The increased consumer awareness of diet and health related aspects has increased the demand for leaner beef. Nutritional factors which influence carcass composition include plane of nutrition, diet type, forage:concentrate ratio and protein supplementation. An experiment has been carried out to examine the independent and interacting effects of protein supplementation and forage:concentrate ratio on performance and carcass composition of finishing beef heifers.

The six experimental diets used consisted of two dietary crude protein (CP) levels (142 (LP) and 175 (HP) g CP/kg dry matter (DM)) each offered at three forage:concentrate ratios in a 2 x 3 factorial design. High (HF), medium (MF) and low(LF) forage diets contained on a DM basis 0.75, 0.50 and 0.30 grass silage and 0.25, 0.50 and 0.70 concentrates respectively. In the HF diets, grass silage was offered ad libitum but intake was restricted in the MF and LF diets so as to equalise total metabolisable energy (ME) intakes for the six diets. In the LP diets, the control concentrate consisted of (g/kg) 925 ground barley, 50 molasses and 25 minerals and vitamins.