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Equine Metabolic Syndrome (EMS)

EMS is a syndrome involving insulin resistance and unusual fat distribution around the body causing an increased risk of laminitis. Although it is not technically the same it is often likened to diabetes in humans, and this can be helpful when thinking about the condition. Some horses will be temporarily affected by EMS due to management and circumstances. This is because insulin resistance can be caused by obesity and lack of exercise (for example a horse who is out of work and on increased grass would be at risk), in these cases adjustments to the management system with or without short term medications can result in a resolution of both the clinical aspects of the disease and evidence on blood tests. Some horses however are genetically predisposed to EMS and these horses require lifelong management changes with or without medication and they may not ever test negative on blood tests despite best efforts.

Symptoms

Regional Adiposity

This refers to fat pad development typically on the crest of the neck, behind the shoulders and at the top of the tail. The horse may not have any excess fat in the abdomen region and can even have good rib exposure and so may not typically be thought of as overweight but still holds a cresty neck for example.

General obesity which is difficult to manage

In some cases the horse is just generally overweight all over.

Laminitis

Horses with EMS are significantly at risk of laminitis.

Exercise intolerance or mild demeanour alterations such as lethargy

Some horses with EMS feel groggy and be less keen for exercise.

Diagnosis

A clinical assessment is likely to cause high suspicion. Confirmation of the condition is obtained via blood tests, either resting or dynamic.

Resting blood test

This will measure (one or all of the following): insulin, glucose, triglycerides and adiponectin at rest. The most significant measurement is insulin as this is the driver of laminitis. A high level of insulin at rest is very significant. Glucose measures the free sugar in the blood and triglycerides is a measure of fat in the blood. Adiponectin is a hormone which is suppressed by metabolically unhealthy fat (bad fat), if the level is low then the horse has too much bad fat in the body.

Dynamic blood test

This measures the response of insulin to a sugar challenge (usually karolyte syrup) and is the most accurate insulin function test. The sugar syrup represents normal grass, hay or hard feed and so is a way for us to see how the body copes with a challenge which it should normally cope fine with. A horse with insulin dysregulation would have an overly high insulin result on this test.

Treatment

Management

Diet

A high fibre low sugar and starch diet is essential. This is because the body has insulin which is not working therefore it cannot process sugar normally, therefore keeping triggers low helps the body out. This usually means no grass, soaked hay and a high fibre, low starch and sugar hard feed.

Exercise

As long as the horse is sound, they should be exercised every day for at least 20 minutes. This has been shown to reduce insulin levels significantly and can be as simple as walking or lunging in-hand. If physical exercise is not an option then clever turnout solutions can be helpful such as track systems.

Don’t over-rug in winter

Allowing horses to regulate their own body temperature gives them the opportunity to use their fat supplies and increase their own insulin sensitivity.

Medication

‘Flozin’ drugs are highly effective. Examples are canagliflozin and ertugliflozin. These work by encouraging glucose to be excreted via urine and this causes weight loss and increased insulin sensitivity very quickly – insulin levels are regularly seen to drop dramatically within 7 days of starting this medication. These drugs can be used short term to rescue a case if for example the horse has laminitis (insulin directly damages the laminae so getting it down quickly helps get the horse better quicker) and then management can continue to manage the horse long term or can be used in an ongoing fashion for genetically affected horses. Side effects include urinary tract infections due to the sugar in the urine and high fat mobilisation in the blood which can be monitored with regular blood tests.

Prevention

Maintaining a healthy weight, providing regular exercise and keeping sugar and starch intake low are all vital parts of prevention of this condition.