EMS in Horses: The Science Behind Insulin Dysregulation, Diet & Laminitis Risk
Equine Metabolic Syndrome (EMS) is a complex metabolic disorder in horses and ponies. Understanding insulin dysregulation, body condition, forage and diet is central to managing the associated risk of laminitis.
For owners of horses prone to weight gain or laminitis, managing nutrition can be challenging.
Advice about sugar, starch, grazing, forage and supplements can sometimes be contradictory.
The science is clearer when these factors are considered together.
This guide explains what current veterinary evidence tells us about EMS, insulin dysregulation, diet, exercise and nutritional management.
Important: EMS is a veterinary health condition. This article is intended for educational purposes and does not replace veterinary diagnosis or advice. A horse with suspected EMS, insulin dysregulation or laminitis should be assessed by a veterinarian.
What is Equine Metabolic Syndrome?
Equine Metabolic Syndrome is a metabolic disorder associated with an increased risk of hyperinsulinaemia-associated laminitis.
The central feature of EMS is insulin dysregulation (ID). This can include abnormally high insulin concentrations at rest or following feeding, as well as reduced tissue sensitivity to insulin.
Obesity is common in horses with EMS, but it is important not to assume that every overweight horse has EMS — or that a horse must be obese to have insulin dysregulation.
Recent veterinary literature confirms that lean horses can also demonstrate insulin dysregulation, meaning that objective assessment is more reliable than judging metabolic status from body condition alone.¹
Why does insulin matter?
Insulin is a hormone involved in maintaining normal glucose and energy metabolism.
Following the consumption of carbohydrate, glucose becomes available for absorption and insulin helps regulate how the body responds.
In horses with insulin dysregulation, the insulin response can become abnormally high.
This is particularly important because hyperinsulinaemia is strongly associated with an increased risk of endocrinopathic laminitis.
Current veterinary understanding therefore places insulin dysregulation at the centre of EMS management rather than treating body weight alone as the defining feature.¹ ²
EMS and laminitis
Laminitis is the major clinical concern associated with EMS.
Research has established an association between prolonged or excessive insulin responses and laminitis, commonly referred to as hyperinsulinaemia-associated laminitis (HAL).
This is why managing an EMS-prone horse involves more than simply trying to make the horse thinner.
The objective is to address the factors that influence metabolic health, including:
Body condition
Total energy intake
Forage quantity and composition
Dietary non-structural carbohydrates
Grazing
Physical activity
Insulin regulation
Appropriate veterinary monitoring
Early recognition and sustained management are important because recurrent or chronic laminitis can result in significant hoof pathology and long-term welfare consequences.¹
What are the signs of EMS?
EMS cannot be diagnosed from appearance alone, but certain characteristics may increase suspicion.
These can include:
Easy weight gain
Difficulty losing weight
Generalised obesity
Regional fat deposits
A pronounced or cresty neck
Abnormal fat distribution
A history of laminitis
Breed or individual predisposition
However, physical appearance is not enough to determine whether a horse has insulin dysregulation.
A horse can appear relatively lean and still have abnormal insulin responses, while obesity itself does not establish a diagnosis of EMS.¹
How is EMS diagnosed?
Veterinary diagnosis focuses primarily on identifying insulin dysregulation.
A single resting insulin measurement can provide useful information, but it has limitations. A normal basal insulin concentration does not necessarily exclude insulin dysregulation.
Dynamic tests can therefore be useful because they evaluate the horse’s insulin response following a controlled carbohydrate challenge.
The oral sugar test (OST) is one such test and is widely used in clinical assessment of insulin dysregulation.
The exact test and interpretation should be determined by your veterinarian because insulin measurements can be affected by factors including the assay used, feeding, management and individual variation.¹
This is one reason why owners should not attempt to diagnose EMS simply by comparing an individual insulin result with a number found online.
Diet: the cornerstone of EMS management
Dietary management is fundamental when managing horses with EMS or insulin dysregulation.
The objective is not simply to remove every source of carbohydrate.
Instead, veterinary recommendations generally focus on controlling energy intake and dietary non-structural carbohydrates (NSC) while ensuring that the horse’s nutritional requirements are still met.¹ ²
NSC includes sugars and starches found in plants.
For an insulin-dysregulated horse, reducing excessive dietary NSC can help minimise exaggerated post-feeding insulin responses.
Current recommendations commonly favour forage with relatively low NSC content, particularly for horses at increased risk of endocrinopathic laminitis.¹ ²
Why forage matters
Forage should normally form the foundation of the horse’s diet.
However, not all forage has the same nutritional composition.
The sugar and starch content of hay and pasture can vary depending on:
Plant species
Stage of maturity
Growing conditions
Season
Weather
Harvesting conditions
Storage
For this reason, forage analysis can be extremely useful when managing an insulin-dysregulated horse.
