Effect of Supplemental Phytase on the Utilization of Phytate Phosphorus by Chicks

Abstract

Chicks were used to determine whether the addition of a mold phytase to a diet containing natural phytate phosphorus caused the phosphorus in the phytate to be hydrolyzed in vivo to a form which could be utilized by the chick. Phytase, produced by Aspergillus ficuum NRRL 3135, was fed as an acetone-dried preparation. The diets contained from 0.18 to 0.24% natural phytate phosphorus supplied primarily by corn and soybean meal. Phytase supplement was added at levels ranging from 1 to 8 g/kg of diet. One gram of the supplement hydrolyzed 950 mg of inorganic phosphate from calcium phytate in vitro in 1 hour under standard conditions. For comparative purposes, graded levels of either monobasic sodium orthophosphate, or beta-tricalcium phosphate were added at levels to supply from 0.04 to 0.21% phosphorus. The percentage of bone ash was used to evaluate in vivo phytase activity. The addition of phytase to the diet produced an increase in percentage bone ash indicating hydrolysis of phytate by the enzyme. Total hydrolysis of phytate occurred when 3 g phytase supplement was used per kilogram diet. Chicks utilized the hydrolyzed phytate phosphorus as well as supplemental inorganic phosphorus. Phytase activity occurred in the alimentary tract of the chick and not in the feed prior to ingestion.