Effects of Different Dietary Carbohydrate Levels on Growth Performance,Body Composition and Serum Biochemical Indices of Juvenile Hybrid Tilapia(Oreochromis niloticus ♀×O.aureus ♂)

Total 450 juvenile hybrid tilapia(Oreochromis niloticus♀×O.aureus♂) [av.Wt.(2.79±0.28) g]were randomly distributed into 5 groups for 10 weeks.Five iso-lipidic(7% crude lipid) diets were formulated containing five carbohydrate(CBH) levels:20%,27%,34%,41% and 48%,whereas protein levels were 48%,41%,34%,27% and 20% respectively.The mass gain rates(MGR) and specific growth rates(SGR) of 41% group were significantly higher than those of 20%,27% and 48% group(P0.05).The feed conversion rates(FCR) of 34% group were the lowest,significantly lower than those of 20% and 48% group(P0.05).The hepatopancreas somatic index(HSI) and viscerosomatic index(VSI) of 41% and 48% group were significantly higher than the other three groups(P0.05).Crude protein content in whole-body and liver of fish decreased with the increasing dietary CBH levels,while body and liver lipid showed converse trend.The cholesterol(CHO),triglyceride(TG) and low density lipoprotein cholesterol(LDL-C)reached to the peak with dietary CBH level at 48%,while high density lipoprotein cholesterol(HDL-C)showed converse trend.The highest activities of aspartate aminotransferase(AST) and alanine aminotransferase(ALT) were observed in 48% group.The results indicated that CBH could spare some protein in the dietary of juvenile hybrid tilapia;the optimal dietary CBH level was 34%~41%;the high dietary CBH level(48%) significantly improved the CHO and TG and damaged liver function of fish.