Effect of zilpaterol hydrochloride on feedlot performance and carcass characteristics of ewe lambs during heat-stress conditions
2010
Macías-Cruz, U. | Álvarez-Valenzuela, F.D. | Torrentera-Olivera, N.G. | Velázquez-Morales, J.V. | Correa-Calderón, A. | Robinson, P.H. | Avendaño-Reyes, L.
The objective of the present study was to evaluate the effects of supplementation of zilpaterol hydrochloride (ZH) to the finishing diets on the feedlot performance and carcass characteristics of hair sheep ewe lambs during hot environmental conditions. Twenty Katahdin × Pelilbuey and Dorper × Pelibuey crossbred females with an average initial liveweight (LW) of 26.2 ± 0.83 kg were blocked by the initial LW, and assigned individually to 20 pens in a closed calf-rearing unit provided with fans. Treatments were (1) control group (basal diet without ZH) and (2) ZH group (basal diet plus 10 mg of ZH/ewe.day). Skin temperatures were measured each 2 days in five ewes by treatment; ambient weather conditions were recorded every day. After a 34-day feeding period, all ewes were slaughtered. Climatic variables during the study showed severe heat stress, with the average temperature-humidity index and temperature 85 units and 34.1°C, respectively. The skin temperature of belly and right flank was greater (P 0.05) to control ewe lambs. With the exception of peritoneum and head (P 0.05) percentages between treatments. However, hot- and cool-carcass weights, dressing percentage, conformation and rib-eye area were greater (P < 0.05) for ewes supplemented with ZH. Likewise, the weight of hindquarter, legs and ribs expressed as a percentage of hot-carcass weight increased (P < 0.05) with ZH supplementation. Growth and deposition of excessive fat in hair-sheep ewe lambs were not improved with ZH supplementation under heat-stress conditions, whereas carcass-quality traits such as dressing and rib-eye area were increased.
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