title: Carcass traits and cutting yields of entire and immunocastrated pigs fed increasing protein levels with and without ractopamine hydrochloride supplementation.
abstract: The objective of this study was to determine the effects of increasing balanced protein, with and without ractopamine hydrochloride (RAC), in the finisher diets of immunocastrates on their carcass cutting yields and respective muscle, fat, and bone proportions. Carcass traits and yields of 120 individually housed entire male pigs and immunocastrates were evaluated following a 2 × 2 × 3 factorial design. Vaccination occurred at 16 and 20 wk of age and slaughtering at 24 wk. Up until 20 wk of age, all pigs received a commercial grower diet. Low-, medium-, and high-protein (7.50, 9.79, and 12.07 g standardized ileal digestible [SID] lysine/kg, respectively) diets were then fed for the last 28 d with RAC supplemented at 0 or 10 mg/kg. Immunocastration and RAC supplementation increased ( = 0.003 and = 0.017, respectively) the live weight at slaughter. The interaction between sex and protein ( = 0.039) for caliper backfat depths showed greater backfat depths in immunocastrates fed medium protein whereas RAC decreased ( = 0.027) the caliper backfat depth. Feeding RAC increased the trotters ( = 0.040), tenderloins (fillets; < 0.001), shoulder ( = 0.002), hindquarter ( = 0.026), loin ( = 0.028), and belly ( = 0.044) percentages. The shoulder ( < 0.001), hindquarter ( < 0.001), and loin ( = 0.005) muscle percentages were increased and the hindquarter fat percentages were decreased ( = 0.032) with RAC supplementation. Immunocastration increased the belly cut ( = 0.006), loin fat ( < 0.001), and belly fat ( < 0.001) percentages. Therefore, carcass cutting and lean yields can be improved by RAC supplementation while decreasing the backfat depth, and the increase in backfat due to immunocastration could be avoided with the correct dietary protein level.
authors.forename: T
authors.initials: T
authors.lastname: Needham
authors.forename: L C
authors.initials: LC
authors.lastname: Hoffman
mesh_terms: D000318:Adrenergic beta-Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D000821:Animal Feed / Q000032:analysis; D000818:Animals; D001823:Body Composition / Q000187:drug effects*; D001835:Body Weight / Q000187:drug effects; D004044:Dietary Proteins / Q000494:pharmacology*; D008239:Lysine / Q000494:pharmacology; D008297:Male; D009919:Orchiectomy / Q000379:methods / Q000662:veterinary*; D010627:Phenethylamines; D010641:Phenotype; D013552:Swine; D022642:Vaccines, Contraceptive / Q000276:immunology*
chemical_list: D000318:Adrenergic beta-Agonists; D004044:Dietary Proteins; D010627:Phenethylamines; D022642:Vaccines, Contraceptive; C060897:ractopamine; D008239:Lysine