Effects of implanting and feeding zilpaterol hydrochloride on performance, carcass characteristics, and subprimal beef yields of fed cows

• Published in: Journal of animal science Vol. 87; no. 2; pp. 704 - 710
• Main Authors: Neill, S, Unruh, J.A, Marston, T.T, Jaeger, J.R, Hunt, M.C, Higgins, J.J
• Format: Journal Article
• Language: English
• Published: Champaign, IL American Society of Animal Science 01.02.2009; Am Soc Animal Sci
• Subjects: Animal productions; Animals; beef; beta-adrenergic agonists; Biological and medical sciences; Body Composition - drug effects; carcass characteristics; carcass yield; Cattle - growth & development; Cattle - physiology; controlled internal drug release devices; cow feeding; culling (animals); dairy cows; Diet - veterinary; dressing percentage; Drug Administration Routes - veterinary; Drug Implants; estradiol; feed concentrates; feed rations; Female; Food industries; Fundamental and applied biological sciences. Psychology; grazing; growth promotion; Meat - standards; Meat and meat product industries; medicated feeds; oral administration; Random Allocation; Terrestrial animal productions; trenbolone; Trimethylsilyl Compounds - administration & dosage; Trimethylsilyl Compounds - pharmacology; Vertebrates; Weight Gain - drug effects; zilpaterol hydrochloride; Implant; Meat product; Cull cow; Carcass; Feeding; subprimal yield; Vertebrata; zilpaterol; Mammalia; Beef cattle; Yield; Artiodactyla; Performance; Ungulata
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/jas.2008-1254

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.