02/23/2026
A great clarification!
CARBOHYDRATES
Fermentable, hydrolyzable, nonstructural, structural, fiber, sugar, starch, soluble, insoluble, water-soluble, ethanol-soluble… UGH!
Are you feeling overwhelmed as you try to manage your equine with metabolic issues? Small wonder, given how incredibly diverse carbohydrates are. To make matters worse, laboratory analytical and equine physiological terms are used interchangeably, adding to the confusion. Let’s straighten this out.
Laboratory terms: Nonstructural carbohydrates (NSC) are the contents of the plant cell – simple sugars (glucose, fructose), disaccharides (sucrose), starch, and long- and short-chain fructans. These can be further quantified by different extraction methods. Starch is extracted using enzyme analysis, sugars and fructans can be extracted with water (water soluble carbohydrates – WSC), and simple sugars and disaccharides with ethanol (ethanol soluble carbohydrates – ESC). NSC, representing all the cell contents, is the sum of WSC and starch. NSC is not “sugar” nor is it the sum of anything other than WSC + starch.
Equine terms: Hydrolyzable carbohydrates (HC) are sugars and starch that are hydrolyzed (broken down) and absorbed as glucose. Fermentable carbohydrates are resistant to mammalian hydrolysis and instead are fermented, the main source of calories for the horse. Because carbohydrates absorbed as glucose (HC) have a profound effect on glucose and thereby insulin, these are especially worth understanding. So how do we get there using laboratory terms? Easy! Just add ESC + starch.
NSC is a good laboratory index for plant biology but it’s not informative for equine digestive physiology. If you’re using NSC to quantify grass hay and using an arbitrary safety threshold of 10-12% NSC, you will likely reject 80-90% of all samples tested because fructans could be making up a large portion of the NSC, yet fructans play no role in glucose or insulin dynamics. Knowing the individual components that make up NSC also helps to understand what is driving the glucose/insulin response, for example, grain-based products that are high in starch, or legumes like clover and alfalfa that use starch (as opposed to fructans) as their storage carbohydrate.
Twenty-five years of ECIR membership experience and feedback have guided our recommendation of 10% or less HC when managing the diet of equines with hyperinsulinemia in order to avoid laminitis*.
*Adjust for level of work if necessary. Exception: Equines on SGLT2 inhibitors for refractory hyperinsulinemia have different requirements. Ask for help if you do not have access to feeding protocols specific for SGLT2 therapy.