Studies on the alimentary tract of merino sheep in South Africa. VI. The role of infusoria in ruminal digestion with some remarks on ruminal bacteria

Abstract

(1) A technique is described for the preservation and counting of ruminal infusoria. (2) Reactions of specific infusoria as well as total infusorial populations to changes in the diet of stable fed sheep were investigated. (3) Seasonal fluctuations of ruminal infusoria of sheep grazing on the veld are described. The amount of protein available in the pasture was shown to have a significant influence on the density of the infusorial population. (4) Data are presented comparing the density and types of infusoria in veld-grazing sheep and different species of antelopes in their natural state. (5) The digestion of maize starch within an infusorium from material in vivo is described. The brown glycogen-like granules formed within the foodsac and plasma of the infusorium have been shown to be glycogen synthesizing bacteria and not actual glycogen granules as hitherto accepted. (6) The rate of digestion of starch within the rumen was shown to be the same whether infusoria were present or not. It was therefore concluded that infusoria do not accelerate the rate of digestion of starch and that they merely act as hosts to starch attacking bacteria and bacterially secreted diastatic enzymes ingested by the organism. (7) That infusoria assist in the digestion of cellulose could not be proved. It was concluded that the digestion of cellulose within the body of the infusorium is primarily due to cellulose digesting bacteria ingested by the infusorium.