Biotin has become commonplace in feed rooms across the world because of its reputation as an effective hoof supplement. And while this is true, some horsemen believe it to be a man-made and mystical creation. Nothing could be further from the truth. Like the more familiar niacin, riboflavin, and thiamin, biotin is first and foremost a B-vitamin. Biotin is similar to other B-vitamins in that it is essential in the conversion of feedstuffs to energy so horses can grow, work, and reproduce. Biotin is found in virtually every cell in the body and is an essential coenzyme in carbohydrate, fat, and protein metabolism. This B-vitamin is also important for normal thyroid and adrenal gland function, reproductive tract health, nervous system stability, and most dramatically, growth and repair of skin and hooves.
Biotin occurs naturally in many feedstuffs commonly fed to horses such as oats, soybean meal, alfalfa, rice bran, and molasses. However, horses derive most of their biotin requirement from the fermentation of forages by the microbial population in the hindgut. Interestingly enough, speculation surrounds exactly how much of the biotin produced in the lower portion of the digestive tract can be absorbed, as the hindgut is typically an inefficient zone for nutrient uptake. In fact, only water seems to be absorbed well from the hindgut. Further, any factor that interferes with normal functioning of the microbial environment would affect biotin synthesis, resulting in less biotin availability.
Biotin presented in the diet may have a better chance of being absorbed as it passes through the upper portion of the digestive tract, where the majority of vitamin and mineral absorption occurs. For this reason, commercially produced biotin and other B-vitamins are often added to high-quality horse feeds. The amount typically found in feeds and produced by microbial fermentation is enough to prevent any outright biotin deficiency.
Researchers found normal blood levels of biotin in horses with poor-quality hoof horn, so unhealthy hooves are not a result of deficiency. Despite normal blood levels, horses responded to megadoses of biotin given orally, which led scientists to believe that this is one of the few nutrients in which more may actually be better. Biotin content in fortified feeds is typically less than 1 mg per day when feeds are given at recommended amounts. Hoof supplements, on the other hand, offer 5 to 25 mg of biotin per daily serving.
Research focusing on biotin as a means of improving hoof quality of the horse started in the mid-1980s. Over the intervening years, various studies have found a statistically significant improvement from biotin supplementation on overall hoof condition with 15 to 25 mg per day. Normal blood values of biotin average around 350 ng/l, but within 24 hours of feeding large doses of biotin, blood levels were greatly increased to more than 1,000 ng/l. Biotin only improves the growth of new hoof horn, not existing hoof. Because of this, the results of biotin supplementation took eight to 15 months to complete, depending on the growth rate of the hoof. This is the approximate length of time necessary for the hoof wall to completely grow out and replace itself.
Throughout some studies, differences were noted in hoof growth rates among numerous breeds as well as individuals, and several factors were thought to cause contrasts in growth. Colder environmental temperatures slowed growth, as did high body temperatures. Other conditions accelerated growth. For instance, the additional concussion experienced by the hooves of horses in regular work may increase the growth rate. In other studies, biotin supplementation did not change growth rate, but the quality of the hoof improved. Hoof quality was determined by measuring hardness, integrity, conformation, and tensile strength (the ability of the hoof to withstand pressure from spreading). One study found growth rates and hardness were greater when horses were dosed with 15 mg per day than with 7.5 mg per day. Intermittent feeding of biotin did not result in rings on the hooves, but if biotin supplementation ceased altogether the hooves regressed to their former state. If the dose was decreased below recommended levels, there was deterioration of hoof quality but not complete reversion to the state observed before biotin supplementation began.
Researchers are unsure how biotin helps the hoof, but the actual improvement seen from doses of 20 mg per day has been documented by electron microscope examination. The hoof horn is made up of keratinized cells arranged spirally to form long tubules that run from the coronary band to the end of the toe. As the cells thicken around the tubules, the hoof horn becomes more resilient to damage.
In order to achieve maximal improvement in hoof health, a horse should consume 20 mg of biotin per day. If improvement has been seen within eight to 15 months, the horse will need to remain on biotin the rest of its useful life to maintain that improvement. Cutting the dose is not advisable because it may affect the results.
Other nutrients such as zinc, methionine, and iodine can also affect hoof quality. A well-balanced supplement will contain all of these nutrients in addition to the 20 mg per serving of biotin.