The ECEIM consensus statement recommends considering forage with an NSC content below approximately 10% for horses with insulin dysregulation, although individual dietary requirements must always be considered.²
How much forage should an EMS horse receive?
This is an area where individualisation is particularly important.
An overweight horse generally needs controlled energy intake to achieve gradual weight loss.
The ECEIM consensus statement describes a forage-based ration of approximately 1.25–1.5% of bodyweight as dry matter per day as a commonly recommended starting range for weight reduction, with more severe restriction requiring careful monitoring.²
However, excessively restricting forage can create its own welfare and nutritional problems.
Weight-loss programmes should therefore be carefully managed rather than simply reducing forage as much as possible.
The objective is gradual, controlled weight loss while maintaining adequate nutrition and forage access appropriate to the individual horse.
What about grass?
Pasture can present a particular challenge for horses with insulin dysregulation.
Grass carbohydrate concentrations can change substantially throughout the year and under different environmental conditions.
For some EMS-prone horses, unrestricted grazing may therefore provide a significant source of dietary NSC.
Management may involve:
Restricted grazing
A suitable grazing muzzle
A bare or heavily grazed paddock
Dry-lot management
Controlled access to pasture
Replacing some or all pasture intake with analysed forage
The appropriate strategy depends on the horse’s metabolic status, body condition, history and current laminitis risk.
Can soaking hay reduce sugar?
Yes — but the evidence needs to be interpreted carefully.
Soaking can reduce water-soluble carbohydrates in hay, but the amount removed varies considerably according to the forage and soaking conditions.
The ECEIM consensus statement reports reductions in water-soluble carbohydrates following prolonged soaking, while also highlighting practical concerns including nutrient losses and microbial growth in warm conditions.²
A veterinary review published in 2026 similarly recognises soaking as one possible strategy for reducing soluble sugar intake when appropriate.¹
This means soaking should not be treated as a guaranteed way of making unsuitable hay suitable.
Where possible, testing the forage is preferable to relying on assumptions about its sugar content.
Should grain and high-starch feeds be avoided?
For horses with EMS or significant insulin dysregulation, veterinary nutritional recommendations generally emphasise avoiding feeds that contribute substantial amounts of rapidly available carbohydrate.
The ECEIM consensus statement recommends excluding grain and cereal-based complementary feeds in the management of obese insulin-dysregulated horses.²
Instead, the ration can be built around suitable forage, with a low-calorie vitamin and mineral balancer or other appropriate nutritional support where necessary to meet requirements.
Every feed should have a purpose.
Exercise and EMS
Exercise is another important component of metabolic management.
Physical activity can improve insulin sensitivity and increase glucose uptake by skeletal muscle. It can also contribute to controlled weight loss when appropriate.¹
However, exercise must be considered in the context of the horse’s physical condition.
A horse with active laminitis should not simply be exercised because exercise is considered beneficial for metabolic health.
Veterinary assessment is essential before introducing or increasing exercise in a horse with suspected or active laminitis.
For a comfortable horse without active laminitis, a progressive exercise programme can form an important part of long-term metabolic management.
Does every overweight horse have EMS?
No.
This is an important distinction.
Obesity is frequently associated with EMS, but obesity and EMS are not interchangeable diagnoses.
Similarly, some horses with insulin dysregulation may not appear obviously obese.
This is why modern veterinary recommendations place increasing emphasis on objective assessment of insulin regulation rather than relying solely on body condition.¹
Can EMS be reversed?
EMS is best considered a condition requiring ongoing management rather than something for which there is a simple “cure”.
Improving body condition, controlling dietary NSC, managing grazing and introducing appropriate exercise can improve metabolic health and insulin regulation in many horses.
However, an individual horse’s susceptibility does not necessarily disappear simply because its body condition improves.
Long-term management is therefore important.
A horse with a previous history of metabolic problems or laminitis may remain susceptible even after reaching an appropriate body condition.
What role can supplements play?
Supplements should be considered within the complete diet, not as a substitute for appropriate management.
For an EMS-prone horse, the first questions should be:
Is the total calorie intake appropriate?
Is the forage suitable?
Is grazing appropriately controlled?
Are sugar and starch being managed?
Are vitamins and minerals being supplied adequately?
Only after these fundamentals have been addressed should supplementation be considered.
A suitable supplement may help provide targeted nutritional support where there is a clear nutritional rationale.
However, no supplement can compensate for unrestricted access to unsuitable forage, excessive calorie intake or poor overall management.
What should you look for in a metabolic support supplement?
When choosing a complementary feed for an EMS-prone horse, consider:
1. Sugar and starch contribution
The product should fit into the horse’s overall dietary strategy.
2. Feeding rate
A small feeding rate does not automatically make a product suitable, but the total nutritional contribution should be understood.
