Dietary Thiamin Requirement of Juvenile Grass Carp, Ctenopharyngodon idella

Dietary thiamin requirement of juvenile grass carp, Ctenopharyngodon idella, was to investigate in this experiment. Eight purified diets were formulated with graded levels of thiamin (0.1, 0.6, 1.1, 2.1, 5.5, 9.8, 21.2, and 41.8mg/kg, respectively). Each diet was fed to triplicate groups of 40 fish (initial average weight 10.7 +/- 0.2 g) for 12 wk in 400-L aquaria (R=1m, h=0.6m). Results showed that weight gain rate, specific growth rate, feed efficiency, protein efficiency ratio, and hepatosomatic indice of fish increased before dietary thiamin increased to the optimum level, then remained similar thereafter (P > 0.05). Thiamin concentration in fish liver was positively correlated with dietary thiamin and it stayed in stable when dietary thiamin level exceed 5.0mg/kg. The serum biochemical indices analysis showed that dietary thiamin had significant effects on serum triglycerides, total cholesterol, glucose, pyruvate contents, and lactate dehydrogenase activity. Body composition was unaffected by dietary thiamin. Broken-line regression analysis showed that, a dietary thiamin level of 1.3 mg/kg diet was adequate for optimum growth, and 5.0mg/kg for maximum liver thiamin accumulation.