Folic acid in its coenzyme form, tetrahydrofolic acid, acts as an intermediate carrier of carbon units (hydroxymethyl or methyl groups) in a large number of metabolic reactions. These reactions are found in the metabolism of amino acids and the biosynthesis of purines and pyrimidines, the bases of nucleotides in DNA and RNA. Deficiency symptoms include poor growth, anorexia and lethargy. Sources of folic acid include dried distillers solubles, cottonseed meal, rice bran, soybean meal and yeast. Recommended supplementation level of folic acid in commercial feeds is 10 mg/kg.