Triacylglycerol Triglycerides R-COO-CH 2 R-COO-CH R-COO-CH 2 Triglycerides found in seeds and animal adipose. Diglycerides found in plant leaves, one fatty.

Triacylglycerol Triglycerides

R-COO-CH2

R-COO-CH R-COO-CH2

• Triglycerides found in seeds and animal adipose.• Diglycerides found in plant leaves, one fatty acid is replaced by sugar (galactose).

Most Common Fatty Acids in Di- and Triglycerides

Fatty acid Carbon:Double bonds Double bonds

Myristic 14:0

Palmitic 16:0

Palmitoleic 16:1 Cis-9

Stearic 18:0

Oleic 18:1 Cis-9

Linoleic 18:2 Cis-9,12

Linolenic 18:3 Cis-9,12,15

Arachidonic 20:4 Cis-5,8,11,14

Eicosapentaenoic 20:5 Cis-5,8,11,14,17

Docosahexaenoic 22:6 Cis-4,7,10,13,16,19

CH3(CH2)nCOOH

Triglyceride Containing Linoleic AcidOmega-6

Linolenic AcidOmega-3

Fatty Acid Isomers

Lipid Content of Feeds

ForagesFat content is low: 1 to 4% of dry matterHigh proportion of linolenic acid (18:3)Diglycerides in fats of leaves

GrainsFat content variable: 4 to 20% of dry matterHigh proportion of linoleic acid (18:2)Triglycerides in oils of seeds

Lipid Digestion - Rumen

DigalDigly MonogalDigly

Galactose

Propionate Diglyceride

Glycerol

Triglyeride Fatty acids

Saturated FA CaFA Ca++ Feed particles

-galactosidase

-galactosidase

Lipase Anaerovibrio lipolytica

H+

Reductases

Lipase

Fat Digestion

Digestibility influenced by:Dry matter intake

Decreases with greater intakeAmount of fat consumed

Digestibility decreases 2.2% for each 100 g of FA intake (Response is variable)

Degree of saturationDigestibility decreases with increased saturationMaximal digestion with fats having Iodine values greater than 40

1. Minimal degradation of long-chain fatty acids in the rumen

Fatty acids not a source of energy to microbes2. Active hydrogenation of unsaturated fatty acids3. Microbial synthesis of long-chain fatty acids in the rumen (15g/kg nonfat org matter fermented)4. No absorption of long chain fatty acids from the rumen

More fat leaves the rumen than consumed by the animal

Lipids leaving the rumen• 80 to 90% free fatty acids attached to feed particles and microbes• ~10% microbial phospholipids leave the rumen• Small quantity of undigested fats in feed residue

Lipid Metabolism - In the Rumen

• Synthesize C 18:0 and C 16:0 in 2:1 ratio using acetate and glucose (straight-chain even carbon #).• If propionate or valerate used, straight-chain odd carbon fatty acids synthesized.• Branched-chain VFA used to produce branched chain fatty acids.• About 15 to 20% of microbial fatty acids are mono- unsaturated. No polyunsaturated fatty acids are synthesized.• Some incorporation of C 18:2 into microbial lipids.

Microbial Fatty Acid Synthesis

Hydrogenation of Fatty Acids in the Rumen

Polyunsaturated fatty acids (all cis)Isomerase (from bacteria) Needs free carboxyl group

and diene double bond

Shift of one double bond (cis & trans)

Hydrogenation Hydrases (from bacteria,

Hydrogenated fatty acid mostly cellulolytic)

(stearic and palmitate)

Hydrogenation of Fatty Acids in the Rumen

All unsaturated fatty acids can be hydrogenatedMonounsaturated less than polyunsaturated

65 to 96% hydrogenationNumerous isomers are producedBiohydrogenation is greater when high foragediets fedLinoleic acid depresses hydrogenation of FA

Conjugated Linoleic Acid - RumenMost Common Pathway (High Roughage)

Linoleic acid (cis-9, cis-12-18:2)

Conjugated linoleic acid (CLA, cis-9, trans-11-18:2)

Vaccenic acid (Trans-11-18:1)

Stearic acid (18:0)

Cis-9, trans-12 isomerase Butyrivibrio fibrosolvens

CLA Isomers - Rumen (High Concentrate)Low Rumen pH

Linoleic acid (cis-9, cis-12-18:2) Cis-9, trans-10 isomerase

CLA Isomer (trans-10, Cis-12-18:2)

This isomer is inhibitory to milk fat synthesis.

