How to Read and Interpret a Forage Analysis for Your Horse: Complete Guide to ESC, WSC, NSC, HC, Fructans, Fiber, Protein, and Minerals

For many horses, forage is more than 80–100% of the diet. A forage analysis (or “hay test”) is simply a lab report that tells you what’s really in that hay or pasture: calories, protein, fiber, carbohydrates, and key minerals. When you know how to interpret a hay test, you can make calmer, more confident feeding decisions—especially for metabolic horses, seniors, and performance partners.

This guide will help you interpret a forage analysis without fear. We’ll explain ESC, WSC, NSC, HC, fructans, fiber, protein, and minerals in plain language, then show how to use those numbers as a data point—not a rigid rule.

What Is a Forage Analysis and Why It Matters

A forage analysis is a laboratory measurement of the nutrients in hay, haylage, or pasture. Most equine panels report crude protein, digestible energy, fiber (ADF, NDF), several carbohydrate measures (ESC, WSC, starch, NSC, sometimes HC), and minerals like calcium, phosphorus, magnesium, potassium, iron, copper, zinc, and selenium.

Because horses are designed to eat forage nearly all day, forage analysis is the most powerful nutrition tool you can use. It helps you:

• See whether your forage is low NSC hay suitable for metabolic horses.
• Identify mineral gaps the rest of the ration or a balancer should address.
• Adjust calories (digestible energy) for easy keepers vs hard keepers.
• Spot potential red flags before they become health problems.

Modern equine nutrition, including the NRC (2007) and university extension programs, emphasizes building the diet “forage first,” then balancing for remaining nutrients. A hay test makes that process less guesswork and more clarity.

How to Collect a Proper Hay Sample

You’ll get the best information from your forage analysis if your sample truly represents what your horse is eating. Several university and extension resources emphasize that poor sampling is the #1 source of misleading hay tests.

Simple Steps to Sample Hay Correctly

• Define a “lot”: One field, one cutting, similar storage (e.g., all 2nd cutting orchard grass from Field A, stored in the same barn).
• Use a hay probe (core sampler): 3/8"–5/8" diameter, attached to a brace or drill. Insert into the butt end (string/twine side) of square bales; sample from the rounded side of round bales.
• Take 15–20 cores per lot from randomly chosen bales.
• Combine and mix all cores in a clean bucket, then take a sub-sample (usually ½–1 lb) for the lab.
• Place in a labeled, airtight bag (often provided by the lab), remove excess air, and send promptly.

For pasture, labs often provide specific instructions for clipping grass at grazing height from multiple random locations. Follow their directions closely, as moisture and plant stage matter more for pasture samples.

How Labs Report Results: Dry Matter vs As-Fed

Most equine forage analyses report nutrients on a dry matter (DM) basis. This means the water has been mathematically removed so you can compare hay, pasture, and feeds fairly. Some reports also show an “as-fed” column, which includes moisture.

• Use DM values when comparing hays or designing a balanced diet.
• Use as-fed values when calculating how many pounds to actually feed (if your nutritionist requests it).

If you’re unsure, it’s safe to assume that the carbohydrate values used to decide whether hay is “low NSC” are on a DM basis unless the lab clearly states otherwise.

Understanding the Major Parts of a Forage Analysis

Crude Protein (CP)

Crude Protein (CP) estimates the total protein in the forage by measuring nitrogen and multiplying by a factor (usually 6.25). It doesn’t tell you about individual amino acids, but it’s a good starting point.

• Grass hay often ranges ~8–14% CP.
• Legume hay (alfalfa) often ranges ~16–22% CP.

CP supports muscle and tissue repair, hooves, haircoat, immune function, and growth. Overfeeding protein is usually more of an environmental and stall-air issue (ammonia) than a direct health risk for healthy horses, but chronically low protein can limit topline and recovery.

Digestible Energy (DE)

Digestible Energy (DE) is the amount of energy (calories) your horse can actually use from the forage, usually reported in megacalories per pound (Mcal/lb) or per kilogram.

• Typical hays range roughly from 0.8–1.1 Mcal/lb DM depending on plant type and maturity.
• Higher DE = more calories per pound (good for hard keepers, performance horses).
• Lower DE = fewer calories per pound (often helpful for easy keepers and metabolic horses).

