What is EMS?

EMS is a condition in which we see insulin dysregulation (basically poor control of insulin) in association with the typical signs of fat accumulation, increased body condition and a tendency for laminitis.

Let’s break this down. Insulin is the hormone released by the pancreas in response to the increase in blood glucose that occurs after eating. It makes the body cells take up glucose to help keep the blood glucose level within the range necessary for life.

With insulin dysregulation the cells don’t respond appropriately to insulin and they can’t take it up. Just as in diabetes, this leads to not only high glucose levels but also high insulin levels because the body continues to release more insulin to try and get on top of its high glucose level.

What causes EMS?

The exact cause of EMS is still not entirely known. There’s research underway to see why insulin dysregulation actually occurs but we have made some advances. It’s clear there is a genetic risk for certain equines. These are generally hardy native-type ponies whose bodies have adapted to be able to survive in harsh environments where food is scarce and they must keep moving constantly to find new grazing.

They have a much lower requirement for food intake and can make the most of poor quality food to maintain a healthy condition. For these animals, being in a more intensively managed lifestyle with regular access to food rich in certain carbohydrate sources such as lusher pastures, concentrate feed and hay leads to an intake way in excess of their needs. This causes weight gain and later obesity which is linked with insulin resistance – it’s quite similar to the situation that occurs in type two diabetes in humans. 

The increased body condition that accompanies insulin dysregulation is reflected in fat accumulation, often in typical areas such as the crest of the neck, above the eyes, and around the rump or tail base. We now know that fat isn’t just an inactive store of fat cells, but actually it can be thought of as a very active organ. It actually produces various types of hormones and inflammatory substances.

Is it the same as Cushings / equine PPID (pars pituitary intermedia dysfunction)?

EMS isn’t the same condition as PPID, which results from age-related change to hormonal signalling pathways in the pituitary gland of the brain; typically in horses and ponies over 10-15 years of age.

However, PPID can be associated with insulin dysregulation in certain cases and we can see the similar cresty neck, or obese appearance in horses and ponies affected by PPID. This is also why it can sometimes be helpful to rule out PPID when we suspect EMS, and vice versa, but it’s not alway necessary. There’s still a lot we need to figure out about the relationships between these two conditions.

So, EMS creates a state of having a high circulating level of insulin (known as hyperinsulinemia). Whilst we know that insulin is important in glucose regulation, it also has other effects. Insulin can cause changes in blood vessel diameter which then can affect blood supply. It is thought that when the blood supply to the delicate tissues of the hooves is affected, as a result of hyperinsulinemia, this can then lead to laminitis. That said – there may be other factors involved as well.

How is EMS diagnosed?

Just the typical physical appearance of a horse or pony with EMS is enough to suspect EMS. A  diagnosis is based on this, coupled with blood analyses to assess general health and assess glucose and insulin levels and see how the body responds when insulin or glucose are given. One or two other tests may be recommended to see whether your horse or pony could also have PPID, and perhaps foot x-rays to assess laminitis.

Can EMS be treated? Will my horse or pony be OK?

The mainstays of EMS treatment are: controlling laminitis if it’s present, weight reduction and exercise. Management of laminitis really depends on its severity (which is a whole other topic) but generally a combination of stable management to maintain confort, shoeing or trimming and painkillers will be used. Weight reduction should be achieved gradually by increasing exercise, as well as reducing food intake. 

Equines with EMS will benefit from a reduction in feeding. which will mean no pasture or at most restricted grazing using a muzzle. You will also need to cut out concentrate feeds and provide a diet rich in forage. This may mean only providing some hay, occasionally soaked to further reduce its energy content, and a balancer to provide necessary vitamins and minerals but with no energy content.

Where a horse or pony can’t be exercised because of laminitis, sometimes they can be prescribed a human medication called Metformin in the meantime. This helps reduce blood glucose levels and promote weight loss whilst we get them comfortable and ready to exercise again.

In short, yes, the prognosis is good for horses and ponies with EMS. However, we have to be mindful of laminitis because this has the greatest negative impact on quality of life, and therefore in deciding prognosis.

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