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Equine Metabolic Syndrome (EMS) in Horses: Causes, Signs & Low-NSC Diet Management
dysbiosis ems equine feeding feeds gut health Information Articles laminitis leaky metabolic nsc syndrome

Equine Metabolic Syndrome (EMS) in Horses: Causes, Signs & Low-NSC Diet Management

What Is Equine Metabolic Syndrome (EMS) in Horses? 

Equine Metabolic Syndrome (EMS) is a condition characterised by insulin resistance, abnormal fat distribution, and a high risk of laminitis. It’s commonly seen in “easy keeper” breeds — horses and ponies that gain weight easily — and is closely linked to obesity and diets high in sugar and starch. 

EMS includes several overlapping disorders, including: 

  •  Insulin resistance 
  •  Pseudo-Cushing’s syndrome 
  •  Peripheral Cushing’s 
  •  Hypothyroidism 
  •  Central (omental) obesity 
 These terms all describe similar metabolic dysfunctions that disrupt how the horse’s body handles blood glucose and insulin.

How Does EMS Affect Horses? 

When a horse eats feed high in non-structural carbohydrates (NSC >12%) — such as grains, sweet feeds, or lush pasture — glucose is released into the bloodstream. In a healthy horse, insulin signals cells to absorb glucose, which is then used for energy or stored. 

In an insulin-resistant horse, the cells don’t respond properly to insulin, so glucose remains in the blood. The body compensates by producing more insulin. This leads to chronically elevated insulin levels, or “insulin spikes”, after meals. Over time, this disrupts metabolism and increases the risk of laminitis. 

Key Signs of Equine Metabolic Syndrome 

You may suspect EMS if your horse shows: 

  •  Obesity or excess weight, especially with: Fatty deposits along the crest of the neck Fat pads over the rump, shoulders, or sheath/udder 
  •  History of laminitis, especially unexplained or recurring episodes 
  •  Lethargy or reduced performance 
  •  Abnormal bloodwork showing elevated insulin and/or glucose levels 
 Horses with Cushing’s disease (PPID) often display similar insulin resistance and are considered part of the EMS spectrum.

What Causes EMS in Horses? 

 EMS is largely a result of modern feeding and management practices. 

The main causes include: 

  •  High NSC diets (grains, molasses, lush pasture) ie modern diets with NSC >12%. 
  •  Lack of exercise 
  •  Obesity 
  •  Genetics (ponies and easy-keeping breeds are more prone) 

 EMS is more common in domesticated horses that have limited opportunity for movement and are often overfed calorie-dense feeds not found in their natural diet.

Understanding Non-Structural Carbohydrates (NSC) 

NSC = Starch + Water Soluble Carbohydrates (WSC) 

This includes: Glucose,  Fructose,  Sucrose,  Starch,  Fructan These carbohydrates are rapidly digested in the small intestine and absorbed into the bloodstream as glucose — which triggers insulin release. In insulin-resistant horses, this process goes awry.  

High-NSC Feeds Include: 

 Cereal grains (oats, corn, barley) Molasses By-products like rice bran, wheat bran, and pollard Ryegrass and oat hays Lush spring pastures 

Low NSC Feeds include

Low NSC feeds (<12%) include copra meal, and most roughages (hay)

What Level of NSC Is Safe for EMS Horses? 

 While individual tolerance varies, field experience suggests that NSC content should be kept below 12%, and ideally below 10%, for horses diagnosed with or prone to EMS. 

Feeding NSC levels above 12% can lead to dangerous insulin spikes and increase the risk of laminitis. Research has shown copra meal does not cause an insulin spike 

 Managing EMS Through Diet 

 Diet is the most effective way to manage EMS and prevent associated complications like laminitis. 

 Recommended Practices: 

  •  Feed low-NSC forage: Use tested hay with <10% NSC; avoid ryegrass or spring pastures unless tightly controlled. 
  •  Eliminate grain and sweet feeds 
  •  Avoid treats with molasses or sugars 
  • Avoid feeds that cause insulin spikes
  • Feed little and often rather than two big feeds a day
  • Use hay nets to limit intake
  •  Provide a balanced mineral supplement such as VitaStance 
  •  Introduce low-starch, high-fibre feeds (such as coconut meal) 
  •  Ensure daily exercise to promote glucose metabolism and weight control 
Important: Forages can vary widely in NSC levels — from <10% to over 30%. Consider forage testing (e.g., through labs like Dairy One) to ensure suitability. 


 The Link Between EMS and Laminitis 

Research from the Dr Pollitt at the University of Queensland has shown that chronically high insulin levels can directly cause laminitis, even in otherwise healthy horses. EMS is now recognised as a leading risk factor for laminitis, making careful dietary management critical. 

 Horses with Cushing’s disease (PPID) also have insulin resistance and are at a similar risk of laminitis if not managed correctly. 

 Why Are So Many Modern Horses Affected? 

 Many equine diseases — including colic, tying-up, gastric ulcers, acidosis, Cushing’s, poor performance, and behavioural issues — can be traced back to modern feeding practices that diverge sharply from a horse’s natural diet. 

 Wild horses consume high-fibre, low-sugar forage across long hours of grazing. In contrast, domesticated horses are often fed large meals rich in grain, starch, and sugar  twice daily — disrupting gut health, metabolism, and hormone balance...causing metabolic chaos

 Key Takeaways: Feeding Horses with EMS 

  •  EMS is a metabolic disorder linked to insulin resistance and obesity. 
  •  Insulin spikes caused by high-NSC feeds are the primary concern. 
  •  Feeds should contain <12% NSC, ideally <10%, to manage EMS.
  •  EMS horses are at high risk for laminitis — prevention is key. 
  •  Test your forage, read feed labels, and avoid sugary treats. 
  •  Exercise and weight management are essential parts of EMS care.


NSC Content of some Auustralian feeds. Only feeds with < 12% NSC should be considered for horses susceptible to EMS. When you have selected a suitable feed, it should be introduced into your horse's diet slowly, as some EMS horses are extremely sensitive and will still react to a feed, even though it may seem suitable. It is also important to feed little and often to avoid insulin spikes associated with the expectation of feeding.




dysbiosis ems equine feeding feeds gut health Information Articles laminitis leaky metabolic nsc syndrome