LIPID DIGESTION

1
LIPID DIGESTION

• References
• Church 298-312
• Jenkins et al. 2008. JAS 86397-412
• French et al. 2000. JAS 782849-2855
• McGuire and McGuire. 2000. JAS 771-af-8-af

2

• Lipids in ruminant diets
• Usually a low percentage of the diet, 1-4 of the
  DM
• Amounts have been increasing
• Lipids in feeds
• Feed EE Form
• Corn and 4-20 Triglycerides
• other seeds
• Forages 4-6 Galactosyl
• 
  glyceryl esters
• pigments
• waxes, essential
• 
  oils

3

• Structure
• Triglyceride O
• 
  
• O C-O- C-R
• R-C-O-C O
• 
  
• C-O-C-R
  
• 46 oleic acid (181) and 42 linoleic acid
  (182)
• Galactosyl diglyceride
• 
  
  
  
• O C-O-gal O
  gal
• 
  
• R-C-O-C O
• 
  
• C-O-C-R
• 31-61 linolenic acid (183)

4

• Common fatty acids in ruminant diets
• Fatty acid CarbonDouble Bonds
  Double bond position
• Myristic 140
• Palmitic 160
• Palmitoleic 161 Cis-9
• Stearic 180
• Oleic 181 Cis-9
• Linoleic 182 Cis-9, 12
• Linolenic 183 Cis-9,
  12, 15
• Arachidonic 204 Cis-5, 8, 11, 14
• Eicosapentaenoic 205 Cis-5, 8, 11,
  14, 17
• Docosahexaenoic 206 Cis-5, 7, 10,
  13, 16, 19

5

• Unsaturated fatty acid isomers
• Cis isomers (Naturally found in feeds)
• H H
• \ /
• CC
• / \
• C C
• / \
• R R
• Trans (Found in ruminant meat and milk as well as
  hydrogenated oils)
• R
• \
• C H
• \ /
• CC
• / \
• H C
• \
• R

6

• Lipid digestion in the rumen
• 
  alpha-galactosidase
  beta-galactosidase
• O CH2-O-Gal-Gal
  O CH2-O-Gal
  O CH2OH
• 
  
  
  
• R1-C-O-CH2 O --------------------?
  R1-C-O-CH2 O ---------------------?
  R1-C-O-CH2 O
• 
  
  
  
• CH2-O-C-R2
  CH2-O-C-R2
  CH2-O-C-R2
• Galactosyl diglyceride
  
  
• 
  
  
• 
  
  
  Lipases
• 
  Galactose
  
• 
  
  
• 
  
  
• 
  Propionate
  ?------------Glycerol?--------
• 
  
  
• 
  
  
  Unesterified
• 
  
  FA
• 
  
  (Rn)

7

• Lipid hydrolysis
• Two lipases are produced by the bacteria,
  Anaerovibrio lipolytica
• One is cell bound
• One is extracellular
• Hydrolysis is a rapid, two-step process
• Slower on a high grain diet
• Intermediates are rapidly metabolized in the
  rumen
• Factors influencing lipid digestion
• Dry matter intake
• Decreases digestibility
• Amount of fat consumed
• Decreases digestibility
• Fatty acid saturation
• Decreases digestibility

8

• Fatty acid metabolism
• Minimal absorption or degradation of long chain
  fatty acids in the rumen
• Lipids leaving the rumen
• 80-90 are free fatty acids bound to feed
  particles or microbes
• 10 leaves as microbial phospholipids
• If not protected, small quantities of undigested
  fats may pass
• More fat leaves the rumen than enters
• Long chain fatty acid alterations in the rumen
• Biohydrogenation
• Microbial synthesis of long-chain fatty acids

9

• Results of long-chain fatty acid metabolism
• 
  Feed
• Fatty acid Corn Barley-SBM-Tallow conc Grass
• Saturated
• 140 - 2.5 4.6
• 160 7.0 32.7 20.8
• 180 2.4 20.6
  3.3
• Unsaturated
• 161 - .8
  2.4
• 181 45.6 25.1 5.7
• 182 45.0 16.5 14.0
• 183 - 1.9 49.2
• 
  Intramuscular fat
• Swine
  Beef
• Saturated Barley-SBM-Tallow conc
  Grass
• 140 2.0 2.3 2.7
• 160 23.8 27.4 22.8
• 18.0 10.6 16.0 14.7
• Unsaturated

