ABSTRACT This study was conducted to evaluate the effect of dietary phytase supplementation on phosphorus (P) bioavailability of the diets and growth performance of catfish (Clarias sp) as well as P loading. Four experimental diets were used in this experiment. Diet (A), as a control, was supplemented with inorganic P; diet (B) supplemented with phytase, without inorganic P; diet (C ) supplemented with phytase and citric acid, without inorganic P; and diet (D) without phytase and inorganic P. Phytase was added to the diet at 50 mg/100 g soy bean meal and pollard. Ten fishes with initial body weight of 6.3 ± 0.05 g distributed into an aquarium. Fish fed on the diets for 60 days, there time daily, at satiation. Results indicated that P digestibility increased from 68.55% to 86.1% by the addition of phytase. P digestibility in diet B and C was higher than diet A and D. Daily growth rate of fish from diet B and C were significantly higher than that of diet D, but similar with diet A. Food conversion ratio (FCR) of fish from diet A, B, and C was better than diet D. P concentration in the whole body, bone, and plasma, of fish from diet A,B, and C was higher than diet D, but the Ca and Zn concentration  in the whole body, bone, plasma was the same in all treatments. P loading by fish fed diet with phytase ware 58% lower than that of the fish fed control diet. Keyword: Clarias sp, phytase, phosphorus, bioavailability
                        
                        
                        
                        
                            
                                Copyrights © 2011