Increasing zinc levels in phytase-supplemented diets improves the performance and nutrient utilization of broiler chickens
Three hundred and thirty-six day-old Ross-308 male broiler chicks were used in a 35-day trial to investigate the effect of different concentrations of dietary Zn and phytase on broiler performance and energy utilization. Twelve day-old birds were used for the initial slaughter group to provide baseline body compositional data, while the remaining 324 birds were randomly distributed to six experimental diets. The treatments consisted of a 3 x 2 factorial arrangement with three levels of Zn (low, mid, and high; 30, 40, and 50 mg/kg, respectively) and two levels (0, 500 FTU/kg) of microbial phytase. Each dietary treatment was fed to 6 cages (9 birds/cage). Low Zn diet significantly decreased feed intake and body weight gain at days 1-24. Phytase supplementation improved body weight gain at d 24, irrespective of Zn level. The digestibility of P was improved in birds fed high-Zn diet with phytase supplementation, and the reverse was the case for Fe and Zn digestibility. High dietary Zn increased the Zn and Fe deposition in liver. The activity of AP, Ca-ATPase and Mg-ATPase in the jejunum was high in the phytase supplemented mid-level Zn diet. Phytase supplemented to the mid and high level Zn diets significantly improved most energy utilization parameters. This result indicate that the Zn concentrations used in this study were not inhibitory to phytase activity and broiler performance. Therefore, it can be concluded that dietary zinc level in phytase-supplemented diets could be increased up to 50 mg/kg without any negative effect on phytase-mediated broiler response.
Keywords: Bone quality, net energy, nutrient utilization