10

• Biohydrogenation
• Microorganisms
• Primarily bacteria, particularly cellulolytic
  bacteria
• Protozoa
• Contain 75 of the microbial fatty acid in rumen
• Not actively involved in biohydrogenation
• Contains high concentrations of 182 CLA
• Obtained by ingesting bacteria
• Fungi have capability for biohydrogenation, but
  make up a small proportion of the microbial
  biomass

11

• Processes
• From Linoleic acid
• High roughage diet
• Linoleic acid (cis-9, cis-12 182)
• cis-9, trans-12
  isomerase
• from Butyrvibrio
  fibrisolvens
• (Rapid)
• Conjugated linoleic acid (CLA, cis-9,
  trans-11 182)
• Also called Rumenic
  acid
• cis-9 reductase
• from Butyrvibrio
  fibrisolvens
• (Rapid)
• Vaccenic acid (trans-11 181)
• trans-11 reductase
• from Clostridium
  proteoclasticum
• (Slow)
• Stearic acid (180)

12

• High grain diet (Low pH)
• Linoleic acid (cis-9, cis-12 182)
• trans-9, cis-12
  isomerase from
• Megasphaera elsdenii,
  Streptococcus bovis
• (Rapid)
• Conjugated Linoleic Acid isomer (trans-10,
  cis-12 182)
• cis-12 reductase from
• Megasphaera elsdenii,
  Streptococcus bovis
• (Rapid)
• Trans-10 181
• trans-10 reductase
• (Slow)
• Stearic acid (180)

13

• From Linolenic acid
• High roughage diet
• Linolenic acid (cis-9, cis-12, cis-15 183)
• Cis-9, trans-11, cis-15 183
• Trans-11, cis-15 182
• Vaccenic acid (trans-11 181)
• Stearic acid (180)

14

• Why do bacteria reduce unsaturated fatty acids
• Mechanism to use excess hydrogen
• Detoxify unsaturated fatty acids
• Results of biohydrogenation
• High roughage diets
• High concentrations of CLA (cis-9, trans-11 182)
  and vaccenic acid (trans-11) 181 in the rumen
• High concentrate diets
• High concentrations of trans-10, cis-12 182 and
  trans-10 181 fatty acids in the rumen
• On all diets
• High concentrations of stearic acid
• These fatty acids will be absorbed in the small
  intestine and represent a high proportion of the
  fatty acids presented to tissues

15

• Tissue metabolism of trans isomers of fatty acids
• Conversion of trans-11 181 to CLA (cis-9,
  trans-11 182)
• Occurs in mammary gland and adipose
• Major source of CLA (cis-9, trans-11 182) in
  meat and milk
• Mechanism
• 9 - desaturase
• Trans-11 181
  CLA (cis-9, trans-11 182)
• 
  2H
• Other pathways for delta-9 desaturase
• Palmitic acid (160) Palmitoleic
  acid (161)
• Stearic acid (180) Oleic acid
  (181)

16

• Effects of biohydrogenation of unsaturated fatty
  acids in ruminants
• Increased concentrations of saturated fatty acids
  in meat and milk
• Increased concentrations of CLA (cis-9, trans-11
  182) in ruminant meat and milk
• Anticarcinogenic
• Reduces atherosclerosis
• Alter body composition
• Diabetes control
• Improved immune response
• Improved bone mineralization
• Milk fat depression in lactating dairy cows
• trans-10 181 produced from linoleic acid in cows
  fed high grain diets will directly inhibit long
  chain fatty acid synthesis in the mammary gland
• Reduces the vitamin E requirement of ruminants
• Indicates a low essential fatty acid requirement
  in mature ruminants

17

• Microbial synthesis of fatty acids
• Distribution of lipid in the rumen
• 
  of total lipid (Wet digesta)
• Bacteria 4.1
• Protozoa 15.6
• Feed particles in rumen fluid 80.3
• Bacterial synthesis
• C180 and C160
• From acetate and butyrate
• Long straight-chain, odd-numbered fatty acids
• From propionic acid or valeric acid at the
  initial step
• Increase in cobalt-deficient animals because
  vitamin B12 is needed for animals to use
  propionate for glucose
• Long branched-chain fatty acids
• From branched chain VFAs (Isobutyrate,
  Isovalerate) at initial step
• Flavor components in meat and milk
• 15-20 of the bacterial fatty acids are
  monounsaturated
• Can not synthesis polyunsaturated fatty acids
• Bacterial synthesis increases on low fat, high
  concentrate diets

