Effects of feeding ractopamine to physically castrated barrows, immunologically castrated barrows, and gilts on carcass characteristics, cutting yields, and fresh meat quality

ABSTRACT Ninety carcasses were used to evaluate the effects of feeding ractopamine (RAC) to gilts, physically castrated (PC) barrows, and immunologically castrated (IC) barrows. Finishing diets (0, 5, and 7.5 mg/kg RAC) were fed for the last 26 d before slaughter starting 7 d after the second dose of Improvest. Carcasses from IC barrows had less ( P P = 0.02) than PC carcasses but had more ( P ≤ 0.04) fat than gilt carcasses. Feeding RAC increased ( P = 0.03) bone-in carcass yields by 1.4 percentage units. Gilt and IC carcasses had 2.0 percentage units greater ( P P = 0.01) bone-in lean yields, and 1.5 percentage units greater ( P = 0.04) bone-in carcass yields than PC carcasses. Loin firmness, pH, and marbling were unaffected by sex and RAC feeding ( P ≥ 0.22). Bellies from IC carcasses were 0.3 cm thinner ( P ≤ 0.05) than PC but 0.3 cm thicker ( P ≤ 0.05) than gilts. Flop distances of IC bellies were similar to gilt bellies but reduced ( P ≤ 0.05) 13 cm compared with PC bellies. Iodine values of IC bellies were similar to PC bellies but reduced ( P ≤ 0.05) 3 units compared with gilts. Feeding RAC did not affect ( P ≥ 0.23) fresh belly characteristics. Overall, immunological castration and feeding RAC were additive in terms of improving carcass cutability but had only minimal effects on fresh pork loin or belly quality.