Effects of the Dietary Protein Levels on the Growth and Feed Utilization of Juvenile Lateolabrax japonicas

To investigate the effect of the diet protein level on growth and feed utilization of juvenile Lateolabrax japonicus, five isoenergetic experimental diets containing 35.0%, 37.5%, 40.0%, 42.5% and 45.0% protein were made up respectively, whose protein source was fish meal.Juvenile Lateolabrax japonicus with initial average weight of (84.81±0.92) g took the feeding experiments for 75days for determination of the best protein level.The results showed that the relative weight gain rate, specific growth rate and feed conversion rate of the group of 39.85% were much higher than those of 34.76% and 37.54% groups (P<0.01) , but not significantly different from the 42.34% group (P>0.05) .Protein efficiency rate of the 39.85%group was also higher than those of the 34.76%, 42.34% and 45.03% groups (P<0.05) , while comparing with the 37.54% group, no significant difference was found (P>0.05) .In this experiment, based on quadratic model regression analysis of the specific growth rate and protein efficiency rate, growth index and feed utilization rate of Lateolabrax japonicus were best while the protein content of juvenile Lateolabrax japonicus feed was 38.87%-41.50%.