Equine metabolic syndrome (EMS)

Veterinary advice should be sought before applying any treatment or vaccine.

Equine Metabolic Syndrome (EMS)

Equine Metabolic Syndrome (EMS) is a complex disorder involving the horse's endocrine system, characterized by obesity and insulin resistance. One of the major complications with this disease is its association with recurrent or chronic laminitis in affected horses. EMS is similar to Metabolic Syndrome (MetS) and Type 2 diabetes in humans.

EMS occurs most frequently in obese horses with regional clusters of body fat, however it is also found in horses with a leaner body condition. These horses are often labeled as "easy keepers" or "good doers" for they are able to maintain their body condition with little feed required.

EMS horses often have a characteristic fat distribution showing deposits such as cresty neck and at the comb, side of the chest, hip region, and tail head. Horses with EMS have a predisposition towards laminitis and often develop it due to grazing in green pasture. Sometimes the horse may have previous history of laminitis or has had mild episodes of laminitis that were mistakenly attributed to foot soreness following a farrier visit, sole bruising, or arthritis.

Clinical signs include a cresty neck score greater or equal to 3 our of 5, a body condition score equal to or greater than 7 out of 9, insulin resistance, enhanced oxidative burst, and a predisposition to laminitis.

The primary treatment goal for horses with EMS is to maintain the horse's body condition score at a seven, ideally a five. This is usually accomplished through conducting a nutrition analysis, modifying the horse's diet accordingly (usually includes switching to a low-carbohydrate diet and regularly soaking hay), and establishing a regular exercise program.


Fat deposits on the neck, shoulders and rump
History of laminitis
Altered reproductive cycle in mares


  • History
  • Physical exam
  • Clinical signs
  • Laboratory tests
  • Radiographs


Diet modificationHorses are usually placed on a low-carbohydrate diet amd fed 1 to 1.5% of their body weight in dry matter, confirmed with regular feed analysis testing. Soaking hay is another method of removing soluble carbohydrates from the horse's diet.
Regular exercise program
Metformin or Thyro-L
Pasture Turnout ManagementControlled grass intake is important in horses with EMS. To achieve this, grazing muzzles are often recommended, along with relocation to a different paddock which contains less lush grass coverage, and turnout schedule modification according to carbohydrate levels in pastures (for example, carbohydrate levels are lower at night and increased in the spring and early fall, after the first frost).


  • Managing weight
  • Limiting grain and increasing forage in diet

Scientific Research References

Good Overviews

Clinical Trials

Risk Factors

  • Obese horses
  • Hardier breeds : Such as Saddlebreds, Tennessee Walking Horses, Paso Finos, Morgans, Mustangs, Arabians and Quarter Horses.
  • Horses that are often described as 'easy keepers', which are able to gain weight without eating very much food.

Commonly Affected Breeds

Morgan iconArabian iconPaso Fino iconShetland Pony iconSaddlebred iconDartmoor Pony iconBelgian Warmblood iconDutch Warmblood iconSwedish Warmblood icon