What is NSC in Nutrition? Understanding Non-Structural Carbohydrates

October 4, 2025 •

2 min read

Did you know that controlling the type and amount of dietary carbohydrates is a critical factor for the health of many animals, particularly equines? Understanding what is NSC in nutrition is the first step towards preventing serious metabolic and digestive disorders, such as laminitis and colic.

Quick Summary

Non-structural carbohydrates (NSC) are the easily digestible sugars and starches in animal feed. Excessive amounts can lead to metabolic and digestive issues like insulin resistance and laminitis in sensitive animals, requiring careful dietary management to ensure wellness.

Key Points

Definition: NSC stands for Non-Structural Carbohydrates, which are the sugars, starches, and fructans found inside plant cells, providing readily available energy to animals.
Equine Importance: High NSC levels are a significant concern for horse health, contributing to conditions like insulin resistance, laminitis, and colic by disrupting the hindgut's microbial balance.
Ruminant Role: For ruminants, NSC is a key energy source that fuels the rumen microbes responsible for digestion and productivity, though balance is still required.
Measurement: The most accurate way to determine NSC content is through laboratory analysis, which reports percentages of starch and water-soluble carbohydrates (WSC).
Management: Controlling NSC is crucial for sensitive animals and can be achieved by feeding low-NSC forage, soaking hay, managing pasture access, and selecting controlled commercial feeds.
Species-Specific Needs: Not all animals require a low-NSC diet; high-performing animals may need more for energy, while metabolically challenged animals need less.

What are Non-Structural Carbohydrates (NSC)?

In animal nutrition, Non-Structural Carbohydrates (NSC) refers to the easily digestible carbohydrates found within plant cells, distinct from the fibrous cell walls. These are a readily available energy source for animals and are primarily composed of starch, water-soluble carbohydrates (WSC), and ethanol-soluble carbohydrates (ESC). Starch is common in grains, while WSC includes simple sugars and fructans, particularly in cool-season grasses. Unlike fiber, which ferments in the hindgut, NSC provides a quicker glucose and insulin response.

NSC vs. NFC: What's the Difference?

Non-Fiber Carbohydrates (NFC) is a calculated value sometimes used in feed analysis, but it's a broader measure than NSC and includes other compounds like pectin. NSC is a more precise measure of sugars and starches, determined by laboratory analysis, and is preferred for animals with metabolic concerns.

The Critical Role of NSC in Equine Health

For horses, managing NSC intake is crucial. Their digestive system is adapted for a high-fiber, low-sugar diet. High-NSC feeds can overwhelm the small intestine, allowing excess sugars and starches into the hindgut. This can disrupt the microbial balance and pH, leading to serious health issues such as laminitis, Equine Metabolic Syndrome (EMS), colic, and Polysaccharide Storage Myopathy (PSSM). However, performance horses may benefit from higher NSC to replenish energy stores.

The Function of NSC in Ruminant Nutrition

Ruminants, like cattle and sheep, have a digestive system that effectively ferments carbohydrates in the rumen. NSC is a valuable, readily fermentable energy source for their rumen microbes, supporting productivity. A balanced diet of both NSC and fiber is important, as excessive NSC can still cause issues like acidosis.

Calculating and Managing NSC in Feed

Accurate NSC levels are essential for effective management. While feed tags may offer some information, a laboratory analysis provides the most precise figures.


Comparing High vs. Low NSC Feeds for Horses	Feed Type	Example Foods	Typical NSC Range	Best For	Considerations
High NSC	Oats, Corn, Barley, Molasses	40–75%+	Performance horses with high energy needs and no metabolic issues.	Can cause digestive and metabolic problems in sensitive horses.
Low NSC	Beet Pulp, Soy Hulls, Alfalfa Hay, Timothy Hay	<12%	Horses with metabolic issues (IR, EMS), laminitis-prone, or easy keepers.	Often higher in digestible fiber and fat for energy.

For horses sensitive to NSC, consider these strategies:

Forage Selection: Choose low-NSC hay and pasture, such as mature timothy, and have hay tested.
Hay Soaking: Soaking hay can reduce soluble sugar content.
Controlled Feeds: Use commercial feeds formulated with controlled NSC for sensitive horses.
Pasture Management: Limit grazing for sensitive horses, especially when NSC levels in grass are high.
Small Meals: If feeding grain, divide it into smaller, multiple meals.

Conclusion

Understanding what is NSC in nutrition is vital for animal owners, particularly those with horses. Non-structural carbohydrates are energy sources, but excessive intake can cause serious health problems in sensitive animals. Careful feed selection, analysis, and management are key to supporting optimal metabolic and digestive health. Resources like Safergrass.org offer valuable information on pasture management and NSC testing.

Frequently Asked Questions

NSC is composed of the easily digestible starches and sugars inside plant cells, which are broken down in the small intestine of horses. Fiber, or structural carbohydrate, makes up the plant's cell walls and is fermented by microbes in the hindgut.

Excessive high NSC can overwhelm the horse's small intestine. Any undigested NSC then ferments rapidly in the hindgut, disrupting the microbial balance, which can lead to metabolic issues like insulin resistance, laminitis, and colic.

Yes, but for different reasons. NSC is a critical and desirable energy source for the rumen microbes in cattle. The main concern is ensuring a balanced diet that avoids excessive NSC, which could lead to digestive problems like acidosis.

The most accurate method is to send a sample to a laboratory for analysis. For commercial feeds, check the guaranteed analysis on the feed tag for maximum percentages of starch and sugars.

For horses with conditions like Equine Metabolic Syndrome (EMS) or a history of laminitis, veterinarians and nutritionists often recommend a total diet with an NSC of 10% or less.

Yes, soaking hay in water can help leach out some of the water-soluble carbohydrates, including simple sugars. This is a common practice for reducing the NSC content of hay for sensitive horses.

NSC is a specific measurement of starches and water-soluble carbohydrates. NFC (Non-Fiber Carbohydrates) is a broader category calculated by difference, which can be less accurate for managing specific health conditions.