NSC stands for non-structural carbohydrates, a measure of the sugars, starches, and fructans in horse feed. It’s the single most important number for evaluating how a feed or forage will affect your horse’s blood sugar and insulin levels. For healthy horses, NSC is worth monitoring. For horses prone to laminitis or metabolic problems, it’s critical.
What NSC Actually Measures
Plants store energy in two broad ways. Structural carbohydrates (fiber) form the rigid cell walls and are slowly fermented in the hindgut. Non-structural carbohydrates are the energy stored inside plant cells: simple sugars like glucose, fructose, and sucrose, plus longer sugar chains called fructans, plus starch. These are the components that get digested more quickly and drive blood sugar and insulin responses.
On a forage analysis report, NSC is calculated by adding water-soluble carbohydrates (WSC) and starch together. WSC captures the sugars and fructans. Starch is measured separately because it doesn’t dissolve in water. Together, they give you the total NSC percentage, which is the number you’ll see on feed labels and hay test results.
How Your Horse Digests NSC
The small intestine is the primary site for breaking down sugars and starch. Feed passes through this 70-foot tube in just one to three hours, so the window for digestion is short. Simple sugars, like those in molasses or leafy pasture grass, are absorbed efficiently. Starch from cereal grains is harder. Oats contain roughly 50% starch and corn about 70%, and the horse’s small intestine can only process so much at once.
When a grain meal is too large, undigested starch spills into the hindgut. This is where the problems start. Hindgut bacteria rapidly ferment that starch, producing lactic acid that drops the pH. As the environment turns acidic, beneficial microbes die off and release toxins. The result can be diarrhea, colic, or laminitis. This is why nutritionists recommend keeping a single grain meal below 0.5% of body weight, roughly 5 to 6 pounds for a 1,100 to 1,200 pound horse.
Why NSC Matters for Metabolic Health
Chronically high-NSC diets reduce insulin sensitivity and lower adiponectin, a hormone that helps regulate metabolism. Over time, this sets the stage for equine metabolic syndrome, a condition marked by insulin dysregulation, abnormal fat deposits, and a significantly increased risk of laminitis. Research published in the Journal of Veterinary Internal Medicine found that postprandial insulin concentration (the insulin spike after eating) is directly associated with laminitis risk in ponies fed high-NSC diets.
Horses with insulin dysregulation respond to dietary NSC very differently than healthy horses. A 2022 study tested meals with varying NSC levels and found that insulin-dysregulated horses had a clear threshold: anything above 0.1 grams of NSC per kilogram of body weight per meal triggered a significantly amplified insulin response. Horses without metabolic issues showed no such spike at the same intake levels. For a 500-kilogram (1,100 pound) horse, that threshold works out to just 50 grams of NSC per meal, a remarkably small amount.
NSC Levels in Common Feeds
Knowing the typical NSC ranges for different feeds helps you estimate what your horse is actually consuming:
- Grass hay: around 12% NSC on average, though individual cuttings range widely from 7% to 18% or more
- Alfalfa hay: roughly 11% NSC
- Bermudagrass hay: about 13.2% NSC
- Oat hay: approximately 22.1% NSC
- Barley hay: around 19.2% NSC
These are averages from the Equi-Analytical database. The actual NSC in your hay depends on the plant species, maturity at cutting, time of day it was harvested, weather conditions, and how it was stored. A hay that looks identical to the eye can vary by 10 percentage points or more in NSC content. This is why testing matters.
Common cool-season grasses or hay can contain 10% to 20% NSC. Even at the low end, a 500-kilogram horse eating 1.5% of its body weight per day in forage would consume about 750 grams of NSC daily. That’s well above the per-meal threshold for insulin-dysregulated horses, which is why managing both total intake and meal size is so important for at-risk animals.
Safe NSC Thresholds
For horses with equine metabolic syndrome, insulin dysregulation, or a history of laminitis, the standard recommendation is to keep total dietary NSC below 10%. The European College of Equine Internal Medicine’s consensus statement specifically recommends forage with less than 10% NSC to limit postprandial insulin responses in these horses. Grains, cereal-based feeds, fruit, carrots, apples, and commercial treats should generally be eliminated from the diet because of their high NSC content.
For healthy horses in moderate work, NSC is less of a concern. These horses handle normal pasture and hay without metabolic consequences. Still, keeping grain meals moderate and spreading them across the day protects the hindgut regardless of metabolic status.
How to Reduce NSC in Hay
If your hay tests above 10% NSC, soaking it in water before feeding is the most practical way to lower the sugar content. A 30-minute soak reduces NSC by roughly 29%, water-soluble carbohydrates by 32%, and starch by 17%. That’s often enough to bring a moderately high hay into an acceptable range. Longer soaking doesn’t necessarily help more. One study found that hay soaked overnight for 10 hours actually retained more NSC than hay soaked for just 30 minutes, likely because prolonged soaking allows microbial activity that complicates the process.
Soaking does wash out other nutrients too, so it’s a trade-off. You may need to supplement minerals lost in the process. The water should be discarded, not dumped where horses can drink it, since it concentrates the sugars you just removed.
How to Read a Forage Analysis
To get your hay’s NSC value, send a sample to an equine forage testing laboratory. The report will list WSC and starch as separate line items, usually expressed as a percentage of dry matter. Add them together and you have your NSC. Some labs calculate this for you, but not all do, so it’s worth knowing the formula: NSC = WSC + starch.
You may also see ESC (ethanol-soluble carbohydrates) on the report. This is the simple sugar fraction within WSC, representing the sugars most readily absorbed in the small intestine. Some nutritionists prefer using ESC plus starch as a tighter estimate of the carbohydrates that directly raise blood sugar, since fructans (included in WSC but not ESC) are fermented in the hindgut rather than absorbed in the small intestine. For most practical purposes, the WSC-plus-starch calculation gives you the standard NSC value that feed recommendations are based on.