A trace element important for fat and carbohydrate metabolism it is also required for the synthesis of chondroitin sulphate in cartilage and in enzyme systems which protect DNA. Adult requirement for a 500kg horse is around 400-450mg/Day and deficiency is unlikely under normal feeding regimes. The foetus has higher body concentration of manganese and supplementation of pregnant mares may be appropriate. Deficiency in calves for example causes bone abnormalities with enlarged joints and deformed limbs. Congenital limb deformities have not been proven to be related to manganese.