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The effects of zilpaterol hydrochloride and shade on blood metabolites of finishing beef steers

E. E. Hales, P. P. Foote, A. A. Jones, D. D. Shackelford, M. M. Boyd, E. E. Erickson
Journal of animal science 2016 v.94 no.7 pp. 2937-2941
animal health, animal pens, beef cattle, blood, blood sampling, cattle feeding, cortisol, diet, finishing, glucose, lactic acid, lung function, lungs, metabolites, shade, slaughterhouses, urea nitrogen, zilpaterol hydrochloride
The effects of feeding zilpaterol hydrochloride (ZH) and shade were evaluated on blood metabolites and lung score in finishing beef steers (n = 480). Cattle were fed 0 or 8.33 mg/kg ZH for 21 d with a 3- or 4-d withdrawal before harvest and were housed in open or shaded pens. Blood samples and lung scores were collected the day before ZH was fed and on the day the cattle were shipped to the commercial abattoir. Lactate concentration was not different between cattle fed ZH in open or shaded pens (P = 0.12). Nonetheless, a tendency for a diet × time interaction was detected for lactate concentration (P = 0.09), in which it was greater in cattle fed the control diet in open pens before being fed ZH. Cortisol concentration was different before and after ZH was fed (P = 0.01) in that it was less after ZH was fed. Glucose was greater for cattle fed the control diet than cattle fed ZH for 21 d (P = 0.03). Cattle fed in open vs. shaded pens did not differ in glucose concentration (P = 0.12); whereas, glucose concentrations were greater before ZH was fed than after (P = 0.02). In contrast, plasma urea nitrogen (PUN) concentration was not different in response to diet (P = 0.24), housing type (P = 0.65), or before vs. after being fed ZH (P = 0.60). Lactate concentrations were not different across diet or shade treatments before ZH was fed, whereas after ZH, lactate concen­trations were greater in control cattle than cattle fed ZH. Additionally, cortisol was less after feeding ZH. Glucose was greater before than after feeding ZH.