Insulin resistance in horses is a growing concern, especially in those prone to metabolic disorders like Cushing’s Disease (PPID) or Equine Metabolic Syndrome (EMS). One of the biggest contributing factors to insulin dysregulation is a diet high in NSC – non-structural carbohydrates. Understanding what NSC is, how it affects your horse’s body, and how to manage it through diet is essential for preventing serious conditions like laminitis.
What Are NSCs in Horse Feeds?
NSC (Non-Structural Carbohydrates) refers to the portion of carbohydrates that includes:
- Sugars (e.g., glucose, sucrose, fructose)
- Starches
- Fructans
These are rapidly digestible carbohydrates found in grains, molasses, sweet feeds, and even some pastures especially in spring or stressed conditions. High-NSC feeds are digested in the small intestine, where they quickly enter the bloodstream and cause a sharp rise in blood glucose and insulin levels.
What Is Insulin Resistance in Horses?
Insulin resistance occurs when a horse’s body becomes less sensitive to the effects of insulin, the hormone responsible for moving glucose out of the bloodstream and into cells. As a result, insulin levels stay high, even when blood sugar is normal or low.
Over time, this state of insulin dysregulation places enormous stress on the horse’s system and is a major risk factor for:
- Laminitis
- Cushing’s/PPID complications
- Obesity and cresty necks
- Poor energy metabolism
Why High NSC Diets Are a Problem for Metabolic Horses
Feeding a high-NSC diet to a horse with insulin resistance or PPID can trigger laminitic episodes and worsen metabolic health. These horses have difficulty regulating blood sugar, and when NSCs are digested rapidly, insulin spikes cause inflammation, vascular dysfunction, and ultimately damage to the laminae in the hoof.
Even healthy horses can develop insulin resistance if they are:
- Fed excess grain or sweet feed
- Grazing lush, high-sugar pasture
- Overweight and under-exercised
- Genetically predisposed (e.g., certain pony and Morgan-type breeds)
Recognising Signs of Insulin Resistance
Some of the common signs of insulin resistance in horses include:
- Fat deposits along the neck (cresty neck) and tailhead
- Recurrent or chronic laminitis
- Increased thirst and urination
- Difficulty losing weight
- Lethargy or poor exercise tolerance
These signs may overlap with conditions like Cushing’s Disease, and many horses have both insulin resistance and PPID.
Managing Insulin Resistance Through Diet
The key to managing insulin resistance is strict control of NSC intake.
This includes:
- Feeding a low-NSC hay (ideally <10–12% NSC)
- Soaking hay for 30–60 minutes to reduce sugar content
- Avoiding grains, sweet feeds, molasses, and high-starch pellets
- Using a low-NSC balancer or mineral supplement to meet vitamin and mineral needs
- Providing slow-feed hay nets to promote natural foraging without overconsumption
- Limiting or managing access to lush pasture, especially during spring and early morning when sugar levels are highest
Final Thoughts
Insulin resistance and high-NSC diets are tightly linked. For horses with metabolic issues, especially those with Cushing’s Disease or a history of laminitis, managing NSC intake is non-negotiable. The right feeding program, combined with veterinary support, can prevent flare-ups and help your horse live a longer, healthier life.