DE is one of the best tools for matching your hay to your horse’s body condition score and workload.

Fiber: ADF and NDF

Acid Detergent Fiber (ADF) and Neutral Detergent Fiber (NDF) describe the structural parts of the plant cell wall. ADF relates more to digestibility, while NDF relates more to bulk and how much a horse can eat.

• Higher ADF → older, stemmier hay → lower digestibility and DE.
• Higher NDF → more bulk → horses feel full sooner, may eat less.
• Extremely low NDF (rare in hay) would mean very lush, highly digestible forage.

For most horses, we want hay that has enough NDF for chew time and gut motility, but not so much ADF that they can’t maintain weight.

Carbohydrates in Forage: ESC, WSC, Starch, NSC, HC, Fructans

This is where many owners feel overwhelmed. Different labs use slightly different carbohydrate systems, but most equine reports will list some combination of:

• ESC – Ethanol-Soluble Carbohydrates (simple sugars).
• WSC – Water-Soluble Carbohydrates (sugars + fructans).
• Starch – Mostly from seeds/grains; some in stem/leaf tissues.
• NSC – Non-Structural Carbohydrates (commonly WSC + starch).
• HC – Hydrolyzable Carbohydrates (ESC + starch, excluding fructans).
• Fructans – Often estimated as WSC – ESC (cool-season grasses).

We’ll break these down in more detail in the next section, including what matters most for metabolic horses forage choices.

Key Minerals: Ca, P, Mg, K, Fe, Cu, Zn, Se

Most equine forage analyses at least report calcium and phosphorus; many also include magnesium, potassium, iron, copper, zinc, and selenium. These minerals affect bone strength, nerve and muscle function, hoof quality, immune health, and the horse’s ability to manage oxidative stress.

• Calcium (Ca) & Phosphorus (P): Essential for bone, teeth, muscle contraction. We aim for a Ca:P ratio of about 1.5–2:1 in the total diet.
• Magnesium (Mg): Important for nerve and muscle function; often adequate in forage but can be on the low end in some regions.
• Potassium (K): Generally high in forages, very important for muscle and acid–base balance. Can be problematic for HYPP horses or some metabolic horses in extreme cases.
• Iron (Fe): Commonly high in hay; excess iron can interfere with copper and zinc absorption.
• Copper (Cu) & Zinc (Zn): Often low in forage relative to modern recommendations and best-practice ratios; vital for hooves, skin, joints, and immune function.
• Selenium (Se): Very region dependent. Some areas are deficient; others approach maximum safe levels, so testing matters.

This is where a good ration balancer or targeted mineral supplement earns its keep—by filling in gaps your forage can’t cover on its own.

Carbohydrate Measures in Detail: ESC, WSC, Starch, NSC, HC, Fructans

The phrase “carbohydrates in forage” covers a lot of ground. For horses, we pay special attention to the non-structural carbohydrates (NSC) because of their relationship to blood sugar, insulin levels, laminitis risk, PSSM, and overall metabolism.

ESC – Ethanol-Soluble Carbohydrates

ESC measures the simple sugars that dissolve in 80% ethanol—mainly monosaccharides and disaccharides (think glucose, fructose, sucrose). These are quickly digested and absorbed in the small intestine.

• ESC is the portion of WSC that directly impacts blood sugar and insulin.
• For EMS/IR/PPID and PSSM horses, we often focus on ESC + starch (HC) to manage glycemic load.

WSC – Water-Soluble Carbohydrates

WSC measures carbohydrates that dissolve in water, including simple sugars plus fructans. Fructans are chain-like carbohydrates that are not digested in the small intestine; they move to the hindgut and are fermented there.

• WSC will usually be higher than ESC because it includes both sugars and fructans.
• Subtracting ESC from WSC gives a rough estimate of fructan content for cool-season grasses.

Starch

Starch is a storage carbohydrate found mostly in seeds and grains, but there can also be meaningful amounts in some forages. High starch intake can produce rapid spikes in blood sugar and insulin.

• In hay, starch is usually much lower than in cereal grains, but it’s still important for PSSM and metabolic horses.
• High-starch feeds are more problematic than most forages, but high NSC hay can contribute to total load.

