Dietary carbohydrate sources influence the growth performance, plasma biochemical parameters and expression of genes involved in glucose metabolism in juvenile Pelodiscus sinensis

Abstract

An 8-week growth trial was conducted to investigate the influences of different dietary carbohydrate sources on growth performance, feed utilization, plasma biochemical parameters and expression of glucose metabolism-related genes in juvenile Chinese soft-shelled turtle, Pelodiscus sinensis. Five isonitrogenous (45 %) and isolipidic (8 %) experimental diets contained 17 % glucose, maltose, sucrose, pregelatinized cassava starch (α-starch) or cellulose, respectively. The results showed that α-starch significantly improved the weight gain rate and specific growth rate of P. sinensis compared to glucose, sucrose and cellulose. No significant difference existed in daily feed intake among all diets. However, turtles fed with cellulose showed a significantly higher feed conversion ratio than that in other treatments except for glucose group. Turtles fed with glucose showed significantly higher plasma glucose content than counterparts in sucrose, α-starch and cellulose treatments. While sucrose induced higher plasma cholesterol and triacylglycerol contents of turtles compared to glucose, maltose, sucrose and α-starch. The plasma insulin in α-starch group showed a higher level than that in glucose group. The glycolysis enzymes including glucokinase and pyruvate kinase in α-starch group exhibited higher mRNA levels than that in other diets, while the mRNA levels of gluconeogenesis enzymes in α-starch group were significantly lower than that in glucose group. The expressions of glycogen synthase and phosphorylase glycogen in glucose group were significantly up-regulated compared with sucrose, α-starch or cellulose groups. In summary, the poor insulin secretion and the up-regulated gluconeogenesis may account for the decreased growth in glucose diets. The most appropriate tested carbohydrate source was α-starch for juvenile P. sinensis based on its positive impacts on growth and metabolism of turtles.