The effect of supplementing a low–protein hay on the cellulolytic bacteria in the rumen of sheep and on the digestibility of cellulose and hemicellulose

Abstract

SUMMARYA study was made of the effects of supplementing low-protein teff (Eragrostis tef) hay with (a) protein (egg albumin), (b) urea and (c) urea plus C4and C5branched-chain volatile fatty acids (VFA) on the cellulolytic flora in the rumen of sheep conditioned to these diets and on the digestibility of cellulose and hemicellulose. Addition of urea, as opposed to no supplementation, increased voluntary hay intake and the percentage digestibility of cellulose and hemicellulose, while counts of cellulolytic bacteria were not greatly affected. The proportion of ruminococci amongst the cellulolytic bacteria increased somewhat and that of the butyrivibrios decreased. When branched-chain VFA were added to the hay together with urea the numbers of cellulolytic bacteria per g rumen ingesta and the proportion of ruminococci increased over those for urea alone. This was accompanied by a further increase in voluntary hay intake. Percentage digestibilities of cellulose and hemicellulose were similar to those for the urea/hay diet. Supplementation with protein resulted in lower digestibility of α-cellulose and hemicellulose when compared with the urea-supplemented diets. The cellulolytic bacteria formed a lower percentage of the ‘total culturable’ counts than was the case for the other diets.