I used to own a horse that had continual hoof problems, until I turned
him out for two months without shoes. He was a pinto with white feet,
and I tried all sorts of hoof oils, massaged into the coronet, to
encourage growth and make them less crumbly. Biotin wasn't well known as
a supplement then. Anyway, turnout without shoes meant new hoof growth
was stronger, to handle the direct contact with the ground. Made a big
difference.