Evolution of the FootHorses have evolved from the four-toed, dog like eohippus into the single toed creature we see today. Evidence of the vanished toes remains. The chestnut and ergot are cartilage like protrusions along the inside of the horse’s legs, and on the underside of the pastern joint. On some horses they grow rapidly and although no harm is done if they are left to break off naturally, they are sometimes trimmed for a neater appearance. There are two bones that run down either sides of the horse’s front leg between the knee and pastern joint. These two ‘splint bones’ are believed to be what remains of the former toes.
Inside the HoofThere are three bones inside the hoof. The longest is the short pastern bone that extends down from the long pastern bone in the horse’s leg. The largest bone within the hoof is the pedal or coffin bone. Within this bone are many minuscule passageways for blood vessels and nerves. Beneath the junction of the short pastern bone and the coffin bone sits the small navicular bone. Several tendons and ligaments run down from the leg and attach to the bones within the foot.
Surrounding these bones is the sensitive laminae. This is a layer of tissue that carries blood to all the components of the hoof. Beneath the sensitive laminae and bone structures sits the digital cushion. This is a rubbery pad of tissue that forms the heel of the hoof and helps absorb the shock as the horse’s hoof makes contact with the ground.
The Visible HoofSurrounding the sensitive laminae is the horny laminae. This layer is quite hard and has no feeling. It attaches to the outer wall of the hoof in a similar fashion to hook and loop fastener. The margin where the wall and the horny laminae attach is called the white line. The white line provides the farrier with a visual indication of how deep he can trim the hoof, and where to set in the nails for horseshoes.
The wall is similar in composition and function to our fingernails and is constantly growing. The wall of the hoof can be very thin, or very thick depending on the type of horse, its nutrition and environment. Wild horses wear down hoof growth naturally, but domestic horses require regular trimming by a farrier. The color of the hoof is influenced by the color of the skin above it, so that if a horse has white markings directly above the hoof the hoof itself may carry down the same pigmentation. Many people believe that hooves with black walls are stronger than hooves with white walls.
Natural ProtectionThe very outside of the wall is protected by the periople. This layer protects the moisture within the hoof. The coronary band runs around the very top of the hoof. This is a blood rich band from which the hoof grows somewhat similar to the cuticle on our fingernail. Severe damage to this band can cause deformities of the hoof wall.
On the underside of the hoof is the sole. This is a concave, thick but flexible padding of hard tissue that protects the sensitive sole directly beneath the bones of the foot. In the middle of the sole sits the V-shaped frog. The frog contacts the ground surface as the horse travels and helps the blood circulate in the foot. The cleft of the frog runs down the middle of the frog and aids in flexion and grip. The bars of the foot run on either side of the frog and they provide stable suspension for the walls and frog as the horse’s foot impacts the ground.