1. Millions of years ago, the ancestors of the modern horse had three or four functional toes. But through evolution, some equid ancestors lost their side toes and developed a single hoof. While only horses with single-toed hooves survive today, the remains of tiny vestigial toes can still be found on the bones above their hooves. The splint bone is formed of two of these former toes, the second and fourth toe. The third, or middle, toe is the cannon bone.
2. Recent research suggests that, while modern horses are still partially genetically “programmed” to create five toes in each foot, those four extra toes either don’t develop fully or essentially disappear during fetal development.
3. The wall of the hoof grows from the coronary band at the rate of 6-9mm (¼ to ½ inch) per month. As the average hoof is 76-100mm (2½ to 4 inches) long at the toe, this means that the horse grows a new hoof in about a year.