Adaptation of Chinese perch (Siniperca chuatsi) to different levels of dietary carbohydrates

Abstract

Abstract This study was conducted to investigate the effects of dietary carbohydrate on growth performance, feed utilization, proximate compositions, and hepatic glucolipid metabolism in Chinese perch. Triplicate groups of Chinese perch (29.51 ± 0.24 g) were fed five isonitrogenous and isolipidic diets containing graded levels of carbohydrate (2.4%, 9.7%, 16.5%, 23.9%, and 30.1%) for 8 weeks. The results showed that 10.93% dietary carbohydrate level provided a maximum growth for Chinese perch based on second-order polynomial regression analysis of specific growth rate (SGR). Compared to 2.4%-carbohydrate group, moderate-carbohydrate (9.7%) group exhibited the increase in daily weight gain (DWG) and protein retention ratio(PER), and the decrease in feed conversion efficiency (FCR). Moreover, moderate-carbohydrate group showed the increase in the mRNA levels of phosphofructokinase (pfk) and citrate synthase (cs) involved in aerobic oxidation pathway, the increase in hepatic glycogen content, and no change in glucose level. Above results suggested that part carbohydrates may be converted into energy for growth by aerobic oxidation pathway, and the remaining carbohydrates may be converted into glycogen for storage to maintain glucose homeostasis in Chinese perch fed with moderate-carbohydrate diet. Differently, high-carbohydrate (23.9% and 30.1%) group showed the decrease in DWG and PER, and the increase in FCR,compared to 2.4%-carbohydrate group. Additionally, high-carbohydrate group presented the increase in the mRNA levels of glucose-6-phosphatase a (g6pca) and pyruvate carboxylase (pc) involved in gluconeogenesis, which caused the increase in plasma glucose level. However, other plasma indices related to TG-metabolite and its transport (total triglyceride, total cholesterol, and low-density lipoprotein) did not show difference, which combined with elevated fatty acid synthesis-related gene acetyl coA carboxylase α (accα) mRNA level resulted in excessive liver lipid deposition. Above results indicated that unregulated gluconeogenesis and invalidoutward transportation of liver TG-rich metabolites may account for the glucose intolerance of Chinese perch fed with carbohydrate-rich diet.