Last Updated on February 24, 2022 by Allison Price
What do researchers know about the biomechanics and physiology of the barefoot hoof
It appears to be an all-weather, ultra-resistant block with a shiny, marble-like surface. This can fool us into believing it is indestructible. Its sharply defined edges make it appear as solid as stone, especially when they hit one of our feet with full force. Its “clip clop”, which strikes against hard surfaces, is a sign of a dense support structure that acts like a steel foundation when massive forces are applied to it.
The truth is, however, that the equine’s foot is not like this.
The foot, or, more accurately, the one-long toe, is a complex structure that contains bones, tendons and ligaments as well as nerves, veins, nerves and cartilage. It’s not inert but active and communicating sensory information, pumping blood and articulating, contracting and flexing over the ground. Unshoed, the shape of the horse’s shoe will change as they use it, both instantly and over time.
The science behind the horse’s foot is similar to the hoof. It expands and contracts, gets shaped and trimmed. As researchers learn more, we can gain a better understanding of how horses’ feet function. With this knowledge, we can improve the health of the whole horse.
The Evolution of the Hoof
Five-toed feet were the norm for early equids. They were about the same size as foxes. These toes were not needed to grab objects, but they did benefit from better limb swing to be able to run faster. Each middle toe grew longer, while the sides toes got shorter. The first and fifth toes eventually disappeared and the second and forth toes became the modern-day splint bone on each side of each cannon bones.
Scientists have recently determined that the splint bone is only the top of the toes. According to Nikos Solounias (Doctor of Osteopathic Medicine, NYITCOM), Old Westbury, the bottom parts of the foot are still there. He says that what we call the V-shaped frog actually is what’s left from the bottom of toes 2 and 4.
Solounias studied markers that were used to track the embryonic growth of the horse’s foot. The embryo looks like a tulip, with all five petals. The markers in the adult horse indicate that the top portions of toes 1 and 5 appear as bony processes (“wings”) emerging from the coffin bone. The ridges that run along the sides of the Frog are made up of the bottom parts of these two toes.
In some ways, he still has five toes in his foot — but four of them are “very embryonic,” Solounias says.
He says that we don’t know what role these remnant structures play in the horse’s true function. It could be more about the sensation of the nerves from the five digits and how they relate to the brain than the actual locomotor mechanics. It’s important that we see things differently and understand how evolution led us to the modern horse.
A Multipurpose Structure
The foot responds to pressure and movement. It can respond more freely if it is not shod.
Hilary Clayton, BVMS (Doctor of Veterinary Science), MRCVS, Dipl. ACVSMR, McPhail Dressage Chair Emerita, Michigan State University (MSU), and president of Sport Horse Science in Mason, Michigan. Its structures absorb shocks from the force that is generated when the foot touches the ground.
If the foot is not trimmed properly and it is completely bare, forces will spread throughout the foot, including the sole, wall (or frog), digital cushion, heels, and the frog. These more elastic tissues are subject to diffused impact. Structures higher up, like the knee, pastern, fetlock and knee, don’t feel as much.
Stephen O’Grady DVM of Virginia Therapeutic Farriery in Keswick says that each footstep is vital in maintaining healthy circulation. He says that the blood vessels of the horse’s foot do not have valves. When the horse lifts his foot up, arterial blood flows into the foot. The vessels become full of blood and the blood is used. When he places weight on his foot, the thousands of capillaries that run across the entire solar surface become compressed and push blood back towards the heart.
Robert Bowker, VMD and PhD, Clayton’s colleague, is the head of MSU Equine Foot Laboratory. His research shows that heels also possess critical sensors for proprioception, which tells horses where their feet are. Clayton states that although they might not feel the same as us, it is important that proprioceptors are located in the soft horn at the heel, where the wall can move the most.
Healthy bare feet usually have thicker soft tissues on their bottom, which includes digital cushions. Debra Taylor, DVM MS, Dipl., believes that this could have protective properties. Auburn University’s College of Veterinary Medicine in Alabama, ACVIM is associate professor and equine poiatry veterinarian. She says that if the digital cushion is too long or thin (which is more common in shod horse), it supports only the middle of the navicular bones. “The edges will not have any soft tissue underneath them, there’s only the deep digital flexor tendon directly. It is intuitive that the digital cushion would play some protective role if it was sufficiently wide.
Our sources tell us that shoes can alter the way the feet function scientifically. Shoes can restrict movement and limit expansion by making the hoof conform to a certain shape. They also prevent the foot’s bottom from touching the ground. According to them, the lack of stimulation from ground causes soft structures to recede, contract, become more supple, and in some cases, atrophy.
What should a bare foot look like?
Taylor says that scientists don’t have a clear understanding of how the barefoot should look on domestic horses despite having basic biomechanical knowledge. She says, “It’s one of the few tissues on horses where veterinarians don’t agree on what’s normal.”
She says that research is still lacking. Scientists continue to debate the existence and function of certain anatomical structures. She says that scientists are now recognizing a ligament under the DDFT and on top of the digital cushions. It’s not even listed in specialized anatomy books. Taylor says that Prof. August Schummer (PhD), the former head of Justus Liebig-Universitat’s Veterinary Anatomy Department in Giessen, Germany had previously described and labeled this ligament in the 1940s. However, the structure was later lost from literature.
Scientists seem to agree that the wild or feral horsefoot is not a reliable indicator of the domesticated horse’s foot.
Clayton states that “Mustangs are not good models.” They do a different type of work.
