The Influence of Overdose Dietary DL-Methionine or HMTBA on Growth,Feed Utilization and Anti-Oxidant Responses of Turbot(Scophthalmus maximus L.)

A growth experiment was conducted to evaluate the influence of overdose dietary DL-methionine(Met) or 2-Hydroxy-4-(Methylthio) butanoic acid(HMTBA) on turbot(initial body weight:(5.49±0.01) g).The control contained 1.35% Met and 0.22% HMTBA.Five different doses of Met or HMTBA were added to the basal diet,respectively.Finally,6 experimental diets were formulated,and the analyzed levels of Met or HMTBA in diets are as follows: Met: 1.35%,1.83%,2.50%,1.45%,1.37%,2.51%;HMTBA: 0.22%,0.22%,0.22%,0.63%,1.38% and 0.29%.Each diet was fed to five replicate groups of turbot for 10 weeks.Results showed that no significant differences in growth responses were found among dietary treatments(P0.05).No significant difference was observed in body composition,condition factor(CF),visceral indexes(VSI),and hepatosomatic indexes(HSI)(P0.05),but the content of body protein of fish in treatment of diet 6 was significantly lower than those in the control and diet 2(P0.05).No significant differences in hepatic catalase activity,superoxide dismutase activity,thiobar-bituric acid reactive substances value were found in liver(P0.05).In conclusion,overdose dietary DL-Met(1.31~1.73 times) or HMTBA(1.32~1.75 times) had no significant effects on growth,feed utilization and anti-oxidant responses in turbot under the current experimental conditions.