Manganese serves as a cofactor for a number of enzymes including phosphate transferases and dehydrogenases, alkaline phosphatase, arginase and hexokinase. Sources of manganese include dried distillers solubles, crab meal, fish solubles, rice bran and by-products. Manganese may be supplemented as manganese sulfate. Recommended level of manganese in commercial feeds is 20 ppm (Akiyama et al., 1992).