Changes in composition of the digesta along the alimentary tract of sheep.

Because of the complexity of the interactions involved very few attempts have been made to trace the fate of ingested food in the course of its digestion and absorption along the alimentary tract of the ruminant. Elsden, Hitchcock, Marshall & Phillipson (1946) made a comparative study of the weights of the digesta and their dry-matter and volatile fatty-acid content in the consecutive parts of the alimentary tract of four sheep. By means of a lignin-ratio method Hale, Duncan & Huffman (1947a, b) showed that maximum digestion in the bovine rumen was obtained within 1 2 h after feeding and tended to come to a standstill thereafter. They found that during the first 6 h the predominant phenomenon was the rapid disappearance from the rumen of the more soluble nutrients. During the next 6 h after feeding, cellulose was rapidly disintegrated. Under the conditions of their experiment an average of I 1.6 yo cellulose and 9-5 % protein was later released from the food residues in their further passage along the tract. No observations were made on the fate of the digesta in the other parts of the tract. When, therefore, an experiment of one of our colleagues made a number of ewes available we investigated changes in the quantity and composition of the digesta along the alimentary tract, and also changes in each part of the tract with time after feeding. The concentrations of dry matter (D.M.), ash, nitrogen, energy and volatile fatty acids (v.F.A.) were estimated. Such information is fundamental to a more dynamic appraisal of the processes of digestion and absorption.