18

• Lipid digestion in the small intestine
• Mechanism similar to nonruminants
• Ether extract digestibility in small intestine is
  lower than in nonruminants
• Saturated fatty acids are better absorbed in
  ruminants than nonruminants
• Unsaturated fatty acids are less absorbed in
  ruminants than nonruminants

19

• Mechanism of lipid digestion in small intestine
• Unesterfied Triglyceride
  Phospholipid
• fatty acids
• Pancreatic
  Phospholipase A1
  lipase
  Phospholipase A2
• Unesterfied Monoglyceride
  Lysolecithin
• fatty acid
• Bile salt
• 
  Phosphatidylcholine
• 
  Phosphatidylethanolamine
• Micelles
• Absorbed into
  mucosa
• Micelles break
  up
• Fatty acids lt 14 C are transported directly
  in the blood
• 10 of the 180 is
  desaturated to 181
• Long chain fatty acids combine with
  lipoproteins to produce VLDL and
  chylomicrons

20

• Lipid transport in the blood
• Transport from the intestine
• Very low density lipoproteins
• Major transport structure from the small
  intestine
• Favored by saturated fatty acids
• Chylomicrons
• Less prevalent than in nonruminants
• Smaller than nonruminants
• Contain 2x more phospholipid than nonruminants
• Freeesterified cholestrol ratio is 41 compared
  to 11 for nonruminants
• VLDLs and chylomicrons contain apoprotein-C
• Inhibits liver removal of VLDLs and chylomicrons
• Activates lipoprotein lipase at muscle, adipose,
  and mammary tissue
• VLDLs and chylomicrons are very short-lived in
  ruminants
• 70 of lipids are on HDL
• 20 of lipids are on LDL

21

• Liver synthesis of lipoproteins
• Little synthesis of fatty acids in liver and
  lipoproteins from intestinal mucosa are not
  utilized by liver
• Liver synthesis of triglycerides are dependent on
  the concentrations of circulating non-esterified
  fatty acids (NEFAS) and glycerol from glucose
• If glucose is limiting glycerol synthesis and
  fatty acid oxidation, the NEFAS are oxidized to
  ketones
• Synthesized triglycerides are incorporated into
  VLDL to be transported throughout the body

22

• Fat depots
• Location
• Subcutaneous
• Inter and intramuscular sites
• Visceral sites
• Fatty acid composition
• General
• 80 of FA are 140, 160, 180, and 181
• Small amounts of 182 and very little 183
• Unsaturated fatty acids will have both cis and
  trans isomers
• Odd-numbered chain length fatty acids
• Branched chain fatty acids
• Effects of body location of fatty acid
  composition
• Subcutaneous fat has more unsaturated fatty acids
  the inter and intramuscular fat which has more
  than internal fat
• Most external subcutaneous fat and fat in limbs
  is more unsaturated than more internal
  subcutaneous fat

23

• Methods to alter fatty acid composition of meat
  and milk
• Increasing the CLA content of meat or milk
• Feeding unsaturated fatty acids
• Dose-dependent
• Excessive amounts may inhibit intake and
  digestion
• Greater with polyunsaturated oils than
  monounsaturated oils
• Processed oil seeds
• More effective than whole seeds
• Less detrimental than pure oils
• Ca-salts
• Fish oil
• Grazing forages
• More effective than stored forages
• Most effective if forages are immature
• Breed differences

24

• Seasonal changes in CLA in dairies in NE Iowa
• Breed differences
• Delta-9
  desaturase activity
• Wagyu
  Holstein
• Muscle 3.3 0.8
• Adipose 132.1 39.5

25

• Increasing the concentrations of polyunsaturated
  fatty acids in meat and milk
• Processes
• Feeding whole oil seeds
• Binding of unsaturated fatty acids with Ca
• Limitations
• Expense
• Undegraded fat in the duodenum may reduce rumen
  motility and feed intake
• Ca complexes are unpalatable
• Product quality concerns

26

• Fat supplementation of ruminant diets
• Amounts
• Added fat should be limited to 3-4 of diet DM
• Since normal diet contains 3 fat, the total
  dietary fat should be limited to 6-7 of DM
• Types
• Unprotected oils
• Vegetable oils
• Highly unsaturated
• Expensive
• Most adverse effects on digestion, intake and
  milk fat
• Animal fats (Tallow, grease etc.)
• Most commonly added to beef and dairy diets
• More saturated
• Less adverse effects
• Difficult to mix in cold weather

