Studies on the alimentary tract of merino sheep in South Africa. VII. Fermentation in the forestomachs of sheep

Abstract

In studies conducted on merino sheep with permanent ruminal fistulae, it has been demonstrated that acute gas production in the forestomachs immediately after the consumption of certain foods is associated with a process of oxidative assimilation. By this process variable proportions of such sugars as glucose, fructose, and sucrose are rapidly oxidised through the agency of a strain of false yeast, Schizosaccharomyces ovis, which is present in large numbers in the rumen of sheep, especially when such animals are kept on a diet of lucerne. Attending this oxidation of part of the ingested sugar, large volumes of gas are suddenly generated within the ruminal mass. Simultaneously with this, the rest of the sugar is rapidly assimilated and stored as glycogen by the yeast cells. Complete starvation or inadequate feeding of the animal is promptly followed by suppression leading up to a total disappearance of this yeast strain. Under these circumstances various iodophilic bacteria normally present in the ruminal ingesta are afforded the opportunity of metabolising the available sugar. This is associated with the synthesis of starch by these organisms instead of glycogen. Moreover, oxidation shows greater restriction as is evident from the reduced amount of gas produced. While this extensive synthesis of glycogen and other polysaccharides forms an integral part in the carbohydrate metabolism of various ruminal micro-organisms, its full significance in the biology of the microflora and especially in the nutrition of the host animal itself is as yet not fully understood. In view of the close relationship existing between ruminant digestion and bacterial activity there are indications, however, that the nutrition of ruminant animals is vitally linked with various products derived from bacterial metabolism, hence the necessity of further investigations in this field.