TAURINE SUPPLEMENTATION IN DIET FOR OLIVE FLOUNDER AT LOW WATER TEMPERATURE  

A study was conducted to evaluate the supplemental effect of taurine in diets for juvenile olive flounder (Paralichthys olivaceus) at low water temperature season. Fish growth performance, feed utilization, the expression levels of liver insulin-like growth factor I (IGF-I) and innate immunity were examined. Five experimental diets were formulated to contain 46% protein and 12.5% lipid and taurine was supplemented at 0%, 0.25%, 0.5%, 1% and 1.5% levels (designated as Control, T1, T2, T3, and T4).  Triplicate groups of fish (initial body weight, 19.54 ± 0.06 g) were fed one of the experimental diets to apparent satiation twice daily for ten weeks. At the end of the feeding trial, higher growth performances were obtained by taurine supplementation. Feed utilization was significantly improved with increasing levels of taurine. Plasma protein level was significantly increased while plasma cholesterol level was decreased with the inclusion of taurine into diets. Blood parameters (hemoglobin, hematocrit and respiratory burst activity) were also significantly affected with taurine supplementation. Innate immunity was enhanced with the supplementation of taurine showing significantly higher lysozyme, myeloperoxidase and superoxide dismutase activities and immunoglobulin level in T3 and T4 fish groups compared to those of fish fed the control diet. Liver IGF-I mRNA expression was significantly higher in T4 group compared to the control. These results indicated that supplementation of taurine in diets for juvenile olive flounder could compensate the growth retardation at low water temperature period and the optimum inclusion level would be approximately 1%.