Researchers study feral and wild horses for a variety of reasons. For instance, they evaluate hoof health to help better understand hoof conformation, disease, and lameness in domestic horses. Information gathered about hoof angles, wall thickness, laminitis incidents, and more all offer insight into keeping horses sound.
Brian Hampson, PhD, co-founder of the Australian Brumby Research Unit at the University of Queensland’s School of Veterinary Science in Australia, presented a study looking at foot morphology and foot health in one herd of the Przewalski’s horse at the 2017 International Hoof-Care Summit, held Jan. 24-27 in Cincinnati, Ohio.
A History of Domestication
Hampson began with a summary of the history of the horse as different genetic branches separated into domestic horse breeds and wild horses, such as the Przewalski’s horse and the Tarpan. He also clarified that what we often think of as “wild horses,” such as mustangs and the Australian Brumbies, aren’t really wild; they’re feral.
Horses were domestication about 5,500 years ago, said Hampson, and were initially used for milk and meat. Researchers estimate humans started riding horses around 3,000 years ago.
While at least 87 breeds have already gone extinct, Hampson said, 25% of the remaining 900-plus breeds are endangered. Additionally, he said, modern horses don’t have as much genetic diversity as previous wild and ancient domestic populations.
What We’ve Learned From Przewalski’s Horses
In the 1960s, the Przewalski’s horse, which originated in Mongolia, came back from near extinction. Current numbers hover near 2,000 worldwide thanks to careful breeding of 16 captive horses in the 1970s.
The Przewalski herd that Hampson studied, lives in Hungary on Europe’s largest steppe area. Researchers collect data on these horses, such as heart rate, body temperature, movement, grazing habits, diet, and location.
During the winter, researchers have learned, the herd goes into a torpor—their heart rates drop by 50%, body temperature by up to six degrees, and in body mass by 20%. The herd stands for long periods, eating only one-third of their usual diet.
The hooves are long and overgrown and are trimmed naturally through movement of the horse.
To learn more about the horses’ hooves and compare it to what researchers know about those of domestic and feral horses, Hampson studied the feet and blood work of 12 stallions and eight mares from the herd, aged 2 and 13 years. He collected radiographs, photographs, lamellar histology, and serum insulin concentrations.
He and his team found several differences in shape and structure (called morphology) between Przewalski’s horse hooves and feral/domestic horses:
- The dorsal hoof wall angle (the angle between the outside of the hoof wall at the toe and the ground) was around 57° compared to Brumbies at 55°;
- The heel angle (the one between the heel wall and the ground) was 42° compared to Brumbies at 45°;
- The coronary band angle (you guessed it … the angle the coronary band forms with the ground) was 21°, which is the same as Brumbies.
- The palmar angle of the distal phalanx (the angle the wings of the coffin bone make with the ground) was 6.3°, whereas it was 5.7° in Brumbies;
- The sinker distance (the depth the bony skeleton had sunk over time into the outer hoof) was 7.7 millimeters compared to 6 millimeters in small breeds of domestic horses;
- The hoof wall thickness was 14.6 millimeters, which was similar to Brumbies and domestic horses;
- Three of the 20 had mild, chronic laminitis but could walk;
- Nine of the 20 horses had normal feet;
- Of the 10 horses’ tissue samples examined microscopically, five showed changes normally associated with hyperinsulinemia (a condition in which there are excess levels of insulin circulating in the blood relative to the glucose level); and
- Ten of the horses had low insulin levels, two of which were laminitic.
Hampson also shared that Lane Wallett, DVM, a veterinarian and paleontologist at the University of Florida, in Gainesville, studied equine fossils up to 3.5 million years old and discovered a 75% incidence of chronic laminitis.
Based on these findings, Hampson hypothesized all horses are vulnerable to laminitis. Diet and lack of exercise might be contributing factors to the disease, he said, but there are likely other unknown factors at play.
“We were really surprised to find laminitis in the Przewalski’s horse,” he said. “We thought there might have been something that was different about that horse’s foot that protected it from laminitis. We thought that most likely we’ve changed the foot of the domestic horse over the last couple hundred years that has made it susceptible to laminitis, but that doesn’t seem to be the case. It’s always been there. Feral and wild horses aren’t exempt to these pathologies.”