Effect of crude protein level and zilpaterol supplementation on growth performance and carcass dressing of finishing hairy lambs

Abstract Text: Forty Pelibuey × Katahdin (37.66 ± 2.2 kg) crossbred intact male lambs were used to evaluate the interaction of two dietary protein levels (15 and 18% CP) and two dietary zilpaterol (ZH) levels (0 and 6 mg/kg of feed) on growth performance and carcass dressing. Lambs were equally grouped by weight into five uniform weight groups and assigned to 5-pen blocks (two lambs per pen). The experiment lasted 30 days. Low protein and high protein diets contained 2.92 and 2.89 Mcal ME/kg, respectively. Treatments were: 1) Low protein-no ZH (LP-0); 2) Low protein-ZH supplementation (LP-ZH); 3) High protein-no ZH (HP-0), and 4) high protein-ZH supplementation (HP-ZH). No interactions were detected between protein level and ZH supplementation. Protein level did not affect (P>0.05) dry matter intake or ADG, but low-protein diets tended to increase (P=0.08) feed efficiency and carcass dressing; however, the latter could be more by the slight difference on energy concentration between LP and HP diets (2.92 vs. 2.89) rather than protein level per se.  ZH supplementation did not affect DM intake, but increased ADG (13.8%, P<0.05) and feed efficiency (16.2%, P<0.05) with no effects on carcass characteristics. The Increases on protein level of diet from 15 to 18% did not improve the response to ZH supplementation.

Keywords: Zilpaterol clorhidrate, CP level, Pelibuey sheep