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Fat Digestion and
Metabolism in Ruminants
Vishnu Vardhan Reddy.P
TVM/2015-029
Department of Animal nutrition
College of Ve...
• Usually the diets of cattle contains 2-4% of lipids.
• And contribute 50% of milk fat and good source of energy.
• The m...
Common fatty acids found in the diet of dairy cows
Fat Digestion and Absorption in Ruminants
• Most of the cattle diets predominantly contains PUFA as part of plant
triglyce...
Lipolysis or Hydrolysis
• Rumen hydrolysis has been most extensively characterised in
Anaerovibrio lipolytica which hydrol...
• This breakdown of dietary lipids is quite rapid and complete so that
no monoglycerides or diglycerides pass to the lower...
Lipid digestion in rumen
DigalDigly MonogalDigly
Galactose
Propionate Diglyceride
Glycerol
Triglyceride Fatty acids
Satura...
• The fatty acids released in the rumen are not absorbed from the
rumen, but rather will pass to the abomasum and then the...
Biohydrogenation
• As unsaturated fatty acids are released from the glycerol backbone in
lipolysis, they are quickly hydro...
• The initial step in biohydrogenation is an Isomerization reaction that
converts the cis-12 double bond in unsaturated fa...
Hydrogenation of fatty acids in the rumen
Polyunsaturated fatty acids (all cis)
Isomerase (from bacteria)
Needs free carbo...
Conjugated Linoleic Acid – Rumen Most Common
Pathway (High Roughage)
Linoleic acid (cis-9, cis-12-18:2)
Conjugated linolei...
• This accounts for the relatively high content of trans-fatty acids in ruminant
products.
• Under low rumen pH conditions...
• In the rumen, most of the free fatty acids are actually found as potassium,
sodium, or calcium salts of fatty acids beca...
• The key to absorption of fatty acids in both ruminants and
nonruminants is formation in the intestine of complexes calle...
Intestinal processing and delivery of dietary fat
• After absorption of fatty acids into intestinal cells, the fatty acids...
• Because these lipoproteins are too large to pass directly into the
venous blood stream draining the intestinal cells, th...
• Triglycerides in chylomicrons or VLDL are broken down to free fatty
acids by an enzyme called lipoprotein lipase that is...
Utilization of dietary lipids by the udder
• About half the fat in the milk is derived from the uptake of fatty acids
by t...
The role of liver and fat mobilization
• During periods of under feeding or in early lactation, cows meet their
energy dem...
• The liver does not have a high capacity to form and to export TG-rich
LP and the excess mobilized fatty acids are stored...
THANK YOU
Vishnu Vardhan Reddy.P
TVM/2015-029
Chemical nature of Triglycerides
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Fat digestion and metabolism in ruminants

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Fat digestion and metabolism in ruminants, lypolysis, bio hydrogenation, animal nutrition, sri venkateswara veterinary university tirupati

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Fat digestion and metabolism in ruminants