Trans-10-18:1

Linolenic Acid – Oleic Acid

Linolenic acid (cis-9, cis-12, cis-15-18:3)

(Cis-9, trans-11, cis-15-18:3)

Trans-11, cis-15-18:2

Trans-11-18:1 (vaccenic acid)

Oleic acid cis-9 (18:1) Stearic acid (18:0)

CLA absorbed from the intestines availablefor incorporation into tissue triglycerides.

Reactions from linoleic acid to vaccinic acidoccur at a faster rate than from vaccinic acidto stearic acid.

Therefore, vaccinic acid accumulates in therumen and passes into intestines where itis absorbed.

Quantities of vaccinic acid leaving the rumenseveral fold greater than CLA.

Conversion of Vaccinic Acid to CLA In mammary gland and adipose

Trans-11-18:1 CLA, cis-9, trans-11 18:2

Stearoyl CoA Desaturase‘9-desaturase’

This reaction probably major source of CLA inmilk and tissues from ruminants.

Also transformsPalmitic PalmitoleicStearic Oleic

Potential Value of CLA in Foods of Ruminant Origin

AnticarcinogenicLab animals given chemicals to cause cancer

Reduce atherosclerosisDirect evidence with rabbitsIndirect evidence with humans

Reduce fat accumulation in the bodyLaboratory animals and pigsEvidence not conclusive with humans

CLA Content of Foods

CLA isomers cis 9, trans 11Food mg/g fat %

Beef 4.3 85Pork 0.6 82Chicken 0.9 84Milk 5.5 92Colby cheese 6.1 92Corn oil 0.2 39

Increasing CLA in Foods of Ruminant Origin

• Grazing grass increases CLA concentration in meat and milk from ruminants• Feeding Ca-salts of unsaturated fatty acids• Processing full fat soybeans to release oil

Extrusion, roasting, heating temperature• Feeding fish oil• Feeding high oil corn - minimal effects

Control milk: 3 to 4 mg CLA/g fatty acidsExperimental milk: 5 to 25 mg CLA/g fatty acids

Less response if high-concentrate diets are fed

Increase in trans-10, cis-12-18:2 CLA isomerwhen unsaturated oils fed in high-grain diets

• Low rumen pH seems to increase trans fatty acids in the rumen • Decrease milk fat• Trans fatty acids increase in low fat milk

High Concentrations of CLA Isomers

Concentrations of Omega-3 and Omega-6 Fatty Acids with Time Fed Grain - Cattle

0123456789

% T

ota

l fa

tty

acid

s

0 28 56 84 112 140 168 196

Days

Omega-3

Omega-6

Duckett et al., 1993

Ratio of Omega-6:Omega-3 Fatty Acids with Time Fed Grain - Cattle

0

10

20

30

40

50

60

70

80

Om

ega-

6/O

meg

a-3

0 28 56 84 112 140 168 196

Days

Stearoyl CoA Desaturase (9-Desaturase) in Wagyu and Holstein Steers

Wagyu Holstein

Muscle 3.3 0.8

Adipose 132.1 39.5

Mono Unsat, % 57.3 53.4

Yang et al., 1999

CLA c9, t11

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

2003

% o

f to

tal f

atty

aci

ds

Baker

Bushman

Cline

Kime

Langland

Feb Mar Apr May Jul Aug SepJunJan

cis9 trans11 CLA Concentrations in Milkfrom Different Farms in Northeast Iowa

Oleic Acid in Milk and Tissues

Oleic acid (18:1) is predominant fatty acidin ruminant fat.

