Effects of supplement type during the pre-finishing growth phase on subsequent performance of Nellore bulls finished in confinement or on tropical pasture

Abstract

Our objective was to evaluate the effect of supplement type fed during the pre-finishing growth phase of grazing Nellore bulls on gain performance during the subsequent finishing phase, either in confinement or on pasture. During the pre-finishing growth phase, bulls were grazed on pastures of Urochloa brizantha cv. Marandu. Bulls were supplemented with 1 of 4 supplements: (1) ad libitum mineral mixture (MM), (2) ground corn (GC), (3) GC with soybean meal (SBM), or (4) GC with dried distillers grain (DDGM). All supplements were administered at 3 g/kg of body weight (BW) on a dry matter (DM) basis. Eighty bulls were distributed in a completely randomized, 4 × 2 factorial arrangement, with 4 pre-finishing supplementation treatments (MM, GC, SBM, or DDGM) and 2 finishing systems (pasture or confinement). Ten cattle from each postweaning treatment were kept on pasture (n = 3 paddocks/treatment), and 10 bulls were housed in confinement pens (n = 3 pens/treatment). Bulls finished on pasture were offered a concentrate supplement consisting of 337.6 g/kg dried distillers grain (DDG), 611.2 g/kg GC, and 56.1 g/kg MM. The final diets offered in the confinement system consisted of 300 g/kg corn silage, 427.8 g/kg GC, 263.3 g/kg DDG, and 35.8 g/kg MM (DM basis). During the finishing phase, bulls that received GC and DDGM in pasture consumed more CP than bulls in the confinement system ( P = 0.001). Nutrient digestibility was greater among the bulls in pasture than those in confinement ( P ≤ 0.001), likely because of the lower proportion of NDF consumed by bulls that expressed selective grazing behavior ( P = 0.001). Daily weight gain was affected by pre-finishing history ( P = 0.03) and finishing system ( P ≤ 0.001) and was lower after SBM supplementation for bulls on pasture ( P = 0.009). The final BW ( P ≤ 0.001), hot carcass weight ( P = 0.005), and fat thickness ( P ≤ 0.001) were greater in bulls finished in confinement, but carcass yield was greater in bulls from pasture ( P ≤ 0.001). Preweaning supplementation affected the intake of nutrients in Nellore bulls finished on pasture postweaning but did not affect the intake of bulls finished in a confinement feedlot. Supplementation with DDGM in the preweaning phase (3 g/kg of BW) did not affect animal performance or carcass traits in either finishing system. Therefore, it is an option for replacing conventional supplements.