How to Interpret Your Hay Analysis Results (Without a PhD in Forage Science)

So you’ve tested your hay — excellent. That alone puts you ahead of 99% of horse owners. But now you’re staring at a report full of numbers, percentages, and acronyms like ADF, NDF, and DE. What does it all mean? Which numbers actually matter? And how do you apply them to your horse’s feeding plan?

This guide cuts through the confusion and gives you a clear, horse-focused interpretation of hay analysis results. We’ll walk through the most important values step by step, with real-world context, red flags to watch for, and practical advice for making better feed decisions.

Relative Feed Value (RFV): Hay Analysis 101

Let’s start with one of the most misunderstood—but shockingly useful—numbers on your forage report: Relative Feed Value, or RFV. If you’ve never heard of it, don’t worry. Most horse owners haven’t. That’s not your fault—it’s the industry’s. But once you understand what RFV means, you’ll wonder how you ever made hay decisions without it.

🔍 What Is RFV?

RFV is a calculated index (not a direct measurement) that estimates how digestible your hay is and how much your horse will want to eat it. It’s derived from two fiber values:

• ADF (Acid Detergent Fiber) – The less ADF, the more digestible the hay.
• NDF (Neutral Detergent Fiber) – The less NDF, the more your horse will eat.

Put simply:

Low ADF + Low NDF = Higher RFV = More digestible, more palatable hay.

It’s like a report card for hay. Instead of memorizing 15 separate values, RFV gives you one easy number to work with.

💡 Why RFV Matters for Horse Owners

Here’s the deal: RFV is directly tied to calories and weight management. That’s priority number one when feeding hay—whether you’re trying to slim down a metabolic pony or fuel a hard-keeping Thoroughbred in work.

Use this cheat sheet to decode what the number means:

📌 Example:
Got a laminitic pony? Look for RFV under 90.
Skinny OTTB in training? Go over 100—maybe even 120+.
Average horse in light work? Stay in the 90–99 range.

RFV gives you a clear starting point when hay shopping.
If you’re overwhelmed by terms like TDN, DE, or NDF, start with RFV.

Then ask: “Does this hay help my horse gain, lose, or maintain weight?”
That’s the question RFV was born to answer.

Understanding “Dry Matter” vs. “As-Fed”

One important note before we dive into your hay report: most forage analyses come with two columns of numbers. One is labeled “As Fed” or “As Is,” and the other is labeled “DM” for Dry Matter.

• As Fed: This shows the nutrient values of the hay as you would feed it, with its natural moisture included. This is the real-world version—what your horse is actually chewing on.
• Dry Matter (DM): These values reflect the hay with all the water removed. It’s the concentrated nutritional profile of the forage when completely dried.

So why list both? Because water dilutes nutrients, and the DM column gives you the most accurate way to compare different types of forage.

🧠 So Which One Should You Use?

• Want to know what your horse is getting when you feed 20 lbs of hay?
  → Look at the As-Fed numbers.
• Comparing different types of hay or evaluating nutrient density?
  → Use the Dry Matter values. That’s the only way to compare apples to apples when moisture content varies.

Example: Dry Matter Affects Feeding Rate

Let’s say your horse weighs 1,100 lbs. He needs to consume about 2% of his body weight in dry matter per day—so 22 lbs of dry matter.

Now let’s compare how much forage he’d need to hit that target:

That’s right—your horse would need to graze over 6x more fresh pasture than hay to meet his fiber needs. Moisture matters.

Key Nutrients

A forage report may look like it was designed to confuse horse owners—but each number on that page tells a story. Here’s what matters most, what those values actually mean, and how to use them to make smart feeding decisions for your horse.

Moisture

Moisture is the amount of water in your hay, and it plays a big role in both nutritional quality and safety.

• ✅ Ideal range: 11–16%
  This is dry enough to prevent spoilage, but moist enough to preserve leaf integrity and palatability—especially in leafy hays like alfalfa.
• ⚠️ Too dry (less than 10%)
  Hay becomes brittle, dusty, and prone to leaf shatter. That means your horse loses out on nutrients, and you lose money to feed waste.
• 🚫 Too wet (more than 18%)
  Now you’re flirting with mold growth, spoilage, and even spontaneous combustion if stored improperly in bulk. Horses eating moldy hay are at risk for colic, respiratory issues, or worse.

