Equine Metabolic Syndrome (EMS)

EMS in horses

Equine Metabolic Syndrome (EMS) is a syndrome that develops in the body due to a disturbed metabolism. In recent years, EMS has received increasing attention and more horses have been diagnosed with EMS. However, Equine Metabolic Syndrome is not a disease itself but rather a collection of multiple symptoms. The development of EMS is primarily caused by an imbalance between the horse’s energy requirements and energy intake from the diet. Therefore, providing an appropriate diet is crucial for managing horses with EMS. 

Equine Metabolic Syndrome
Synovium Myocare E muscle supplement for horses


Equine Metabolic Syndrome is a term used since 2002 for the physical symptoms caused by an impaired metabolism, which makes these horses more likely to develop Insulin Resistance (IR), obesity and laminitis 1.

Besides a dysfunctional metabolism, most horses diagnosed with EMS also suffer from a hormonal imbalance. An inappropriate diet is considered the main cause of the development of EMS, but more recent research suggests that the development of EMS may also depend on genetic factors in addition to the known environmental factors 2.

A diagnosis is often made after a horse has developed symptoms such as obesity and laminitis. Horses with these symptoms are then tested for Insulin Resistance to confirm the diagnosis of EMS.

Insulin resistance and EMS

One of the symptoms commonly seen in horses with EMS is insulin resistance. Insulin resistance often occurs in overweight horses that receive a diet that continuously exceeds the horse’s energy requirements.
Insulin resistance occurs when a horse’s cells no longer respond properly to insulin, which is an important hormone for regulating blood glucose levels 3. When blood glucose levels increase, after digesting a meal, the pancreas produces insulin.
Insulin stimulates the absorption of glucose by body cells, with extra glucose being stored in the liver, which helps to stabilise blood glucose levels 4.
The more glucose the horse’s diet contains, the more insulin is required to be taken up and stored by the body to keep blood glucose levels stable 5. If blood glucose levels increase continuously, body cells can become resistant to insulin 3.
In horses with insulin resistance, cells stop responding to amounts of insulin. The pancreas then produces more insulin to compensate, ensuring glucose is absorbed and stored 5.
Because the body has become resistant to insulin and is less responsive to this hormone, the insulin concentration becomes too high and the blood glucose levels remain too high for too long. This leads to inflammation in the body and increases the risk of laminitis in horses with IR 6.
Equine Metabolic Syndrome (EMS) - Synovium Horse Health

Body weight and Equine Metabolic Syndrome (EMS)

Obesity in horses is one of the symptoms most commonly seen in horses with EMS. Adipose tissue can accumulate all over the body in horses with obesity and EMS, or accumulate in specific areas, such as the neck, which is typical for EMS 7. Obesity, similar to insulin resistance, occurs when the diet contains too much energy in comparison to the requirements of the horse. Often, this is due to a misjudgement of the intensity of the daily exercise, resulting in the horse being provided with a diet containing too much energy compared to their daily energy requirements 1. The Body Condition Score scheme can be used to estimate whether the horse is receiving too much energy through their current diet 8. A score between 4 and 6 on the 9-point score system is considered the ideal score for a horse. Scores above 6 are too high and suggest that the horse receives a diet that exceeds their daily requirements. Horses with EMS often receive a score between 8 and 9 9.

Laminitis and Equine Metabolic Syndrome (EMS)

Laminitis is a disease where an inflammation develops between the hoof wall and the coffin bone 10. The hoof capsule, the non-living part of the hoof protecting the soft tissue of the hoof, is connected to the hoof bone by soft tissue called laminae 10.

In severe cases, the laminae can become detached and cause the coffin bone to tilt and pierce through the sole of the hoof 11. In cases where the laminae become detached and the coffin bone tilts, this can no longer be treated.

The development of laminitis has multiple causes, but in the case of EMS, it occurs due to the inflammation caused by IR and obesity 12.

Besides, in horses diagnosed with laminitis, their feed usually contains excessive amounts of sugar and starch. When the feed is high in sugar and starch, the digestive system is unable to digest all of it completely.

As a result, some of it passes to the intestines where these nutrients are fermented 13. This process kills the beneficial bacteria present in the hindgut, disrupting the hindgut microbiome composition. When bacteria die off, they produce toxins that enter the bloodstream 10. These toxins can enter the hoof through the bloodstream, causing inflammation and ultimately leading to laminitis 10.

