Zilpaterol Hydrochloride Improved Growth Performance and Some Carcass Characteristics in Finishing Ram Lambs in Feedlot

Twenty-four Dorper x Pelibuey ram lambs (initial body weight [BW] = 32.19 ± 0.69 kg and age = 5 mo) were housed in individual pens during a 31-d feeding period, and then slaughtered to determine the effects of zilpaterol hydrochloride (ZH) supplementation on productive performance, carcass characteristics and wholesale cut yields. Lambs were assigned to four treatments (n = 6) under a randomized complete block design, where initial BW was used as the blocking factor. Treatments consisted of offering a basal diet and three different daily doses of ZH: 0 (control), 0.1, 0.2 and 0.3 mg/kg BW. All data collected were analyzed with analysis of variance using the GLM procedure of SAS (SAS Inst. Inc., Cary, NC). Means were separated with a PDIFF STDERR statement. Significance was declared at P < 0.05 and tendency when 0.05 < P < 0.10. Final BW (P = 0.02) and average daily gain (ADG, P = 0.04) were greater for lambs that received 0.2 mg/kg BW. Supplemental ZH tended to improve dry matter intake (DMI, P = 0.008) and ADG:DMI ratio (P = 0.078). Water intake was lower (P < 0.01) in lambs supplemented with ZH. ZH supplementation did not affect carcass characteristic as hot and cold carcass weight, dressing, KPH, conformation, fat thickness, carcass and leg length, thorax depth, and pH of LM at 45 min; however, cooling loss (P = 0.06) and pH at 45 min (P = 0.06) showed a trend to increase as ZH supplementation increased. Wholesale cut yields were not affected by ZH supplementation. Percentage of head was greater (P = 0.043) in lambs treated with ZH. LD area increased (P = 0.01) with ZH addition. Percentage of blood presented a trend (P = 0.051) of decreasing with ZH supplementation. Also, liver decreased in size (P < 0.05) for treatments where ZH was included. In conclusion, using a daily ZH dosage of 0.2 mg per kg of BW produced the best productive performance and carcass characteristics in hair-breed rams.