She says wild horses don’t need to be ridden, they can’t do lateral movements or dressage work and have less force on their DDFTs, navicular bones and lungs. She adds that wild horses can also be affected by pathology (disease or injury).
Taylor said that she is currently conducting research to better understand the characteristics of a fully-developed domesticated horse foot. This is because the horse’s development as a young horse appears to play an important role in the foot’s ability support the forces associated with riding. Through MRI and physical examinations, she said that they are currently trying to determine the heel structure and predict how digital cushions and cartilages will be shaped.
Good Husbandry for Bare Feet
Although horses may have evolved great feet, it is not surprising that humans started shoeing them. Shoes were a recent invention, appearing in the Middle Ages. This was around the time that humans started housing horses in stalls. Angelo Telatin, PhD is associate professor of horse studies at Delaware Valley University in Doylestown.
He says that the Romans used barefoot horses to travel and work. “But, more than a thousand year later, thieves and pirates forced horses to be moved into stalls within castles. They couldn’t move and were standing in their own urine. They started having hoof problems.
He says that horses should be allowed to roam and grow their feet. They should be able to move on small, smooth rocks like pebbles or stone dust (also called screening). Mud, wet grass and urine, as well as feces, can cause hoof structures to be weakened. However, stronger and more stable footings will strengthen them.
Telatin explains that Romans kept their horses in large paddocks with oval-shaped stones sticking out from the ground. This meant that the hooves never soaked in urine. Today, most horses live on carpet. It’s not surprising that their feet are unable to withstand the demands of riding on different surfaces.
Telatin has all 50 school horses at his university barefoot. However, two to three of them may need front shoes in more difficult situations like outings on rugged terrain.
Declan Cronin, a farrier, has managed to keep nearly the entire Thoroughbred racehorse training team barefoot in Dubai (the United Arab Emirates). Cronin was hired by Mike de Kock to work with Taylor following Bowker’s work. Cronin managed “as many horses possible” unshod at the stables of Sheikh Mohammed Bin Khalifa Al Maktoum, Dubai Royal Family. Horses race in shoes per racing rules. Farriers take them off shortly afterward.
Cronin believes that hoof health is influenced by genetics and it is important to choose horses with high-quality hooves. It’s important to take care of them.
He says, “We live in a world with manicured arenas and that doesn’t encourage healthy hoof growth.” You have to work your horse and allow it to live. If he has a good foot, he will adjust to his environment. You can’t leave him in a stall with fluffy bedding that has been soaked in urine and feces, and then expect him to work hard under saddle at the track. He can’t jump that high.
Taylor suggests that working with young horses, especially racehorses, before their hooves are ready could be dangerous for bare feet. She says, “The hoof is a smart structure, just as bone is.” It must be stimulated just like going to the gym to get the best out of a workout. They won’t get that from just 45 minutes of training per day and 23 hours a days locked up in a stall as a 3 year-old. They would be most benefited if they were allowed to move freely on varied terrain.
She adds that bones and hooves are still developing at this age and can develop for many years. She has learned that cattle need strong hooves, and bones. This is why she encourages them to move on hard surfaces from the moment they are babies.
Back to Nature–Within Limits
According to our sources, a natural horse foot is one that allows horses to run free and unrestrained. Their sources agree that domestication and riding have created problems for the horse’s foot, making it harder to keep it bare. Research suggests that horses who are barefoot have better hoof and musculoskeletal health. However, not all horses can go completely barefoot. This decision is dependent on the horse’s individual characteristics, genetics, management, use, as well as their individual traits. Hilary Clayton, BVMS (Doctor of Veterinary Science), MRCVS, Dipl., says that some demands, such as jumping, can exceed equine’s ability to sustain the forces they receive. ACVSMR. ACVSMR.
—Christa Leste-Lasserre, MA
The Barefoot Trim
Sources agree that trimming bare feet is an art that requires knowledge of supporting science. Although it’s not difficult, people sometimes get it wrong.
They say two common mistakes are to trim the foot like a wild horse’s foot or to trim it as if it’s going for a shoe.
O’Grady prefers to refer to it as shaping because that is the best approach. “Just wrap the walls around and let friction do the rest.
To create a bevel in your hoof wall, he recommends trimming the heels as well as the frog to ensure they are on the same plane. The farrier can smoothen out any unevenness on the bottom to ensure load sharing and force distribution. If the sole is strong and thick, the trimmer can increase breakover (the moment the heel lifts off of the ground and the toe rolls during movement). He does this by slightly angling the tip of the toe, just enough to slide a credit card between the toe and the ground.
If the horse is not ridden, it might be a good idea to let him develop his own natural shape. However, a working horse will need to be shaped to adjust to the additional weight. The horse will feel like he is going to get a shoe, so trimming him as though he was a shoe can cause fragile side angles and reduce the sole.
Clayton and Bowker studied Arabian riding horses who had been barefooted for many years. They then began shaping their feet using barefoot trimming principles. The feet changed in shape over 16 months. This led to rounder hooves, even in the hind legs. There was also less variation in the hoof shape of horses from one another. The horses’ feet reflected more of the goals for barefoot shaping. They had a wider frog and a thicker digital cushion, which was confirmed by radiographs. Higher heel angles, which more closely corresponded to the dorsal wall, greater sole concavity, easier breakover, and a wider frog.
Take-Home Message
Researchers are only just beginning to understand how to combine the natural horse foot and the more natural riding state. There are many assumptions and misunderstandings in this field, which makes solid research even more crucial as we move forward.
