There is an increasing demand for heavy lean carcases and, at the same time, an increasing proportion of barley beef animals being finished as bulls. Bulls have a high potential for muscle growth and, therefore, have a high demand for dietary protein. In addition, since the banning of hormone implantation of beef animals, there has been increasing interest in the use of feed additives.

This trial was designed to measure the response of Holstein/Friesian bulls to increasing protein content in barley beef rations, and to measure the benefits of including lasalocid sodium (a feed additive). Responses were measured in terms of improved liveweight gains and feed conversioin efficiencies but also of interest was the effect of treatments on the weights at which animals reached a given fat class at slaughter.