title: Effects of implanting and feeding zilpaterol hydrochloride on performance, carcass characteristics, and subprimal beef yields of fed cows.
abstract: Sixty crossbred cull cows were used to determine the combined effects of a trenbolone acetate-estradiol implant and feeding zilpaterol hydrochloride on performance, carcass characteristics, and subprimal yields of mature cows fed for 70 d. Cows were assigned to 1 of 5 treatments: 1) grazing native grass pasture (G); 2) concentrate-fed (C) a grain sorghum-sorghum silage diet; 3) concentrate-fed and implanted (CI) with Revalor-200 (trenbolone acetate-estradiol); 4) concentrate-fed and fed Zilmax (zilpaterol hydrochloride) beginning on d 38 of the feeding period (CZ); and 5) concentrate-fed, implanted, and fed Zilmax beginning on d 38 (CIZ). The concentrate diet consisted primarily of ground grain sorghum and sorghum silage. During the last 34 d of the feeding trial, concentrate-fed (C, CI, CZ, and CIZ) cows had greater (P < 0.05) gains than G cows. Hot carcass weights and dressing percentages were greater (P < 0.05) for the concentrate-fed cows than for G cows. Longissimus muscle area was largest (P < 0.05) for CIZ cows, whereas subprimal weights from the chuck were heavier (P < 0.05) from CIZ cows than C and G cows, and carcasses from CI and CZ cows had heavier (P < 0.05) chuck subprimal weights than G cows. Rib and round subprimal weights were heavier (P < 0.05) for concentrate-fed cows compared with G cows. In addition, carcasses from CIZ cows had heavier (P < 0.05) total subprimal weights, and total subprimals were a greater percentage of their initial BW than C cows. Rib cut-out and total soft tissue weights from the 9-10-11th rib were less (P < 0.05) for G cows than concentrate-fed cows. Feeding cull cows a concentrate diet increased carcass weight, dressing percentage, and subprimal yields compared with feeding cows a grass-based pasture diet, and the combination of a trenbolone acetate-estradiol implant and feeding zilpaterol hydrochloride can maximize trimmed beef yields from cull cows fed a high-concentrate diet.
authors.affiliation: Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506, USA.
authors.forename: S
authors.initials: S
authors.lastname: Neill
authors.forename: J A
authors.initials: JA
authors.lastname: Unruh
authors.forename: T T
authors.initials: TT
authors.lastname: Marston
authors.forename: J R
authors.initials: JR
authors.lastname: Jaeger
authors.forename: M C
authors.initials: MC
authors.lastname: Hunt
authors.forename: J J
authors.initials: JJ
authors.lastname: Higgins
mesh_terms: D000818:Animals; D001823:Body Composition / Q000187:drug effects*; D002417:Cattle / Q000254:growth & development / Q000502:physiology*; D004032:Diet / Q000662:veterinary*; D004333:Drug Administration Routes / Q000662:veterinary; D004343:Drug Implants; D005260:Female; D008460:Meat / Q000592:standards*; D011897:Random Allocation; D014297:Trimethylsilyl Compounds / Q000008:administration & dosage / Q000494:pharmacology*; D015430:Weight Gain / Q000187:drug effects
chemical_list: D004343:Drug Implants; D014297:Trimethylsilyl Compounds; C475840:Zilpaterol