Consumer demand for leaner beef necessitates a reduction in the fat content of a major proportion of the beef carcasses currently produced. It is generally accepted that reducing the plane of nutrition of beef cattle reduces fat content. However the effects on growth rate and overall efficiency of production are also important. The effects of reducing energy intake on performance and carcass composition may be influenced by the nature of the change in energy intake. An experiment has been carried out to examine the effects of reducing energy intake, either by increasing forage: concentrate ratio (F:C) in the diet or reducing dry matter intake at constant F:C.

Thirty-six Friesian (F), Limousin x F and Belgian Blue x F 12-month old steers which were initially 368 kg, and which had been reared under uniform management and nutrition were used. They were purchased from dairy farms during October and November at approximately 10 days old, were aritifically reared and were at pasture from April until October. After a three week acclimatization period they were divided into blocks according to breed and live weight and allocated to the three treatments at random with each block. The three treatments were a complete diet consisting of 0.67 grass silage (719 g digestible organic matter and 144 g crude protein/kg DM; 82 g ammonia N/kg total N) and 0.33 concentrates (0.9 rolled barley and 0.1 soyabean meal) offered (1) ad libitum or (2) at 0.8 of ad libitum intake.