The hoof of a horse is the total weight-bearing structure carrying a 900-1200 pound horse. It’s care and soundness are paramount to the ability of a horse to function.
The Walls: It is comprised of a hard outer shell (wall) with a soft-tissue “living” center. The upper limit of the hoof is called the coronet band from which the walls of the outer portion descend. The walls are very strong and elastic and devoted to dissipating the energy of concussion. As the walls of a barefoot horse grow, they will self-trim by breaking or chipping off to keep the hoof in proper shape. However, horses kept with shoes or in artificial confinement must have their feet trimmed to maintain the optimum shape.
The mustang hoof, through natural selection, is one of the strongest hooves of all breeds. Thoroughbred hooves are some of the weakest. (see barefoot discusson)
The frog is a part of the rear underside of a horse’s hoof . It functions as a shock absorber and part of the horse’s circulatory system. It is triangular in shape, the base of the triangle located at the heel and the top pointing toward the toe of the hoof.
It should cover about 25% or more of the bottom of the hoof and be in contact with the ground in order to cushion the force of impact to the navicular bone, coffin bone, and deep digital flexor tendon of the leg. Care of the feet should encourage keeping the frog as large, ground covering, and cushioning as possible.
Blood located in the digital cushion of the hoof just above the frog is compressed with each step and pumped back up the leg, actually aiding the heart in moving blood. A horse whose frog is healthy is less likely to experience leg problems and lameness. (see barefoot discusson)
The sole of the hoof is the layer of tissue surrounding the frog. When it maintains good contact with the ground, it is a deep cushion layer with a smooth surface. When seen on a shod horse whose sole does not touch the ground it can appear crumbly and unhealthy.
The bars are the inward folds of the wall originating from the heels following the frog’s outer edge at an abrupt angle. When overgrown, they bend outwards, away from the frog and cover the surface of the sole.
Front and rear hooves are identical in the foal but markedly different in the adult horse due to variation of use. At first both front and rear are round. As walking and movement increase, the rear hooves generally take on a more oval shape.
Slow changes in hoof shape occur under any consistent change in a horse’s movement patterns. That is why it is so critical to keep the hooves in good shape and to keep the horse’s movement as natural as possible. Sore or improperly tended feet can change a horse’s movement patterns and result in pathological hoof changes. (See Barefoot)
“Quarter Cracks” are cracks in the wall of a hoof. Like a split in a fingernail, they can be benign such as a small sufrace crack. Or they can be very damaging, penetrating the soft tissue and causing irreparable damage. They are most often caused by dry hooves, poorly trimmed or shod feet, or an injury to the coronet that results in a weak spot that grows abnormally.
Horses with inherently poor hoof conformation such as thoroughbreds frequently suffer from quarter cracks.
If found, a quarter crack should be tended to immediately, as leaving it to erode further can lead to severe damage. Cases that threaten to penetrate into the soft tissues will take considerable expertise to add stabilization to the hoof so that the new wall tissue can grow out intact.