3. Ingredient transparency
The ingredients and their quantities should be clearly declared wherever appropriate.
4. Nutritional purpose
Every ingredient should have a reason for being included.
5. Overall diet
The supplement should complement the horse’s forage and feeding programme rather than attempting to replace good nutritional management.
A science-led approach to metabolic management
Managing EMS is not about finding one “magic” ingredient.
It is about bringing several factors together:
FORAGE
Choose and manage forage carefully, considering its nutritional composition.
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ENERGY INTAKE
Control calories sufficiently to achieve gradual weight loss where required.
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NSC MANAGEMENT
Reduce unnecessary exposure to high levels of dietary sugar and starch.
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GRAZING
Manage pasture access according to the individual horse’s metabolic risk.
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EXERCISE
Use appropriate physical activity to support fitness, weight management and insulin sensitivity when the horse is physically able.
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MONITORING
Work with your veterinarian to assess insulin regulation and monitor laminitis risk where appropriate.
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TARGETED NUTRITIONAL SUPPORT
Use supplementation where there is a clear nutritional rationale.
This is the approach we believe makes sense: look at the horse as a whole rather than focusing on a single ingredient or intervention.
Dr Silver’s approach
At Dr Silver, we believe good supplementation starts with understanding the horse.
Our philosophy is simple:
Horse First. Science Led.
That means looking beyond marketing trends and asking what a formulation is actually designed to provide.
For horses requiring nutritional support as part of a carefully managed metabolic programme, our Metabolic range is designed around targeted nutritional formulation rather than simply adding a long list of ingredients.
TARGETED METABOLIC SUPPORT
If you’re looking for targeted nutritional support to complement a carefully managed diet, explore our EMS & Insulin Support PRO.
Supplements are one part of the picture.
Forage, feeding, body condition, exercise and veterinary oversight remain fundamental.
When should you speak to your vet?
Veterinary advice should be sought if your horse:
Has previously suffered from laminitis
Shows signs of laminitis
Is repeatedly gaining weight despite controlled feeding
Has unexplained regional fat deposits
Is suspected of having insulin dysregulation
Has recurrent metabolic problems
Requires significant dietary restriction
Is showing unexplained changes in body condition
If laminitis is suspected, veterinary assessment should be sought promptly.
Frequently Asked Questions
Can an EMS horse eat grass?
Some horses with EMS may tolerate carefully controlled grazing, while others require much stricter pasture restriction. Management should be based on the individual horse’s metabolic status and laminitis risk.
What is the best hay for an EMS horse?
There is no single “best” hay for every horse. Generally, forage with a relatively low NSC content is preferred for insulin-dysregulated horses, and forage analysis can help determine its nutritional composition.¹ ²
Does soaking hay remove sugar?
Soaking can reduce water-soluble carbohydrates, but the reduction varies according to the forage and soaking conditions. It should not be assumed that soaking automatically makes unsuitable forage suitable.²
Can EMS horses have treats?
Treats can contribute additional sugar and calories. For horses requiring strict dietary management, treats should be considered part of the total ration rather than ignored because they are given in small quantities.
Can exercise improve insulin sensitivity?
Yes. Research supports exercise as a useful component of metabolic management in horses, provided the horse is physically able to exercise safely.¹
Is EMS the same as PPID?
No. EMS and PPID are different endocrine disorders, although a horse can have both. Veterinary assessment is required when endocrine disease is suspected.
Can supplements cure EMS?
No supplement should be presented as a cure for EMS. Management centres on appropriate diet, weight control, pasture management, exercise where appropriate and veterinary monitoring.
References & Further Reading
1. Bertin, F.R. (2026). Diagnosis and management of equine metabolic syndrome. Equine Veterinary Education, 38, 471–480. DOI: 10.1111/eve.70094.
2. Durham, A.E., Frank, N., McGowan, C.M., et al. (2019). ECEIM consensus statement on equine metabolic syndrome. Journal of Veterinary Internal Medicine, 33, 335–349.
3. Frank, N., Geor, R.J., Bailey, S.R., Durham, A.E. & Johnson, P.J. (2010). Equine Metabolic Syndrome. Journal of Veterinary Internal Medicine, 24, 467–475.
4. Frank, N. & Tadros, E.M. (2014). Insulin dysregulation. Equine Veterinary Journal, 46, 103–112.
5. Longland, A.C. & Byrd, B.M. (2006). Pasture nonstructural carbohydrates and equine laminitis. Journal of Nutrition, 136, 2099S–2102S.
Dr Silver
Horse First. Science Led.
This article is provided for general educational purposes only and is not intended to diagnose, treat or cure any disease. Veterinary advice should always be sought for horses with suspected EMS, insulin dysregulation or laminitis.
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