Triacylglycerol Triglycerides

1
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).

2
Most Common Fatty Acids in Di- and Triglycerides
CH3(CH2)nCOOH
3
Triglyceride Containing Linoleic Acid Omega-6
4
Linolenic Acid Omega-3
5
Fatty Acid Isomers
6
Lipid Content of Feeds
Forages Fat content is low 1 to 4 of dry
matter High proportion of linolenic acid
(183) Diglycerides in fats of leaves Grains Fat
content variable 4 to 20 of dry matter High
proportion of linoleic acid (182) Triglycerides
in oils of seeds
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Lipid Digestion - Rumen
?-galactosidase
DigalDigly MonogalDigly Galactose Propiona
te Diglyceride Glycerol Triglyeride Fatty
acids Saturated FA CaFA Ca Feed particles
?-galactosidase Lipase Anaerovibrio
lipolytica H Reductases
Lipase
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Fat Digestion
Digestibility influenced by Dry matter
intake Decreases with greater intake Amount of
fat consumed Digestibility decreases 2.2 for
each 100 g of FA intake (Response is
variable) Degree of saturation Digestibility
decreases with increased saturation Maximal
digestion with fats having Iodine values greater
than 40
9
Lipid Metabolism - In the Rumen

• 1. Minimal degradation of long-chain fatty acids
  in
• the rumen
• Fatty acids not a source of energy to microbes
• 2. Active hydrogenation of unsaturated fatty
  acids
• 3. 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

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Microbial Fatty Acid Synthesis

• Synthesize C 180 and C 160 in 21 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 182 into microbial
  lipids.

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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)
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Hydrogenation of Fatty Acids in the
Rumen All unsaturated fatty acids can be
hydrogenated Monounsaturated less than
polyunsaturated 65 to 96 hydrogenation Numerous
isomers are produced Biohydrogenation is greater
when high forage diets fed Linoleic acid
depresses hydrogenation of FA
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Conjugated Linoleic Acid - RumenMost Common
Pathway (High Roughage)
Linoleic acid (cis-9, cis-12-182) Conjugated
linoleic acid (CLA, cis-9, trans-11- 182)
Vaccenic acid (Trans-11-181) Stearic acid
(180)
Cis-9, trans-12 isomerase Butyrivibrio
fibrosolvens
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CLA Isomers - Rumen (High Concentrate)Low Rumen
pH
Linoleic acid (cis-9, cis-12-182) Cis-9,
trans-10 isomerase CLA Isomer (trans-10,
Cis-12-182) This isomer is inhibitory to milk
fat synthesis. Trans-10-181
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Linolenic Acid Oleic Acid
Linolenic acid (cis-9, cis-12, cis-15-183) (Cis
-9, trans-11, cis-15-183) Trans-11,
cis-15-182 Trans-11-181 (vaccenic acid)
Oleic acid cis-9 (181) Stearic acid (180)
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CLA absorbed from the intestines available for
incorporation into tissue triglycerides. Reaction
s from linoleic acid to vaccinic acid occur at a
faster rate than from vaccinic acid to stearic
acid. Therefore, vaccinic acid accumulates in
the rumen and passes into intestines where it is
absorbed. Quantities of vaccinic acid leaving
the rumen several fold greater than CLA.
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Conversion of Vaccinic Acid to CLA In
mammary gland and adipose Trans-11-181 CLA,
cis-9, trans-11 182 Stearoyl CoA
Desaturase ?9-desaturase This reaction
probably major source of CLA in milk and tissues
from ruminants. Also transforms Palmitic Palmit
oleic Stearic Oleic
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Potential Value of CLA in Foods of Ruminant
Origin
Anticarcinogenic Lab animals given chemicals to
cause cancer Reduce atherosclerosis Direct
evidence with rabbits Indirect evidence with
humans Reduce fat accumulation in the
body Laboratory animals and pigs Evidence not
conclusive with humans
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CLA Content of Foods
CLA isomers cis 9, trans 11 Food mg/g
fat Beef 4.3 85 Pork 0.6 82 Chicken 0
.9 84 Milk 5.5 92 Colby cheese 6.1 92 Corn
oil 0.2 39
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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 acids
• Experimental milk 5 to 25 mg CLA/g fatty acids
• Less response if high-concentrate diets are fed

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High Concentrations of CLA Isomers

• Increase in trans-10, cis-12-182 CLA isomer
• when 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

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Concentrations of Omega-3 and Omega-6 Fatty Acids
with Time Fed Grain - Cattle
Duckett et al., 1993
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Ratio of Omega-6Omega-3 Fatty Acids with Time
Fed Grain - Cattle
24
Stearoyl CoA Desaturase (?9-Desaturase) in Wagyu
and Holstein Steers
Yang et al., 1999
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cis9 trans11 CLA Concentrations in Milk from
Different Farms in Northeast Iowa
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Oleic Acid in Milk and Tissues
Oleic acid (181) is predominant fatty acid in
ruminant fat. Stearic acid Oleic acid
Delta-9 desaturase Delta-9 desaturase found in
ruminant adipose and mammary gland
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Fatty Acid Concentrations by Wt
FA Alf Grass Corn SB Bac Pro Beef
Mut 140 0.9 1.1 0 0.1 3.9 1.5 3.7 2.6 160 3
3.9 16.9 10.9 10.3 31.0 37.8 24.2 23.0 180 3.8 2.
0 1.8 3.8 15.0 13.5 13.5 25.8 161 1.2 2.5 0 0.2
4.0 6.8 6.0 1.9 181 3.0 3.4 24.1 22.8 6.0 11.5 43
.7 37.9 182 24.0 13.2 58.0 51.0 2.7 6.3 2.6 2.2 1
83 31.0 61.3 0.7 6.8 1.0 4.7
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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