Stearic acid Oleic acid Delta-9 desaturase

Delta-9 desaturase found in ruminant adiposeand mammary gland

Fatty Acid Concentrations% by Wt

FA Alf Grass Corn SB Bac Pro Beef Mut14:0 0.9 1.1 0 0.1 3.9 1.5 3.7 2.616:0 33.9 16.9 10.9 10.3 31.0 37.8 24.2 23.018:0 3.8 2.0 1.8 3.8 15.0 13.5 13.5 25.8

16:1 1.2 2.5 0 0.2 4.0 6.8 6.0 1.918:1 3.0 3.4 24.1 22.8 6.0 11.5 43.7 37.918:2 24.0 13.2 58.0 51.0 2.7 6.3 2.6 2.218:3 31.0 61.3 0.7 6.8 1.0 4.7

Postruminal Fat Digestion and Absorption

• Fatty acids from the rumen mostly saturated• No absorption of fatty acids from the rumen• Fatty acids attached to feed particles, Ca and microbes dissociate in the acid environment of the abomasum• pH of duodenum and jejunum remains acidic in ruminants

- Affects solubility of fatty acids in aqueous environment• Fatty acid emulsification and micelle formation in the small intestine is essential for efficient absorption• Fatty acids absorbed predominantly from the jejunum into lymph

Intestine Liver PancreasFree fatty acids

Bile salts Micelle Phospholipases

Lecithin LysolecithinPhospholipids Fatty acids

Epithelial cellTriglycerides Lymph

Fatty acids Chylomicronsx

Fatty Acid Absorption

Bile of ruminants contains predominantly taurine-conjugated bile acidsrather than glycine conjugate. The taurine conjugate is more effectiveat acid pH

In digestion and metabolism of fats:No energy lost as methaneNo energy lost in the urine

So: Digestible energy = metabolizable energy Energy value of fat determined by digestibility

Digestibility of supplemental fats is variable

Use of metabolizable energy from fat is about80% or ME x 0.80 = Net Energy

Gross EnergyTallow - 9.2 Mcal/kg Free fatty acids - 9.39 Mcal/kgCa salts of free fatty acids - 8.03 Mcal/kg

Energy Value of Fats

Effects of Fats on Rumen Fermentation

Effects of adding fat to ruminant dietsReduced feed intakeReduced fiber digestionReduced milk fatIncrease propionate/acetate ratio

• Polyunsaturated fats more inhibitory than saturated fats• Feeding oil seeds of polyunsaturated fats less inhibitory• Up to 3% of diet as tallow or yellow grease can be fed without major effects

Mechanism of Inhibition

Lipids coat feed particlesInterfere with microbial attachmentInterfere with attachment of enzymesComplex Ca

Direct antimicrobial effectsCytotoxic effects on cell membranes

Interfere with energy metabolismFree carboxyl group needed

Triglycerides less toxic than free fatty acidsCa salts of fatty acids less toxic

Metabolic Pathways in Ruminant Adipose

Adipose Cell TriglyceridesGlycerol-3-P

Free fatty acidsGlycerol

NADPHAcetate Glucose

GlucoseGlycerol NEFA VLDL AcetateBlood triglycerides Lipoprotein lipase

Adding Fat to Ruminant Diets

Ruminant feeds normally contain low levelsof fats or oils - usually 2 to 4%.

Why add fat?Increase energy density in the diet

Fat 2.5 times more energyIncrease milk production or gain(Benefits should be greater than costs)

Secondary benefits:Improve diet and pellet characteristics

Reduces dustLubricate feed processing equipment

Pellet mills, mixers, etc

Adding Fat to Ruminant Diets

Need to add proper level and kind of fatHow much fat is in basal dietKind of fatty acids in basal dietLevel of production

Potential limitationsHydrogenated fats less digestibleUnsaturated fatty acids depress fiber digestionDecreased feed intakeProduce trans fatty acids and reduce milk fat

Usually limit the quantity of added fat to lessthan 5% of total diet of ruminants

Types of Fat Fed to Ruminants

Rumen inert (Protected) Ca salts of fatty acids, hydrogenated fats

Have little if any effects on fiber digestion in the rumen

Sold commercially in dry form Easy to mix Expensive source of fat

UnprotectedAnimal fats (tallow, grease, etc)

More difficult to mix - Cold weather - Melt fatsMost commonly used as feed

Plant oils (soybean, corn, etc)Unsaturated fatty acids depress fiber digestionUsually cost prohibitive

