Effects of dietary supplementation with branched-chain amino acids (BCAAs) during nursing on plasma BCAA levels and subsequent growth in cattle

To determine the effects of short-term dietary supplementation of branched-chain amino acids (BCAAs) during nursing (from 3 to 28 days of age) on plasma BCAA levels and subsequent growths in cattle, 12 nursing male Holstein calves, randomly assigned to control and treatment groups (n = 6 in each group), orally received a daily supplement of essential BCAAs (2 g/kg body weight/day; 1:1:1 of valine, leucine and isoleucine) or not. The plasma BCAA levels increased linearly after the administration. During the treatment period, average daily gain (ADG) was lower in the treatment group (0.43+/-0.07 kg/day) than the controls (0.71+/-0.07 kg/day, p<0.05). However, at 2 months of age, ADG was significantly higher in the BCAA-treated group (1.16+/-0.26 kg/day vs. 0.51+/-0.06 kg/day, p<0.05). Furthermore, at age 8, 9 and 10 month, ADG in the treated group (1.35+/-0.23, 1.46+/-0.07 and 1.60+/-0.16 kg/day, respectively) showed a linear increase and was significantly higher than that in the control group (0.88+/-0.14, 0.70+/-0.21 and 1.11+/-0.11 kg/kg, respectively, p<0.05). Overall, ADG was 15.6% higher in the treatment group (1.26+/-0.05 kg vs. 1.09+/-0.04 kg; p<0.05). The final body weight at slaughter was 14.8% higher in the treatment group (759.5+/-17.7 kg vs. 661.7+/-21.2 kg, p<0.01). Thus, the supplementation of BCAAs during nursing improves ADG and carcass weight in cattle and is a useful husbandry technique for beef cattle.