Evaluation of Heat-Stable Phytases in Pelleted Diets Fed to Broilers from Day Zero to Thirty-Five During the Summer Months

Supplementing phytase to broiler diets has been shown to improve phytate P digestibility in commercial broilers. Broiler rations are typically pelleted to promote improved broiler performance, but high pelleting temperatures can inactivate phytase enzymes. Before the introduction of heat-stable phytase products, phytase enzymes were generally added postpelleting to limit the effect of pelleting temperature on phytase activity. Therefore, the objective of this study was to evaluate postpelleting phytase activity of 3 concentrations of 2 heat-stable phytase enzymes and their efficacy when fed to 0- to 35-d-old broilers. After pelleting the phytase-supplemented diets at 93.3 degrees C, the retained phytase activities of the 2 enzymes were similar, suggesting equivalent heat stability. Supplementing phytase to deficient nonphytate P diets improved FCR by 3% (P = 0.05) compared with the FCR of birds fed an unsupplemented deficient diet. No differences in tibia ash ( TA) were detected between the 2 phytase sources; however, TA of birds fed supplemental phytase at the 2 greatest concentrations was improved ( P = 0.05) compared with the TA of birds fed nonphytate P-deficient diet. These results suggest that the prepelleting inclusion of heat-stable phytase enzymes may be a viable alternative to postpellet application of phytase for improving P utilization in broilers.