Biotin has proven to aid in the proper development of healthy hooves. Studies have concluded that adding 10 to 30 mg of biotin per day, depending on weight, results in improved hoof hardness, integrity and conformation (6). Biotin has proven to have a direct effect on the epidermis associated with hoof horn formation and it's quality (7). Biotin is required as a micro nutrient and is rate limiting in the metabolic process of removing fatty acids from the liver. Through the elimination of a fatty liver, the horse can properly metabolize nutrients and supply the hoof with proper amino acids and minerals to grow healthy hooves.

DL Methionine, an essential amino acid, is required for proper hoof protein development. DL Methionine is a sulfur-bearing amino acid. Research has shown that sulfur bearing amino acids play an important role in the proteins of the equine hoof wall (8).Vitamin A is most commonly associated with disorders of the eye such as night blindness and xerophthalmia. However, Vit. A is also important for the hoof as it plays a role in the formation & protection of epithelial tissue which comprises the bulk of the hoof wall. Vit A. is thought to have this action through being a participant in the synthesis of glycoproteins which control both cell differentiation and gene expression (10).

Vitamin D3 aids in the control of calcium homeostasis, helps coordinate phosphate metabolism and participates in the regulation of bone growth and metabolism (7). Vit. D3 is metabolized in the horse through the exposure of sunlight. However, if horse's are not receiving adequate sunlight, supplementation is important for the proper metabolism of both Calcium and Phosphorus which is needed for proper hoof development.

Vitamin E and Selenium work synergistically as antioxidants to protect molecules that are vulnerable to oxidation. Both work to retain cellular integrity as they are important for cell membranes. Selenium works as a part of the intracellular enzyme glutathione peroxidase. This helps prevent free radicals from causing damage to tissues. Vit. E works to block free radicals from attacking lipids and forming lipid peroxides. Both Selenium and Vit. E are necessary to minimize oxidation-induced tissue damage.

Choline and Inositol, are B vitamins which act as lipotropic agents to aid in the prevention of fat accumulation in the liver (9). Like biotin, choline plays a rate limiting role in the removal of fatty acids from the liver. If choline is deficient, a fatty liver can result which leaves the

horse with higher concentrations of triglycerides in the liver and a reduction in the release of lipoproteins into the blood. Instol helps to properly utilize choline and promotes healthy hair, hoof, and bone.

Niacin is important for metabolic process to insure healthy skin as well as proper function of the digestive tract (9). Like other B vitamins, Niacin is produced in the horse's gastrointestinal tract by microbes. Niacin is also produced by the body from the amino acid, tryptophan, however, many cereal grains contain high levels of luecine which interfere with the conversion of niacin from tryptophan (10).

Zinc is important in many of the horses tissues including skin , liver, bone and muscle. When a zinc deficiency persists the horse may have the following symptoms: hair loss, lethargy, diarrhea, decreased feed intake as well as decreased growth rate (10). Zinc deficiency along with copper, have been associated with the occurrence of metabolic bone disorders in young growing foals such as O.C.D., epophysitis and contracted tendons.

Copper is needed for bone, cartilage, elastan formation, utilization of  iron, and improves pigmentation and the structure of the hair and the hoof. Iodine is most commonly associated with enlargement of the thyroid gland, known as goiter. The condition can be either a result of excess iodine in the diet or an iodine deficiency. Many fear the use of iodine for this very reason. However, iodine toxicity is unlikely to occur under normal feeding conditions (4). The NRC has estimated that iodine is safe at levels up to 5 mg/kg of dry matter intake per day. Common equine feeds range from 0 to 2 mg/kg of iodine. These levels vary depending upon the iodine content in the soil. (5).

Iodine is a key trace mineral which is necessary for many biological processes. Iodine is utilized by the thyroid in the production of thyroid hormones. These hormones aid in regulating the horse's basal metabolic rate as well as affecting intracellular processes of oxidation (3). Ethylenediamine dihydriodide (EDDI), a source of iodine, has been supplemented in the diet of cattle to prevent foot rot (2). Not only has this treatment been proven on the farm, scientific research has supported EDDI's effectiveness. Studies in the late 70's and early 80's were conducted with cattle to test whether orally administered EDDI would aid in the prevention and treatment of hoof rot. EDDI was found to be effective as a nutritional therapy to assist the animal in the prevention and control of foot rot (1). Field study surveys have indicated the use of supplements containing controlled amounts of iodine are effective in the treatment and prevention of white line disease (3).