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Fatty Acid Absorption
Epithelial cell Triglycerides Lymph Fatty
acids Chylomicrons x
Intestine Liver Pancreas Free fatty acids Bile
salts Micelle Phospholipases Lecithin
Lysolecithin Phospholipids Fatty acids
Bile of ruminants contains predominantly
taurine-conjugated bile acids rather than glycine
conjugate. The taurine conjugate is more
effective at acid pH
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Energy Value of Fats
In digestion and metabolism of fats No energy
lost as methane No 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 about 80 or ME x 0.80 Net Energy Gross
Energy Tallow - 9.2 Mcal/kg Free fatty acids -
9.39 Mcal/kg Ca salts of free fatty acids - 8.03
Mcal/kg
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Effects of Fats on Rumen Fermentation

• Effects of adding fat to ruminant diets
• Reduced feed intake
• Reduced fiber digestion
• Reduced milk fat
• Increase 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

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Mechanism of Inhibition
Lipids coat feed particles Interfere with
microbial attachment Interfere with attachment of
enzymes Complex Ca Direct antimicrobial
effects Cytotoxic effects on cell
membranes Interfere with energy metabolism Free
carboxyl group needed Triglycerides less toxic
than free fatty acids Ca salts of fatty acids
less toxic
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Metabolic Pathways in Ruminant Adipose
Adipose Cell Triglycerides Glycerol-3-P
Free fatty acids Glycerol NADPH Acetate
Glucose Glucose Glycerol NEFA
VLDL Acetate Blood triglycerides Lipoprotein
lipase
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Adding Fat to Ruminant Diets
Ruminant feeds normally contain low levels of
fats or oils - usually 2 to 4. Why add
fat? Increase energy density in the diet Fat 2.5
times more energy Increase milk production or
gain (Benefits should be greater than costs)
Secondary benefits Improve diet and pellet
characteristics Reduces dust Lubricate feed
processing equipment Pellet mills, mixers, etc
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Adding Fat to Ruminant Diets
Need to add proper level and kind of fat How much
fat is in basal diet Kind of fatty acids in basal
diet Level of production Potential
limitations Hydrogenated fats less
digestible Unsaturated fatty acids depress fiber
digestion Decreased feed intake Produce trans
fatty acids and reduce milk fat Usually limit
the quantity of added fat to less than 5 of
total diet of ruminants
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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 Unprotected Animal fats
(tallow, grease, etc) More difficult to mix -
Cold weather - Melt fats Most commonly used as
feed Plant oils (soybean, corn, etc) Unsaturated
fatty acids depress fiber digestion Usually cost
prohibitive Whole oil seeds Soybeans, cotton
seeds, high-oil corn Oils are not as readily
available Less effect on rumen fermentation Easies
t for smaller producers to feed
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Finishing Steers - Rolled Barley
305 kg steers fed 88 concentrate diet Blended
fats yellow grease and animal vegetable
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Finishing Steers - Rolled Barley
Steers fed 88 concentrate diet Blended fats
yellow grease and animal vegetable
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Finishing Steers - Rolled Corn
350 kg steers fed 93 concentrate diet
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Adding Fat to Lactation Diets Factors affecting
response to supplemental fat Basal
diet Digestibility of corn silage affected more
than other roughages Stage of lactation Energy
balance Greater response when cow needs
energy Composition of added fat Unsaturated -
saturated fatty acids Availability of fat in the
rumen Amount of supplemental fat Response is
curvilinear
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Lactation Diets Supplement during peak
lactation From 7 - 8 weeks to 11 - 15
weeks Amount to feed Milk production reaches
maximal efficiency when fatty acids contribute
16 of ME Equates to about 600 to 700 g
of supplemental fat per day Will support about
3.5 kg increase in milk Total dietary fat should
not exceed 6 to 7 of dietary DM
42
Lactation Diets Full fat oil seeds Available
oil increased with processing Extruding -
heat Usually minimal effects on rumen
fermentation Unprotected fats Tallow - saturated
fatty acids Add up to amount that will not
affect rumen fermentation Protected fats Use if
addition of unprotected fat does not meet the
energy needs More expensive
43
Adding Fat - Lactation
50 corn silage
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Adding Fat - Lactation
Corn silage, alfalfa hay cottonseed
hulls Choice white grease
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Adding Fat - Lactation
Corn silage, alfalfa hay cottonseed
hulls Choice white grease
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Effects of Supplemental Fat on Reproduction
Variables Animal 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, unless control animals are energy
deficient Response Metabolic hormones Insulin,
growth hormone, IGFs Cholesterol Progesterone
concentrations LH secretion and follicular
development Prostaglandin synthesis PGF2?