Effect of microbial phytase produced from a fungus Aspergillus niger on bioavailability of phosphorus and calcium in broiler chickens

Phytase was produced from a fungus Aspergillus niger through 10-day ferment ation in a maize starch-based medium. Activity of the enzyme was found to b e 1.075 phytase units per minute per mi of the crude culture filtrate, at p H 5.5 and 40 degrees C. A 4-week feeding trial was conducted on 90-day-old broiler chickens, fed on diets based on maize and soyabean meal, to study t he efficacy of phytase enzyme on growth performance, apparent availability of P and Ca, tibia-and-toe ash and mineral contents of tibia. Treatments in volved a normal-P level (control, 4.5 g/kg non-phytate phosphorus, nP), a n ormal-P diet with phytase enzyme-treated maize and soyabean meal and a low- P diet plus phytase (1.075 PU/gm of substrate). Phytase supplementation inc reased (p < 0.05) BW in normal-P plus phytase diet by 2.65 percentage units as compared to control. Gain in weight was almost similar with both, low-P plus phytase, and control diets (645 vs. 653 g). Added phytase increased t he feed intake in the same manner as weight gain, however, feed conversion ratio (FCR) was similar to that for all diets. Phytase treatment of low-P d iet increased (p < 0.05) the relative retention of P and Ca by 20.1 and 5.0 percentage units, respectively, than with the control diet. The tibial-and -toe ash contents were increased (p < 0.05) by the normal-P plus phytase di et than with the control diet. Tibial-and-roe ash contents of low-P plus ph ytase diet were comparable (51.2 vs. 48.6 and 10.9 vs 10.5) with that of th e control diet. Phytase treatment had no effect on the concentration of any of the minerals measured in whole tibia ash, but did increase (p < 0.05) P and Ca in tibia DM of chicken by 4.5 and 9.8 percentage units, respectivel y, in normal-P plus phytase, and 1.2 and 2.2 percentage units, respectively , in low-P plus phytase diets. These results show that microbial phytase tr eatment of a low-P diet increased growth and relative retention of P and Ca , and improved bone mineralization in broiler chickens. (C) 2000 Elsevier S cience B.V. All rights reserved.