  1. 1. Fat Digestion and Metabolism in Ruminants Vishnu Vardhan Reddy.P TVM/2015-029 Department of Animal nutrition College of Veterinary Science, Tirupati Sri Venkateswara Veterinary University
  2. 2. • Usually the diets of cattle contains 2-4% of lipids. • And contribute 50% of milk fat and good source of energy. • The major lipid constituents in dairy cow nutrition are: Triglycerides: Major lipid type found in cereal grains, oilseeds, animal fats, and byproduct feeds. Glycolipids: Major lipid type found in forages. Phospholipids: Form the cell membrane of all animal cells, and the surface of milk fat globules. Free fatty acids: Minor component of dairy feeds, but major component of certain fat supplements.
  3. 3. Common fatty acids found in the diet of dairy cows
  4. 4. Fat Digestion and Absorption in Ruminants • Most of the cattle diets predominantly contains PUFA as part of plant triglycerides and glycolipids. • Bacteria in the rumen split off the fatty acids (and sugars) from the glycerol backbone called as lipolysis or Hydrolysis. • Then the released fatty acids undergo hydrogenation called as Biohydrogenation.
  5. 5. Lipolysis or Hydrolysis • Rumen hydrolysis has been most extensively characterised in Anaerovibrio lipolytica which hydrolyses Triglycerides and Butyrivibrio fibrisolvens which hydrolyses Phospholipids and Glycolipids. • Lipase enzyme secreted by bacteria involves in this lipolysis. • The glycerol and the sugars released from glycolipids are fermented to the volatile fatty acids (VFA) where Propionic and Butyrate acids are major end products.
  6. 6. • This breakdown of dietary lipids is quite rapid and complete so that no monoglycerides or diglycerides pass to the lower digestive tract. • The major exception to this would be when a highly saturated triglycerides are fed. • Protozoa are not involved to any great extent in hydrolysis, except for that of phospholipids. • Salivary lipase present in ruminants has a very low activity, where as in monogastric animals it play a more important role.
  7. 7. Lipid digestion in rumen DigalDigly MonogalDigly Galactose Propionate Diglyceride Glycerol Triglyceride Fatty acids Saturated FA CaFA Ca++ Feed particles -galactosidase -galactosidase Lipase Anaerovibrio lipolytica H+ Reductases Lipase
  8. 8. • The fatty acids released in the rumen are not absorbed from the rumen, but rather will pass to the abomasum and then the small intestine, which is the primary site for absorption of the fatty acids. • However, the profile of fatty acids that reaches the intestine will be very different from what the animal has consumed. • This is because of the extensive Biohydrogenation that occurs in the rumen as a result of bacterial activity.
  9. 9. Biohydrogenation • As unsaturated fatty acids are released from the glycerol backbone in lipolysis, they are quickly hydrogenated to saturated fatty acids. • In cows fed most typical diets, more than 90% of the unsaturated fatty acids will be biohydrogenated to produce saturated fatty acids that flow to the small intestine. • Lipolysis occurs more rapidly than the biohydrogenation thus large amounts of unsaturated oils can “overwhelm” the biohydrogenation process and result in undesirable effects on the rumen microbial population.
  10. 10. • The initial step in biohydrogenation is an Isomerization reaction that converts the cis-12 double bond in unsaturated fatty acids to a trans- 11 isomer. • During the biohydrogenation process due to isomerization , intermediate compounds with trans-double bonds are produced e.g. conjugated linoleic acid (CLA). • Some of these trans-intermediates escape from the rumen and are incorporated into body fat and milk fat of ruminants.
  11. 11. 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, mostly cellulolytic) Hydrogenated fatty acid (stearic and palmitate)
  12. 12. Conjugated Linoleic Acid – Rumen Most 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 At low rumen pH, trans-10, cis-12 isomer of CLA is produced.
  13. 13. • This accounts for the relatively high content of trans-fatty acids in ruminant products. • Under low rumen pH conditions a different set of trans-intermediates may be produced. Some of these products, particularly those with a trans-double bond between the 10th and 11th carbons, have very powerful inhibitory effects on milk fat synthesis and so milk fat depression may result. • The lipids after hydrogenation leave the rumen predominantly as free fatty acids (85-90%) and phospholipids (10-15%) found as part of microbial cell membranes.
  14. 14. • In the rumen, most of the free fatty acids are actually found as potassium, sodium, or calcium salts of fatty acids because of the near-neutral pH in the rumen contents (6.0 – 6.8). • After passing through the acid conditions (pH ~2.0) of the abomasum, however, the fatty acid salts are dissociated and the free fatty acids will be found adsorbed to the surface of small feed particles that pass as part of the digestive contents. • The fatty acids making up the free fatty acid portion will be predominantly saturated (80-90%), with about two-thirds stearic acid and about one- third palmitic acid.
  15. 15. • The key to absorption of fatty acids in both ruminants and nonruminants is formation in the intestine of complexes called micelles. • which are bi-layer disks consisting of bile salts, phospholipids, and the insoluble lipids in the middle. • Micelles are needed to move the fatty acids to the surface of the intestinal cells where they can be absorbed into the cells.
  16. 16. Intestinal processing and delivery of dietary fat • After absorption of fatty acids into intestinal cells, the fatty acids are reconverted to triglycerides by combining with glycerol produced from metabolism of blood glucose. • These triglycerides, some free fatty acids, cholesterol and other lipid like substances are coated with protein to form triglyceride-rich lipoproteins (TG-rich LP) also called chylomicrons or very low density lipoproteins (VLDL).
  17. 17. • Because these lipoproteins are too large to pass directly into the venous blood stream draining the intestinal cells, they are secreted into the lymph, which is delivered back into the blood stream near the heart. • After the blood is oxygenated through the lungs, then, the lipoprotein particles or chylomicrons are delivered to various organs of the body such as the mammary gland, muscle, and heart that can use the triglycerides.
  18. 18. • Triglycerides in chylomicrons or VLDL are broken down to free fatty acids by an enzyme called lipoprotein lipase that is found in the capillaries of these tissues. • The free fatty acids then enter the cells where they can be formed back into triglycerides (such as milk fat) or burned to release energy that can fuel cell functions. • It should be noted from the scheme for lymphatic absorption described here that dietary fats do not reach the liver directly, in contrast to other absorbed nutrients.
  19. 19. Utilization of dietary lipids by the udder • About half the fat in the milk is derived from the uptake of fatty acids by the mammary gland these fatty acids primarily from the triglyceride-rich lipoproteins formed during the intestinal absorption of lipids. • An increase in long chain fatty acids (i.e., acids made of more than 16 carbons) In the diet increases their secretion in milk, but it also inhibits the synthesis of short and medium chain fatty acids in the mammary tissue Thus, the marked depression in fat secretion is seen.
  20. 20. The role of liver and fat mobilization • During periods of under feeding or in early lactation, cows meet their energy demand by mobilizing fat from adipose tissues to obtain energy in addition to that provided by the diet. • Mobilized fatty acids are taken up by the liver where they can be used as an energy source or be converted to ketones. • These ketones may be released in the blood and used as an energy source by many tissues.
  21. 21. • The liver does not have a high capacity to form and to export TG-rich LP and the excess mobilized fatty acids are stored as triglycerides within the liver cells. • The fat deposited in the liver contributes to development of metabolic disorders (e.g. , ketosis-and fatty liver) in early lactation.
  22. 22. THANK YOU Vishnu Vardhan Reddy.P TVM/2015-029
  23. 23. Chemical nature of Triglycerides Back

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