Relationship between bacteria and ciliate protozoa in the rumen of sheep fed on a purified diet

Abstract

Summary Two sheep, with and without ciliate protozoa, were fed on a wood-pulp cellulose, corn starch, soya-bean protein diet and the microbiological and chemical characteristics of the rumen ingesta of both sheep were studied. The purified diet led to a simplified rumen flora enabling some deductions to be made about the interactions of the principal bacterial species and their interactions with the protozoa in relationship to the biochemical analysis of the rumen. Ammonia concentrations were similarly low in each animal. Total volatile fatty acid concentrations were higher in the faunated sheep though the proportion of propionic acid was highest in the unfaunated sheep. Cellulose digestion in the faunated rumen was about twice that in the unfaunated one. Total bacterial concentrations in the unfaunated rumen were over twice those in the faunated rumen, but the numbers of cellulolytic bacteria were higher in the latter while the numbers of amylolytic bacteria were higher in the unfaunated rumen. The principal species of bacteria differed in the two rumens.