by Bob Peacock
published in the ANVIL Magazine, June 1997
Vitamin A is most commonly associated with disorders of the eye such as night blindness and zerophthalmia. However, vitamin A is also important for the hoof as it plays a role in the formation and protection of epithelial tissue, which comprises the bulk of the hoof wall. Vitamin A is thought to have this action as a participant in the synthesis of glycoproteins, which control both cell differentiation and gene expression (10). Vitamin A promotes tissue growth, strong bones and hoofs, healthy skin, hair, teeth and gums, building resistance to disease.
Vitamin D aids in the control of calcium homeostasis, helps coordinate phosphate metabolism and participates in the regulation of bone growth and metabolism (7). Vitamin D is metabolized in the horse through the exposure of sunlight. If horses are not receiving adequate sunlight, supplementation is important for the proper metabolism of both calcium and phosphorus, which are 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 part of the intracellular enzyme, glutathione peroxidase. This helps prevent free radicals from causing damage to tissues. Vitamin E works to block free radicals from attacking lipids and forming lipid peroxides. Both selenium and vitamin E are necessary to minimize oxidation-induced tissue damage (10). As an antioxidant, Vitamin E helps to retard cellular aging and supplies oxygen to the cells for endurance. It helps fight fatigue and accelerates healing and growth.
Choline and Inositol are B vitamins that 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 increasing concentrations of triglycerides in the liver and a reduction in the release of lipoproteins into the blood. Choline helps eliminate poisons from the system through the liver and helps nerve responses to aid the healing.
Niacin is important in the 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 horseþs 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).
Biotin has been 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 its 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. Biotin is the second most important nutrient in hoof growth and repair. It helps alleviate eczema and dermatitis through the utilization of proteins.
Zinc is important in many of the horseþs 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, has been associated with the occurrence of metabolic bone disorders in young, growing foals such as osteochondritis dessicans (OCD), epiphysitis and contracted tendons.
Methionine, an essential amino acid, is required for proper hoof protein development. 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). DL-methionine is the most important amino acid for hoof growth. It helps prevent edema and infection, and it works with choline to fight against tumors.
Iodine is most commonly associated with an 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 National Research Council 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 necessary for many biological processes. Iodine is utilized by the thyroid in the production of thyroid hormones. These hormones aid in regulating the horseþs 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 EDDIþs effectiveness. Studies in the late þ70s and early þ80s were conducted with cattle to test whether orally administered EDDI would aid in the prevention and treatment of foot rot. It was found to be effective (1). Field studies indicate that supplements containing controlled amounts of iodine are also effective in treatming and preventing white line disease. It has been found that 10 mg. of iodine can stop the spread of fungus and some dreaded bacteria and viruses in the hoof and skin. Certain amounts work through the thyroid gland to produce bacterial antibodies needed for good health.
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