Nutritional benefits of phytase and dietary determinants of its efficacy

Over 60% of the total P in cereal grains and oil seeds and their by-products is found as phytate, myo-inositol hexakisphosphate. Phytases are a group of enzymes that initiate the phosphate hydrolysis from phytate and produce myo-inositol and inorganic phosphate by catalyzing the stepwise removal of the phosphate groups. Microbial phytases effectively improve dietary phytate-P utilization and may partially or completely replace inorganic P with phytase in these diets can reduce P excretion by up to 50% and enhance bioavailabilities of Ca, Zn and Fe. The improvement in nitrogen retention and protein and amino acid utilization by dietary phytase supplementation is relatively small and highly variable. The efficacy of supplemental phytase is affected by at least three dietary factors: Ca:P ratio, cholecalciferol and organic acids.