Zilpaterol hydrochloride (ZH) has been used in the United States of America, Canada, Mexico and South Africa as performance enhancing additive in cattle feedlot finishing. Several studies have shown that the use of this synthetic compound belonging to the group of beta-adrenergic agonists provides improvement in average daily gain, feed efficiency, carcass weight, carcass yield and yield of boneless meat. It also showed that this compound decreases the sensory tenderness score and the juiciness score of sirloin, besides providing a tendency to increase the perception of connective tissue. Although there are several studies in the literature, Brazilian termination farms have special characteristics that were not considered in previous studies, which could alter the responses of the ZH. One feature is the predominance of Bos indicus animals and, in particular, Nellore. Another typical occurrence in Brazilian termination farms is the prevalence of bovine uncastrated. In addition, the feedlot period are shorter than those used in previous work. In this sense, the objective of this study is to evaluate the effects of ZH feeding time and feedlot days on performance, carcass characteristics, commercial cuts yield and meat quality of Nellore bulls.
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