ABSTRACT The objective of this study was to determine the effects of different zilpaterol hydrochloride (ZH) levels and feeding methods on the growth performance and carcass traits of Japanese quails. In this trial, 224 male quails with 34 days of age were distributed into seven treatments. A factorial arrangement with three ZH levels (0.2, 0.225, and 0.25 mg zilpaterol/kg of live weight−1) × two feeding methods (ZH supplementation daily or every two days) plus a control treatment (no ZH supplementation) was applied. The weight gain of birds fed ZH every two days was significantly higher than those fed ZH daily during the period of 41-47 days (p=0.03). During the period of 34-40 days, ZH-supplemented birds presented higher weight gain (p<0.001) and better feed conversion ratio (p=0.005) compared with the control group. Moisture, protein, ash, and cholesterol levels of the combination of breast and leg were not affected (p≥0.10) by zilpaterol supplementation. Leg muscle fat and protein contents of control birds were higher and lower compared with ZH-supplemented birds, respectively (p=0.002 and p=0.05). In conclusion, ZH supplementation in the diet of male Japanese quail improved growth performance during the finishing period (34-40d), and the most economical level of ZH is 0.2 (mg/kg of LW−1 d−1), when supplemented every two days.

The present study was carried out to examine the effect of vitamin premix reduction or withdrawal in finisher diet (29 to 42 days of age) on the performance and meat quality of chicks fed a wheat/barley based diet and reared on floor pens. A total of 504 male broiler chicks (Ross® 308) were allocated to seven treatment groups, with four replicates per treatment and 18 birds per replicate. All data were analyzed according to a completely randomized design. Results showed that the reduction or withdrawal of the vitamin premix from diets in different weeks of finisher period did not affect chicken performance (p>0.05). There were no significant differences in TBARS values of thigh samples of birds slaughtered at 35 days of age. However, the TBARS value of the treatment without vitamin premix was significantly higher than in the other treatments (p < 0.05) when birds were slaughtered at 42 days of age. Finally, the results of this study demonstrated that it is not possible withdrawal all premix vitamin of the diet. However, it may be possible to reduce vitamin supplements in finisher broiler diets without any negative effects on performance or meat quality during freezing.