Zinc is a component in more than 80 metalloenzymes and a cofactor in enzyme systems. These metabolic processes include protein, nucleic acid, lipid, carbohydrate and micropolysaccharide metabolism. Sources of zinc include dried distillers solubles, corn gluten meal, fish solubles, fish meal, krill meal, rice mill by-products, wheat bran and by-products, and yeast. Zinc may be supplemented by zinc sulfate and zinc gluconate. Recommended level of zinc in commercial feeds is 110 ppm (Akiyama et al., 1992).