EFFECTS OF DIETARY CARBOHYDRATE LEVEL ON GROWTH PERFORMANCE, BODY COMPOSITION AND DIGESTIVE ENZYME ACTIVITIES OF JUVENILE CRAB, SCYLLA PARAMAMOSAIN

To investigate the effects of dietary carbohydrate on growth performance, body composition and digestive enzyme activities of juvenile crab, Scylla paramamosain, five isonitrogenous and isolipidic diets with varying carbohydrate contents of 20.34%, 25.59%, 30.17%, 35.30% and 39.95% were fed to juvenile crabs with an average body weight of (38.11±0.55) mg of triplicate groups, respectively, for a 3-week feeding trial. Results showed that the survival rate, weight gain ratio and specific growth rate of the juvenile crabs significantly increased firstly and then decreased under the increased dietary carbohydrate level (P<0.05) with the highest level at 30.17%. With the increasing dietary carbohydrate level, the body crude protein and body ash contents of the crabs were significantly increased firstly and then decreased (P<0.05) with the highest level at 35.30%. Dietary carbohydrate level significantly affected amylase activity (P<0.05) without any significant influence on protease and lipase activities (P>0.05). The amylase activity significantly induced by high carbohydrate level (P<0.05). These results indicate that the diet with 25.59%—35.30% carbohydrate could greatly support growth performance. The regression model analysis showed that the most suitable dietary carbohydrate level reach the highest weight gain ratio is 29.93%.