Equine Metabolic Syndrome (EMS): symptoms, causes, and prevention

You hear more and more about ‘Equine Metabolic Syndrome’ or EMS these days. Horses with EMS have a disrupted metabolism due to being overweight. Their hormones are out of balance, they perform less, and can develop laminitis. What are the symptoms and causes of EMS and what can you do about it?

What is EMS?

In the Netherlands, about 55% of recreational horses are overweight. So overweight that these horses develop EMS. EMS is a combination of overweight, insulin resistance, and laminitis. Due to being overweight, these horses often perform less well, may have trouble dissipating heat and regulating their body temperature, and become less fertile. Benign fat tumors can also develop in the abdomen, which can lead to severe colic. Additionally, an overweight horse may become insulin resistant. The horse then has difficulty maintaining a balanced blood sugar level, which could result in laminitis. Finally, overweight horses can develop a disrupted fat metabolism. EMS involves multiple problems:

• Disrupted sugar metabolism
• Disrupted fat metabolism
• Disrupted hormone balance
• Risk of fat tumors, decreased performance, and decreased fertility

Symptoms of EMS

There is no test that can rule out EMS. EMS is a combination of overweight, insulin resistance, and laminitis. Therefore, the veterinarian will measure the amount of insulin in the blood and may take an X-ray of the hooves to rule out laminitis. The following symptoms may indicate EMS in horses:

• Overweight
• Infertility
• Fat pads on the crest, tail base, or in the udder
• Insulin Resistance
• Laminitis
• Overheating
• Lameness in front legs
• Diverging growth rings on hooves

Insulin resistance

Insulin resistance (IR) can be caused by a disease (PPID / Cushing), but is also often caused by a horse receiving too much or energetically rich food for a prolonged period. If a horse receives more energy than it uses for daily life and work over a longer period, various problems arise. Horses naturally eat all day, but small amounts of energy-poor plants. We often give them food in larger meals that can contain a lot of energy. Especially for horses of more robust breeds (such as Haflingers or Tinkers), this can quickly become too much. Also, our grassy pastures are much richer in energy than the steppes where the wild horse comes from. So, not only concentrated feed is a problem!

The relationship between fat and hormones

There is a connection between fat storage and hormones. This has to do with the living conditions of wild horses. In the wild, horses come out chubby in summer. They store a lot of fat for the winter when there is hardly any food. When this fat is stored, something also changes in the hormone balance in late summer and autumn. Fat and muscle cells become less sensitive to insulin. This is useful, as it keeps the blood sugar level stable when there is little food. This decreased insulin sensitivity (insulin resistance) disappears in the spring when the extra fat is used and the horses come out skinny again in winter. Especially robust breeds are very good at adapting to low food conditions. But this does mean that problems arise when they live the whole year in a food-rich environment.

Accumulation of health problems

A constantly overweight horse faces a pile-up of related problems. Fat tissue also produces hormones. If an animal has a lot of fat tissue, relatively large amounts of hormones are released. In humans, we know that these extra hormones cause high blood pressure, inflammation, and atherosclerosis. Moreover, heavy accumulations of fat often (internally) inflame, leading to damage of the veins and the production of even more hormones that, for example, also cause insulin resistance. This creates more and more problems. Insulin resistance can lead to laminitis, a very painful and sometimes life-threatening disease.

Is my horse overweight?

Overweight is the primary risk factor for EMS. On the internet, you can find scorecards (body condition score) that you can use to assess your horse to see if it is overweight. For example, look at the crest of the neck (is it large and hard?), the fat storage at the shoulder (is it thick and cushiony?), and the fat storage at the tail (do you see cushions here?). A thick and hard crest of the neck can indicate insulin resistance. Fat pads in the shoulder and tail can indicate overweight. In a horse with a healthy weight, you should be able to easily feel the ribs but not see them very clearly. If your horse is overweight, it is essential for it to lose weight.

Does my horse have a risk of EMS?

To determine if your horse is at risk for EMS, it is essential to know whether your horse is not overweight. Because more than half of Dutch recreational horses are overweight, as horse owners, we are often somewhat blinded to this. It can also be more challenging to see in some breeds, for example, because they naturally have a baroque neck or are sturdier in build. Therefore, it can be a good idea to seek the opinion of your veterinarian. He or she can also perform blood tests to determine if your horse is insulin resistant or at risk for it. Your veterinarian can also help you make a plan for responsible weight loss.

Conclusion: EMS is a complex problem

EMS is truly a syndrome. This means that multiple health problems play at the same time, which influence and reinforce each other. Unfortunately, there is no blood test or other test that identifies EMS. EMS is diagnosed purely based on symptoms. It is a serious disease that requires action. The most important thing is to prevent your horse from becoming overweight, and if it already is, work on healthy weight loss. There is no medication that solves the syndrome. If you have a horse with EMS, you can ensure that you support the horse as much as possible. You do this by getting the horse to a healthy weight, limiting sugars, and restoring hormonal balance with, for example, cannabinoids or triphala