27

• Whole oil seeds
• Whole soybeans, cottonseed, high oil corn
• Increases proportion of oil escaping ruminal
  metabolism
• Less adverse effects than free oils
• Easy to use
• Cost effectiveness
• Ruminally inert fats
• Types
• Ca salts of long chain fatty acids
• Prilled fat (Saturated fat processed in small
  spheres)
• Escapes ruminal digestion of fat
• Less adverse effects than free oils
• Will reduce feed intake
• Expensive
• Use only if fat percentage from feed sources is
  greater than 5 of the diet dry matter

28

• Advantages of fat supplementation
• Increase energy concentration of the diet
• Energy content of fats
• Gross energy of tallow is 9.4 Mcal/kg
• Digestible energy of fats Metabolizable energy
• Little fermentative energy loss
• Can increase dietary energy concentration without
  decreasing forage level of diet
• It is essential to maintain adequate forage in
  the diet to minimize the negative effect of fat
  on milk fat percentage indairy cows
• Also need to maintain adequate levels of nonfiber
  carbohydrates (30-40)
• Fats increase energy without increasing heat
  increment
• In lactating dairy cows, it may elevate fat test
• Particularly if protected fats are fed
• Milk fat depression may occur after use

29

• Improved reproduction
• Conception rate may be increased by 17
• Mechanism
• Increased energy balance
• Reduce insulin and increase progesterone
• Increases follicle size and number
• Reduce prostaglandin F2alpha
• Increases persistence of corpus luteum
• Response may not occur if the cows use the
  supplemental energy for milk production
• Improved diet characteristics
• Reduce dust
• Increase pellet strength

30

• Limitations of fat supplementation
• Reduced fiber digestion in the rumen
• Mechanisms
• Physically coating the fiber
• Toxic effects on microbes
• Decreased cation availability
• Free fatty acids are more toxic than
  triglycerides
• Reduced feed intake
• Mechanisms
• Reduced fiber digestion
• Reduced gut motility
• Reduced palatability
• Oxidation of fat in liver
• Milk fat depresssion
• Mechanisms
• Production of trans fatty acids
• Reduced fiber digestion

31

• Decreased mineral digestion
• Mechanism
• Formation of soaps with Ca and Mg
• Reduction in milk protein in dairy cows
• Relationship
• Milk protein, 101.1-.6381x.0141x2
• where x total dietary fat,
• Caused more by increased milk production than a
  decrease in protein synthesis

32

• Approaches to limit negative effects of fat
  supplementation
• Effects on intake, digestibility and milk fat
• Method of feeding
• Do not feed greater than 4 supplemental fat
• Feed small amounts several times daily
• Feed fats in total mixed rations (TMRs)
• Meet fiber requirement
• Type of fat
• Feed saturated fats instead of unsaturated fatty
  acids
• Feed inert fats
• Whole seeds
• Calcium salts of long chain fatty acids
• Prilled fat

33

• Effects on mineral absorption
• If feeding unsaturated fats, the amounts of Ca
  and Mg fed should be increased by 20 to 30
• Effects on milk protein percentage
• Supplementing ruminally undegraded amino acids
• Supplementing nicotinic acid at 12 gm/d

34

• Considerations in choosing a supplemental fat
  source
• Inertness
• CaLFA or gt Whole oil seeds gt Tallow gt Vegetable
  oils
• Prilled fat
• Other nutritional concerns
• Protein
• In no protein needed, supplement tallow
• If degradable protein needed, supplement raw
  seeds
• In undegradable protein needed, supplement with
  undegradable protein source
• Heat-treated soybeans
• DDGS
• Fiber
• If fiber is needed, supplement whole cottonseed
• Antiquality factors
• Gossypol in whole cottonseed
• Limit whole cottonseeds to 8 lb/day

35

• Price per pound of fat
• Protected fats (1.50/lb fat)
• Oil seeds (.82-1.12/lb fat)
• Tallow (.25/lb fat)
• Vegetable oil (.49/lb fat)
• Timing of supplementation for dairy cows
• Delay supplementation of fat until weeks 6-7 of
  lactation
• If cant delay because of feeding TMR, limit
  maximum supplementation to 2.5 of DM
• Fat supplementation should be terminated to
  prevent the cows body condition to not go above
  3.5 on a 5-point scale