Equine Metabolic Syndrome (EMS)

Group of horses in a field of wheat

Equine Metabolic Syndrome (EMS) is the name given to a group of clinical conditions, similar to human metabolic syndrome and Type 2 Diabetes. A proportion of horses are genetically at risk of developing EMS. The disease is induced by a combination of dietary and management factors.

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Horses and ponies can be affected by EMS. Breeds that are often described as “good-doers” (those that gain weight easily), and typically have a high body condition score (BCS), are most susceptible. As a result of EMS, they are at high risk of developing laminitis, a very painful inflammatory in the tissues around the hoof. Any breed can be affected by EMS; however, those most predisposed include: Warmbloods, Arabian horses, Welsh, Dartmoor and Shetland ponies.

It is important to note that EMS and Cushing’s Disease (Pituitary Pars Intermedia Dysfunction, PPID) are two different diseases; however, they are sometimes confused. Both often result in insulin resistance and laminitis, and therefore have similar presenting signs. Keep in mind that EMS typically occurs in younger horses and ponies, whilst PPID typically occurs in those that are older. Rarely, EMS and PPID will both be present at the same time.

What are the causes/risk factors of EMS?

Insulin is a hormone which has a central role in how the body uses and stores glucose and fat. In horses with EMS, the body does not respond effectively to insulin. This is termed insulin resistance. As a result, the body is less able to take up and store glucose from the blood.

In addition to insulin resistance, there is also an impact on fat storage. Other metabolic problems include inflammation, clotting disorders and damage to blood vessels. These metabolic changes often result in laminitis, because the blood vessels in the feet are particularly susceptible to metabolic disturbances.

The reason for laminitis being so common in horses suffering from EMS is thought to be due to their unique anatomy. Possible mechanisms include: constriction or dysfunction of the blood vessels in the feet, reduced glucose uptake, altered hoof horn production, and increased activity of certain enzymes. Sadly, severe episodes of laminitis have long lasting consequences and can sometimes be fatal.

What are the signs of EMS?

  • Obesity: Monitor for regional fat deposits, particularly in the nuchal ligament, found in the dorsal neck region. This is also described as a ‘cresty neck’. Other areas to look for fat deposits include around the eyes, the tail head, and the prepuce or mammary glands. Alternatively, obesity may be generalised. It is important to note that EMS cannot be ruled out in horses or ponies with a healthy BCS.

  • Laminitis: Subclinical laminitis is indicated by a pottery, short-strided gait. Growth rings in the feet that are wider at the heels. In acute laminitis the pony or horse will be reluctant to walk, and have increased digital pulses and warm feet, more commonly in the front feet.

What can owners do to prevent their horse developing EMS?

EMS is preventable and reversible in all breeds with appropriate dietary restriction. This, combined with exercise, is essential to preventing and treating EMS. Weight loss and increased exercise improve the way that the body responds to insulin; losing fat and building muscle helps to combat insulin resistance because muscle tissue has more insulin receptors. Essentially, it helps to reverse insulin resistance and makes the body sensitive to insulin again.

If you want to reduce your horse’s weight, eliminate access to pasture until the ideal body condition has been achieved, but ensure that you are feeding a mineral balancer to meet the correct nutrient requirements for your animal. Any weight loss programme must be gradually.

If your horse or pony has active laminitis it should not be exercised and you should seek veterinary advice immediately. If possible, avoid all grazing until the laminitis has fully resolved.

Many horses with EMS and laminitis are managed with zero grazing, as they are highly sensitive to the levels of sugar and carbohydrates in grass; even an hour of turnout can cause foot soreness. An all weather turn-out area is a good solution, allowing horses and ponies to spend risk-free time outside.

What should you do if you think that your horse may have EMS?

If your horse seems to be a bit pottery or short-strided, is reluctant to walk out, has signs of laminitis, or if you or your farrier are concerned about their feet, you should contact your vet for an examination and further investigation.

Treatment may involve radiographs of the feet to assess their condition, blood tests for EMS and PPID, blood tests to monitor EMS during a weight-loss diet, as well as prescription drugs to aid weight loss, if deemed necessary.

What does treatment involve

The most important aspects of EMS treatment are diet and exercise. Aim to reduce calorie intake to 1-1.5% of current body weight per day for 3-6 months. That is 5-7.5kg for a 500kg individual. Use a weighbridge or weight tape to accurately measure and track the weight of your horse or pony, and use a body condition scoring system to monitor their progress.

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