Equine Metabolic Syndrome (EMS) and insulin resistance are two closely related metabolic disorders that are gaining increasing attention in the equine world. EMS is a term that encompasses several conditions, including:
- Peripheral Cushing’s syndrome
- Pseudo-Cushing’s syndrome
- Hypothyroidism
- Central (omental) obesity
- Insulin resistance syndrome
At the core of EMS is a problem with how the horse’s body responds to insulin, a vital hormone responsible for regulating blood sugar. If not managed properly, insulin resistance can lead to serious conditions such as laminitis.
What Is Insulin Resistance in Horses?
Insulin resistance (IR) occurs when a horse’s cells, especially in the muscle and liver, become less responsive to the effects of insulin. As a result, more insulin is needed to manage the same amount of blood glucose.
How It Works:
- A horse eats a meal high in non-structural carbohydrates (NSC) like sugar or starch.
- The carbs are broken down into glucose, which enters the bloodstream.
- Insulin is released by the pancreas to signal cells to absorb glucose.
- In an insulin-resistant horse, cells don’t respond properly, so insulin levels remain elevated longer.
- Persistent high insulin levels increase the risk of laminitis and other metabolic issues.
Causes of Insulin Resistance in Horses
Several factors can contribute to the development of insulin resistance:
- High-NSC diets: Grains, molasses, and lush pastures rich in sugar and starch. (NSC >12%)
- Obesity: Overweight horses, especially those with fat pads on the neck, rump, or above the eyes, are more prone to IR.
- Breed susceptibility: Ponies, Morgans, Arabians, Quarter Horses, and some Warmbloods may be genetically predisposed.
- Age: Horses over 20 years old are more likely to develop insulin resistance, often linked with pituitary dysfunction (Cushing’s).
- Lack of exercise: Inactivity contributes to obesity and reduced insulin sensitivity.
- Genetic predisposition to laminitis: Horses with a family or personal history of laminitis are at higher risk.
The Role of Non-Structural Carbohydrates (NSC)
NSC refers to the simple sugars, starches, and water-soluble carbohydrates in horse feed. These are quickly digested in the small intestine, leading to a spike in blood glucose, which triggers insulin release.
In insulin-resistant horses, high NSC feeds can:
- Cause prolonged elevated insulin levels
- Lead to dysbiosis and “leaky gut” in the hindgut
- Trigger cortisol release from the adrenal glands
R
- Result in laminitis, even in otherwise healthy horses
How to Recognise Insulin Resistance in Horses
Horses affected by IR often show the following signs:
- Overweight or “easy keeper”
- Cresty neck or fat pads over the rump, shoulders, or above the eyes
- History of laminitis, especially without a clear cause
- Abnormal hoof rings or slow-growing hooves
- Patchy fat despite a lean frame
- Poor energy levels or performance
The Dangers of Untreated Insulin Resistance
The most serious complication of insulin resistance is laminitis.
A study at the University of Queensland demonstrated that artificially elevating insulin levels in ponies induced Obel Grade 1 laminitis within 36 hours, progressing to Grade 2 in all four feet. Even horses that appear normal can develop laminitis from prolonged insulin elevation. Feeding high NSC feeds that cause an insulin spike is a major cause of insulin resistance.
Can Insulin Resistance Be Reversed?
Yes, in many cases, insulin resistance can be improved through proper diet and controlled exercise.
Research shows that:
- Weight loss and increased activity restore insulin sensitivity in obese horses.
- Even lean horses with regional fat benefit from a customised exercise plan.
- Horses with Cushing’s disease require strict dietary management due to the hormonal imbalances contributing to IR.
Feeding the Insulin-Resistant Horse
A successful feeding plan for insulin-resistant horses must focus on:
Key Goals:
- Weight loss, if the horse is overweight
- Low-NSC diet to prevent glucose and insulin spikes
- Balanced vitamins and minerals to maintain hoof, coat, and immune health
Suitable Forages and Feeds
Safe Feeds for Insulin-Resistant Horses:
- Weather-damaged lucerne (alfalfa)
- Stemmy or mature grass hay
- Low-NSC coconut meal (e.g., premium copra meal)
- Beet pulp (soaked and drained)
- Soybean hulls
- Full-fat soy, Vegetable oils (as calorie boosters for underweight horses)
- Always test hay for NSC if possible. Aim for <10–12% NSC for EMS horses.
Feeds to Avoid:
- Ryegrass or oat hay
- Any feed containing grains or grain by-products
- Heavily molassed sweet feeds
Lush spring or frost-stressed pasture
- Feeds without clear NSC content labeling
These feeds are typically high in sugar and starch >12%) . For insulin-resistant horses, they can rapidly raise insulin levels, triggering laminitis in susceptible individuals.
Getting the Balance Right
While calorie restriction is essential for weight loss, don’t compromise on protein, vitamins, and mineral intake. Deficiencies can lead to poor coat, hoof, and skin condition and may reduce immune function or performance.
Premium Feeds for Insulin Resistance - Why Coolstance Copra
Modern nutrition companies now offer specialised low-NSC feeds. One of the most effective ingredients is copra meal (CoolStance coconut meal), which is:
- Very low in starch and sugar (<12% NSC)
- Rich in digestible fibre and oil-based energy
- Naturally GMO- and chemical-free
- Highly palatable and safe for metabolic horses
Products like those from Stance Equitec offer tailored solutions, expert advice, and feed formulation tools to help owners manage horses with insulin resistance.
Final Thoughts: Managing Equine Insulin Resistance
To keep insulin-resistant horses healthy and laminitis-free:
- Choose forages and feeds with <10–12% NSC, such as Coolstance copra
- Avoid grains and sugary feeds
- Feed balanced minerals such as Vitastance, especially for overweight horses on restricted diets
- Monitor weight and fat distribution closely
- Combine proper feeding with regular, controlled exercise
- Consider forage testing and consult your vet or equine nutritionist
