Effects of feeding level and duration on finishing performance and slaughter traits of Holstein-Friesian young bulls

In two factorial experiments, autumn/winter-born Holstein-Friesian bull calves were reared conventionally and spent their first summer at pasture. They were then offered low (L), medium (M) or high (H) feeding levels and slaughtered after a short finishing period (S) or after a long finishing period (E). In Experiment 1, L, M and H feeding levels were concentrates at 3 kg/day, 6 kg/day and ad libitum, respectively. L and M also had ad libitum access to grass silage while H received a minimum of 1 kg silage dry matter (DM) per head daily. Finishing periods were 179 (S) and 272 (E) days. In Experiment 2, L, M and H target feeding levels were proportionately 0.3, 0.6 and 0.9 concentrates with grass silage. Target slaughter weights were 550 (S) and 640 (E) kg. Initial live weights were 306 kg and 282 kg in Experiments 1 and 2, respectively. There were 54 animals (9 per pen) in Experiment 1 and 48 animals (8 per pen) in Experiment 2. In Experiment 1, mean live-weight gains for L, M and H were 914, 1141 and 1358 (s.e. 25.1) g / day, respectively. Corresponding mean carcass weights were 274, 304 and 338 (s.e. 3.3) kg. Carcass conformation score improved and carcass fat score increased with increasing feeding level. In Experiment 2, mean live-weight gains for L, M and H were 946, 1182 and 1223 (s.e. 27.5) g/day, respectively. Corresponding mean carcass weights were 322, 329 and 306 (s.e. 4.3) kg. It is concluded that Holstein-Friesian bulls of about 300 kg live weight that have spent a season at pasture have the capacity to grow at 1.2 to 1.4 kg / day during a finishing period of 6 to 9 months. A carcass weighing around 320 kg and of acceptable conformation and fatness can be produced from feed inputs of either 1.3 t concentrates plus 1 t silage DM or 1.8 t concentrates plus 0.2 t silage DM.