The work was carried out to evaluate the effect of animal sex, genetic group and slaugher weight on fedlot lambs performance. One hundred and three male and female lambs, purebred Santa Inês (SS) and crosses between Santa Inês and Texel (TS), Ile de France (FS) and Bergamacia (BS) were fedlot in individual cages. Diet and orts were daily collected to calculate the intakes of dry matter (MS), metabolizable energy (EM), digestible protein (PD) and neutral fiber detergent (FDN). The lambs were slaughtered at four weights: 15, 25, 35 and 45 kg of live weight. Weight gain (GPD), number of days in confinement (ND), feed:gain ratio (CA) and intakes of MS, PD, EM and FD were analyzed during three growing phases: 15 to 25 kg (1), 25 to 35 kg (2) and 35 to 45 kg (3), for each genetic group and each sex. The slaughter age (IA) and the empty body weight (PCVZ) were also analyzed. At high weights, TS and FS male lambs showed inferior IA, and the female lambs, superior IA. ND of BS lambs from 35 to 45 kg was superior than TS lambs. From 35 to 45 kg, PCVZ of TS and FS lambs was inferior. The best GPD was observed for TS lambs, followed by FS and SS. The intakes of MS, PD, EM and FDN were similar among the genetic groups, during the phases 1 and 2. TS lambs intake tended to increase as body weight increased, whereas the other groups showed tended to decrease. CA increased as slaughter weight increased. The males did not show differences in CA among the genetic groups, but TS and FS females showed better results. At 35 and 45 kg, the females showed superior RC than the males. At 35 kg, the TS males showed better RC than the other groups.
sheep; breeding; intake; weight gain
