A comparison of soya-bean, sunflower and fish meals as protein supplements for yearling cattle offered grass silage-based diets

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Abstract
Two experiments were carried out to examine the relative value of soya-bean, sunflower and fish meals as protein supplements for growing beef cattle offered grass silage ad libitum. In each experiment, well preserved grass silage (116 and 119 g crude protein (CP) per kg dry matter (DM) and 69 and 76 g ammonia-N per kg total N in experiments 1 and 2 respectively) was supplemented with (1) barley (107 g CP per kg DM), (2) barley/soya-bean meal (224 g CP per kg DM), (3) barley/sunflower meal (223 g CP per kg DM) and (4) barley/fish meal (218 g CP per kg DM). Each of the supplements was offered at a rate of 1·3 kg per head daily to 32 British Friesian castrated male cattle (mean initial live weight 334 kg) n i each experiment. The treatments were imposed for 118 and 134 days in experiments 1 and 2 respectively and the animals were slaughtered 8 months after the end of the treatment periods. On average over the two experiments for supplements 1 to 4 respectively, silage DM intakes were 6·2, 6·3, 6·3 and 6·2 (s.e. 0·053) kg/day; live-weight gains 0·69, 0·78, 0·71 and 0·80 (s.e. 0·039) kg/day; carcass weights 375, 377, 377 and 374 (s.e. 8·1) kg, carcass fat classification (1 = leanest, 5 = fattest); 3·5, 3·5, 3·4 and 3·6 (s.e. 0·14) and areas of m. longissimus dorsi 19·8, 19·9, 19·7 and 19·3 (s.e. 0·66) mnv/kg carcass weight. It is concluded that when part of a barley supplement given in addition to well preserved grass silage was replaced with soya-bean, sunflower or fish meals, silage intake was not affected. The inclusion of fish meal in the diet increased live-weight gain by HOg/day and the response to soya-bean meal was 0·78 of the response to fish meal per unit of crude protein. Sunflower meal did not affect performance. The treatments did not affect carcass weight or fatness 8 months after the end of the treatment periods.