If you’ve ever seen a laminitic pony trying to hobble across a paddock, you know how sore those tiny feet can get. A lightweight therapeutic shoe, however, could give these little animals some pain relief, say Dutch and Belgian researchers.
A special, custom-fitted thermoplastic glue-on shoe, designed to support the frog, made study ponies more comfortable within three days, said Janneke Sleutjens, DVM, PhD, ambulatory equine veterinarian in the Utrecht University Faculty of Veterinary Medicine, in the Netherlands.
In their study, Sleutjens and her fellow researchers measured various foot-related forces in healthy and sound Shetland ponies (half obese and half a healthy weight) as they walked with and without thermoplastic shoes (thermoplastic materials become plastic on heating, harden on cooling, and are able to repeat these processes). The moldable shoes had a heart-bar design and rolled toe, intended to relieve laminitic pain in affected horses. They were lightweight, custom-sized and fit to each horse, and glued to the hooves.
The researchers opted to not test laminitic ponies in their study for ethical reasons. “From a welfare aspect, it is not justifiable to walk laminitic ponies repeatedly over a force plate,” Sleutjens said. However, the obese ponies were a representative group of ponies at risk of developing laminitis, she added.
The researchers walked and trotted the barefoot ponies over a combined force/pressure platform covered by a rubber mat. Afterward, a farrier experienced in thermoplastic glue-on shoes fitted them on each pony’s two front feet. The researchers then walked and trotted the ponies across the platform again. After 72 hours of wearing the shoes, they walked and trotted the ponies across the platform again.
The researchers measured each front foot’s peak vertical force, stance duration, time from peak vertical force to liftoff, time to peak vertical force, vertical force, and vertical impulse during each treatment. They also calculated the “toe-heel balance”—the comparative pressures within a single foot between the toe and the heel against the ground.
When ponies were barefoot, the obese group had greater loading on the heel than the toe at both walk and trot, compared to their counterparts of a normal weight, Sleutjens said. Obese ponies also spent more of their stance time on the heel than on the toe at each step and took longer to “breakover” (essentially, turn the hoof over to complete the step) than normal-weight ponies.
“The combination of these findings could indicate that the obese ponies experienced some degree of discomfort or pain in their toe region, possibly because they were in a subclinical stage of laminitis, given that obesity and hyperinsulinemia are risk factors for the development of laminitis,” the researchers said.
None of the ponies showed much difference in movement just after the farrier placed the shoes. However, after three days, the ponies seemed to have adjusted to the shoes and discovered their benefits, said Sleutjens. The differences they noted between obese and normal-weight barefoot ponies more or less disappeared when the ponies had been shod for 72 hours.
“The proposed theory behind the shoe is that, owing to the heart bar shape, the palmar structures of the hoof contribute to the weight-bearing surface, and the rolled toe should ease breakover,” the researchers said.
Some veterinarians and farriers use metal heart bar shoes and/or foam frog supports on laminitic feet, Sleutjens said. But a glue-on thermoplastic shoe could have additional benefits, she said.
“The plastic material is lighter and moldable, and it could be beneficial to not have to nail into an already traumatized foot,” she said. Furthermore, the shoes last longer (several weeks) than foam frog supports, which must be replaced frequently.
While the shoes offer promise for laminitis-prone ponies, the best weapon against the disease remains prevention. “First of all, laminitis needs to be prevented by eliminating the risk factors,” Sleutjens said. “Therefore, it is important for ponies to lose weight. But in addition to that, owners could consider using the special thermoplastic shoes,” several varieties of which are commercially available.
Such a decision requires qualified teamwork, however, Sleutjens added. “It is important for the farrier to first have proper training on how to apply these shoes, and for him or her to work together with the treating veterinarian,” she said.
The study, “Mouldable, thermoplastic, glue‐on frog‐supportive shoes change hoof kinetics in normal and obese Shetland ponies,” was published in the Equine Veterinary Journal.