Dietary vitamin B ₆ requirement of the pacific white shrimp, Litopenaeus vannamei, at low salinity

The dietary requirement of vitamin B ₆ (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 B ₆ were added to the basal diet, yielding the final vitamin B ₆ 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 B ₆ 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 B ₆, 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 B ₆ and the maximum value reached at 96.97 mg vitamin B ₆/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 B ₆/kg. Broken-line regression analysis using weight gain, specific growth rate, and amino transferase activities indicates that the optimal dietary vitamin B ₆ requirement is 106.95-151.92 mg/kg at 3‰ salinity.