Thiamin plays a role controlling carbohydrate metabolism as a coenzyme for oxidative decarboxylation of pyruvic acid in energy metabolism. Thiamin is readily destroyed in the presence of minerals, especially copper and fresh fish tissues. Deficiency symptoms include anorexia, poor growth, pigmentation and mortality. Sources of thiamin include dried distillers solubles, fish solubles, rice bran, wheat middlings and yeast. Recommended supplementation level for thiamin in commercial feeds is 50 mg/kg (Akiyama et al., 1992).