1.Pearl River Fisheries Research Institute,Chinese Academy of Fishery Sciences,Guangzhou 510380,China;2.College of Fisheries,Guangdong Ocean University,Zhanjiang 524088,China
Abstract: A 56 day feeding trail was conducted to evaluate the effects of dietary phytase levels（0,500,1 000,and 1 500 U/kg） on growth and digestive enzyme activities in largemouth bass Micropterus salmoides with initial body weight about 23 g.The results showed that the fish fed the diets containing 1 000 U/kg phytase had significantly better growth and lower feed conversion ratio（P〈0.05）.The hepatopancreas index was found to decrease with increase in dietary phytase levels,with the minimum in the fish fed the diet containing 1 500 U/kg phytase,significantly different from the control.There were 28.14% and 20.09% higher protease activities in the stomach of the fish fed the diets containing 1 000 U/kg and 1 500 U/kg phytase than that in the control group（P〈0.05）.The pylorus protease activities were found higher in the experimental groups than that in the control group（P〈0.05） without significant differences in gut protease activities.The amylase activities in the liver and gut showed increase with the phytase addition,but not significantly different level（P〉0.05）.The fish fed the diets containing 1 000 U/kg and 1 500 U/kg phytase had lower amylase activities in the stomach without significant difference（P〉0.05）.
2010, Vol. 25 
