Supplementation with Yea-sacc - yeast (Saccharomyces cerivisiae ‘1026’) and its growth medium - has been found by several workers to alter rumen fermentation patterns, increase milk yield and growth rate in dairy cows and calves. This experiment investigated the effect of inclusion in the diet of intensively fed bulls on rumen fermentation and animal performance.

Twenty-six Limousin x Friesian bulls reared to 3 months of age on a common diet were allocated to treatment on the basis of liveweight and previous growth rate at an average liveweight of 133 kg.

The Treatments were Control ‘C” and Yea-sacc ‘YC’ - the control diet supplemented with Yea-sacc. (Alltech Inc. USA) at 1.5 kg/tonne of fresh feed. The diet was a mixture of barley and soyabean meal (Tables 1 & 2) with the inclusions of the latter reduced at 159 days. Mineral and vitamin supplements were included together with molasses to bind the ingredients.