Additives in beef cattle supplementation grazing Marandu pasture

Brazil has the bigger beef market production in the world, however to keep this position, increase productivity is necessary. By this sense, the use of addictives in diet it seems to be a way. The aim of this study was evaluate the effect of supplementation with virginiamycin (V) or essential oil (EO) in animal grazing Brachiaria brizantha cv Marandu pasture during winter (July - September). The experiment was conducted at the Forage sector in Faculty of Agricultural Sciences and Veterinary (FCAV) of Sao Paulo University with 40 Nellore young bulls (404?23 kg). The treatments were: protein / energy supplement with V and EO, provided the amount of 3 or 6 g kg^-1 of BW, totaling four treatments. Herbage mass, stock rate and animal performance was evaluated. Were used eight paddocks (n = 8), managed in continuous stocking during 90 d. The treatments were arranged in a completely randomized design in factorial arrangement 2 x 2 (level x additives) with repeated measures in time (three periods) utilizing SAS. No differences were found in forage characteristics (P > 0.09). Animals supplemented with 6 g kg^-1 showed bigger stock rate 2331 kg ha^-1 (P=0.002) and animal performance 0.77 kg d^-1 (P=0.034). Animals supplemented with virginiamycin achieved larger performance compared with essential oils 0.78 kg d^-1 (P = 0.022). Higher level of supplementation (6 g kg^-1) with virginiamycin showed better performance in animal grazing Marandu pasture.