Influence of level of zilpaterol chlorhydrate supplementation on growth performance and carcass characteristics of feedlot lambs
2008
Estrada-Angulo, A. | Barreras-Serrano, A. | Contreras, G. | Obregon, J.F. | Robles-Estrada, J.C. | Plascencia, A. | Zinn, R.A.
Forty-eight PelibueyxKatahdin (38.8±0.67kg) crossbred male lambs were used in a 32-day feeding trial (four pens per treatment in a randomized complete block design), to evaluate the influence of zilpaterol (β₂-agonist) supplementation level on growth performance and carcass characteristics. Lambs were fed a dry-rolled corn-based finishing diet (3.04Mcal/kg of ME) supplemented with 0, 0.15, 0.20, or 0.25mg/kg of live weightd⁻¹ zilpaterol (as zilpaterol chlorhydrate, Zilmax®, Intervet México, México City). DM intake averaged 1.099±0.042kg/d and was not affected (P =0.40) by treatments. Compared with control lambs, zilpaterol supplementation increased gain efficiency (15.8%, P <0.03), apparent energy retention per unit DMI (10.9%, P =0.03), and tended to increased daily gain (16%, P <0.07) and total gain (17.7%, P <0.08). Zilpaterol supplementation did not affect (P =0.20) carcass weight, longissimus muscle area (LM), or fat thickness, but increased (2.3%, P =0.04) carcass dressing percentage and reduced (36%, P <0.01) kidney-pelvic fat. Increasing level of zilpaterol supplementation increased total weight gain (linear component, P <0.05), gain:feed (linear component, P <0.01), and dressing percentage (linear component, P <0.02), and decreased (linear component, P <0.01) kidney-pelvic fat. We conclude that zilpaterol supplementation enhances growth performance and dressing percentage in lambs in a manner comparable to that of cattle (greater muscle accretion, reduced body fat). Responses to zilpaterol was optimal when supplemented at 0.20mg of zilpaterol/kg of live weightd⁻¹.
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