Effect of Varying Carbohydrate Fractions on Growth,Body Composition,Metabolic, and Hormonal Indices in Juvenile Black Carp,Mylopharyngodon piceus

This study was conducted to investigate the effects of varying carbohydrate (CHO) fractions on growth, body composition, metabolic, and hormonal indices in juvenile black carp, Mylopharyngodon piceus. Juvenile black carp, M. piceus (average weight: 1.5 ± 0.05 g) were fed with graded levels of dietary available CHO (0.06, 10.65, 19.43, 28.84, 37.91, and 47.38%) for 9 wk, respectively. Results showed that the highest weight gain could be obtained at 24.98% dietary CHO using second‐order polynomial regression model; and optimal dietary available CHO content (28.84%) could significantly increase the final body weight and the protein efficiency ratio (PER) while reducing the feed conversion ratio (FCR) (P < 0.05). Dietary available CHO could gradually increase the hepatosomatic index, the crude lipid contents in the whole body and the glucose and triglyceride content in the plasma. The activities of glycolysis enzymes and glucose‐6‐phosphate dehydrogenase could be increased with increasing dietary available CHO. The activities of glucose‐6‐phosphatase and fructose‐1,6‐bisphosphatase were firstly decreased at 10.65% dietary available CHO and increased to stable level at 19.43% dietary available CHO. In addition, both 19.43 and 28.84% dietary available CHO could increase the adiponectin contents in the plasma of black carp, M. piceus. Meanwhile, both 19.43 and 28.84% dietary available CHO could significantly increase the mRNA expression levels of growth hormone, insulin, ghrelin, neuropeptide Y, somatostatin I, and somatostatin II in juvenile black carp, M. piceus, compared with the CHO‐deficient diet (0.06%). These results suggest that optimal inclusion of dietary CHO fractions (19.43–28.84%) could improve metabolic homeostasis and promote growth and feed efficiency in juvenile black carp, M. piceus.