To determine the effects of zilpaterol hydrochloride (Zh) on carcass composition and growth performance of Lory growing lambs, 21 lambs with age 78 month and body weight 37.5±1.2 kg was assigned in three groups with 7 replications: group one as control, group 2 received Zh every two days, and group 3 received Zh every day. Lambs orally received 0.2 mg/kg of live body weight mixed with their daily diets during finishing period (as zilpaterol hydrochloride, Zilmax, Intervet South Africa). Dry matter intake compared to control group was significantly decreased by treatments (P<0.01). Zilpaterol supplementation had no significant effect on gain and feed efficiency, daily and total gain in treatment groups compared to control group. Also, Zilpaterol supplementation did not affect carcass weight, longissimus muscle area (LM) and carcass dressing percentage. The results showed that the tail-fat weight in treated groups was significantly reduced (P<0.05) compared to control group. The back fat (in group 3), kidney-pelvic fat (in group 2), and liver fat compared to control group was significantly reduced (P<0.05). In treatment groups, lean protein in fillet muscle was higher than control group. Zilpaterol supplementation did not affect the level of insulin, T4 and T3, triglycerides, cholesterol and glucose in plasma. We conclude that Zh decrease the fat of tail and carcass and enhance growth performance but had no effect on carcass protein in Lory growing lambs.
30 Apr - 04 May 2011
European Society of Endocrinology