NSC – Non-Structural Carbohydrates

NSC is a term used to describe the easily digestible, non-fiber carbohydrates in a feed. In practice, most equine forage labs and extension references define NSC as:

NSC = WSC + Starch (on a dry matter basis)

NSC is helpful when you want a single number to compare hays for metabolic, laminitic, or PSSM horses. However, it does not distinguish between sugars (fast insulin response) and fructans (hindgut fermentation).

HC – Hydrolyzable Carbohydrates

Hydrolyzable Carbohydrates (HC) are defined as the carbohydrates that are digested and absorbed in the small intestine—primarily simple sugars (ESC) plus starch. Many practitioners use:

HC = ESC + Starch

Because HC excludes fructans, it’s often the best indicator of glycemic and insulin response for metabolic and PSSM horses.

Fructans

Fructans are chains of fructose molecules stored in many cool-season grasses. They are not digested in the small intestine; instead, they reach the hindgut and are fermented by microbes. In large, sudden amounts, some fructan types have been associated with laminitis via disruption of the hindgut microbiome.

Fructans are rarely measured directly. Instead, we estimate them as:

Fructans ≈ WSC – ESC (for cool-season grasses)

Fructans are especially important for lush spring and fall pasture, where they can spike with sunlight and cool nights. Long-cured hay often has lower fructans than the original pasture, but still may carry some load.

Comparison Table: ESC, WSC, Starch, NSC, and HC

Which Values Matter Most for Different Types of Horses

Every horse is an individual, and there is no one perfect number that works for every situation. The following are common target ranges and priorities often used by veterinarians and nutritionists, always on a dry matter basis unless stated otherwise.

Metabolic Horses (EMS/IR/PPID)

For horses with Equine Metabolic Syndrome, insulin resistance, or PPID, many guidelines based on laminitis and EMS research recommend:

• NSC (WSC + Starch): Aim for ≤10–12% DM; many high-risk horses do best closer to 10% or below.
• HC (ESC + Starch): Preferably ≤10% DM when possible, because these are the carbs driving insulin response.
• DE: Moderate to lower DE forage to help manage body weight if the horse is overweight.

For some horses, soaking hay in cool water for 30–60 minutes can help reduce WSC (and thus NSC), but a forage analysis before and after soaking is ideal if you rely on this routinely.

PSSM Horses

Polysaccharide Storage Myopathy (PSSM) horses are particularly sensitive to starch and sugars. Many management programs recommend:

• HC (ESC + Starch): Keep as low as practical, often ≤10% DM.
• Total diet NSC: Often targeted at ≤10–12% DM when you combine forage and any concentrates.
• Provide extra calories from fat and highly digestible fiber sources rather than starch-rich grains.

Laminitic Horses (Current or History)

Laminitis risk is closely tied to total NSC intake, body condition, and abrupt changes in pasture/fructan intake. Recommendations often mirror EMS/IR targets:

• NSC: Aim for ≤10–12% DM, preferably closer to 10% for high-risk horses.
• HC: Keep as low as practical (ideally ≤10% DM).
• Fructans: Be especially careful with spring and fall pasture and rapid weather changes; avoid turnout when fructan risk is highest (bright sun, cold nights, stressed grass).

Ulcer-Prone Horses

For horses with or at risk for gastric ulcers, the main priorities revolve around forage availability and buffering more than a specific NSC cutoff:

• Provide frequent or near-continuous access to forage to buffer stomach acid and support chewing and saliva production.
• Choose hay with adequate fiber (ADF/NDF) and moderate DE so you can feed enough volume without excessive calories.
• Avoid very high-starch or high-NSC concentrates; use forage-based or low-NSC feeds when extra energy is needed.

Senior Horses

Senior horses may have dental issues, reduced digestive efficiency, and metabolic changes.

• Fiber: Prioritize softer, more digestible fiber (lower ADF) and consider soaked hay cubes or pellets if chewing is difficult.
• CP & DE: Many seniors need slightly higher protein and DE per pound to maintain topline and weight.
• Carbs: If the senior is also metabolic, follow the same NSC/HC guidelines as above.

Performance Horses

Performance horses need adequate calories, amino acids, and electrolytes to support workload and recovery.

