Dietary Vitamin B6 Requirement of the Pacific White Shrimp, Litopenaeus vannamei, at Low Salinity

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The dietary requirement of vitamin B6 (pyridoxine) of Pacific white shrimp, Litopenaeus vannamei, at 3‰ salinity was evaluated by examining the growth responses, survival, and amino transferase activities. The basal diet was formulated using vitamin-free casein as the protein source. Six levels (0, 35, 70, 105, 140, and 200 mg/kg diet) of vitamin B6 were added to the basal diet, yielding the final vitamin B6 contents of 2.17, 32.43, 65.79, 96.97, 137.13, and 189.56 mg/kg, respectively. Each diet was fed to the triplicate groups of shrimp for 30 d. Percent body weight gain and condition factor of shrimp significantly increased with the increasing levels of dietary vitamin B6 up to 137.13 mg/kg diet. Exceeding this level, however, did not further improve the weight gain. The survival rate also increased at each incremental increase of dietary vitamin B6, but no significant increase was observed beyond 65.69 mg/kg. Both glutamic oxalacetic transferase (GOT) and glutamic pyruvic transferase (GPT) activities increased with increasing levels of dietary vitamin B6 and the maximum value reached at 96.97 mg vitamin B6/kg. No significant differences were observed in both GOT and GPT activities of the shrimp-fed diets containing 96.97, 137.13, and 189.56 mg vitamin B6/kg. Broken-line regression analysis using weight gain, specific growth rate, and amino transferase activities indicates that the optimal dietary vitamin B6 requirement is 106.95‐151.92 mg/kg at 3‰ salinity.