Hind limb shoes—whether flat or grooved—improved lameness scores and might even make horses move more “freely” in the hind limbs, said Sarah Reed, PhD, associate professor at the University of Connecticut, in Storrs.

Analyzing Gait Before and After Shoeing

Reed’s fellow researcher, farrier Katelyn Panos, was training for her Certified Journeyman Farrier exam when she realized her second-level dressage horse “went drastically better” in flat shoes—also known as plain stamp shoes—compared to traditional fullered shoes, which are rounded with central grooves, Reed said. The observation made both scientists wonder how the different shoes might affect a horse’s movement. And because all the school horses at the University of Connecticut had been barefoot for months due to COVID-19 lockdowns, the team decided it was the perfect opportunity to examine this concept.

They selected 14 sound, barefoot horses—mostly Morgans and Thoroughbreds—that had just completed six weeks of reconditioning exercises, barefoot, after six months of lockdown. The researchers ran gait analyses on the horses using inertial motion sensors (IMSs) and videography with body markers to measure angles and range of motion while the horses trotted in a straight line in an arena with TruStride footing. The team also performed lameness exams using to the American Association for Equine Practitioners’ (AAEP) guidelines and scoring system.

Panos then trimmed the horses’ front and hind feet and placed shoes on them. Half the horses were fitted with plain stamp shoes on the hind feet, and the other half were shod with traditional fullered shoes. Six weeks later Panos trimmed and reshod the horses with the same kind of shoe they had been wearing before. After 12 weeks of wearing hind shoes, the horses underwent the same analyses as they did at the start of the study.

Less Lame, More Flexion in the Hind Limbs When Shod

The scientists found no significant differences between the groups, for any of the parameters, said Reed. “We were surprised … because the riders were reporting that horses in plain stamp shoes were ‘feeling better’ under saddle,” she told The Horse. “The study wasn’t designed to incorporate rider input, so we did not quantify those responses, but we are interested in following up with different measures of gait quality in the future.”

Despite the lack of distinction between horses wearing different shoe types, however, the researchers noted a marked difference in hock angles and lameness scores when they were shod versus barefoot, she said.

In particular, shoeing increased the maximum angle both hocks achieved by approximately 4 degrees and the minimum angle of the left hock by approximately 5 degrees, regardless of shoe type, during movement and when standing, said Reed. AAEP lameness scores were, on average, 44% lower when the horses were shod than barefoot.

Less Traction, Less Concussion, Better Dig With Shoes?

Farrier textbooks indicate shoes might reduce horses’ traction—although more research is necessary to confirm this, Reed said. While that might initially sound concerning—as it could make the horse “slip”—on a smaller scale such slip could potentially be beneficial if it comes into play during the stance phase of a step, which usually creates significant concussion forces, she explained. “We hypothesize that less traction might also protect joints further up the limb from these forces,” Reed said.

The shoe might also “add purchase”—meaning the toe can sink into the ground better for more improved takeoff, she added. “The hind feet are shaped like a shovel spade, and their function is similar,” Reed said. “We hypothesize that this purchase would make propulsion easier for the animal.”

A Lack of Consistency Across Shoeing Studies

The researchers note it’s difficult to compare farrier studies due to the wide variety of shoeing techniques used. In fact, most published papers do not include farrier protocol details, said Reed. “This makes it challenging to compare across studies, and it’s one of the reasons we specifically chose to shoe to the standards set out by the American Farrier’s Association (AFA),” she said.

Panos agreed. “As an industry, we have done a poor job of conveying that good basics in farriery, anecdotally, prove to keep horses sounder in shoes because the shoe actually fits the foot, the nails drive in the proper place, the proper structures of the foot are supported, and there is enough steel fit for the foot to expand and contract among other aspects,” she explained. “In studies that don’t include farriery protocols, it’s hard to determine if those basic requirements are being met.” New research initiatives headed by the AFA to address the issues are underway, she added.

Take-Home Message: Keep an Open Mind About Shoes

“Overall, the findings suggest that hind limb shoes may be helpful to athletic horses. Open communication between the farrier, veterinarian, trainer, and owner is critical,” Panos explained, noting her message applies to everyone in the horse industry—from leisure riders to professionals.

“Veterinarians, keep an open mind about shoeing interventions please,” she continued. “Farriers don’t have the data your practice has, but we do have centuries of orally passed-down basics that work. We are trained to know biomechanics and how they can be used to help various issues not only in lameness but in preventing lameness. Communicating directly with a phone call to the farrier can often be the best way to discuss cases.

“Owners, you’re asking your horses to be athletes, so sometimes they may need a bit extra help to do what you’re asking well,” she continued. “Adding hind shoes can be one of those interventions that could make your horse’s job more comfortable.”

The scientific article appeared in the Journal of Animal Science in November 2022.