Biotin is a water-soluble vitamin that is found, in varying levels, in typical equine feeds (alfalfa, oats, soybean and corn) and is synthesized by the microbial organisms found within the horse’s large intestine (within the cecum and colon). These microbes appear to be sufficient in synthesizing biotin for the horse, as biotin deficiency has not been documented and there is no dietary biotin requirement for horses. Biotin functions as a component of several metabolic enzymes, and is involved in cellular growth. Biotin supplementation has been shown to improve hoof horn quality in horses that have poor hoof quality. This affect appears to take upwards of six to nine months, and, while some studies have reported increases in hoof growth and hardiness, these effects are inconsistent. Research has suggested that the outer component of the hoof wall is sensitive to biotin supplementation, while the inner structures may be more sensitive to deficiencies in other nutrients, such as protein and calcium.
Specific components of protein, such as the sulfur-containing amino acids methionine and cysteine, may play more of a role in hoof health because hoof keratin is relatively high in sulfur. While these and other amino acids (such as lysine, threonine, arginine and leucine, among others) have been found to be components of healthy hooves, specific research on the effectiveness of supplementation with these on hoof health is lacking.
Similarly, low zinc concentrations have been reported in the hooves of horses with poor quality feet. However, supplementation with zinc and copper and other trace minerals in either organic (attached to amino acids) or inorganic forms has not shown consistent effects in adult horse hooves. Supplementation may, therefore, be more important in growing horses.
Supplemental biotin (above “required” amounts, because there is no such requirement for vitamin) is the only nutrient that has been specifically shown to improve hoof quality. A well-balanced diet should provide the amino acid profile, calcium and trace minerals to support hoof structure and growth. Therefore, in many cases, straight biotin supplementation is likely sufficient. A target intake of 3-4mg/ 100kg body weight per day is suggested (about 20mg per day for a 500kg horse), but uptakes up to 30mg/day may be warranted. Horses should not receive more than 60mg per day of supplemental biotin.
Many hoof supplements contain added methionine, zinc and copper. While these may not have a proven clinical benefit above an overall healthy diet, they also will likely not hurt (as long as other supplements are not given that may also contain these minerals).
It should also be noted that environmental and managerial practices likely play a more significant role in hoof health. Fluctuations between wet and dry conditions can affect the natural moisture content of the hoof and predispose hooves to cracks or other issues. Regular cleaning of hooves and regular exercise for the horse is also important to keep hooves healthy.