A comparison of the effect of dietary fungal phytase and dicalcium phosphate supplementation on growth performances, feed and phosphorus utilization of tra catfish juveniles (Pangasianodon hypophthalmus Sauvage, 1878)

Six isonitrogenous (320gkg(-1)) and isolipidic (60gkg(-1)) diets were formulated with graded levels (0, 5, 10 and 15gkg(-1)) of dicalcium phosphate (DCP) and fungal phytase (750 and 1500FTUkg(-1)diet). Tra catfish (Pangasianodon hypophthalmus), 9.6g, were fed the diets for 12weeks. Each experimental diet was fed to eight replicates of fish to apparent satiation. At the end of the trial, fish fed the diets containing 15gkg(-1) DCP, 750 and 1500FTUkg(-1) phytase had higher growth performances, protein efficiency ratio and phosphorus retention than those fed the control diet, 5gkg(-1) DCP and 10gkg(-1) DCP diets (P<0.05). Whole body ash and phosphorus concentration of fish fed the 10gkg(-1) DCP and 15gkg(-1) DCP diets were significantly higher than those of fish fed the control diet. Higher apparent digestibility coefficient of phosphorus was observed in fish fed the phytase supplemented diets. The present results indicate that supplementation of phytase at 750 FTUkg(-1) and 1500FTUkg(-1) improves growth performances, feed and phosphorus utilization. The supplementation can completely replace dicalcium phosphate or other phosphorus sources in tra catfish feed and reduce the phosphorus discharge into environment.