Using zilpaterol in an intensive feeding system for steers in Yucatán, México.
The effect of zilpaterol, which is sold legally in Mexico, on growth and carcass yield and composition of zebu-type crossbred steers, was studied during the summer season in Mérida. A commercial product with a concentration of 4.8% of zilpaterol chlorhydrate was used, two treatments being randomly assigned to 95 finishing steers: control (C) and zilpaterol-treated (Z), during 33 days. All animals received the same finishing diet, composed of ground corn grain, soybean hulls, soybean meal, wheat bran, corn stalks, vegetable oil, and a vitamin-mineral premix (1.93 Mcal NEm and 1.29 Mcal NE g/kg; 13.2% CP). Post-slaughter warm and chilled carcass weights, and weight of internal fat were recorded. Fat thickness, area of the Logissimus muscle and marbling were measured between the 12th and 13th ribs. Carcass yield and yield grade were calculated. Steers in the Z group grew 3.1% faster and had heavier and leaner carcasses than those of the C group (P < 0.005). It was concluded that use of oral zilpaterol (0.14 mg/kg bodyweight daily equivalent) in finishing zebu-type steers, stimulates faster grains in weight of whole body and carcass and provides a more desirable carcass composition. (In Spanish).