Abstract: An experiment was carried out to evaluate the effects of microbial phytase on apparent digestibility of Amino Acids (AA) and cmde protein in female broiler chickem. The 240 day-old female broiler chcks were wing banded, weighted and randomly allocated to six treatment groups with 4 replicates of 10 chcks in each batteIy cages appropriate for completely randomized design. The treatments included supplementation of 6 dietaq levels of phytase (0,250, 500, 750, 1,000 and 1,250 FTU kg-) during 0-28 days of age. All chicks were fed a nutritionally adequate typical commercial broiler staJter and grower ration (adequate in phosphoms and calcium). During days 21 to 24 excreta totally were collected for AA and CP analyzing. 250 and 500 FTU kg- phytase significantly improved digestibility of amino acids (except than alanine, valine and threonine) and CP (p<0.05). Phytase hadno significant effect on live body weight, feed intake and feed efficiency (p>0.05) of the broiler chicks up to 28 days of age.

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