Eco-fitness Requirement Of Protein In Diets For Juvenile Turbot (Scophthalmus Maximus L.)

Abstract: Based on the theory and methods of Eco-Nutrition, to study the protein nutrition fitness and environment stability in turbot (Scophthalmus maximus L.) culture. One-way experiment was designed. Five experimental extruded diets containing different protein level(45%,48%,50%,52% and 54%) were fed to triplicate groups of juvenile turbot(n=225;average body weight 34.5±5.5g ). Evaluating the effects of different protein level diets on turbot growth, feed utilization, seawater environmental factors, and protein digestive characteristics of turbot. In order to aquire the eco-fitness requirement of protein for juvenile turbot. The results are as follows: Growth performance and feed utilization of juvenile turbot were all affected significantly by different protein level diets(P<0.05). As protein level increased, weight gain ratio and specific growth rate increased;reversed, feed conversion ratio decreased. As protein level was below 50%,the range of growth performance increased significantly. But as protein level was up 50%,the range of growth performance increased slowly. WGR of 50% group was 95% of 54%group and got the best protein efficiency ratio. FCR of 50% group was lower 14.4%and 10.9%(P<0.05)than 45%and 48% group;only higher 1.6%and 2.3% than 52%and 54%group. Seawater ecofactors except pH were all affected significantly by different protein level diets(P<0.05). COD,NH3-N,NO2-N and PO4-P all increased with increasing protein level diets. As protein level was below 50%,NH3-N increased slowly;But as protein level was up 50%,NH3-N increased significantly. Twice NH3-N of 50% group was lower 18.8%and 17.0% than 52% group;and lower 32.5%and 30.4% than 54% group. As protein level increased, protein intake, protein digested and nitrogen in feces of juvenile turbot increased significantly(P<0.05). As protein level increased, diets digestibility were not affected significantly;but protein digestibility were affected significantly which increased first, then decreased, and 50% group got the best digestibility. Nitrogen in feces of 50% group was higher 3.9%and 2.4% than 45%and 48% group;but lower 10.6%and 17.6% than 52%and 54%group(P<0.05). Besides, two commercial diets comparing with our five experimental diets were also used in the growth trial of juvenile turbot. Growth performance of turbot fed 50-54% protein level experimental diets were preferable than domestic commercial diet, and were close to overseas commercial diet. Feed conversion ratio of 50% protein level diet was lower 21.6% than domestic commercial diet, and NH3-N was decreased by 28.8% than overseas commercial diet. So, analyzing the growth performance,feed utilization, protein digestive characteristics of juvenile turbot and seawater environmental factors, we considering the eco-fitness requirement of protein for juvenile turbot is 50%.