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Effects of Dietary Carbohydrate-to-Lipid Ratios on Growth and Body Composition of Orange-spotted Grouper Epinephelus coioides

Wang, Ji-teng, Jiang, Yu-dong, Han, Tao, Li, Xin-yu, Wang, Yong, Liu, Yong-jian
North American journal of aquaculture 2017 v.79 no.1 pp. 1-7
Epinephelus coioides, body composition, body weight, crude protein, diet, energy, feed conversion, fish, glycogen, growth performance, hepatosomatic index, juveniles, lipid content, lipids, liver, nitrogen, protein efficiency ratio, satiety, specific growth rate, water content, weight gain
Growth performance of juvenile Orange-spotted Grouper Epinephelus coioides fed isonitrogenous (45% crude protein) and isoenergetic diets with varying carbohydrate-to-lipid ratios (0 to 10.9) were evaluated. Triplicate groups of 18 fish (initial mean individual body weight, 16.4 g/) were fed to satiety for 8 weeks. At the termination of this trial, significant differences (P < 0.05) were found on the growth performance. Weight gain and specific growth rate values increased with decreasing dietary carbohydrate-to-lipid ratios. The highest feed conversion ratio value and the lowest protein efficiency ratio value were observed in fish fed the 10.9 carbohydrate-to-lipid ratio diet. Besides, fish fed the 10.9 carbohydrate-to-lipid ratio exhibited the lowest nitrogen retention and energy retention values. With the diet carbohydrate-to-lipid ratios decreasing, hepatosomatic index values were reduced significantly (P < 0.001), while the intraperitoneal fat index values showed an inverse trend. Whole-body protein content was reduced with the decrease in dietary carbohydrate-to-lipid ratios, whereas whole-body lipid content increased significantly with decreasing dietary carbohydrate-to-lipid ratios (P < 0.001) while the whole-body moisture content showed a reverse trend. Additionally, liver lipid content increased with the decrease in dietary carbohydrate-to-lipid ratios, while contrasting results were found in liver glycogen content. The results of this study suggest that the suitable dietary carbohydrate-to-lipid ratio for Orange-spotted Grouper is 0.5 in the isonitrogenous (45% crude protein) and isoenergetic diets, and this species is better adapted to utilizing lipids rather than carbohydrates. Received December 1, 2015; accepted May 4, 2016 Published online November 11, 2016