Effects of dietary carbohydrate on growth, feed utilization, hepatic glucose and lipid metabolism in endangered Yangtze sturgeon (Acipenser dabryanus)

Abstract

The aim of this study was to determine the effects of dietary carbohydrate levels on growth performance, feed utilization and metabolism of juvenile Yangtze sturgeon (Acipenser dabryanus). Six isonitrogenous (crude protein 45 %) and isolipidic (crude lipid 10 %) experimental diets were formulated containing 7.35 %, 10.2 %, 13.4 %, 16.5 %, 19.4 % and 22.4 % carbohydrate. Triplicate groups of 15 fish (initial weight, 51.4 ± 0.16 g) were fed twice daily for 8 weeks. The significantly higher (P < 0.05) growth performance was recorded in dietary 19.4 % group compared with the dietary 7.35 % and 10.2 % groups. Meanwhile, higher dietary carbohydrate (16.5 %, 19.4 % and 22.4 %) also significantly improved feed conversion ratio compared with the lowest one (7.35 %). Protein efficiency ratio exhibited similar tendency with growth performance. And the highest muscle crude protein was found in 19.4 % group and was significantly higher than the lower dietary carbohydrate groups (7.35 %, 10.2 %, 13.4 %) (P < 0.05). Liver glycogen content was positively correlated with dietary carbohydrate levels. The highest dietary carbohydrate level (22.4 %) led to much more lipid deposition in the body. Furthermore, the highest mRNA expression of Acetyl-CoA carboxylase and fatty acid synthesis were also recorded in dietary carbohydrate 22.4 % group. mRNA expression of glycolysis related genes hexokinase was significantly (P < 0.05) up-regulated by higher levels of carbohydrate (19.4 % and 22.4 %) compared with other treatments. Quadratic broken-line analysis of weight gain against carbohydrate levels showed that the optimal value was 20.6 % of diet for Yangtze sturgeon.