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 h ealth and performance was investigated in 90 double-muscled and 48 non -double-muscled Belgian White-blue bulls during 60 and 51 days, respec tively, upon arrival at the experimental farm. The yeast was incorpora ted in the concentrate, which was fed at 2 kg d(-1) during the first t en 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 antib iotic therapy for each yeast level within each beef strain. Rumen samp les taken from 6 non-double-muscled bulls in the last but one week sho wed a decreased concentration of volatile fatty acids when 6 g yeast w as fed daily. Except butyric acid concentration, rumen fermentation pa rameters were not altered. Yeast supplementation during an adaptation periode after purchase did not affect health status and growth perform ance.