aInstituto de Investigaciones en Ciencias Veterinarias, Universidad Autónoma de Baja California, Mexicali, 21100 Baja California, México.
bFacultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Sinaloa, Culiacán 1084, Sinaloa, México.
1 Correspondig author: E-mail: aplas_99@yahoo.com.
To assess the effect of feeding two β-adernergic agonists [β-AA, type β1: 20 ppm ractopamine hydochloride (RAC), type β2: 6 ppm zilpaterol hydrochloride (ZIL)] on performance, 60 Pelibuey x Katahdin (34.4 ±2.94 kg) crossbred male lambs were used in a 32-d feeding trial. DM intake was not affected by treatments. Compared with controls, average daily gain and feed efficiency were improved with RAC supplementation, but final live weight, average daily gain and gain: feed were the best on ZIL supplemented group. No differences in carcass characteristics were detected among control group and RAC supplementation. It is concluded that β-AA supplementation increase growth performance in lambs as results of greater muscle accretion and for reduction of body fat. Use as feed additive, β2-AA compound has a greater response in feedlot lambs than β1-AA compound.
β-adrenergic agonists, carcass characteristics, lambs, performance, ractopamine, zilpaterol
