I saw the perfect image response to this today, but I can no longer find it. The tag apparently does not have it. (It was an AJ + mac comparison picture.)
Basically, in Equestrian stallions, just like in the case of Earth horses, the hoof and the upper part of the leg are separated. Mares and filles or colts though merge the two for some reason and their entire leg is covered in hair. The reason is unknown and probably sinister.