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This Article Free Via Open Access Full Text Full Text (PDF) All Versions of this Article: jas.2009-1885v1 87/11/3764    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Brooks, J. C. Articles by Miller, M. F. PubMed PubMed Citation Articles by Brooks, J. C. Articles by Miller, M. F.

Effects of zilpaterol hydrochloride feeding duration and postmortem aging on Warner-Bratzler shear force of three muscles from beef steers and heifers

J. C. Brooks^*,1, H. C. Claus, M. E. Dikeman, J. Shook, G. G. Hilton, T. E. Lawrence, J. M. Mehaffey^*, B. J. Johnson^*, D. M. Allen^#, M. N. Streeter^||, W. T. Nichols^||, J. P. Hutcheson^||, D. A. Yates^|| and M. F. Miller^*

^* Department of Animal and Food Sciences, Texas Tech University, Lubbock 79409; and Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506; and Department of Animal Science, Oklahoma State University, Stillwater 74078; and Department of Agricultural Sciences, West Texas A&M University, Canyon 79016; and ^# Private Consultant, Derby, KS 63037; and ^|| Intervet/Schering-Plough Animal Health, DeSoto, KS 66018

¹ Corresponding author: chance.brooks{at}ttu.edu

To determine the effects of zilpaterol hydrochloride (ZH; 6.8 g/t on 90% DM basis) feeding duration (0, 20, 30, and 40 d) on Warner-Bratzler shear force (WBSF) of longissimus lumborum (LL), triceps brachii (TB), and gluteus medius (GM) muscles, beef from feeding trials was collected and shipped to participating universities. Animals were slaughtered at commercial processing facilities across the United States. Strip loin, shoulder clod, and top sirloin butt subprimals (IMPS 180, 114, and 184, respectively) were obtained from a portion of USDA Choice and Select grade carcasses for WBSF using standardized procedures and equipment. Feeding ZH increased (P < 0.001) LL WBSF values of USDA Choice and Select steaks. A significant linear contrast existed for both quality grades, indicating increased WBSF values were associated with longer feeding durations. Increased postmortem aging decreased LL WBSF of control and treated steaks. Postmortem aging from 7 to 21 d decreased LL WBSF values by 17.6 and 16.4% for USDA Choice and Select steaks, respectively. The percentage of LL steaks from ZH-supplemented cattle with a WBSF value <4.5 kg was significantly less than control steaks for both quality grades. Postmortem aging from 7 to 21 d postmortem increased (P < 0.001) the percentage of LL Choice and Select steaks with WBSF <4.5 kg for all ZH feeding durations. Feeding ZH for 20, 30, or 40 d increased (P < 0.01) WBSF of USDA Choice TB and GM steaks compared with 0-d controls. Feeding ZH for 0, 20, and 40 d had a similar effect on WBSF of USDA Select GM steaks, and produced lesser values than steaks from cattle fed ZH for 30 d. Feeding ZH for 20, 30, and 40 d had no effect on WBSF values of USDA Select TB steaks. However, the 20-, 30-, and 40-d duration produced WBSF values greater (P < 0.05) than control (0 d) TB steaks. Postmortem aging decreased (P < 0.05) WBSF of USDA Choice and Select TB and GM steaks, but the percentage improvement in WBSF attributed to aging was less than observed for LL steaks. The results of this study indicate feeding ZH increased (P < 0.001) WBSF of LL, TB, and GM. The ZH feeding also decreased (P < 0.01) the percentage of steaks with WBSF <4.5 kg regardless of US quality grade, whereas postmortem aging increased (P < 0.01) the percentage of US Choice and Select steaks with WBSF <4.5 kg. Finally, postmortem aging reduced (P < 0.05) WBSF of steaks from ZH-supplemented beef cattle.

Key Words: aging • β-adrenergic agonist • beef • shear force • zilpaterol hydrochloride