A comparison of silage-based and dried forage-based diets, and the effect of protein supplementation of a silage-based diet for finishing beef cattle

Abstract

ABSTRACTAn experiment was carried out to compare silage-based and dried forage-based diets for finishing beef cattle and to examine the effects of protein supplementation and formaldehyde treatment of silage on performance and carcass composition. The four diets used consisted, on a dry matter basis, of (1) 700 g/kg formic acid-treated grass silage and 300 g/kg low protein cereal-based concentrate (LPC), (2) 720 g/kg formic acid-treated silage and 280 g/kg high protein cereal/fish meal concentrate, (3) 600 g/kg formaldehyde-treated silage and 400 g/kg LPC, and (4) 480 g/kg artificially dried grass and grass hay and 520 g/kg LPC. The silages were well preserved with 33 to 40 g ammonia N per kg total nitrogen. The diets were offered to 40 British Friesian castrated male cattle which were initially 387 (s.e. 2·9) kg live weight. For diets 1 to 4 respectively metabolizable energy intakes were 91·8, 94·7, 94·9 and 91·8 MJ/day; total nitrogen intakes 192, 234, 189 and 191 g/day; live-weight gains 0/89, 0/93, 0/86 and 0/82 (s.e. 0/045) kg/day; carcass gains 0·51, 0·52, 0·52, 0·52 and 0·50 (s.e. 0·33) kg/day; mean subcutaneous fat depths 5·6, 5·4, 5·3 and 6·0 (s.e. 0·41) mm; marbling scores 3·0, 3·3, 3·2 and 2·6 (s.e. 0·19) and areas of m. longissimus dorsi 65·7, 66·4, 64·7 and 64·3 (s.e. 1·66) cm2. It is concluded that performance, efficiency of energy utilization and carcass fatness were similar for a diet containing 700 g/kg well preserved grass silage and a dried forage-based diet with a similar intake of energy and protein. Protein supplementation of a diet based on formic acid-treated silage or formaldehyde treatment of silage did not affect performance or carcass fatness.