Published online by Cambridge University Press: 02 September 2010
Two experiments were carried out to examine the effects on the intake and performance of calves of supplementing a diet, based on high-digestibility, well-preserved grass silage, with fish meal. The effects of fish-meal supplementation were examined at each of two amounts of concentrate intake (1·05 and 2·2 kg/day) in a 2 × 2 factorial design. Fish meal was offered at a rate of 75 g/kg silage dry-matter (DM) intake. Experiments 1 and 2 involved 36 and 40 castrated male calves, respectively, which were initially 7 weeks old and had a live weight of 70 kg. The treatments were imposed for 20 weeks. The silages used in the two experiments had mean concentrations of 22-8 g nitrogen (N) per kg DM; 524 g protein N per kg total N; 59 g ammonia N per kg total N; 0·4 g butyric acid per kg DM; and 712 g digestible organic matter per kg DM. The concentrate consisted of (g/kg) 800 ground barley, 125 soya bean meal, 50 molasses and 25 mineral and vitamin supplement, respectively, and contained 29 g N per kg DM. Silage DM intakes and live-weight gains for the low and high amounts of concentrate supplementation were 1·93 and 1·46 (s.e. 0·055) kg/day and 0·84 and 1·01 (s.e. 0·013) kg/day respectively. The supplement of fish meal did not affect silage DM intake or animal performance for either concentrate intake. Proportionately, only 0·21 of the difference in live weight at the end of the treatment periods between the two amounts of concentrate intake remained at slaughter at 18 months of age. It is concluded that the optimum growth rate for autumn-born calves during their first winter can be sustained by a diet of high-digestibility grass silage supplemented with a maximum of 1·0 kg cereal-soya bean meal concentrate and that no response in performance was obtained to supplementation of this diet with fish meal.