Effects of dietary betaine on growth, nutritional components and serum biochemistry of Rachycentron canadum

We conducted an 8-week feeding experiment by designing 6 kinds of feed ( addition levels of betaine: 0, 0. 05% , 0. 10% , 0. 20% , 0. 30% , 0. 40% ) to investigate the effects of dietary supplementation of betaine on the growth, nutritional components, ser- um biochemistry and enzyme activity on liver of juvenile Rachycentron canadum. The results show that when the addition level is 0. 05% , the weight gain ( WG) and specific growth rate ( SGR) reach the maximum; the condition of liver is the best; the protein content is the highest in both whole body and muscle. When the addition level is higher than 0. 20% , the condition factor ( CF) shows a negative correlation with the level of dietary betaine. Hepatosomatic index ( HSI) of each group is significantly lower than that of the control ( P < 0. 05) , and the lipid mass fraction ( except for 0. 10% group) is lower than that of the control. The concentration of tri- glyceride ( TG) in serum is higher than that of the control, showing an"increase-decrease"trend. The activity of glutamic-pyruvic transaminase ( GPT) of all groups are significantly lower than that of the control ( P < 0. 05) . The results indicate that dietary supple- mentation of betaine can improve the growth and lipid metabolism for R. canadum, doing good to reduce the lipid of the fish.