Moisture won’t tell you about nutrient content—but it does tell you whether your hay is safe and usable. Always check it first.

Digestible Energy

Digestible Energy (DE) is your hay’s built-in calorie count, measured in megacalories per pound (Mcal/lb). It tells you how much usable fuel your horse is actually getting from the forage.

• 🟢 Typical DE range for hay: 0.75–1.0 Mcal/lb
  Lower numbers usually mean mature, stemmy hay. Higher numbers come from early-cut, leafy, nutrient-dense hay (like alfalfa or high-quality grass).
• 🐴 Maintenance-level horse (1,100 lbs): needs ~16.7 Mcal/day

That means:

• 22 lbs of hay at 0.75 Mcal/lb = just enough for maintenance
• 22 lbs of hay at 1.03 Mcal/lb = 22.6 Mcal — enough for light work or weight gain
• Lower DE hay? You’ll be reaching for grain, fat, or beet pulp to bridge the gap in horses with higher needs.

💰 Why Higher-DE Hay Can Be Smarter

Buying higher-DE hay may look more expensive per bale (in some situations it’s the same price!), but it often saves money (and hassle) long term. Why?

• You feed less to meet high energy needs
• You don’t need to buy and manage extra feeds or fat supplements
• It simplifies your feeding program, especially for barns with multiple horses
• Fewer feed changes = fewer digestive upsets

For hard keepers, performance horses, or growing foals, starting with higher-DE hay can reduce or even eliminate the need for added calories from grain or oil — which adds up quickly.

On the flip side, if you’ve got an easy keeper or a laminitic pony, a lower-DE hay may actually be your best tool for weight control—because you never actually want to give less than 1.5% body weight.

Crude Protein

Crude protein is a rough estimate of total protein in your hay, based on its nitrogen content. For most adult horses at maintenance, 10–12% CP (dry matter basis) is plenty. Horses in intense work, young growing horses, and broodmares in late gestation or lactation typically need 14–16% or higher.

Alfalfa tends to be naturally high in protein—15–22%—while mature grass hays can fall below 10%, especially if they were harvested late or overly mature. That’s where issues show up.

Hay that’s too low in CP may not support a healthy topline, hoof growth, or immune function—especially in horses with higher metabolic demands. Even if the calories are there, they can’t build muscle or repair tissue without enough protein.

If your hay tests low in CP, consider adding a ration balancer with essential amino acids, or top-dress with protein-rich feeds like alfalfa pellets or cubes. Protein is one of the most overlooked—and most critical—pieces of a balanced forage-based diet.

Lysine: The Limiting Amino Acid

Lysine is the most commonly deficient essential amino acid in equine diets—especially grass hay–based ones. And if lysine is low, your horse can’t fully use the rest of the protein in the diet, no matter how high the crude protein percentage is.

Why it matters:

• Lysine is required for muscle development, topline, collagen repair, hoof quality, and immune function.
• It plays a key role in the formation of tissue, hormones, enzymes, and antibodies.
• Young, growing horses, broodmares, and working horses have especially high needs.

💡 A diet with adequate lysine can support growth and repair more efficiently than one with higher crude protein but poor amino acid balance.

If your hay is low in lysine (which most are), the best solution is to feed:

• A ration balancer with added amino acids, or
• L-lysine as a standalone supplement (especially useful during stress, illness, or poor hoof/muscle condition).

ADF and NDF

These two fiber values—ADF (Acid Detergent Fiber) and NDF (Neutral Detergent Fiber)—give you a snapshot of how mature, coarse, and digestible your hay is. They’re critical for understanding how much your horse will get out of the hay—and how much they’ll want to eat it.

🟢 Ideal Ranges:

• ADF: 30–35% ( for performance horses, broodmares, weanlings)
• NDF: 40–50% (good digestibility and palatability)

If your hay has ADF over 45% or NDF over 65%:

It’s likely over-mature and low in nutritional value. That means fewer calories, less digestibility, and reduced voluntary intake—your horse may not even want to eat it. This kind of hay might still work for donkeys or easy keepers who need low-calorie forage, but it’s a poor choice for horses with higher nutritional needs.

