Equine Metabolic Syndrome: Diet Management for EMS

What Is Equine Metabolic Syndrome?

Equine Metabolic Syndrome (EMS) is a collection of metabolic abnormalities that significantly increase your horse's risk of laminitis — a painful, potentially life-threatening hoof condition. EMS is one of the most common endocrine disorders in horses and ponies, and understanding it is the first step toward managing it effectively.

At its core, EMS involves insulin dysregulation. This means your horse's body either produces too much insulin in response to sugars and starches, or its tissues don't respond properly to insulin (a state called insulin resistance). Over time, chronically elevated insulin levels can trigger laminitis, even without any obvious dietary "mistake."

Horses and ponies with EMS typically share some recognisable traits:

• Regional adiposity — fat deposits on the crest of the neck, over the tailhead, behind the shoulder, and around the sheath or udder
• Generalised obesity or a body condition score above 7 out of 9
• A history of laminitis or recurring foot soreness
• Difficulty losing weight despite what seems like a restricted diet

EMS is not the same as Cushing's disease (PPID), although the two conditions can occur together. Your vet can distinguish between them using blood tests, including a resting insulin level and an oral sugar test.

Why Diet Is the Cornerstone of EMS Management

Unlike many health conditions, EMS cannot be solved with a single medication. While your vet may prescribe metformin or recommend other interventions, dietary management is the single most important tool you have for keeping an EMS horse healthy.

Every time your horse eats sugars and starches, its blood glucose rises, and insulin is released. In an EMS horse, that insulin response is exaggerated and prolonged. The goal of dietary management is simple in principle:

1. Reduce the intake of non-structural carbohydrates (NSC) — the sugars and starches that trigger insulin spikes
2. Promote gradual, sustainable weight loss if the horse is overweight
3. Meet all essential nutrient requirements so the horse stays healthy while on a restricted diet

Getting this balance right is crucial. A diet that's too restrictive can lead to nutrient deficiencies, muscle wasting, or even hyperlipidaemia (a dangerous mobilisation of fat in the blood, especially in ponies). A diet that's too generous will perpetuate the metabolic problems.

Understanding Non-Structural Carbohydrates (NSC)

NSC is the combined total of water-soluble carbohydrates (WSC) and starch in a feed or forage. For EMS horses, the widely accepted target is to keep total dietary NSC below 10% on a dry matter basis.

To put this in perspective:

• Lush spring and autumn grass can contain 15–30% NSC or higher
• Average meadow hay ranges from 8–18% NSC depending on grass species, maturity, and growing conditions
• Most commercial sweet feeds and cereal-based mixes contain 25–40% NSC
• Soaked hay typically has its NSC reduced by 20–40%, though results are variable

The only reliable way to know the NSC content of your hay is to have it tested. This is a critical point — you simply cannot tell by looking at hay whether it's safe for an EMS horse.

Step-by-Step Dietary Management for EMS Horses

1. Restrict or Eliminate Pasture Access

This is often the hardest step for owners, but it's one of the most impactful. Pasture grass — especially during spring growth, sunny autumn days, and periods of frost stress — can contain dangerously high NSC levels.

For horses with active laminitis or poorly controlled EMS, complete removal from pasture is usually necessary, at least initially. Options include:

• A dry lot or surfaced paddock with hay provided
• A track system that encourages movement without access to lush grass
• A grazing muzzle for horses with mild or well-controlled EMS (note: muzzles reduce intake by approximately 30–80% depending on design and grass length, but they don't reduce NSC concentration)

Grazing muzzles are a compromise, not a solution. They work best for horses that are metabolically stable and at a healthy weight.

2. Choose the Right Forage

Forage (hay or haylage) should form the foundation of every EMS horse's diet. Aim for:

• Late-cut, mature meadow hay — these tend to be lower in sugar and higher in fibre
• NSC tested below 10% on a dry matter basis — the gold standard
• A feeding rate of 1.5–2% of current bodyweight per day (dry matter) for weight maintenance, or 1.5% of ideal bodyweight for weight loss

Never feed less than 1.5% of bodyweight in forage dry matter. Restricting forage below this level increases the risk of gastric ulcers, stereotypic behaviours, and hyperlipidaemia.

If your hay tests above 10% NSC, soaking it in cold water for 30–60 minutes (or warm water for 15–30 minutes) can help reduce sugars. However, soaking is inconsistent — it may remove anywhere from very little to nearly half the WSC, depending on water temperature, hay type, and how finely the hay is chopped. Soaking also leaches minerals and vitamins, so you'll need to compensate for those losses.

Steaming hay is not a substitute for soaking when it comes to NSC reduction. Steamers are designed to reduce respirable dust and bacteria, not to lower sugar content.

3. Eliminate High-Starch Concentrates

Remove all cereal-based feeds from the diet. This includes:

• Sweet feeds and coarse mixes containing oats, barley, or maize
• Most traditional competition or conditioning feeds
• Bread, carrots in large quantities, apples, and sugary treats

If your EMS horse needs supplementary calories (which is uncommon — most need fewer calories, not more), choose feeds that derive their energy from digestible fibre and oil rather than starch and sugar. Look for feeds specifically labelled as suitable for horses with metabolic conditions, and check that the combined sugar and starch content is below 10%.

