Efecto de tiempo de suplementación de Clorhidrato de Zilpaterol sobre residuos en músculo, hígado y riñón de corderos de pelo en finalización

Zilpaterol hydrochloride (ZH) supplementation is marketed for cattle only, and its use has not been widely adopted as growth promoter in other species. The objective of this study was to assess the residual ZH in various tissues of feedlot hair lambs administered with this growth promoter. Forty Intact male lambs were randomly assigned to one of the following four treatments: ZH for 0, 10, 20, and 30 d before the end of the fattening period. All lambs were fed a basal diet and slaughtered 48 h after the feeding trial. Regarding muscle, a linear increase (P≤0.05) in ZH concentrations with increasing days of administration was observed (0.0, 0.19, 0.26, and 0.64 ng/g for 0, 10, 20, and 30 d of administration). For the liver, a linear increase (P≤0.05) in ZH concentrations with increasing days of administration was also observed (0.0, 0.18, 0.27, and 0.44 ng/g for 0, 10, 20, and 30 days of administration). Higher values of ZH were found in the kidney with 0.0, 0.49, 0.66, and 0.71 ng/g for 0, 10, 20, and 30 days of administration). It was concluded that, regardless of tissue, residues of ZH increased with increasing days of administration of this growth promoter. Also, the observed levels of ZH were lower than those established by SENASICA (Mexico) for cattle, and the values presented in the present study could be the basis for establishing the maximum permissible limits of this growth enhancer in various tissues of sheep.