Studies on the alimentary tract of Merino sheep in South Africa. IV. Description of experimental technique

Abstract

1. The importance is stressed of a more intensive study of digestion in ruminant animals, whose food, apart from being disintegrated by enzymes liberated from the digestive tract itself, is first of all subjected to a predigestion, the significance of which is as yet not fully recognised. Through the action of a varied and rich bacterial flora accompanied by large numbers of different species of infusoria, the food mass is exposed to carefully controlled fermentation occurring within the forestomachs and similar in many respects to that occurring in silage fermentation. 2. In order to study the different stages in the process of digestion, the use of permanent bowel fistulae in experimental animals has been widely resorted to in the past, and an account is given of some of the experimental methods which have been used. 3. An account is given of our experimental technique which involves the use of suitable ebonite fistula tubes and the creation of permanent “closed” fistulae at different levels of the digestive tract of adult Merino sheep. 4. In this study attention has thus far been devoted mainly to some phenomena exhibited within the rumen of fistula sheep, kept on various controlled diets. 5. A method has been devised whereby any pressure change occurring within the rumen could be accurately recorded on slow moving kymographs and the limits of fluctuation in the motility of this organ registered under varying conditions. 6. The technique is described whereby samples of ingesta could repeatedly be collected from the rumen and subjected both to chemical and bacteriological study. 7. By the use of a large water manometer attached to the rumen fistula, continuous volume recording of gas from the rumen could be conducted under constant pressure. Likewise repeated sampling of gas for chemical analysis could simultaneously be undertaken. 8. Methods are described whereby different materials could be administered through the fistula opening directly into the rumen. By enclosing small samples of a variety of foodstuffs within cylindrical bags made from thin natural silk and subsequently suspending these within the food mass of the rumen, the rate at which disintegration took place as also its nature, could be followed microscopically.