Meta-analysis of effects of microbial phytase on digestibility and bioavailability of copper and zinc in growing pigs

A meta-analysis was conducted to determine the effect of microbial phytase in pig diets on digestibility and bioavailability of Cu and Zn. Studies (n = 22) into effects of microbial phytase on digestibility and plasma levels of Cu and Zn were included in a dataset and regression analysis was performed to quantify the effect of Aspergillus niger derived 3-phytase in studies (n = 14) with a maximum dietary Zn content of 100 mg/kg and a maximum Cu addition of 20 mg/kg. Phytase inclusion increased digestibility of Zn (P = 0.003) and plasma Zn content (P <0.001) without affecting digestibility and plasma level of Cu. Based on a comparison with dose-response studies with Zn, we estimated 500 phytase units (FTU) of microbial phytase is equivalent to 27 mg of Zn from ZnSO(4).