Effects of mineral buffers on the rumen flora of sheep fed grain diets

The structure of the microbial population of rumen liquor froom sheep fed diets of roughage and of whole wheat grain with and without mineral buffer additives was studied. Addition of either 2 per cent of a mixture of 1/1/1/1 sodium bicarbonate, potassium bicarbonate, disodium hydrogen phosphate and calcium hydrogen phosphate or of 1 per cent of aluminium hydroxide to grain diets acted to increase microbial concentration, allow persistance of a rumen flora of predominatly Gramnegative staining characteristic, and to increase the proportion of rods. Animals consuming these diets had an improved production performance. In the absence of dietary buffers the microbial population shifted towards a Gram-positive population with no reduction in the proportion of coccal forms.