title: Effects of feeding ractopamine hydrochloride (Paylean) to physical and immunological castrates (Improvest) in a commercial setting on growth performance and carcass characteristics.
abstract: Growth performance and carcass characteristics of physically castrated (PC) and immunologically castrated (IC) pigs fed ractopamine hydrochloride (RAC; 5 mg/kg) were evaluated in 64 pens of 22 pigs each. Male pigs were randomly assigned to castration method at birth. Pigs in the PC group were physically castrated at 5 d of age while IC pigs were administered Improvest at 11 and 18 wk of age. Pigs entered the grow-finish barn at approximately 9 wk of age (d 0). Dietary treatments (control or RAC) were initiated on d 87. Final treatment arrangement was a 2 × 2 factorial of castration method and diet. Data were analyzed using a mixed model with fixed effects of castration method, diet, market group, and all 2- and 3-way interactions. Pen was the experimental unit. From d 0 to 65, IC pigs had 11.2% greater (P < 0.01) G:F and 11.6% less (P < 0.01) ADFI than PC pigs, but ADG was increased 1.0% in PC pigs compared with IC pigs (P < 0.01). From d 65 to 87, IC pigs had 7.9% greater (P < 0.01) ADG and 12.1% greater (P < 0.01) G:F than PC pigs while having similar (P = 0.16) ADFI. At the initiation of diet (RAC) treatments, BW of all treatments were similar (P ≥ 0.32). From d 87 to 120 (RAC feeding period), IC pigs had 10.0% greater (P < 0.01) ADG and 10.5% greater (P < 0.01) ADFI than PC pigs while having similar (P = 0.64) G:F. Feeding RAC increased (P < 0.01) ADG by 16.9% and G:F by 17.9% while having no effect (P = 0.42) on ADFI from d 87 to 120. There were no significant interactions between castration method and diet on growth performance from d 87 to 120. For the entire study (d 0-120), IC pigs had 2.6% greater (P < 0.01) ADG, 4.6% less (P < 0.01) ADFI, and 7.3% greater (P < 0.01) G:F than PC pigs. Averaged over market groups, IC pigs were 2.5 kg heavier (P < 0.01) and had similar (P = 0.10) carcass weights and 1.8 percentage units less (P < 0.01) dressing yields than PC pigs. Additionally, IC pigs had 1.3 mm less (P < 0.01) fat and 1.7 mm less (P < 0.01) loin depth than PC pigs. Pigs fed RAC were 2.9 kg heavier (P < 0.01) and had 2.3 kg heavier (P < 0.01) carcasses and 2.2 mm deeper (P < 0.01) loins but similar (P = 0.21) dressing yields and tended (P < 0.10) to have 0.4 mm less fat than control-fed pigs when averaged over market groups. Group 3 pigs were the heaviest (P < 0.01) at slaughter and had the heaviest (P < 0.01) carcasses, greatest (P < 0.01) dressing yields, and the most (P < 0.01) carcass fat of all market groups. Overall, immunological castration and RAC were additive in terms of improving growth performance and carcass characteristics.
authors.affiliation: Department of Animal Science, University of Illinois, Urbana 61801.
authors.forename: B K
authors.initials: BK
authors.lastname: Lowe
authors.affiliation: Department of Animal Science, University of Missouri, Columbia 65211.
authors.forename: G D
authors.initials: GD
authors.lastname: Gerlemann
authors.affiliation: Elanco Animal Health, Greenfield, IN 46140.
authors.forename: S N
authors.initials: SN
authors.lastname: Carr
authors.affiliation: Elanco Animal Health, Greenfield, IN 46140.
authors.forename: P J
authors.initials: PJ
authors.lastname: Rincker
authors.affiliation: Zoetis, Kalamazoo, MI 49007.
authors.forename: A L
authors.initials: AL
authors.lastname: Schroeder
authors.affiliation: Triumph Foods, St. Joseph, MO 64504.
authors.forename: D B
authors.initials: DB
authors.lastname: Petry
authors.affiliation: Department of Animal Science, University of Illinois, Urbana 61801.
authors.forename: F K
authors.initials: FK
authors.lastname: McKeith
authors.affiliation: Department of Animal Science, University of Missouri, Columbia 65211.
authors.forename: G L
authors.initials: GL
authors.lastname: Allee
authors.affiliation: Department of Animal Science, University of Illinois, Urbana 61801 adilger2@illinois.edu.
authors.forename: A C
authors.initials: AC
authors.lastname: Dilger
mesh_terms: D000821:Animal Feed / Q000032:analysis*; D000818:Animals; D001823:Body Composition / Q000187:drug effects; D004032:Diet / Q000662:veterinary*; D008297:Male; D008460:Meat / Q000592:standards*; D009919:Orchiectomy / Q000379:methods*; D010627:Phenethylamines / Q000008:administration & dosage / Q000494:pharmacology*; D013552:Swine / Q000254:growth & development; D022642:Vaccines, Contraceptive / Q000276:immunology*
chemical_list: D010627:Phenethylamines; D022642:Vaccines, Contraceptive; C060897:ractopamine
keywords: Paylean; carcass; growth; immunological castration; ractopamine