 5cmstubble height, then 2⁄

3 × 800kg = 533kg

DM available. If there are 50 cows, thiscomes to 533 ÷ 50 = 10.6kg DM per cow .

A prerequisite for allocating pasture inthis manner is obviously a reasonableestimate of block or paddock size.

The table on the next page shows aworked example.

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To calculate: Example for ryegrass pasture

meter reading on entering block = 15650;meter reading on leaving block = 16880;no. of readings = 56;residue of 1000 kg DM/ha after grazing;1.8 ha, 180 cows

DM on offer per ha: take 60–80 readingsbefore grazing and use the equations fromstep 1 to calculate pasture on offer

(16880 – 15650) ÷ 56 ÷ 2 × 195 = 2142 kgDM/ha on offer

DM available per ha: subtract theestimated post-grazing residue

2142 – 1000 = 1142 kg DM/ha available

total DM available: multiply by area ofpasture grazed per day

1142 × 1.8 = 2056 kg DM available per day

DM available per cow per day: divide bythe number of cows

2056 ÷ 180 = 11.4 kg DM available per cowper day

To calculate: Example

Daily feed requirements:maintenance: 5.5 kg DM per cow per day for average Friesians (use 6.5 for large);milk production = 2 L milk/kg DM.Assume daily production = 20 L milk per cow

feed intake per cow per day: use values formaintenance and milk production

5.5 + 20 ÷ 2 = 15.5 kg DM per cow per day

supplements required: subtract availableDM from requirements

15.5 – 11.4 = 4.1 kg DM per cow per day

Step 3. Calculate DMsupplements per cow perday

Note that the supplement required iscalculated on a dry-matter basis. This willhave to be corrected to ‘as-fed’ beforefeeding stock. For example, you need4.1kg DM supplements but grain is 91%DM. Therefore you actually need 4.1 ÷0.91 = 4.5kg.

Thus cows can be fed to theappropriate level by first determiningpasture available.

Many farmers end up simply using thepasture meter periodically to ‘get their eyein’ (that is, to check their estimates), andthen estimate DM/ha by eye.

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Budgeting and monitoring pasture

We should aim to budget pasture (andother feeds), just as we budget our cashflow. The success of pasture budgetingdepends on obtaining accurate pasturegrowth rates for your property and havinga means of monitoring actual pasturecover relative to previous years, whichyou can compare with budgeted cover. Afortnightly farm walk, during which youestimate pasture cover, satisfies both theseneeds.

On your walk, assess feed on offer oneach block with the pasture meter. Thisshould not be a chore but an opportunityto assess the health of your farm. The datawill give you:

• growth rates for various pasture typesat fortnightly intervals throughout theyear

• post-grazing residues: Are cowsgrazing too hard? Hard grazing willreduce regrowth and is an indicationthat cows are being underfed (approx.1000kg DM/ha is ideal for ryegrassand 300kg DM/ha is ideal for kikuyu)

• pre-grazing DM on offer: Is it toohigh? Cows tend to waste pastureabove 2400kg DM/ha.

Compare feed on offer on the farm thisyear with last year and calculate surplus ordeficit.

Table 8 shows how the results can berecorded. Figure 24 shows how they canbe represented. If you have a computerand a spreadsheet program you canautomate calculations (one, called PASTURE

ASSESSMENT, is available from NSWAgriculture).

Block 3 has obviously been grazedsince the last farm walk and so its resultsare discarded.

Figure 24 clearly indicates a 60t DMdeficit compared with last year. Someways to remedy this might be:

• to remove heifers from the milkingarea:

agisting 50 heifers (average age 15months) × 8kg DM per heifer per day× 90 days saves 36t DM

• to buy 60t hay

• to dry off 20 cows @ 15 L of milk percow per day (1 month early):

feed saved = 20 × 13kg per cow perday × 30 days = 7.8t DM

• to apply 50 kg N to 20 ha at anexpected response of 24kg DM/kg N;this should give 24t DM

• to increase concentrate feeding by 4 kgper cow per day for the 180 cow herd:

4kg × 180 cows × 30 days provides21.6t DM.

* When working out average pasture cover for kikuyu, use kg DM/ha = 200 × meter reading (cm) – 1300.

Block Area(ha)

Pasturetype

1 July 15 July Growthrate

kg DM/dayMeter readings on offerkg

DM/ha

Meter readings on offerkg

DM/hain out no. in out no.

1 0.6 Ryegrass 15600 15980 50 741 780 1490 50 1385 46

2 1.4 Ryegrass 15980 16940 60 1560 1490 2410 55 1631 5.1

3 0.8 Kikuyu* 16940 18420 70 814 2480 3300 80 –275 –

Table 8. Sample fortnightly record of pasture growth.

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Figure 24. Feed on offer on the farm last year and this year estimated fromfortnightly farm walks with the rising plate meter.

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

last year

this year

200

150

100

50

0

t DM

on

farm

Thus, accurate estimates of growthrates can give reliable budgets, andmonitoring pasture can flag the need totake action early.

34


References

1. Curtis, A., Edmondson, C. and Findsen, C.1989. Pasture Management for DairyFarmers. Agriculture Victoria, Melbourne.

2. Donaghy, D., Scott, J. and Fulkerson, W.1997. Grazing frequency affects Loliumperenne and Trifolium repens survival inthe subtropics. Australian Journal ofExperimental Agriculture (in press).

3. Fulkerson, W. J. 1994. Effect ofredefoliation on the regrowth of water-soluble carbohydrate content of Loliumperenne. Australian Journal of AgriculturalResearch 45, 1809–15.

4. Michell, P. and Franks, D. 1993. Theeffects of grazing duration on herbageintake, composition, quality and regrowthof temperate pastures. Report on Dairy

Research and Extension in Tasmania.Department of Primary Industries, Hobart.

5. Rogers, G. L., Porter, R. H. D. andRobinson, I. 1982. Comparison of ryegrassand white clover for milk production. In:Dairy Production from Pasture,Proceedings of the Conference of NewZealand and Australian Societies ofAnimal Production, Hamilton, NZ.

6. National Research Council 1989. Nutrientrequirements of dairy cattle, 6th ed.National Academic Press, Washington,DC.

7. Davison, T. M. and Elliott, R. 1993.Response of lactating cows to grain-basedconcentrates in northern Australia. TropicalGrasslands 27, 229–37.

Questions

Grazing kikuyu at the 4–41⁄2-leaf stage optimises quality. What is the penalty inquantity by not letting it grow longer?

If there is a high residue of ryegrass after grazing (well in excess of 5cm) for whateverreason, is it better to regraze or to wait for a full regrowth cycle?

Many ryegrass plants are lost through sod-pulling. What can be done to reduce this?

Is there any benefit in using nitrogen fertiliser on white clover to increase dry matteryields and take advantage of the high-quality herbage?

Is there any advantage in harrowing pastures to prevent dung pads, especially whenshort grazing rotations are being used?

When feed is in short supply, what value does concentrate have relative to silage?

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