Effect of zilpaterol hydrochloride on feedlot performance, nutrient intake, and digestibility in hair-breed sheep.

Twelve Dorper × Pelibueywether lambs (26.8 ± 1.6 kg initial BW, 5 mo of age) were used to evaluate effects of zilpaterol hydrochloride (ZH) on feedlot performance, and effects of a ZH and ZH supplementation period (15 and 30 d) on nutrient intake and digestibility. Lambs were blocked by initial BW, and assigned randomly within BW blocks to 1 of 2 treatments: i) control (no ZH), and ii) supplemented with ZH (10 mg ZH/wether lamb daily). Measurements of intake and digestibility were performed on d 9 to 15 and 24 to 30. Feedlot performance data were analyzed as a randomized complete block design, and nutrient intake and digestibility data were analyzed as a randomized complete block design with a 2 × 2 factorial arrangement of treatments. Final BW, ADG, total BW gain, and G:F were greater (P ≤ 0.04) for ZH than for control lambs. No treatment × feeding duration interaction for nutrient intake and apparent total tract digestibility were observed (P > 0.05). Intake of DM, OM, CP, and GE were less (P ≤ 0.03) for ZH than for control. Lambs fed for 30 d had greater (P ≤ 0.04) NDF and GE intake compared with those fed for 15 d. Total tract digestibility of DM, OM, CP, EE, and ADF (P ≤ 0.03) was less for ZH than control. Furthermore, calculated DE, ME, and TDN intake decreased (P < 0.01) with ZH supplementation. Also, DM, CP, and ether extract [AU: Please confirm definition](EE) digestibility were greater (P < 0.01) for 30 d than for 15 d. Additionally, greater (P ≤ 0.01) DE, ME, and TDN intake was observed for 30 d compared with 15 d. In conclusion, ZH supplementation of wether lambs consuming feedlot diets resulted in improved feedlot performance and reduced the intake and digestibility of some nutrients.