Insulin Problems – Forget about NSC

Hay or pasture is a major component of any horse’s diet, and is likely to be virtually the complete diet in animals that are obese.  Since insulin resistance is often part of the reason why a horse or pony becomes obese, it’s important to know how to determine if their diet contains a safe amount of carbohydrate but not all carbohydrates are created equal.

Carbohydrates in forage plants include soluble and insoluble fiber (cellulose, hemicellulose, pectins, galactans, beta-glucan), starch, simple and complex sugars and fructans. NSC = Non-Structural Carbohydrates. These are plant cell carbohydrates that are free in the cell and not part of the cell wall.  NSC includes starch plus water soluble carbohydrates – simple sugars, plant sugars and fructans.

So far it sounds like looking at NSC would be smart if you have a horse with high insulin. The problem is, NSC also includes things that do not influence insulin, most  notably fructans.  By including fructans in the evaluation of a forage’s safety/suitability, many perfectly appropriate hays are being rejected and owners are spending a lot more time, analysis fees and energy than they need to be.

The answer is to look at the tests that are most relevant to insulin rising – starch and ESC.  ESC = Ethanol Soluble Carbohydrates.  It is the best measure of the simple sugars that can trigger an insulin response when they are digested and absorbed.

Does it make that much difference?

Evaluation of 221 grass  hay samples from Oregon (K. Gustafson, personal communication) showed if using 10% NSC as a cutoff for hays that would need to be soaked or not used, 87% would be called a problem. If the threshold is raised to 12% NSC, 70% were identified as problematic.  When 10% ESC + starch was used as the guideline, only 4% were an issue. Hays passing the 10% or less ESC + starch test were subsequently fed to horses diagnosed as having Equine Metabolic Syndrome without issues.

An argument is sometimes made that NSC should be used because the other carbohydrates contribute calories and most of these horses need to lose weight or have their calorie intake controlled.  However, a lot more than fructan goes into determining the DE [Digestible Energy = calories] of a forage and the hay analysis also actually provides a DE number. That is what should be used to determine caloric content and how much to feed, not NSC.

The take-home message here is that the scientific studies on Equine Metabolic Syndrome and laminitis are all now clearly showing that insulin is the issue. When evaluating possible hays for these horses, the focus needs to be on elements that can cause an insulin rise – ESC + starch. It’s time to stop talking about NSC.

Eleanor Kellon, VMD


About Dr. Kellon

Graduate of University of Pennsylvania Veterinary School. Owner of Equine Nutritional Solutions,, industry and private nutritional consultations, online nutritional courses. Staff Veterinary Expert at Uckele Health and Nutrition.
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2 Responses to Insulin Problems – Forget about NSC

  1. Dr. Kellon says:

    The 10% is the sum of ESC + starch so yes, you would be over.

  2. Chris McSherry says:

    Dr. Kellon, a question for clarification please. “10% ESC + starch” Is the “+starch” part of that 10%? or in addition to. Suppose I have grass hay that is 10% ESC (for my IR horse) and 1.2% starch, totaling then 11.2. Am I then out of range or still within? Thank you.

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