Effects of Feeding Rates on Growth Performance and Liver Glucose Metabolism in Juvenile Largemouth Bronze Gudgeon...

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 (Coreius guichenoti). 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^-1 for 8 w. The results indicated that the feeding rates significantly increased the body weight, weight gain rate, and specific growth rate (p < 0.05), while showing no significant effects on the condition factor and survival rate (p > 0.05). The feed conversion ratio was significantly enhanced by the feeding rate (p < 0.05), although no significant differences were observed when the feeding rate exceeded 3% (p > 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) (p < 0.05), while showing no significant differences on enzyme activities (PC, PEPCK, and G6P) and mRNA (pepck and g6p) levels of gluconeogenesis (p > 0.05). In addition, the mRNA levels of hepatic glut2 and glut4 in the 5% group reached the highest levels (p < 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 (gysl) was significantly increased (p < 0.05), while no significant difference was observed in glycogen phosphorylase (pygl) (p > 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.