Impact of supplementation during the dry season on performance of young Nellore bulls in the post-weaning phase on pasture in the wet season
This study evaluated the impact of nutritional strategies on the performance of young Nellore bulls during the post-weaning phase. The experimental period was divided into dry (July-November 2012) and wet (November 2012 to May 2013) seasons. The design was completely randomized, using 60 young Nellore bulls which were distributed into 12 paddocks (experimental units) formed by Brachiaria brizantha pastures (5 animals/lot; 6 lots/treatment). In the summer, the paddocks were subdivided (3 from each dry season treatment in each new wet season treatment). In the dry season, the animals were assigned to two treatments: a) protein supplement (1 g/kg of body weight; BW) and b) protein and energy supplement (5 g/kg of BW); in the summer were assigned to two treatments: a) mineral supplement ad libitum and b) protein and energy supplement (5 g/kg of BW). To determine the average daily gain (ADG), the animals were weighed at time zero (onset of the experiment) and subsequently every 28 d after being deprived of feed and liquids for 16 h. The data were analyzed as repeated measures over time using the PROC MIXED procedure of SAS. In the dry season, the protein and energy supplementation provided greater ADG (0.434 kg) as compared with the protein supplement (0.293 kg), resulting in heavier animals at the end of this season (225.38 and 208.87 kg, respectively; P = 0.093). In the summer, animals fed the protein and energy supplement gained more weight (0.972 kg/day; P < 0.0001) in relation to those fed mineral salt (0.623 kg/day). Although no interaction was found in ADG (P = 0.4798) between the nutritional plants of dry and wet seasons, the animals which received protein and energy supplementation in the dry season gained less weight (0.766 kg/day; P < 0.001) in comparison with those supplemented with protein (0.830 kg/day); this made it possible, at the end of the summer, to eliminate the difference in BW obtained during the dry season. At the end of the post-weaning phase, the young bulls fed protein and energy supplement in the summer completed the period heavier as compared with those fed mineral salt (286.75 and 261.76 kg, respectively; P = 0.0045). Protein and energy supplementation during the dry season had negative impact on the ADG in the summer, and increased the BW of the animals at the end of the dry and wet season by 7 and 9%, respectively.
Keywords: energy, performance, protein