EFFECT OF DIETARY CIMATEROL ON PERFORMANCE AND CARCASS TRAITS IN BULLS AND ON ASPECTS OF DIGESTION IN CATTLE AND SHEEP

Forty-eight finishing Belgian White-blue bulls were used to examine the effect of 4 ppm cimaterol on liveweight gain, feed efficiency and carcass traits. Cimaterol was incorporated in a complete dry feed, which was fed ad libitum for 225 d. The digestibility and the rumen fermentation pattern of the diet were determined with wethers fed near maintenance. Digestibility was also determined with growing bulls fed to appetite. During the first half of the production trial, cimaterol improved growth rate and feed efficiency. During the second part, daily gain and feed efficiency were decreased by cimaterol. Cimaterol significantly increased dressing percentage and EUROP conformation score and altered carcass composition towards more meat and less fat. Other than a decrease for crude fibre, digestibility coefficients were not affected in cimaterol-treated sheep. In bulls fed ad libitum, the digestibilities of dry matter, organic matter, crude fibre and energy were reduced by cimaterol. Rumen fluid of cimaterol-treated sheep contained a significantly higher level of acetic and propionic acid and a significantly lower level of butyric acid.