Growing youngsters, lactating mares, and performance horses require more digestible, nutrient-dense hay—ideally with ADF around 30–35% and NDF around 40–50%. Hay above those ranges can’t support muscle development, milk production, or athletic effort.

High-ADF/NDF hay is diet hay. Great for weight loss, not for growth or work. As plants mature, fiber increases, protein and energy drop, and digestibility suffers. This is why high-ADF/NDF hay is usually not appropriate for:

• Weanlings or young horses
• Lactating mares
• Performance horses in heavy work

But for easy keepers or metabolic horses, hay with slightly higher ADF/NDF can be a smart choice—it fills them up without overloading calories.

Want low-calorie “diet” hay? Look for higher ADF and NDF.
Need weight gain or fuel for performance? Choose hay with lower ADF and NDF to improve digestibility and intake.

Understand NSC (Non-Structural Carbohydrates)

When it comes to choosing hay for horses with metabolic issues, NSC (non-structural carbohydrates) is one of the most critical numbers on the analysis. If your horse has laminitis, EMS, PPID (Cushing’s), or insulin resistance, ignoring sugar and starch content is asking for trouble.

But what exactly is NSC—and why do different labs and nutritionists calculate it differently?

What Is NSC?

NSC refers to the rapidly digestible carbohydrates in forage—essentially, the sugars and starches that spike blood glucose or disrupt the hindgut. It includes:

• Starch – Digested in the small intestine (unless overfed, in which case it hits the hindgut and causes chaos)
• WSC (Water-Soluble Carbohydrates) – Sugars and fructans that dissolve in water
• ESC (Ethanol-Soluble Carbohydrates) – Just the simple sugars (glucose, fructose, sucrose)

Most labs define NSC as either:

• NSC = WSC + Starch
• NSC = ESC + Starch

So… Which Should You Use?

Here’s the short version:

• WSC + Starch = more conservative, better for horses prone to laminitis or gut upset
• ESC + Starch = better estimate of glycemic response (relevant for insulin issues)

For hay and pasture, most equine nutritionists recommend using WSC + Starch, because fructans matter. They don’t spike blood sugar like simple sugars do, but they ferment rapidly in the hindgut—and that can trigger laminitis, even if blood glucose looks fine.

Tip: Estimate fructan content by subtracting ESC from WSC.

What’s a Safe NSC Level?

For metabolically sensitive horses, the general rule is:

• NSC < 12% (dry matter basis) = safer
• Some go as low as <10% for high-risk horses, but the difference is usually marginal in forage due to slow intake

Remember: you can’t guess NSC by color or texture. Some “stemmy” hay can test high, and some soft, green hay can be surprisingly low. Always test.

🌱 Hay Types & NSC

Certain hays tend to run lower in NSC:

• Warm-season grasses (like coastal Bermudagrass and teff) are often lower
• Cool-season grasses (like timothy, orchardgrass, and ryegrass) can be much higher—ryegrass is notoriously risky
• Surprisingly, alfalfa is often lower in NSC than grass hay and may be a safer option for some metabolic horses

Other factors that influence NSC:

• Stage of maturity (more mature = lower NSC, generally)
• Time of day cut (sugars peak in the afternoon)
• Curing speed (faster drying tends to preserve more sugar)
• Rainfall before baling (can reduce sugar content slightly)

If your horse is on a forage-based diet, and especially if they have health conditions, a hay analysis is your best friend. It lets you build the diet around actual numbers—not guesses.

Feeding without a forage test is like baking a cake without measuring cups: you might get lucky… but you probably won’t.

Minerals

Your hay can be loaded with minerals—or nearly barren. But even more important than the numbers themselves is how they interact with each other. When it comes to minerals, balance beats volume every time.

A comprehensive hay analysis will often list:

Iron (Fe) – Often excessive in hay, especially if you’re in a high-iron region or feeding from soil-contaminated bales

Calcium (Ca) and Phosphorus (P) – Aim for a 2:1 ratio, especially in young, growing horses

Zinc (Zn) and Copper (Cu) – Commonly deficient in grass hays and nearly always out of balance

Selenium (Se) – Can be dangerously low or too high, depending on soil origin

Compare Results to NRC Guidelines

Once you’ve got your hay analysis in hand, the next step is simple but crucial: compare it to what your horse actually needs.

