Question

Please note that this is an ANIMAL SCIENCE QUESTION. do not answer if unsure.

Please read question carefully and answer it thoroughly. All answers must be typed and brevity is appreciated. (be detailed)

1. Describe the processes involved in lipid absorption from the small intestine in the ruminant.  Include the compound(s) that cross the luminal side of the epithelial cell and the processes that occur within the cell. Also describe the fate of the lipid compounds once they leave the epithelial cell.

Answer 1

In ruminants, first stage of lipid digestion begins in reticulorumen as bacteria split fatty acids from glycerol by hydrolysis. The fatty acids released in rumen, after biohydrogenation will pass to abomasum then the small intestine where they form aggregates called micelles by combining with bile and pancreatic secretions. 15-20% of total FA are absorbed in the upper jejunum, 55-65% in the middle and lower jejunum. The efficiency of the bile salt and lysophospholipid micellar system to solubilise FA and the acidic conditions of duodenal and jejunal contents account for the ability of ruminants to absorb saturated fatty acids.

The initial step of biohydrogenation is isomerization reaction to form a trans-11 isomer of PUFA. The lipids after hydrogenation, leave the rumen as free fatty acids and phospholipids. The free fatty acids will be stearic acids and palmitic acids. The bilayer discs called micelles are formed in the intestine with bile salts and phospholipids in the middle which help fatty acids to move to the surface of the intestinal cells. After absorption to the intestinal cells, FA are reconverted to triglycerides by combining with the glycerol produced by the metabolism of blood glucose. These along with some free fatty acids and cholesterol get coated with proteins to form chylomicrons or VLDL. These are secreted into the lymph and delivered to blood. Then the chylomicrons are delivered to the various organs of the body such as mammary glands that can use the triglycerides. VLDL are broken down to free fatty acids by lipoprotein lipase enzyme in the capillaries of these organs. These free fatty acids enter the cells, where they can be formed back to triglycerides, such as milk fat, or burnt to release energy.