Description: Copper (Cu) deficiency in the sheep. This deficiency produces a marked decrease in the rate of wool growth and a depigmentation of black wool (right sample). Copper is involved in the synthesis of melanin to color the wool so deficiency results in bleached hair or wool in cattle, rats, rabbits and sheep (achromotrichia). "Steely" wool is characterized by limp, glossy fibers lacking the normal crimp (left sample). The alternating white and dark bands in the center sample were caused by alternately feeding a Cu deficient diet and a diet adequate in Cu. In certain areas, the above symptoms may not be caused simply by dietary Cu deficiency but by a complex interaction of Cu, Molybdenum (Mo) and Sulfate. Excess soil Mo reduces Cu absorption and Cu storage in the liver. Such areas are called 'Teart' pastures. The interaction with Sulfate is particularly complex as excess Sulfate increases excretion of both Cu and Mo but Teart problems can be treated with Copper Sulfate where the Sulfate promotes Mo excretion, thus reducing the Mo excess.