Whole oil seedsSoybeans, cotton seeds, high-oil cornOils are not as readily availableLess effect on rumen fermentationEasiest for smaller producers to feed

Finishing Steers - Rolled Barley

% Added fat

0 4 8

Feed DM, kg/d 6.19 6.18 6.42

ADG, kg/d 0.83 0.92 1.02

Feed/gain 7.51 6.80 6.30

Back fat, cm 1.17 1.23 1.33

Marbling 4.09 4.21 4.35

305 kg steers fed 88% concentrate dietBlended fats: yellow grease and animal + vegetable

Finishing Steers - Rolled Barley

% Added fat0 4 8

DM intake, kg/d 5.28 5.30 5.28Rum dig starch, % 90.3 90.3 90.4Rum dig ADF, % 27.3 19.0 6.7SI dig, starch, % 77.3 80.6 78.7SI dig, ADF, % 13.7 16.5 23.0TT dig, starch, % 99.4 99.3 99.2TT dig, ADF, % 45.5 41.1 37.4

Steers fed 88% concentrate dietBlended fats: yellow grease and animal + vegetable

Finishing Steers - Rolled Corn

--- 0 Fat--- --4% Tallow--

Monensin 0 + 0 +

Feed DM, kg/d 9.86 10.04 9.95 9.06

ADG, kg/d 1.38 1.52 1.48 1.32

Gain/feed 0.139 0.151 0.149 0.145

Back fat, cm 1.22 1.37 1.37 1.22

Marbling 5.75 5.50 5.22 5.03

350 kg steers fed 93% concentrate diet

Adding Fat to Lactation Diets

Factors affecting response to supplemental fat:Basal diet

Digestibility of corn silage affected more thanother roughages

Stage of lactationEnergy balance

Greater response when cow needs energyComposition of added fat

Unsaturated - saturated fatty acidsAvailability of fat in the rumen

Amount of supplemental fatResponse is curvilinear

Lactation Diets

Supplement during peak lactationFrom 7 - 8 weeks to 11 - 15 weeks

Amount to feedMilk production reaches maximal efficiencywhen fatty acids contribute 16% of ME

Equates to about 600 to 700 g ofsupplemental fat per dayWill support about 3.5 kg increase in milk

Total dietary fat should not exceed 6 to 7% of dietary DM

Lactation Diets

Full fat oil seedsAvailable oil increased with processing

Extruding - heatUsually minimal effects on rumen fermentation

Unprotected fatsTallow - saturated fatty acids

Add up to amount that will not affectrumen fermentation

Protected fatsUse if addition of unprotected fat doesnot meet the energy needs

More expensive

Adding Fat - Lactation

Choice white grease, %

0 2 4

DMI, kg/d 26.3 24.4 23.8

Milk, kg/d 42.3 41.5 38.1

Fat, % 3.30 2.93 2.85

Fat, kg/d 1.39 1.21 1.08

50% corn silage

Adding Fat - Lactation

21% ADF 28% ADF

Added fat 0 6 0 6

DMI, kg/d 24.4 21.7 23.7 21.5

Milk, kg/d 37.5 38.9 34.7 38.0

Fat, % 3.4 2.9 3.5 3.2

Fat, kg/d 1.3 1.1 1.2 1.2

Corn silage, alfalfa hay & cottonseed hullsChoice white grease

Adding Fat - Lactation

21% ADF 28% ADF

Added fat 0 6 0 6

VFA, mM 90.1 84.2 89.8 80.8

Acetate, % 61.8 58.2 66.3 64.0

Propionate, % 21.3 25.4 17.7 20.2

Butyrate, % 11.8 10.0 11.4 10.2

Corn silage, alfalfa hay & cottonseed hullsChoice white grease

Effects of Supplemental Fat on Reproduction

VariablesAnimal: Body condition score, age (parity), nutrients available

Type of fat: Digestibility, fatty acid composition, quantity of fat

Research is inconclusive on response to added fat, unlesscontrol animals are energy deficient

ResponseMetabolic hormones – Insulin, growth hormone, IGFsCholesterol – Progesterone concentrationsLH secretion and follicular developmentProstaglandin synthesis –PGF2