Unveiling what EMS and ID really look like

Equine metabolic syndrome (EMS) is not a single disease, say members of the Equine Endocrinology Group in their most up-to-date guidelines¹ and authors of the ECEIM consensus statement.² Rather, EMS is a collection of risk factors for endocrinopathic laminitis—the leading cause of laminitis in horses caused by hyperinsulinemia (elevated circulating insulin levels). The most consistent feature of EMS is insulin dysregulation (ID), which veterinarians can measure relatively easily in horses. Another feature they commonly see in EMS cases is increased generalized or regional adiposity—fat deposits all over the horse or in certain spots.

“EMS results from an interaction between genetic and environmental factors, and the risk of laminitis in the individual animal therefore depends on the cumulative effects of these influences,” states the Equine Endocrinology Group in the guidelines.

This means genetically high-risk horses can develop EMS with only minimal environmental (e.g., dietary) influences, whereas other horses that have a lower genetic risk might develop EMS with improper environments, such as diets high in nonstructural carbohydrates (NSCs).

In this article we’ll describe horses and ponies with a higher genetic risk for EMS followed by some examples of other animals with lower genetic risk for EMS that might still benefit from EMS (ID) testing.

“Recognizing EMS in horses other than the ones we expect, the overconditioned equine population, is important because even nonobese and athletic horses are at risk of career- and life-threatening endocrinopathic laminitis if not recognized and treated,” says Teresa Burns, DVM, PhD, Dipl. ACVIM, an associate professor of equine internal medicine at The Ohio State University, in Columbus.

The True Face of EMS: Obese Ponies

The overconditioned population with regional adiposity at the tail head as well as a “cresty” neck is truly the face of EMS, especially ponies. Current estimates suggest 22-27% of ponies are hyperinsulinemic (Durham et al., 2019).¹

“If there ever were a poster child for anything, overconditioned ponies are it for EMS,” says Burns.

“Ponies come by their EMS risk honestly, it seems,” she adds. “But as we are all increasingly aware, there are many other breeds at elevated risk, including—but definitely not limited to—American Saddlebreds, Morgans, Tennessee Walking Horses, Paso Finos, and Arabians