Lame Horse? Test for EMS and PPID

Two major concerns with equine metabolic syndrome (EMS) and pituitary pars intermedia dysfunction (PPID, equine Cushing’s disease) include exercise intolerance and hyperinsulinemia-associated laminitis (HAL). A swell of evidence shows that these common endocrine disorders may also contribute to back pain, suspensory ligament desmitis, and osteoarthritis.

In humans, “metabolic osteoarthritis” is a recognized subset of arthritis believed to be caused by chronic, low-grade, systemic inflammation. Although this condition has yet to be recognized in horses, experts say that due to the similarities between metabolically challenged horses and humans, research in this field should be pursued.^*

In contrast, studies do show that horses with PPID have a higher risk of soft-tissue injuries, particularly of the suspensory ligament. For example, horses with PPID had greater degeneration of the suspensory ligament than age-matched control horses in one study. Further, sport horses over 10 years of age with clinical signs of PPID had an increase in suspensory ligament injuries.

“Sixteen percent of those sport horses also had evidence of insulin dysregulation, a feature of EMS. These data raise interesting questions about how insulin regulation, inflammation, disease state, and lameness are all related,” said Ashley Fowler, Ph.D., a nutritionist for Kentucky Equine Research.

Horses with PPID sometimes have muscle loss along the topline, which can result in poor saddle fit and back pain. In many cases, that back pain may present as lameness.

“Muscle wasting can contribute to the destabilization of joints, which may potentially cause or worsen lameness,” Fowler added.

 In sum, EMS and PPID contribute to the lameness landscape not only through laminitis but also suspensory ligament damage and metabolic osteoarthritis. Lameness results in lost performance and training days, and can be financially draining for some horse owners.

 Clinicians should consider testing for endocrine disorders if the horse’s age, breed, or performance suggests a problem, according to the authors of a recent research paper.^* Once diagnosed, appropriate treatment should be initiated, which for many, but not all, horses with PPID and EMS involves weight management.

“The goal of a weight loss program is to reduce calories while ensuring all other nutrient requirements, including protein, minerals, and vitamins, are met. Reducing or eliminating high-energy concentrate feeds and adding a ration balancer or vitamin and mineral supplement can help achieve that goal,” advised Fowler.

Some overweight horses also require a restriction in hay intake or pasture access.

Fowler explained, “Because EMS and PPID are often associated with general inflammation, add 60 mL of an anti-inflammatory supplement that features the long-chain polyunsaturated fatty acids known as EPA and DHA. In these instances, choose EO-3.”

^*Manfredi, J.M., S. Jacob, and E. Norton. 2023. A one-health lens offers new perspectives on the importance of endocrine disorders in the equine athlete. Journal of the American Veterinary Medical Association 261(2):153-164.