Effect of zilpaterol hydrochloride duration of feeding on performance and carcass characteristics of feedlot cattle

• Published in: Journal of animal science 2009-06, Vol.87 (6), p.2133-2141
• Main Authors: Elam, N.A, Vasconcelos, J.T, Hilton, G, VanOverbeke, D.L, Lawrence, T.E, Montgomery, T.H, Nichols, W.T, Streeter, M.N, Hutcheson, J.P, Yates, D.A, Galyean, M.L
• Format: Article
• Language: English
• Subjects: Adrenergic Agents - administration & dosage; Adrenergic Agents - pharmacology; Animal Feed - analysis; animal growth; Animal Nutritional Physiological Phenomena; Animal productions; Animals; beef; beef cattle; beef quality; beta-adrenergic agonists; Biological and medical sciences; Body Composition - drug effects; body fat; carcass composition; carcass yield; Cattle; cattle feeding; Diet - veterinary; dietary supplements; dressing percentage; Drug Administration Schedule; feed additives; feed deprivation; feedlots; finishing; Food industries; Fundamental and applied biological sciences. Psychology; lean meat; liveweight gain; Male; marbling; Meat and meat product industries; steers; temporal variation; Terrestrial animal productions; Trimethylsilyl Compounds - administration & dosage; Trimethylsilyl Compounds - pharmacology; Vertebrates; Weight Gain - drug effects; zilpaterol hydrochloride
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/jas.2008-1563

Four trials, each with a randomized complete block design, were conducted with 8,647 beef steers (initial BW = 346 ± 29.6 kg) in 3 different locations in the United States to evaluate the effects of zil-paterol hydrochloride (ZH) on performance and carcass characteristics of feedlot cattle. Treatments consisted of feeding ZH (8.33 mg/kg of dietary DM) for 0, 20, 30, or 40 d, at the end of the feeding period, followed by a 3-d withdrawal period before slaughter. Cattle were weighed on d 0 and 50 before slaughter (in 3 of the 4 studies), and on the day of slaughter. Data from the 4 trials were pooled for statistical analyses. No differences (P greater-than-or-equal 0.78) were detected among treatments for ADG and G:F from the start of the study until the final 50 d on feed. Final BW was greater for the average of the 3 ZH-treated groups (P < 0.01) than for the 0-d group. Average daily gain was greater for ZH-treated vs. control cattle during the final 50 d on feed (P < 0.01) and for the entire feeding period (P < 0.01). No differences in DMI were noted for any periods of the experiment (P greater-than-or-equal 0.42) for ZH-treated cattle vs. controls. No differences were noted for DMI among the ZH-treated groups for the final 50 d on feed (P = 0.81) or for the overall feeding period (P = 0.31). Feeding ZH for any length of time increased G:F (P < 0.01) for the final 50 d and overall compared with 0-d cattle. In addition, a linear increase with more days of ZH feeding was observed for G:F during the period that ZH was fed (P = 0.01), as well as for the overall feeding period (P = 0.01). The ZH-treated cattle had heavier HCW (P < 0.01), greater dressing percent (P < 0.01), reduced marbling scores (P < 0.01), less 12th-rib fat (P < 0.01), larger LM area (P < 0.01), less KPH (P = 0.01), and a lower USDA yield grade (P < 0.01) than the 0-d cattle, regardless of the duration of ZH feeding. Dressing percent increased linearly (P < 0.01) with increased duration of ZH feeding, whereas 12th-rib fat (P = 0.07), marbling scores (P < 0.01), and USDA calculated yield grade (P = 0.01) decreased linearly with increased duration of ZH feeding. Feeding ZH increased ADG and G:F and decreased overall carcass fatness. In addition, effects of ZH on measures of carcass fatness were enhanced by feeding the product for a greater length of time.