Performance and carcass traits of crossbred cattle raised in pastures supplemented or not with virginiamycin.

he aim of this study was to assess performance and carcass traits of crossbred cattle raised grazing tropical grasses, receiving supplement with or without virginiamycin (VM). Steers (n = 49) and heifers (n = 56) produced from matting Nellore, ½ Nellore x ½ Angus and ½ Nellore x ½ Caracu dams with Braford, Charbray and Caracu sires were raised grazing tropical grasses ( Brachiaria brizantha cv. Marandu) from 9 to 20 mo of age. The animals were divided into eight paddocks of eight hectares each, with care to form groups containing individuals of all genetic groups and balanced in age and average body weight (BW). During the dry season (July to October) cattle received protein supplements containing (n = 52) or not VM (n = 53), formulated for intake of 1 g kg -1 of BW and during the rainy season (November to June) cattle received mineral mixtures containing (n = 52) or not VM (n = 53). The VM was included in the supplements to provide an intake of 45 mg 100 kg -1 of BW. Supplements were provided in open troughs ad libitum and intake was evaluated by weighing monthly leftovers.