Editor’s Note: This is an excerpt from Understanding Equine Preventive Medicine by Bradford G. Bentz, VMD. 

A number of nutritional factors are promoted as hoof growth aids.  Such products may include gelatin, numerous vitamins, minerals, amino acids, and other dietary supplements. However, if a horse’s nutritional requirements are being met with good-quality forage, grain, or pellets, none of these supplements have shown significant effect on hoof growth.

However, feeding extra biotin may benefit horses with thin, brittle hoof walls, crumbling hoof walls, and/or thin, tender soles. Biotin is therefore recommended for such hoof defects at a dose of 1.2 to 1.5 mg/100 lbs of body weight daily.  Smaller doses of 0.10 to 0.15 mg/100 lbs of body weight or 0.1 mg/ lb of total diet may help maintain good hoof structure and prevent the recurrence of hoof problems in horses. Generally speaking, one should also try to ensure that the diet fed meets the protein and calcium requirements of the individual horse based on its athletic use or other function. Oversupplementation with protein and/or calcium may be associated with other health problems.
Supplements of Benefit to the Performance Horse (when used appropriately).

An increase in exercise also directly increases the needs for vitamins A, E, B-1, and for folic acid. Vitamin E and selenium supplementation may help decrease oxidative damage from energy production.  Adding 1mg of selenium and 1,000 IU of vitamin E to the daily diet may provide selenium and vitamin E supplementation. Only using salt mixes that contain selenium is an alternative way of providing the element.  A balanced vitamin supplement may best provide the additional needed vitamins. However, once again, it is important not to overestimate the intensity of exercise and competition your horse performs so that you do not oversupplement with potentially harmful levels of these additives and you do not waste money