Taurine is an essential nutrient for juvenile parrot fish Oplegnathus fasciatus

Two consecutive feeding trials were conducted to investigate taurine essentiality and requirement for parrot fish (Experiment I) and to determine whether taurine supplementation to high soybean meal (SM) diets would improve its growth performance (Experiment II). In Exp I, a fish meal (FM) based diet was used as a control and supplemented with 0.2, 0.4, 0.8, 1.2 or 1.6% taurine, and fed to triplicate groups of juvenile parrot fish (initial body weight, 13.5 g) to apparent satiation for 8 weeks. The growth and feed utilization were significantly improved by taurine supplementation up to 0.8% and thereafter plateaued. An optimum dietary taurine level was determined by a broken-line regression analysis based on weight gain and estimated at 0.88% diet. In Exp II, six experimental diets were prepared by supplementation of 0 or 1.0% taurine to a FM-based diet or addition of 0, 0.1% (low), 1.0% (medium) or 2.0% (high) taurine to a basal diet in which 30% of FM was replaced with SM (designated as FM, FM + T1, SM, SM + T0.1, SM + T1 and SM + T2, respectively). Each experimental diet was fed to juvenile parrot fish (initial body weight, 6.4 g) twice daily to apparent satiation for 12 weeks. The fish fed SM diet showed significantly lower growth performance compared to fish fed FM-based diets. Supplementation of taurine to SM diet significantly affected fish growth and higher performances were observed in fish fed SM + T1 or SM + T2 diets that were comparable to that of the fish fed FM diet. However, no significant changes were observed regarding the inclusion of taurine into FM-based diet. These results clearly demonstrated the positive effects of dietary taurine supplementation on feed utilization and growth performance of juvenile parrot fish when 30% FM was replaced with SM. The optimum dietary level of taurine seems to be approximately 1% in diets.