Effect of yeast supplementation on health, performance and rumen fermentation in beef bulls

The effect of 0, 6 or 60 g yeast (Saccharomyces cerevisiae) daily on health and performance was investigated in 90 double-muscled and 48 non-double-muscled Belgian White-blue bulls during 60 and 51 days, respectively, upon arrival at the experimental farm. The yeast was incorporated in the concentrate, which was fed at 2 kg d-1 during the first ten days and at 2.5 kg d-1 afterwards. Besides, maize silage was fed up to 8 kg d-1, while grass hay was offered ad libitum. Feed intake, growth rate and number of sick animals were not affected by the yeast addition. Morbid animals required a similar number of days with antibiotic therapy for each yeast level within each beef strain. Rumen samples taken from 6 non-double-muscled bulls in the last but one week showed a decreased concentration of volatile fatty acids when 6 g yeast was fed daily. Except butyric acid concentration, rumen fermentation parameters were not altered. Yeast supplementation during an adaptation period after purchase did not affect health status and growth performance.