Wang, J., Department of Aquaculture, Zhejiang Ocean University, Zhoushan, China
Li, X., Department of Aquaculture, Zhejiang Ocean University, Zhoushan, China
Han, T., Department of Aquaculture, Zhejiang Ocean University, Zhoushan, China
Yang, Y., Department of Aquaculture, Zhejiang Ocean University, Zhoushan, China
Jiang, Y., Department of Aquaculture, Zhejiang Ocean University, Zhoushan, China
Yang, M., Department of Aquaculture, Zhejiang Ocean University, Zhoushan, China
Xu, Y., Department of Aquaculture, Zhejiang Ocean University, Zhoushan, China
Harpaz, S., Department of Aquaculture, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet Dagan, Israel

Six isoproteic and isolipidic diets were designated to investigate the effects of dietary carbohydrate level (from 0% to 30%) on growth performance, feed utilization and body composition of juvenile grouper Epinephelus akaara (initially weighing, 7.79 ± 0.01 g/fish). Each diet was given to triplicate groups (20 juvenile grouper per cage) for 8-weeks. The weight gain (WG) and final body weight (FBW) were quadratically and linearly related to the increase of dietary carbohydrate level (P < 0.05). The weight gain (WG) values increased with increasing dietary carbohydrate from 0% to 6% while at higher levels WG values decreased. Feed conversion ratio (FCR), protein efficiency ratio (PER) and daily feed intake (DFI) were found to be not significantly related to the dietary carbohydrate (P > 0.05). As the level of dietary carbohydrate increased both quadratic and linear responses were observed on the intraperitoneal fat ratio (IPF). The whole body and muscle lipid content were relatively lower in fish fed the 30% dietary carbohydrate diet compared with the other treatments. Liver glycogen content generally increased with increasing dietary carbohydrate levels. Energy retention (ER) and lipid retention (LR) decreased significantly with increasing dietary carbohydrate levels. Based on second-order polynomial regression analysis of WG, this study suggests that 7.64% dietary carbohydrate level provides a maximum growth for juvenile E. akaara. Statement of relevance: The main aim of this study is to determine the effects of dietary carbohydrate levels on growth performance, feed utilization and body composition of juvenile E. akaara. The research outcomes will develop formulated diets for E. akaara and will have good potential of being commercialized. © 2016.Published by Elsevier B.V.