Deficiency is associated with epiphysitis, contracted tendons, lower fertility in mares, rupture of the uterine artery of older mares during parturition, anemia, and depigmentation of the skin around the eyes and muzzle. The copper level in feeds needs to be evaluated in regard to what other minerals are present in the ration because, in excess, they may combine with the available copper and make it unavailable. Copper at the level listed in Table 6 is good for a horse, but toxic to some other livestock, especially sheep. Therefore, horse feeds fortified with copper should not be used indiscriminately for other livestock. It can also be toxic if it exceeds 200 ppm.
Deficiency causes reduced growth rates and lesions of the skin on the lower extremities.
All of the trace minerals can be normally supplied by trace mineralized salt. However, if you are dealing with a deficiency in the ration, special high mineral salt may be needed to overcome the deficiency in the normal feedstuffs. There are also some high mineral feeds now on the market to help overcome ration deficiencies. High mineral broodmare feeds may be especially useful so that the mare may deposit sufficient trace minerals in the developing foal prior to birth and for growth after foaling. Mares milk should provide enough trace minerals for the growing foal for the first two months of life.