Dietary thiamine requirement and its effects on glycolipid metabolism in oriental river prawn (Macrobrachium nipponense)

Abstract

A 10-week feeding trial was conducted to investigate the optimal dietary thiamine requirement of oriental river prawn Macrobrachium nipponense with the effects on glycolipid metabolism evaluated. A total of 960 prawns with an average weight of 0.18 g were selected and randomly fed six semi-purified diets containing graded levels of thiamine (14.10, 35.20, 43.30, 61.40, 95.60 and 165.00 mg/kg, respectively) in an indoor water circulation system. Each diet was tested in 4 replicates. Final weight, weight gain, specific growth rate, protein efficiency rate, hemolymph thiamine and triglycerides concentrations all increased significantly (P < 0.05) with increasing dietary thiamine levels up to 61.40 mg/kg, and then decreased. A similar result was also observed in hemolymph transketolase activities except for the fact that the maximum value was observed in the 95.70 mg/kg group (P < 0.05). However, the opposite was true for hemolymph glucose and pyruvate concentrations with no statisticaldifference observed (P > 0.05). As dietary thiamine levels increased, the expressions of hexokinase and acetyl-CoA carboxylase both increased significantly (P < 0.05), and peaked at the 95.70 mg/kg group. Similar results were also observed in the expressions of glucose transporter 2, pyruvate kinase, glycogen synthase and fatty acid synthase except that the maximum values were all observed in the 61.40 mg/kg group. Furthermore, the expressions of pyruvate carboxylase, phosphoenolpyruvate carboxykinase, carnitine palmitoyltransferase I and hormone-sensitive triglayceride lipase all decreased significantly (P < 0.05) with increasing dietary thiamine levels up to 61.40 mg/kg, and then plateaued. Based on the broken-line regression analysis of growth performance and hemolymph thiamine content, the optimal thiamine requirement of M.nipponense was estimated to be 66.80 and 67.57 mg/kg, respectively.