Taurine is a β sulphonic amino acid and is conditionally essential for many fish species. In the present study, the effect of dietary taurine (tau) on Pangasianodon hypophthalmus fry (initial mean weight 0.8 ± 0.6 g) was evaluated by feeding six isonitrogenous (370 g/kg crude protein) and isolipidic (100 g/kg crude lipid) casein-based purified diets with graded levels of tau at 0 (basal diet), 5, 10, 15, 20, and 25 g/kg feed. Fish were randomly stocked in triplicate groups in 100 L plastic tubs

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... and fed to apparent satiation over two feedings at 10.00 and 16.00 hr daily for 45 days. Final weight, weight gain, specific growth rate, and protein efficiency ratio improved significantly (p < .05) with increasing dietary tau up to 15 g/kg feed and plateaued thereafter. Whole-body protein content did not change beyond tau 15 g/kg feed, but carcass lipid content significantly (p < .05) decreased. The group of fish fed with tau 25 g/kg feed exhibited significantly higher (p < .05) superoxide dismutase, catalase, and glutathione s-transferase activity. According to the findings of this study, the optimum dietary tau content in P. hypophthalmus fry feed was estimated to be 15.05-16.31 g/kg feed as per the broken-line regression