The influence of concentrate supplementation during the dry and rainy seasons on performance of young Nellore bulls grazing tropical grass pastures

Context In the tropics, there is a substantial demand for a broader understanding of the impact of supplementation strategies on animal growth. Aims The aim of this study was to evaluate the effects of different concantrate supplementation strategies during the dry, rainy, or both seasons on intake, digestibility, performance, and carcass weight of young Nellore bulls. Methods Twenty-eight young Nellore bulls with an initial average liveweight (LW) of 327 ± 4.2 kg of were used. Animals had ad libitum access to a Urochloa brizantha pasture and a mineral mixture sequentially in dry and rainy seasons. Treatments consisted of the following four concentrate supplementation strategies: (1) no concentrate supplementation (−/−); (2) 8 g/kg LW in rainy season (−/+); (3) 8 g/kg LW in dry season (+/−); and (4) 8 g/kg LW in both dry and rainy seasons (+/+). Key results Forage intake was lesser (P < 0.05) in cattle fed +/+ when contrasted against all other supplementation strategies. In the dry season, concentrate supplementation increased (P < 0.04) LW gain from 0.40 to 0.74 kg/animal.day. Considering performance in both the dry and rainy seasons, all supplementation strategies increased (P < 0.05) total LW gain, hot carcass weight, carcass fat and muscle when compared with the negative control treatment −/−. Bulls receiving +/+ had greater (P < 0.05) total LW gains and hot carcass weights than did −/+ and +/− treatments. Directly contrasting −/+ and +/−, supplementation in the rainy season tended (P < 0.10) to increase total LW gain and hot carcass weights. Conclusions Under the conditions of this experiment, concentrate supplementation decreased forage intake but increased LW gain, hot carcass weight and carcass quality. Concentrate supplementation in both the dry and rainy seasons provided greater LW gain and hot carcass weights than did concentrate supplementation during only the dry or rainy seasons. Concentrate supplementation only during the rainy season produced greater hot carcass weights and LW gains than did concentrate supplementation only during the dry season. Implications To achieve maximum LW gains and hot carcass weights, concentrate supplementation should be provided during both dry and rainy seasons. If supplementation costs are a limiting factor, concentrate supplementation during the rainy season is likely to provide greater LW gains and carcass weights than does concentrate supplementation only during the dry season. However, pasture nutritive value, carcass prices and supplement costs must be evaluated before selecting a supplementation strategy.