The differences in weight gain (7.20%) and FCR (3.48%) between Diets A and Diets C were significant (P < 0.05). From 1 to 40 days post-hatch, phytase improved weight gain in broilers offered diets B by 11.8% (P < 0. 001) and those offered diets C by 13.4% (P < 0. 001) and both treatments outperformed diets A (P < 0. 001).