Every horse owner knows the truth of the statement, “No hoof, no horse.” Thoroughbred Big Brown was never able to run for the Triple Crown because of a quarter crack. Sir Barton, the winner of the first Triple Crown in 1919, lost in a match race to Man o’War on the hard surfaces of Kenilworth Park in Windsor, Ontario, thanks to his poor hooves. It costs us farrier bills, lost riding time and poor fitness when our horses’ hooves don’t hold up. Despite significant research into building stronger hooves, we are still left with the basic foundations of hoof health – excellent farrier care, a clean environment and proper nutrition.
What are you Actually Feeding?
The hoof is comprised of the dermis and epidermis layers, that protect the bony structures within the equine foot, help to give stability to the horse in movement, absorb concussion from the horse’s body weight and facilitate blood flow. The epidermis is the outer layer, the “horn,” that includes the periople, coronary band and the hoof wall, as well as the under layers of the sole, heel, bars and frog. The dermis, also known as the corium, includes the sensitive vascular structures that surround the coffin bone, and ultimately grow the hoof horn. The horn is generated through the proliferation of basal cells at the corium that differentiate and become cornified through the synthesis of keratin, specialized lipids and other proteins that form the hoof tubules.
Keratin and other proteins within the hoof make up 93 per cent of its structure, and research has found this protein to comprise of a wide variety of amino acids. Remember that a protein is simply a long, complex chain of amino acids. Therefore, offering a well-balanced diet that provides sufficient quality and quantity of protein is important.
Protein: Remember that protein requirements in the horse are measured as total grams of protein in the diet, but we also need to be concerned with the protein quality; that is the amino acids found in the dietary protein.
Protein deficiency in the diet results in a lack of amino acids available for tissue protein synthesis, and, therefore, manifests itself with a horse developing a poor hair coat and poor hoof horn quality, along with retarded hoof growth.
Further, even if protein quantity (total grams of protein in the diet) is sufficient, but key essential amino acids are lacking, the entire protein synthesis system is hindered.
Amino Acids: Some of the essential amino acids that are found in the hoof include the sulfur-containing amino acids methionine and cysteine, which are required for keratin synthesis. Methionine is considered an essential amino acid, which is used to build cysteine within the body. Cysteine is considered semi-essential, as it is not required in the diet provided there is sufficient dietary methionine. Cysteine is the most prevalent amino acid in the hoof and, in fact, research has demonstrated a correlation between cysteine content of the hoof and hoof hardness. However, dietary supplementation of these amino acids and others has not resulted in any improvements in hoof horn growth or hoof quality. Furthermore, research has suggested that increased homocysteine (another amino acid produced from methionine) can negatively affect endothelial cell (cells that line blood vessels) function and should be avoided by horses prone to laminitis. Therefore, for hoof health perhaps only cysteine should be supplemented directly. Both methionine and cysteine are found in high protein feeds such as alfalfa, soybean meal, flaxseed meal and wheat bran.
Biotin: Another important nutrient for hoof growth is the B vitamin, biotin. Biotin functions as a coenzyme for many metabolic reactions, particularly those associated with amino acid metabolism and cell division. As with all B vitamins, biotin is normally synthesized by the microbial population within the horse’s large intestine in adequate amounts, such that biotin deficiency in the horse has never been unequivocally documented. In other species, and as would be expected in the horse, biotin deficiency results in dermatitis and impaired hoof quality. As such, biotin supplementation, in amounts of approximately 15-20 mg/day, has resulted in improved hoof wall integrity, structure, tensile strength and hardness, as well as increased growth in some studies.
Because biotin is water-soluble it has a low risk of toxicity, and is, therefore, a popular component of hoof supplements. It should be noted that biotin appears to be more effective in horses with poor hooves as a corrective effect, rather than an enhancement of already healthy hooves.
Biotin can be found in many common equine feeds. Alfalfa is known to have particularly high levels of biotin (0.2 mg/kg DM hay, 0.49 mg/kg DM fresh forage), and is found in moderate quantities in oats (0.11 – 0.39 mg/kg DM) and soybean meal (0.18 – 0.5 mg/kg DM).
Zinc and Copper: Zinc is a micro-mineral that functions as a cofactor of numerous enzymes, and is associated with hoof health. Zinc concentrations in hooves and blood have been reported to be higher in horses with good feet, compared to those with poor hoof horn quality.
Horses with white line disease were associated with diets low in zinc and copper. Because copper and zinc compete for similar transport mechanisms, it is recommended to feed zinc to copper ratios of about 4:1 (four parts zinc for every one part copper).
Many hoof supplements contain zinc and copper as well as magnesium. One study reported that organic minerals (i.e. those attached to protein, or proteinated minerals) resulted in greater hoof growth than horses fed inorganic forms of these minerals. However, another study found no improvements in hoof hardness, growth or tensile strength in weanlings fed organic minerals.
Calcium: This mineral plays a major role in bone strength, and is also responsible for supporting the sulfur cross-links within keratin. The addition of alfalfa (rich in calcium and protein, as well as many other nutrients) improved the hoof structure in horses with brittle feet in various studies.
What to Avoid
Increased consumption of non-structural carbohydrates (NSC; such as starches from grains and sugars in lush pasture) is associated with insulin resistance and laminitis. The direct effect of excessive NSC on hoof growth rate or strength has not been reported, but warrants investigation.
A solid diet built from good quality forages is of the utmost importance to overall horse health. Based on a hay analysis, nutrients that may be missing in the diet, such as key amino acids, calories, minerals or vitamins can be supplemented in the form of a commercial feed or from specific nutritional supplements.
The addition of biotin directly is relatively non-toxic and can be effective to help improve poor hoof quality and may be an easy fix for minor problems assuming the rest of the diet is adequate.
Some hoof supplements contain the additive selenium, but no benefits have been demonstrated in feeding selenium above required amounts. In fact, excess selenium may decrease the quality of hoof growth, as selenium can replace sulfur within the keratin molecules, compromising their structure and integrity. Symptoms of alkali disease resulting from selenium toxicity include hoof cracks, hoof rings and separation of the hoof walls.
Mixing several different supplements together, or mixing them with commercial feeds runs the risk of doubling (or tripling) some nutrients and can pose toxicity issues. It is recommended that a nutritionist be consulted to identify gaps and overages in your horse’s diet to determine if it is negatively affecting your horse’s hoof health.
Cofactor: A substance, such as a metallic ion or coenzyme, that must be associated with an enzyme for the enzyme to function.
Cornification: The process by which squamous epithelial cells in vertebrate animals develop into tough protective layers or structures such as hair, hooves and the outer layer of skin; the final stage of keratinization.
Essential amino acids: Those amino acids the body cannot build that are required to be provided in the diet, such as methionine and cysteine.
Keratin: 1. Any of a class of filamentous proteins that are abundant in the cytoskeleton of vertebrate epithelial cells and are the main constituents of the outer layer of skin and tough epidermal structures such as hair, nails, hooves, feathers, and claws; 2. Material composed principally of keratin proteins.