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

N. A. Elam, J. T. Vasconcelos, G. Hilton, D. L. VanOverbeke, T. E. Lawrence, T. H. Montgomery, W. T. Nichols, M. N. Streeter, J. P. Hutcheson, D. A. Yates, M. L. Galyean

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Abstract

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 zilpaterol 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 > or = 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 > or = 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.

Original languageEnglish
Pages (from-to)2133-2141
Number of pages9
JournalJournal of animal science
Volume87
Issue number6
DOIs
StatePublished - Jun 2009

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    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. (2009). Effect of zilpaterol hydrochloride duration of feeding on performance and carcass characteristics of feedlot cattle. Journal of animal science, 87(6), 2133-2141. https://doi.org/10.2527/jas.2008-1563