Two randomised block experiments, involving 64 British Friesian and Friesian cross steers, have been carried out to compare extracted soyabean, extracted sunflower and fish meals as protein supplements for yearling cattle offered grass silage ad libitum. Two formic acid-treated, precision chopped silages, each made from the primary growth and first regrowth of a perennial ryegrass sward, were used. The control concentrate consisted of (g/kg) 925 barley, 50 molasses, 25 minerals and vitamins. The three high protein concentrates were similar to the control but with 0.30, 0.54 and 0.20 of the barley replaced by soyabean, sunflower and fish meals respectively. The mean chemical compositions of the silages and concentrates used in the two experiments are given in Table 1. All animals received 1.3 kg concentrates per head daily. They were initially 11 months old and 334 kg live weight. The treatments were imposed for 126 days.