Does the Supplementation during the Growing Phase and Finishing Phase Influence the Performance of Nellore Cattle?

The objective of this study was to evaluate the effect of the supplementation level during the growing and the finishing phase on the performance of Nellore bulls in pasture. Forty calves (172 ± 26 kg, 8 mo) were used in a randomized block designed study with a 2×2×2 factorial arrangement of treatments (2 supplementation levels in the cold, warm season and in the finishing phase). The growing phase comprises all the seasons of the year, so it was subdivided into cold (fall/winter) and warm (spring/summer) seasons. Thus, twenty animals were fed 1 g/kg BW per day (CP = 54%, TDN = 40%) and twenty animals were fed 5 g/kg BW per day (CP = 25%, TDN = 58%) during the cold season. Afterwards, in the warm season, the animals from each supplementation during the cold season were fed either mineral salt ad libitum or 5 g/kg BW. Then, in the finishing phase, the same animals of each supplementation strategies during the growing phase were fed with one of two levels of concentrate (15 or 20 g/kg BW per day, CP = 17% or 14%, TDN = 76 or 77%, respectively). At the end of the experiment (405 days) bulls were weighed and slaughtered. All parts of the body were weighed separately to quantify the empty body weight (EBW). All data (EBW, HCW, no-carcass components [NCC = blood, heart, lung, spleen, liver, kidney, gastrointestinal tract and KPH] and gut fill) were analyzed using the PROC MIXED of SAS with an alpha = 0.05. There were no interactions between supplementation levels during the phases (P > 0.05), so the factors were analyzed separated. The cold season supplementation did not affect any variables (P > 0.05). In the warm season, animals fed 5 g/kg BW had greater EBW (471 vs. 425 kg, P < 0.01), HCW (303 vs. 269 kg, P < 0.01) and NCC (168 vs. 156 kg, P = 0.01) compared with animals fed mineral. On the finishing phase, animals fed 20 g/kg BW had greater EBW proportion (940 vs. 923 g/kg BW, P < 0.01) and lower gut fill (30 vs. 37 kg, P = 0.03) than those fed 15 g/kg BW. In conclusion, supplementation in the cold season does not influence the performance of finishing Nellore bulls in pasture. However, the greater level of supplementation in the warm season and in the finishing phase produce animals with greater BW.