The National Research Council (NRC) 2007 guidelines provide the gold standard for equine nutrient requirements. You’ll want to pair those numbers with your hay results and a calculator (or a cheat sheet like this one).

Match the forage profile to your horse’s:

• Weight and workload
• Life stage (senior, growing, broodmare)
• Health status (e.g. ulcers, EMS, PSSM)

Step 3: Identify What’s Missing—or Excessive

✅ Low NSC (8.5%) – This hay is a good match for laminitics, EMS, or overweight horses.
✅ Safe energy level (0.85 Mcal/lb) – Won’t overfeed a pasture pet, but may fall short for high-work horses.
✅ Adequate crude protein for adult horses, though borderline for performance horses or broodmares.
⚠️ Lysine is marginal – If this is your only protein source, consider a balancer with extra amino acids.
⚠️ Sodium is too low – You must add salt.
⚠️ Zinc is borderline; copper is adequate but tight.
❌ Iron is extremely high – Common in grass hay, and can antagonize copper/zinc absorption.

This hay is an excellent base for easy keepers, metabolic horses, or anyone needing a lower calorie forage. But:

• You’ll need to add salt
• You should still supplement zinc and possibly lysine, depending on the rest of the diet.
• Be mindful of the high iron—don’t skimp on copper and zinc in the balancer.

🛠 Tools to Make This Easier:

• MadBarn’s Equine Nutrition Calculator (Free)

• FeedXL (Paid, but powerful)

Use the Data to Choose a Balancer or Supplement

Once you’ve tested your hay, now comes the fun part: using that data to feed smarter—and stop wasting money on random tubs of powder with pretty labels.

What Your Hay Analysis Might Be Telling You:

Here’s what to scan for—and what it means for your next feed room purchase:

Two Smart Ways to Fill Nutritional Gaps

🟢 Ration Balancer

A concentrated protein + vitamin + mineral pellet, designed to fill in everything your hay doesn’t provide — without the extra calories of a full grain ration. Ideal for horses on all-forage diets, easy keepers, and anyone trying to avoid “feed bloat.”

• Feed just 1–2 lbs/day
• Balanced levels of lysine, copper, zinc, selenium, etc.
• No mystery ingredients or filler calories

👉 Ready to learn which balancer is best for your hay and your horse?
Read: What Is a Ration Balancer and Does Your Horse Need One?

🟠 Vitamin-Mineral Supplement

Great for when your hay is only missing a few things. These come in powder, pellet, or loose form and are typically top-dressed on feed. You’ll still need to meet protein requirements separately if hay is low in CP or lysine.

🚫 Don’t Play Supplement Roulette 🚫
Adding three different “hoof,” “mane,” and “performance” powders without a plan?
That’s how you accidentally create a copper:zinc imbalance, selenium overload, or iron swamp

Targeted nutrition is safer, cheaper, and more effective than throwing everything in the bucket and hoping something sticks.

Test Every New Load

Hay isn’t uniform — even if it looks the same, the nutrients inside can vary widely depending on how, where, and when it was grown.

🌾 Why hay nutrient levels change:

• Cutting stage: First, second, and third cuttings differ in maturity, leafiness, and nutritional value. Later cuttings often have more energy and protein but may also be softer and dustier.
• Growing conditions: Rain, drought, heat, and frost all affect sugar and mineral levels.
• Soil differences: Poor soil = poor hay. Even hay from the same field can vary year to year if soil fertility changes.
• Storage and transport: Exposure to sunlight, moisture, and temperature shifts can degrade vitamin levels (especially vitamin E) and reduce palatability.

🔄 What this means for feeding:

Don’t assume that this year’s hay is nutritionally identical to last year’s — even if it came from the same supplier or field.

Always test each new delivery of hay before adjusting your horse’s diet or supplements. Last year’s analysis won’t give you accurate information.

A simple core sample sent to a forage lab can help prevent nutrient imbalances, unnecessary supplement costs, or even health problems like colic or laminitis.

Tip: Label and store your analysis results by load and cutting, so you can track trends and feed strategically throughout the year.

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