The optimum post-weaning growth using different levels of dietary protein in Pakistan calves

The aim of this study was to provide different levels of dietary protein for optimum growth performance in calves and to investigate the impact on the concentration of insulin-like growth factor-1 (IGF-1) in serum. Female Sahiwal calves (n = 12, body weight (BW) = $40{\pm}4.3kg$ and age = $60{\pm}10days$) were selected and divided into three groups with 4 animals in each group. Three diets of T0, T1 and T2 with 18, 20 and 22% of crude protein levels, respectively, were given to the calves to assess the post-weaning growth performance. Calves fed the T2 diet showed a higher (p < 0.05) dry matter (DM) intake than those fed the T0 and T1 diets. The feed conversion ratio (FCR) for the calves fed the T2 diet was lower (p < 0.05) than those of the calves fed the T0 and T1 diets. The T2 group had the highest BW (p < 0.05) compared with the other groups. The concentration of IGF-1 in serum increased (121.9, 143.3, and 152.9 ng/ml for T0, T1, and T2, respectively) as the crude protein (CP) level increased. Overall, the results of this study suggest that post weaning diets T1 and T2 with 20 and 22% crude protein in Sahiwal female calves had significantly increased the BW and serum IGF-1 concentration. The IGF-1 estimation might be a physiological indicator for growth performance.