• DE: Choose higher DE hay (often slightly lower ADF/high-quality grass or grass/alfalfa mix) to support energy needs.
• CP: Ensure sufficient protein, often 10–12%+ CP forage plus appropriate concentrate or balancer.
• Minerals: Forage often provides plenty of potassium but little sodium, so provide free-choice salt and/or electrolytes.
• Carbs: Many performance horses tolerate moderate NSC well; focus more on matching total DE to workload and maintaining a healthy body condition score.

How to Use ESC, WSC, NSC, and HC Together

Different labs may emphasize slightly different metrics, but the goal is the same: understand how much rapidly available carbohydrate your horse is consuming. A simple way to think about it:

• Step 1 – Check lab definitions: Confirm how your lab defines NSC (usually WSC + starch) and whether they provide ESC and HC.
• Step 2 – For metabolic & PSSM horses: Focus on HC (ESC + starch) first when available, since these carbs drive insulin response. Then ensure NSC (WSC + starch) is also in a safe range.
• Step 3 – For laminitis and pasture issues: Use WSC and fructan estimates (WSC – ESC) to gauge hindgut load and laminitis risk from lush grass.
• Step 4 – For healthy horses: Use NSC more as a general reference, not a reason to panic over a difference of 1–2 percentage points.

Also consider testing method: wet chemistry is generally preferred over NIR when precise NSC values are critical for high-risk horses.

Interpreting Regional Mineral Trends

Many forage analyses show similar patterns within a region. For example, surveys of hay from various areas often find:

• High iron (Fe) and sometimes manganese (Mn).
• Low or marginal copper (Cu) and zinc (Zn).
• Low selenium (Se) in many regions.
• High calcium and/or potassium compared to magnesium and phosphorus in some forages.

These patterns matter because minerals interact. Excess iron, for example, can interfere with copper and zinc absorption, contributing to hoof and immune issues even when the diet technically meets minimum Cu and Zn levels.

A forage mineral analysis lets you build a targeted, evidence-based mineral plan rather than guessing with generic supplements—which may add more iron or unbalanced minerals on top of an already skewed base.

Turning Test Results into Balanced Feeding Decisions

Here’s a practical way to move from numbers on the page to an actual feeding plan:

1. Start with forage amount: Ensure your horse is getting at least 1.5–2% of body weight per day in forage on a DM basis (e.g., 16–22 lb DM for a 1,100 lb horse).
2. Check DE vs body condition: If your horse is overweight, consider slightly lower DE hay; if underweight, look for higher DE, better-quality forage.
3. Evaluate CP: Confirm the forage provides enough crude protein for age and workload, then decide if you need additional protein from a ration balancer or concentrate.
4. Assess carbohydrates: Look at NSC and HC to decide whether your hay is appropriate for your horse’s health status. Metabolic, laminitic, and PSSM horses usually need lower NSC/HC; others may not.
5. Review minerals: Compare Ca, P, Mg, K, Fe, Cu, Zn, and Se to recommended ranges and ratios. Use a forage-focused balancer or supplement designed to fill those specific gaps.
6. Layer in concentrates only if needed: Add calories or specialized feeds only after the forage and mineral base is in place.

And most importantly: forage testing informs, but does not dictate, your decisions. It’s one powerful data point alongside your horse’s body condition, soundness, bloodwork, behavior, and veterinary guidance.

When to Retest Hay—and When You Don’t Need To

You don’t need to send every single load of hay to the lab, but retesting is wise when something meaningful changes.

Good Times to Retest

• You switch to a new field, cutting, or supplier.
• You’re managing a high-risk metabolic, laminitic, or PSSM horse and want confirmation that a new lot is still “low NSC hay.”
• Your horse develops a new health issue (e.g., laminitis, unexplained weight change) and you want to rule out forage as a contributor.
• You’re relying heavily on forage mineral balance and want to confirm formulation for a new year.

When You May Not Need to Retest Immediately

• You are still feeding from the same lot that was previously tested.
• Your horses are healthy, stable in weight, and performing well.
• The hay source is highly consistent year to year and you use a conservative, well-balanced ration balancer that buffers minor variation.

