Digestion in the Ruminant

Abstract

Summary 1. The diet of ruminants is peculiar in that it contains large quantities of cellulose and other carbohydrates which are indigestible except by the aid of bacteria; it is probable that the numerous protozoa of the rumen do not play a vital part in digestion. 2. Food passes to the fermentation chamber formed by the reticulum and rumen where it is kept in continual motion by rhythmic contractions of this organ. Regurgitation is caused by an inspiratory effort with a closed glottis; the bolus after being remasticated returns to the fermentation chamber. 3. Passage of ingesta from the rumen is slow and spread out over a period of days. Digestion is more efficient in the ruminant than in the horse and pig owing to the greater time spent by the food in its alimentary tract rather than owing to the act of remastication. 4. The voluminous secretion of saliva is responsible for the maintenance of a moisture content and reaction of the ingesta of the rumen suitable for the bacterial fermentation of carbohydrate. The conditions are anaerobic, since carbon dioxide and methane are the chief gases present, oxygen being found only in traces, if at all. 5. The breakdown of cellulose and other carbohydrates is accomplished mainly by bacteria, though plant enzymes may play a minor part. The products of this fermentation are largely carbon dioxide, methane and the volatile fatty acids, though it has been suggested that a starch‐like polysaccharide is synthesized. The degree of digestion of cellulose is affected by the other constituents of the diet. 6. The rate and degree of digestion observed by the use of an indigestible constituent of the food as an index show that the total digestion and in particular that of cellulose in the rumen is considerable within 14 hr.; this is supported by measurements of the rate of evolution of methane. 7. Absorption of the volatile fatty acids and of certain drugs has been proved to occur from the rumen. 8. Fermentation is not confined to the rumen; it also occurs in the caecum of the ruminant. The authors are greatly indebted to Sir Joseph Barcroft, F.R.S., for his constructive criticism and help in the preparation of the manuscript.

Factors Affecting the Utilization of Food by Dairy Cows

“…5. These were presumably the peristaltic waves that occur at the pyloric end of the abomasum (McAnally & Phillipson, 1944). There was no apparent relationship between the cycle of movements in the reticulo-omasal orifice and the movements of the abomasum.…”

“…Paloheimo (1939) slaughtered cows at intervals after giving them chromium sesquioxide, and found that the passage of this very heavy substance to the omasum had begun even in those cows killed immediately after administration. Phillipson (1946) suggested that there must be a constant flow of digesta through the reticulo-omasal orifice because the omasum, abomasum and intestines contain digesta at all times. In sheep the flow of digesta from the abomasum was found to be in gushes with usually less than 15 min.…”

The Absorption of Ammonia Through the Rumen of the Sheep

“…Total steam volatile fatty acids were estimated by the method of McAnally (1944). The pH of solutions was measured with either a Cambridge or a Pye Universal pH meter.…”

Herbal extracts as antiviral agents

“…Ruminants, or four-stomached animals such as cow, goat, sheep, and buffalo, differ in their digestion physiology compared to other livestock (McAnally and Phillipson, 1944). Livestock provides a huge impact on the agricultural industry as a source of protein from meat and milk in large-scale or small-scale production.…”