Do Protein Supplementation Levels Influence the Performance of Male Nellore Calves Under a Grazing System at...

This study aimed to evaluate the effects of sequential supplementation with different crude protein levels and periods on performance, nutritional and metabolic characteristics, and efficiency of nitrogenous compounds use in grazing male Nellore calves at pre-weaning. Fifty male Nellore calves during pre-weaning were distributed in a completely randomized design in a 2 × 2 factorial arrangement. The strategies were as follows: Supplementation period in the initial pre-weaning was 1-78th experimental day and in the final pre-weaning was 79-156th experimental day. The Low and high protein levels in the supplement were 150 g CP/kg) and 300 g CP/kg, respectively. All animals received 6 g/kg BW of supplement. Protein levels in the supplement did not affect intake of forage DM, and neutral detergent fiber in the animals. However, a higher CP intake and the CP to DOM ratio (p-value < 0.05) was evidence for the high calves compared with low calves. Supplementation strategies did not affect the blood concentrations of IGF-1, glucose, and total protein. Likewise, protein levels in the supplement did not affect the ADG and number and diameter of muscle fibers. In conclusion, the decrease in protein levels in the supplement from 300 to 150 g CP/kg DM does not detrimentally affect performance and nutritional and metabolic characteristics in male beef calves under a grazing system at pre-weaning.