EFFECTS OF FEED ON THE COMPOSITION OF THE RUMEN CILIATE PROTOZOAL POPULATION IN CATTLE AND ITS RELATIONSHIP TO CELLULOLYTIC CILIATE PROTOZOA

A cross feeding trial of barley alone or barley straw alone, using six fistulated cattle, was conducted to survey the effects of diet on the composition of the rumen ciliate protozoal population and to evaluate the contribution of cellulolytic protozoa to the digestion of plant materials. The average value for total ciliates ml-1 of rumen contents was much higher in cattle fed barley straw (4.6 × 104) than in those fed barley (8.5 × 103). The average number of genera appearing per host was 5.4 in cattle fed straw and 2.2 in cattle fed on barley. In both feeding regimes, Entodinium was always predominant. Other than Polyplastron, cellulolytic protozoa such as Eremoplastron, Diploplastron, Ostracodinum, and Diplodinium were not detected when animals were fed barley. Our experimental observations of the ingestion of straw fragments by cellulolytic protozoa and the vicissitudes of cellulolytic protozoal populations are likely to be indicative of diet-dependent metabolic differences in rumen function and of the contribution of protozoa in the digestion of plant materials, and suggest that protozoa may play an important role. © 1990.