ractopamine in diets for finishing pigs of different sexual categories

Abstract

Performance and carcass and cut yield of finishing pigs of three sexual categories fed diets with different levels of ractopamine were studied. Forty-eight hybrid animals (initial weight of 92.1±2.4 kg) were distributed in a completely randomised design in 3 × 2 factorial arrangement (three sexual categories: surgically castrated males, two females and immunologically castrated males - with or without 10 ppm of ractopamine), totalling six treatments and eight repetitions with one animal per experimental plot during 28 days. Ractopamine improved weight gain and feed conversion of all sexual categories. The best results were obtained with immunologically castrated males, which, in turn, had lower carcass yield and backfat thickness in the belly. In the absence of ractopamine, depth and loin eye area were higher in females but no differences in these variables were observed between categories when this additive was used. Ractopamine increased the sirloin yield in all sexual categories. There was no difference in bonus index. Ractopamine improves the performance of pigs of 92 to 125 kg. Immunologically castrated males have the best performance responses to ractopamine, but with losses in carcass yield, loin characteristics and backfat thickness of the belly.