Digestion and Absorption of Lipids and Bile Acids in Sheep Fed Stearic Acid, Oleic Acid, or Tristearin

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Abstract
Sheep were fed diets containing 7.5% added stearic acid, oleic acid or tristearin for 21 days. In addition, 50 .mu.Ci/kg 141Ce was included for the last 10 days on experimental diets as an unabsorbed reference substance. In the rumen, dietary triglycerides were .apprx. 50% hydrolyzed, and hydrogenation resulted in saturation of the free fatty acid fraction. Some net synthesis of phospholipids, presumably microbial phospholipids, occurred in the rumen. In the intestine immediately distal to the pylorus, extensive secretion of bile acids, cholesterol, phospholipids, triglycerides, free fatty acids and lipase occurred. This resulted in doubling of fatty acid fluxes through the duodenum. These endogenous secretions were reabsorbed rapidly, with the major site of lipid and bile acid absorption in the region 0.6-4 m distal to the pylorus. Additional but less absorption occurred in the more distal segments of the small intestine. Overall absorption of stearic acid, oleic acid and tristearin supplements was in the range 60-70%, and no differences were apparent between fats. Unsaturated fatty acids were > 90% absorbed as compared with 55-65% for saturated fatty acids. No significant effect of any supplement was observed on ruminal total volatile fatty acids, ratio of volatile fatty acids or on overall cellulose or caloric digestion.
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