Photo credit: David Goldman, Associated Press
Performance and Therapy
Despite the hoof being a very resilient and adaptive structure, horses engaging in strenuous performance sports often require shoes for extra support, protection to preserve the hoof capsule and structures contained within it, and traction for the safety of both horse and rider (Bryant, 1999). Horseshoes can be shaped to compensate for hoof irregularities while offering support to the feet and legs and protecting the toe of the hoof from wear. The majority of shoes remain open at the heel to allow for the natural flexion and expansion of the hoof when it comes into contact with the ground, leaving the frog and sole uncovered because of their important role in shock absorption (Bryant, 1999; O’Grady, 2008).
A variety of shoeing materials and styles are used based on the discipline in which the horse performs, the breed and natural conformation of the horse, and the ground surface it performs on. For example, Thoroughbreds are shod with very thin aluminum shoes called racing plates, whereas hunters wear much thicker, but still lightweight, aluminum shoes. In contrast, high-stepping horses like the Tennessee Walker are often (controversially) outfitted with weighted shoes and pads on hooves with an extra long toe and disproportionately short heel to exaggerate their natural gait, as the heavier shoe forces the horse to heighten its step (Bryant, 1999; Montgomery, 2014).
For therapeutic purposes, shoes can be used to provide additional heel support to horses that have low heels, treat cases of laminitis and navicular disease, and repair quarter cracks by shifting the weight distribution on the hoof wall (Bryant, 1999).
The Farriers Role
The role of the farrier is to maintain and promote a healthy hoof wall, an appropriate sole depth, and soft tissue structures of a sufficient mass to properly support the bones, tendons, and ligaments within the hoof (O’Grady, 2007). There are three main forces that are altered by farriery – independent of the application of shoes – and play a role in foot pathology and therapy. These are 1) ground reaction force – the upward force of the ground on the hoof; 2) the force of the horse’s weight transmitted downward through the limb; and 3) the upward pull of the deep digital flexor tendon (Corp-Minamiji, 2015).
Once the hoof has been evenly trimmed and balanced by the farrier, a variety of shoes can be applied for performance and therapeutic purposes. The following list highlights those that are used in therapy (Bryant, 1999; Corp-Minamiji, 2015; O’Grady, 2008).
- Straight bar shoes provide extra heel support for damaged or under-run heels and stabilize the downward pressure of the foot, creating an evener distribution of weight.
- In feet with well-developed frogs, the heart-bar shoe may be used. This shoe covers the frog and transfers some of the weight from the wall of the hoof to the soft tissues, which can be helpful in treating cases of laminitis and quarter cracks.
- The oval egg-bar covers the back portion of the hoof to offer extra support for horses with low heels.
- The practice of wedging with pads and/or rails applied to the shoe shifts the forces on the foot and affects the position of the coffin joint, which can be beneficial for horses that have advanced cases of laminitis with coffin bone rotation.
- Wooden shoes cut from plywood are strictly used for therapeutic purposes, easing breakover and decreasing force on the lamella.
- Glue-on shoes can be used on horses to eliminate the need for nails in cases where the horse has poor-quality feet but requires shoes for a short time.
Under the right circumstances, horseshoes can be highly beneficial to the health, comfort, and conformation of a horse, however, not all shoes are created equal. For example, O’Grady (2008) indicates that egg-bar and other bar-type shoes increase concussive forces from hard surfaces, and Ovnicek (2003) believes that “conventional shoes (non-orthopedic) can stand in the way of the hoof’s natural function”.
A Few Problems with Horseshoes
“Horseshoes are a necessary evil!” say some (Pullen, 2001). “Forcing the flexible hoof to function when restricted by a rigid, steel shoe is a powerful prescription for promoting the hoof’s deterioration”, says Tomas Teskey (2005), one of the more vocal critics.
The hoof is a flexible structure designed to expand and contract in response to the ground surface (footing), moisture and concussive force. The natural response of the hoof is to flex outward 2 to 4 millimeters when it is bearing weight. The degree of flexion is in response to the hardness of the footing. When shod this movement is impeded and the hoof is not able to function as it normally would. “If you draw a chalk line around the foot of a shod horse standing on hard ground, then do the same thing 15 minutes after the shoe has been pulled, you will find that the foot has expanded beyond the original line” (Pullen, 2001).
Furthermore, when a horse is shod, the majority of its weight is loaded onto the perimeter of the hoof wall. According to Robert Bowker, “only a small percentage of the load should be on the hoof wall, with the sole, frog, and bars bearing the majority” of the force, which will strengthen the foot and reduce the concussive force transmitted to the bone through connective tissues (DeFee Mendik, 2016).
Improperly fitted shoes can also cause a variety of problems, including hoof cracks, low heels, and sheared heels. Sheared heels are caused by uneven heel trimming in shod horses but are rare in barefoot horses because the taller heel is naturally worn down (Equine Research, 2004).
Bryant, J. (1999). “A Footwear Primer.” The Horse. Retrieved from www.thehorse.com/articles/10364/a-footwear–primer
Corp-Minamiji, C. (2015). “Therapeutic Shoeing Part 2: Hardware and Healing.” The Horse. Retrieved from www.thehorse.com/articles/28437/therapeutic-shoeing-part-2-hardware-and-healing
DeFee Mendik, N. (2016) “Back to Barefoot.” The Horse. Retrieved from http://www.thehorse.com/articles/31022/back-to-barefoot
Equine Research. (2004). Horse Conformation: Structure, Soundness, and Performance. Guilford, Connecticut: The Lyons Press.
Montgomery, M. (2014). “Exposed! Tennessee Walking Horse Celebration: Celebrating Cruelty?” One Green Planet. Retrieved from www.onegreenplanet.org/animalsandnature/exposed-tennessee-walking-horse-celebration-celebrating-cruelty
O’Grady, S. (2007). “Barefoot vs. Shod? It depends…” Virginia Therapeutic Farriery. Originally published in American Farriers Journal Jan/Feb 2007. Retrieved from http://www.equipodiatry.com/article_barefoot_v_shod.htm
O’Grady, S. (2008). “Basic Farriery for the Performance Horse.” Veterinary Clinics: Equine Practice vol. 24 (2008) 203-218
Ovnicek, G. et al. (2003). “Natural balance trimming and shoeing: its theory and application.” Vet Clin Equine 19 (2003) 353-377
Pullen, G. (2001). “Barefoot Benefits.” The Horse. Retrieved from http://www.thehorse.com/articles/10855/barefoot-benefits
Teskey, T. (2005). “The Unfettered Foot” A Paradigm Change for Equine Podiatry.” Journal of Equine Veterinary Science 25(2) (2005) 77-83