EFFECT OF PHYTASE SUPPLEMENTATION IN SOYBEAN MEAL BASED DIET ON NUTRIENT DIGESTIBILITY AND GROWTH PERFORMANCE OF GREEN CATFISH (Hemibagrus nemurus)

h is experiment was conducted to evaluate the eff ect of phytase supplemented to the diet on phosphorus (P) digestibility and growth performance of the green catfi sh Hemibagrus nemurus . Five kinds of experimental diets were used in this experiment, namely diets A, B, C, D and E. Diet A, as a control, was supplemented with inorganic P, without phytase supplementation. Diet B, C, D and E were supplemented with 0, 20, 40 and 60 mg phytase/100 g soybean meal (SBM), respectively, without inorganic P supplementation. Fifteen fi sh with initial body weight of 6.9 + 0.2 g were stocked into each 60-l aquarium. Fish were fed on the diets for 60 days. Results indicated that P digestibility increased from 64.5% to 87.0% as phytase supplement increased from 0 mg in diet B to 60 mg phytase/100 g SBM in diet E. P digestibility in diet E was higher than that in diet A (77.6%). h e daily growth rate and feed conversion ratio followed similar trend. P, Ca and Zn concentration in the whole body and bone of fi sh fed diet E were higher than the fi sh fed diet B, C and D, but were insignifi cant compared to the fi sh fed diet A. Nitrogen (N) and P loading by fi sh fed diet E were, respectively, 76% and 20% lower than those in fi sh fed the control diet. It is concluded that the inclusion of 60 mg phytase/100 g SBM in the diet of the green catfi sh could replace the utilization of inorganic P increase the digestibility of the diet thereby resulting in increased growth rate and reduced excretion of P and N into the waters.