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 fermentation in a maize starch-based medium. Activity of the enzyme was found to be 1.075 phytase units per minute per mi of the crude culture filtrate, at pH 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 the efficacy of phytase enzyme on growth performance, apparent availability of P and Ca, tibia-and-toe ash and mineral contents of tibia. Treatments involved a normal-P level (control, 4.5 g/kg non-phytate phosphorus, nP), a normal-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 increased (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 the 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 diet 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 diet than with the control diet. Tibial-and-roe ash contents of low-P plus phytase diet were comparable (51.2 vs. 48.6 and 10.9 vs 10.5) with that of the 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, respectively, 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 treatment of a low-P diet increased growth and relative retention of P and Ca, and improved bone mineralization in broiler chickens. (C) 2000 Elsevier Science B.V. All rights reserved.