If in doubt, remember: forage analysis is relatively inexpensive and can prevent costly health problems later.

Quick Reference Cheat Sheet

• CP (Crude Protein): Supports muscles, hooves, hair, immune function. Aim for 8–14% in most grass hays, higher for growing, lactating, or some performance horses.
• DE (Digestible Energy): Calories per pound. Higher DE for hard keepers and performance horses; lower DE for easy keepers and metabolic horses.
• ADF/NDF: Fiber maturity and bulk. Higher ADF = lower digestibility; higher NDF = more “fill.”
• ESC: Simple sugars; drives blood sugar and insulin; key for IR/EMS/PPID and PSSM horses.
• WSC: ESC + fructans; used for NSC calculation and fructan estimation.
• Starch: Rapidly digestible carb; keep low for metabolic and PSSM horses.
• NSC (WSC + Starch): Total non-structural carbs. Metabolic/laminitic/PSSM target: ≤10–12% DM in forage, often closer to 10%.
• HC (ESC + Starch): Small-intestine-digestible carbs; best indicator of glycemic load when available.
• Fructans: Estimated as WSC – ESC; important for pasture laminitis risk.
• Minerals: Forage often high in Fe & K, low in Cu, Zn, Se; balancing these with a targeted supplement is usually essential.

FAQ: Forage Analysis, Carbohydrates in Forage, and Low NSC Hay

What is a “good” NSC level for metabolic horses?

Many veterinarians and nutritionists recommend forage NSC (WSC + starch) ≤10–12% DM for horses with EMS, IR, PPID, or a history of laminitis, with high-risk individuals often doing best closer to 10% or below. HC (ESC + starch) should also be kept as low as practical, ideally ≤10% DM. Always consider the total diet, not just the hay.

Do all horses need low NSC hay?

No. Healthy horses in good body condition without metabolic or PSSM issues can often thrive on moderate NSC forage. For them, it’s more important that the hay is clean, palatable, appropriately mature, and nutritionally balanced with their workload. NSC becomes a bigger priority when there are clear risk factors.

Is soaking hay always necessary to reduce sugars?

Not always. Soaking hay can lower WSC (and therefore NSC) but also washes out some minerals and may reduce palatability if overdone. It’s usually most helpful when your forage analysis shows borderline NSC for a high-risk horse and you cannot obtain lower NSC hay. Testing before and after soaking provides the most confidence.

How often should I repeat a hay test?

Retest when you change hay lots, suppliers, or regions, or when your horse’s health situation changes. If you purchase large, consistent lots and your horses are doing well, you may not need to test every load—but testing periodically keeps your feeding program grounded in reality.

Can I interpret a hay test without a nutritionist?

Yes—with guides like this, you can understand the basics and make better decisions. That said, a good equine nutritionist or veterinarian can help integrate your forage analysis with your horse’s body condition, hoof health, bloodwork, and medical history for a truly individualized plan.

Conclusion: Forage Analysis as a Compassionate Data Point

A forage analysis is not a report card for your hay, and it’s not a judgment on your horse care. It’s simply a snapshot of nutrients that lets you feed with more clarity and less guesswork.

When you understand what ESC, WSC, NSC, HC, fructans, fiber, protein, and minerals mean, you can look at a hay test and say, “I see what’s here, I see what’s missing, and I know how to support my horse better.” That’s the heart of forage-first, species-appropriate, compassionate care.

Use forage testing as a data point, not a rigid rule. Your horse’s eyes, feet, energy, and body condition will always have the final say—but now, you have the numbers to back them up.

Key References (for your internal use and veterinarian/nutritionist discussions)

• Equi-Analytical, “Glossary of Nutrient Terms” – definitions of ESC, WSC, NSC, NFC and related metrics.
• UC Davis and other laminitis/forage resources – forage testing methods, NSC = WSC + starch, and low-NSC recommendations for laminitis/EMS.
• University extension guides (e.g., UMN, Rutgers, others) – practical interpretation of hay analysis for horses, including DE, CP, fiber, and basic minerals.
• Nutrient Requirements of Horses (NRC, 2007) – foundation for modern equine nutrient recommendations.
• Regional forage mineral surveys – typical patterns of high iron/manganese and low copper/zinc/selenium in many hays.