| Summary: | Twenty-four Dorper x Pelibuey lambs were housed in individual pens during a 31-d feeding period and assigned to four treatments (<i>n</i> = 6) under a randomized complete block design with different daily doses of zilpaterol hydrochloride (ZH): 0 (control), 0.1, 0.2, and 0.3 mg/kg BW to determine the effects of ZH supplementation on productive performance, meat quality, and wholesale cut yields. Final BW (<i>p</i> = 0.02) and average daily gain (ADG, <i>p</i> = 0.04) were greater in lambs supplemented with 0.2 mg/kg BW. Supplemental ZH tended to improve dry matter intake (DMI, <i>p</i> = 0.008) and ADG:DMI ratio (<i>p</i> = 0.078). Wholesale cut yields were not affected by ZH supplementation. Percentage of head was greater (<i>p</i> = 0.04) in lambs treated with ZH. The ZH supplementation did not affect carcass characteristics. However, longissimus thoracis et lumborum (LTL) presented a linear trend (<i>p</i> = 0.08) of increasing with ZH supplementation. Percentage of blood presented a trend (<i>p</i> = 0.051) of decreasing with ZH supplementation. Also, liver decreased in size (<i>p</i> < 0.05) for treatments where ZH was included. Values of luminosity decreased (<i>p</i> < 0.02) when ZH dosage increased. The value of protein Lowry was greater, with 0.3 mg kg<sup>−1</sup> (<i>p</i> = 0.04). Cathepsin B + L was greater in the lambs from the control treatment (<i>p</i> = 0.05). In conclusion, using a daily ZH dosage of 0.2 mg per kg of BW produced the best productive performance, carcass characteristics, and some changes in the meat of hair-breed lambs.
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