ems heritability
Researchers have learned that genetics have more influence on a horse’s risk of developing equine metabolic syndrome (EMS) than we previously thought. Recent study results suggest that certain metabolic traits linked with EMS have a heritability as high as 80%.

Heritability is a foal’s likelihood of inheriting specific genetic factors from both parents, said Elaine M. Norton, DVM, MS, Dipl. ACVIM, a PhD candidate at the University of Minnesota (UM) College of Veterinary Medicine, in St. Paul.

Equine metabolic syndrome is a complex disorder associated with an increased risk of laminitis (in which the leaflike laminae that suspend the coffin bone within the foot become inflamed or fail and separate from the coffin bone and the hoof wall, allowing the bone to rotate or sink) that includes insulin dysregulation (abnormal insulin responses) and any combination of:

  • Increased or regional adiposity (fat deposits);
  • Inability to lose weight;
  • Dyslipidemia (abnormal lipids, or fat, levels in the blood); and
  • Altered adipokine (proteins secreted by adipose tissue) concentrations.

“We expected that the heritability of genetic traits linked to EMS would be about 40%,” said Molly McCue, DVM, MS, PhD, Dipl. ACVIM, professor and interim associate dean of research at the UM College of Veterinary Medicine. “The fact that several traits had higher estimates is surprising and exciting.”

Norton, McCue, and colleagues studied 264 Welsh ponies and 286 Morgan horses—the largest study population to date for EMS research of this type.

While researchers already know that some breeds—such as Welsh ponies and Morgans—are predisposed to developing EMS, these study findings emphasize the importance of strategic breeding decisions.

“We will never be able to breed out EMS—there are hundreds of genetic factors to consider,” Norton said. “However, it is important to consider when making breeding decisions in breeds with a higher predisposition to the condition.”

Norton said she hopes this research can be used to develop a test to determine whether a horse is a high-risk individual. While controlling the horse’s environment through diet and exercise will still remain key to EMS management, knowing a horse’s genetic tendency would allow veterinarians to recommend and owners to make those modifications earlier and, thus, reduce the chances for laminitis.

The study, “Heritability of metabolic traits associated with equine metabolic syndrome in Welsh ponies and Morgan horses,” was published in the Equine Veterinary Journal.