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 causA§dthe 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 ace tone-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 supple ment 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 oc curred in the alimentary tract of the chick and not in the feed prior to ingestion. J. Nutr. 101: 1289-1294, 1971. The ability of poultry to utilize phytate phosphorus is a controversial subject (1, 2). The probability that the differences re ported for the availability of phytate phos phorus to the chick are caused by dietary variables was discussed in a recent review (3). The presence of phytase, an enzyme which hydrolyzes phytate to phosphoric acid and inosinic acid (4-6) in some feed ingredients (7, 8) may have enhanced the utilization of phytate phosphorus. Phytase of plant origin appears to retain its activity when added to animal diets (7-10). The reaction conditions of in vitro studies with some phytases suggest that the enzyme is active in the digestive tract of animals (11, 12) since the in vitro conditions are similar to those found in the chick's ali mentary tract. A purified extract of phytase from wheat bran was inactive in the rat (13). Phytase obtained from Escherichia coli was active when fed to chicks (14). The present report describes quantitative studies of the effect of a mold phytase on J. NUTRITION, 101: 1289-1294. the utilization of phytate phosphorus by chicks. EXPERIMENTAL PROCEDURE The breed, sex and number of chicks used are listed in the design of each ex periment. The replication of treatments varied and was dependent on the amount of phytase preparation available. Day-old chicks were allotted to the treatments and were housed in electrically heated brooders with raised wire mesh floors. Feed and water were supplied ad libitum. Body weights and feed consumption were re corded weekly. At the end of week 3 the Received for publication February 9, 1971. 1Presented in part at the 51st annual meeting of the Federation of American Societies for Experimental Biology, Chicago, Illinois, 1967. Federation Proc. 26: 416 (abstr.). 2Present address: Department of Animal Sciences, University of Arkansas, Fayetteville, Arkansas 72701. 3Reprint requests should be addressed to this au thor. 4Present address: Department of Biological Sci ences, Florida Technological University, Orlando, Flor ida 32816. 5Present address: 2921 Glenwood Lane, Billings, Montana 59102.