Effect of ractopamine hydrochloride and zilpaterol hydrochloride on growth,diet digestibility,intake and carcass characteristics of feedlot lambs |
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| Authors: | MA López-Carlos RG Ramírez JI Aguilera-Soto CF Aréchiga F Méndez-Llorente H Rodríguez JM Silva |
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| Institution: | 1. Unidad Académica de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Zacatecas, Carretera Panamericana Zacatecas-Fresnillo Km 31.5, El Cordovel Enrique Estrada, Zacatecas, 98500, Mexico;2. Facultad de Ciencias Biológicas, Universidad Autónoma de Nuevo León, Ave. Universidad S/N, Cd. Universitaria, San Nicolás de los Garza, Nuevo León, 66450, Mexico |
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| Abstract: | The effects of the β-adrenergic agonists ractopamine hydrochloride (RH; 0.35, 0.70 and 1.05 mg kg− 1 of BW d− 1) and zilpaterol hydrochloride (ZH; 0.10, 0.20 and 0.30 mg kg− 1 of BW d− 1) on growth performance and carcass characteristics were determined in 84 Dorper × Katahdin lambs (12 lambs per treatment), that were randomly assigned to a complete block design during a 42-day feeding trial. Lambs were fed a corn grain-based diet (18.71% CP and 12.9 MJ/kg ME). Nutrient digestibility of diets and blood serum metabolites were also determined. There were no significant (P > 0.05) differences in growth characteristics by effect of ZH or RH administration. However, lambs final weight, total weight gain and ADG increased linearly (P < 0.05) as levels of both β-adrenergic agonist increased. RH or ZH administration did not affect feed efficiency, diet digestibility or particular blood serum metabolites of lambs. Carcass characteristics of lambs consuming ZH were significantly better (P < 0.01) than RH or control lambs; RH produced significant linear response on carcass weight, dressing percentage, longissimus muscle area, carcass conformation and quality grade, and improved quadratically (P < 0.05) fat thickness and USDA yield grade of lamb carcasses. On the other hand, increasing levels of ZH decreased linearly (P > 0.01) fat thickness and improved (P > 0.05) USDA yield grade and carcass quality grade. Both β-adrenergic agonists improved carcass characteristics; although greater improvements were obtained with ZH than RH for most carcass characteristics. |
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| Keywords: | Feedlot lambs Growth performance Carcass characteristics Zilpaterol hydrochloride Ractopamine hydrochloride |
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