Effects of dietary Betaine on growth,fat content and biochemical indexs in blood of tilapia(Oreochromis niloticus×Oreochrmis aureus)

750 juvenile tilapia(Oreochromis niloticus×Oreochrmis aureu.s) were randomly allotted to five groups,and were fed diets supplemented with different level Betaine(0、0.15%、0.30%、0.45% and 0.60%) for 65 d to investigate the effects of Betaine on growth,fat content and biochemical indexs of blood of tilapia.The results showed that tilapia' WGR were 19.52%、16.63% and 21.38% higher than that of control group(P0.05) respectively when tilapia feed were added with 0.30%-0.60% Betaine;FRC reduced by 25.55%、20.44 % and 29.93%(P0.05)respectively;the HSI reduced by 9.29%、38.57% and 29.29%(P0.05);the contents of TG in Tilapia's plasma reduced by 66.28%、55.81% and 80.23%(P0.05) respectively;the activities of AMY in Tilapia's plasma reduced by 88.78%、37.59% and 62.41%(P0.05);the contents of ALB and TP in Tilapia's plasma were improved,the contents of CHOL in Tilapia's plasma reduced;the activities of LDH、ALT and AST in Tilapia's plasma reduced respectively.Therefore,under this research condition,it is suggested that the supplement of Betaine in diets of juvenile tilapia was the best at 0.45%~0.60%.