Intestinal digestion of subterranean clover by sheep

Abstract

Quantitative studies have been made of digestion in the small and large intestines of sheep offered a diet of subterranean clover (Trifolium subterraneurn c.v. Clare) at levels approaching ad libitum. As in previous studies with a similar diet, most of the digestion of organic matter and of cell wall constituents occurred in the stomach; by contrast, the release of long-chain fatty acids and amino acids mainly occurred in the intestines. Although two-thirds of the dietary long-chain fatty acids were C18:2 and C 18: 3, hydrogenation in the rumen reduced their proportion to less than 20 % in the digesta leaving the stomach. The amounts of long-chain fatty acids that passed from the stomach were equivalent to about 127 % of intake. Approximately 70 % of these fatty acids were removed from the digestive tract subsequently, and most of the absorption occurred in the small intestine. The total amounts of these fatty acids absorbed from the intestines were equivalent to approximately 90% of the amount consumed, even though their apparent digestibility in the whole tract was only 61 %. Most of the nitrogen that passed from the stomach was in the form of amino acids. Of the 189 g amino acids that passed from the stomach, less than one-third reached the terminal ileum. The net losses of individual amino acids in the small intestine ranged from 66% to 84% of the amounts that passed from the stomach. It was estimated that approximately one-third of the organic matter and almost 60% of the nitrogen that passed from the stomach was present in bacterial cells. A major component of bacterial cell walls, diaminopimelic acid, was apparently not absorbed from the small intestine, though appreciable amounts of this amino acid were lost in the large intestine.