Equine Metabolic Syndrome (EMS)

The Management of a Horse with EMS

When a horse is diagnosed with EMS, it is important to adjust their management to provide the horse with the right support and promote their health and well-being.

It is important to adjust management and prevent further health problems, especially when a horse has not yet developed symptoms like laminitis.

Currently, there is no treatment available to treat EMS. Reducing the amount of energy provided through the diet, especially starch and sugar, is one of the important adjustments to manage EMS 1.

This can be achieved by for example, reducing the amount of concentrate feed that is being fed. However, it is crucial for horses with EMS to consume sufficient roughage, and they should have access to 1.5% of their desired body weight in kilograms of roughage per day 1.

In addition to an appropriate diet, exercise is crucial to ensure gradual weight loss in horses 3.
Regular exercise is important to support weight loss but has also shown to have a positive effect on insulin resistance 14.
Losing too much weight too quickly is not desirable for the horse’s health.
A good rule of thumb is to ensure that horses lose no more than 1% of their body weight per week until they reach their desired body weight 9. By using the BCS the weight loss process can be monitored until the horse reaches the desirable weight.

As mentioned earlier, it is important to reduce sugar and starch intake. It is therefore important to limit the amount of concentrate feed a horse receives daily due to its high sugar and starch content.

However, sufficient vitamins and minerals are important for maintenance and various processes in the horse’s body.

Therefore, it is recommended to supplement the horse’s diet with a vitamin and mineral supplement when reducing concentrate feed, so that the horse’s daily needs are still met.

Synovium Prefit is an ideal supplement for horses to provide them with essential vitamins and minerals when their concentrate feed is reduced. The supplement contains high-quality nutrients that are important for the horse’s body.

Synovium Myocare-E is essential to provide horses with EMS the natural vitamin e that is required by the horse from their diet, but maybe reduced due to reduced grass consumption and diet.

Providing the horse with sufficient roughage is important for its well-being and (intestinal) health.

However, it is recommended to select a type of roughage that is low in energy. Using a slow feeder/hay net allows horses to consume roughage at a slower pace and in smaller portions throughout the day.

To ensure that the horse has enough roughage throughout the day, it is recommended to split the total amount of roughage into several smaller portions.

It is not recommended to give horses with IR and EMS access to grass due to the difficulty in controlling the amount of fructan in the grass, even though it is also a type of roughage 1. To ensure horses are turned out enough, it is recommended to turn them out in a paddock with access to enough low-energy hay.

Adjusting the diet, improving body condition and providing the horse with sufficient nutrients is not easy. It is therefore recommended to consult with an equine nutritionist and veterinarian to formulate a suitable diet and treatment plan for managing a horse with EMS.
Equine Metabolic Syndrome (EMS) - Synovium Horse Health


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4.           Röder, P.V., Wu, B., Liu, Y., Han, W. (2016) Pancreatic regulation of glucose homeostasis. Experimental & Molecular Medicine, 48(3):1-19.

5.           Kaczmarek, K., Janicki, B., Glowska, M. (2016) Insulin resistance in the horse: a review. Journal of Applied Animal Research, 44(1): 424-430.

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10.         Marcato, P.S., Perillo, A. (2020) Equine Laminitis. New insights into pathogenesis. A review. Large Animal Review, 26(6):353-363.

11.         Laskoski, L.M., Valadão, C.A.A., Dittrich, R.L., Deconto, I., Faleiros, R.R. (2016) An update on equine laminitis. Clinic and Surgery, 46(3):547-553.

12.         Johnson, P.J., Wiedmeyer, C.E., LaCarrubba. A., Ganjam, V.K., Messer, N.T. (2010) Laminitis and the Equine Metabolic Syndrome. Veterinary Clinics of North America:
Equine Practice, 26(2):239-255.

13.         King, C., Mansmann, R.A. (2004) Preventing laminitis in horses: Dietary strategies for horse owners. Clinical Techniques in Equine Practice, 2004;3(1):96-102.

14.         Freestone, J.F., Beadle, R., Schoemaker, R., Bessin, T., Wolfsheimer, K.J., Church, C. (1992) Improved insulin sensitivity in hyperinsulinaemic ponies through physical conditioning and controlled feed intake. Equine Veterinary Journal, 24(3):187-190.