JOURNAL OF THE WORLD AQUACULTURE SOCIETY Vol. 41, No. 5 October, 2010 Dietary Vitamin B 6 Requirement of the Pacific White Shrimp, Litopenaeus vannamei, at Low Salinity Erchao Li, Na Yu, and Liqiao Chen 1 School of Life Science, East China Normal University, Shanghai 200062, China Ceng Zeng Marine Science College, Hainan University, Haikou, Hainan 570228, China Lihe Liu Department of Feed Science, Wuhan Polytechnic University, Wuhan 430023, China Jian G. Qin School of Biological Sciences, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia Abstract 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. The Pacific white shrimp, Litopenaeus van- namei, is a tropical species that has been widely cultured in extensive, intensive, and semi- intensive saltwater systems (Frías-Espericueta et al. 1999). Recently, it has become an attrac- tive cultivar for inland saline water farming in many parts of the world including the USA (McGraw et al. 2002), Thailand (Saoud et al. 2003), and China (Cheng et al. 2006), partially because of low incidence of shrimp epidemic diseases on inland grow-out sites. Although 1 Corresponding author. the impacts of salinity on survival (Ogle et al. 1992), molting frequency (Pante 1990), oxy- gen consumption (Villarreal et al. 1994), and growth of L. vannamei (Huang 1983; Ponce- Palafox et al. 1997) have been addressed in previous studies, other issues associated with the culture of this species at low salinities have recently emerged. Poor growth performance, low survival, and high susceptibility to ambi- ent stressors (Li et al. 2007) are the typical concerns for inland water shrimp farmers. The inferior performance of shrimp at low salinities is partially because of excessive energy being  Copyright by the World Aquaculture Society 2010 756