4. Balance Vitamins and Minerals

This step is frequently overlooked, and it matters enormously. A forage-only diet will almost certainly be deficient in several key nutrients:

• Copper and zinc — often low in UK and European hays
• Selenium — variable by region but commonly inadequate
• Vitamin E — degrades rapidly in stored hay
• Salt (sodium chloride) — virtually absent from hay

A good-quality ration balancer or vitamin and mineral supplement designed for horses on forage-based diets will fill these gaps without adding significant calories or NSC. Choose a product that provides minerals in bioavailable forms (chelated or organic minerals) where possible.

Magnesium supplementation is often discussed in the context of EMS, as magnesium plays a role in insulin signalling. While some horses may benefit, the evidence for magnesium as a standalone treatment for insulin resistance is limited. It's best used as part of a balanced mineral profile rather than in isolation at high doses.

For a clear picture of what's missing in your horse's current diet, analysing your horse's diet with a tool like MyEquibalance can help you identify specific nutrient gaps and build a properly balanced feeding plan.

5. Use Appropriate Carriers for Supplements

EMS horses still need a small "meal" to deliver their supplements. Suitable low-NSC carriers include:

• Unmolassed sugar beet pulp (soaked) — approximately 5% NSC
• Unmolassed chaff — check the label; some chaffs contain molasses or added sugars
• Low-calorie, high-fibre balancer pellets — specifically formulated for good doers

Keep the total amount small — a handful or two is usually sufficient to deliver a supplement effectively.

6. Encourage Movement

Diet alone is only part of the equation. Regular, appropriate exercise improves insulin sensitivity independently of weight loss. Even walking in-hand for 20–30 minutes a day can make a meaningful difference.

Track systems or large dry lots that encourage natural movement throughout the day are far more beneficial than small, static paddocks where horses stand still.

Of course, if your horse is experiencing active laminitis, box rest or very restricted movement may be necessary until your vet gives the all-clear to resume exercise.

Monitoring Progress

Managing EMS is not a one-off adjustment — it's an ongoing process. Here's how to track whether your approach is working:

Body Condition Scoring

Learn to body condition score your horse using the 1–9 Henneke scale, and assess them every two weeks. Aim for a gradual weight loss of approximately 0.5–1% of bodyweight per week. Rapid weight loss is dangerous, particularly in ponies and donkeys.

Weigh Tape Tracking

A weigh tape isn't perfectly accurate, but it's excellent for tracking trends. Record measurements fortnightly under consistent conditions (same time of day, before feeding).

Veterinary Blood Tests

Your vet can monitor resting insulin and glucose levels, as well as ACTH if Cushing's disease is a concern. Re-testing every 3–6 months helps you see whether dietary changes are translating into metabolic improvements.

Hoof Health

Keep a close eye on hoof quality and any signs of foot soreness. Regular farrier visits (every 5–6 weeks) and prompt attention to any changes in gait are essential.

Common Mistakes in EMS Dietary Management

Even well-intentioned owners can fall into traps. Here are the most common mistakes:

• Relying on a grazing muzzle as the sole intervention — muzzles help, but they don't address NSC levels in the grass itself
• Feeding "low-calorie" feeds without checking NSC — some products marketed as "lite" still contain significant sugar and starch
• Over-restricting forage — starving an EMS horse creates new health problems without solving the metabolic ones
• Ignoring mineral balance — deficiencies in copper, zinc, and other trace minerals can worsen metabolic function and hoof quality
• Assuming all hay is safe — hay NSC content varies enormously; testing is essential
• Adding oil excessively — while oil is a low-NSC energy source, EMS horses rarely need extra calories, and excess oil can contribute to weight gain

When to Involve Your Vet

Dietary management should always work alongside veterinary care, not replace it. Consult your vet if:

• Your horse shows any signs of laminitis (shifting weight, increased digital pulse, reluctance to walk)
• Weight loss stalls despite appropriate dietary restriction
• You suspect concurrent Cushing's disease (PPID), which is common in older horses with EMS
• You're unsure about insulin test results or what they mean for management

In some cases, your vet may recommend metformin or levothyroxine to support metabolic management alongside dietary changes. These medications are tools to be used in conjunction with diet, not substitutes for it.

The Bottom Line

Equine Metabolic Syndrome is a serious but manageable condition. The horses and ponies that do best are those whose owners commit to a consistent, well-planned dietary strategy built around four pillars:

1. Low-NSC forage at appropriate quantities
2. Restricted or eliminated pasture access
3. Balanced vitamins and minerals without unnecessary calories
4. Regular exercise appropriate to the horse's soundness

It takes patience, and it takes precision. But with the right feeding plan and close monitoring, most EMS horses can live comfortable, active lives with a dramatically reduced risk of laminitis. Your horse's metabolism may be working against you — but a well-managed diet puts you firmly back in control.