RESUMO
At approximately 68 kg live weight, crossbred barrows and gilts (n = 144) were allocated to be fed to one of two weight end points (107 kg and 125 kg). Pigs from each weight group were treated with Ractopamine (RAC) (0, 10, or 20 ppm; n = 24/ treatment for the last 40 kg of gain. Feed consumption and weight gain were measured. Pigs were slaughtered and carcass measurements made at 24 h postmortem. Carcasses were fabricated into wholesale, trimmed wholesale, and boneless wholesale cuts for cutting yields. Hams were separated into muscle, fat, and bone. The RAC improved growth characteristics and carcass characteristics. Pigs fed RAC had increased (P < .01) average daily gain and improved (P < .01) feed:gain ratio over controls in each weight group. Carcasses from pigs treated with RAC had larger (P < .01) longissimus muscle area and reduced (P < .01) fat at the 10th rib. Cuts from 125-kg pigs were generally heavier than those from 107-kg pigs. The RAC increased (P < .05) the boneless cut weights of both weight groups. Percentage of dissected lean from the hams of RAC-treated pigs was (P < .05) higher than that of controls. Few consistent differences were observed between the 10 and 20 ppm of RAC treatments. Results from this study indicate that RAC had positive effects on the growth characteristics, carcass characteristics, and carcass cutting yields of pigs representative of the broad spectrum of market weights.
