Cobalt requirement of beef cattle - feed intake and growth at different levels of cobalt supply

In a study using a total of 36 German Simmental beef bulls weighing between 236 kg and about 620 kg the question of what constitutes an adequate Co su pply was investigated with reference to the performance criteria growth, fe ed intake, energy intake, nutrient intake and carcass criteria. The bulls r eceived a diet of corn silage dd libitum and 2.5 kg concentrate for a perio d of 280 days. Ten rations (R) with graduated Co supplements were fed with mean concentrations of 0.07 (R1), 0.09 (R2), 0.11 (R3), 0.15 (R4), 0.18 (R5 ), 0.26 (R6), 0.33 (R7), 0.42 (R8), 0.59 (R9) and 0.69 (R10) mg Co per kg d ry matter (DM) intake. The Co supplement was added as CoSO4. 7H(2)O. The di ets with no or low Co supplementation produced either distinctly lower dail y gains of 1045 g (R1) and 1130 g (R2) or lower daily gains of about 1260 g (R3, R4) than rations R5-R10, where daily gains averaged 1340 g. The mean daily feed intake per animal was also significantly or marginally affected with values of 6.0 kg DM (R1) rising to 7.7 kg DM (R2-R4) versus 7.9 kg DM on average (R5-R10). Calculations using the broken line model and the quadr atic model show that the optimal Co supply for maximum growth is 0.12 mg/kg dietary DM and for maximum feed intake, 0.16-0.18 mg Co/kg dietary DM. Aft er taking further biochemical criteria into account (STANGL et al. 2000), a level of 0.20 mg/kg dietary DM is recommended as an adequate Co supply for growing cattle.