Effects of Feeding Rates on Growth Performance and Liver Glucose Metabolism in Juvenile Largemouth Bronze Gudgeon ( Coreius guichenoti )

The experiment was conducted to investigate the effects of feeding rates on growth performance, liver glycolysis, gluconeogenesis, glycogen synthesis, and glycogen decomposition in juvenile largemouth bronze gudgeon ( ). A total number of 600 fish were randomly distributed into 12 cylindrical plastic tanks with 50 fish per tank and triplicate tanks per treatment. Fish were fed with 2%, 3%, 4%, and 5% feeding rates (body weight per day) three times day for 8 w. The results indicated that the feeding rates significantly increased the body weight, weight gain rate, and specific growth rate ( < 0.05), while showing no significant effects on the condition factor and survival rate ( > 0.05). The feed conversion ratio was significantly enhanced by the feeding rate ( < 0.05), although no significant differences were observed when the feeding rate exceeded 3% ( > 0.05). The plasma glucose levels in the 4% and 5% groups were significantly higher than those in the 2% and 3% groups. Compared with other groups, the 5% group significantly increased the crucial rate-limiting enzyme activities and mRNA levels of glycolysis (PFKL and PK) ( < 0.05), while showing no significant differences on enzyme activities (PC, PEPCK, and G6P) and mRNA ( and ) levels of gluconeogenesis ( > 0.05). In addition, the mRNA levels of hepatic and in the 5% group reached the highest levels ( < 0.05). When the feeding rate exceeded 3%, hepatic glycogen and lipid accumulation were significantly increased, leading to a fatty liver phenotype. Meanwhile, the mRNA level of liver glycogen synthetase ( ) was significantly increased ( < 0.05), while no significant difference was observed in glycogen phosphorylase ( ) ( > 0.05). In summary, under the conditions of this study, a feeding rate exceeding 3% significantly accelerated hepatic glycogen and lipid accumulation, which ultimately induced fatty liver formation.