Studies on the alimentary tract of Merino sheep in South Africa. XI. Digestion and synthesis of starch by ruminal bacteria

Abstract

1. The only diastases present in the rumen seem to be those secreted by ruminal bacteria, which would then be responsible for the entire starch disintegration seen there. 2. In the rumen of sheep receiving a regular supply of starch in the diet, the bacterial disintegration of starch granules commenced after 5 hours and was completed within 18-20 hours. In the case of sheep not receiving starch in the diet, disintegration of the starch administered through the fistula commenced after 7 hours and took 8-10 hours to complete. 3. Starch granules of the various cereals differ in size and shape. The diameter of starch granules influences their rate of disintegration within the rumen. 4. Some of the products of starch degradation are resynthesized into glycogen and starch-like polysaccharines within certain ruminal bacteria and pseudo-yeasts. 5. The iodophilic micro-organisms encountered in the rumen and associated with the disintegration and digestion of starch, are described. 6. An iodophilic streptococcus closely associated with the disintegration of starch was isolated in pure culture and some of its characteristics described.