A hay quality test (forage analysis) is the only reliable way to know what's actually in the hay you're feeding. Visual inspection tells you about physical quality — moisture, color, leafiness — but not nutritional content. Two bales that look identical can differ by 6 percentage points in crude protein. For high-demand animals or precision feeding, testing is worth the $15–$25 it costs. This guide explains every number you'll see on a standard forage report.
How to Get a Hay Test
Use a hay probe (a hollow coring tool) to sample multiple bales — at least 10–15 bales per lot — by drilling into the flat end of each bale and collecting a core sample. Mix all cores in a plastic bag and send to a certified forage testing laboratory. In most states, your cooperative extension office can recommend certified labs; the National Forage Testing Association (NFTA) maintains a directory of certified labs at foragetesting.org. Results typically return in 3–5 business days.
The Key Numbers — Explained
Moisture (%)
The water content of the hay. Well-baled dry hay should be below 15–18% moisture. High moisture (above 20%) at baling causes internal heating and mold development. Results reported "as-fed" include moisture; "dry matter" results are calculated as if all moisture were removed. Compare values on a dry matter basis for meaningful comparisons between samples.
Crude Protein (CP %)
The most commonly referenced number. Measures total nitrogen content, which approximates protein. Higher CP = more protein available for animal growth, reproduction, and milk production.
- 8–10% CP: Adequate for horses and beef cattle at maintenance; dry ewes and does
- 10–13% CP: Good general-purpose hay; appropriate for most small farm animals in moderate production
- 13–18% CP: High protein; appropriate for growing animals, lactating dairy animals, horses in work
- 18%+ CP: Dairy-quality; appropriate for high-producing dairy animals, late pregnancy, rapid growth
Acid Detergent Fiber (ADF %)
Measures the least digestible fiber components (cellulose and lignin). Lower ADF = more digestible hay. Higher ADF = more of the hay passes through as waste.
- Below 31%: Excellent digestibility (premium)
- 31–35%: Good digestibility
- 36–40%: Fair — adequate for most livestock at maintenance
- Above 40%: Low digestibility; poor for high-demand animals, adequate for dry cows
ADF is the number most directly related to energy value — it's used to calculate TDN and NEL.
Neutral Detergent Fiber (NDF %)
Measures total cell wall fiber including ADF components plus hemicellulose. Higher NDF = more physically filling hay that slows intake. Lower NDF = animals can eat more dry matter per day (important for high-producing dairy animals that need to consume large quantities).
- Below 40%: Very low NDF — may limit intake in dry matter terms for some animals
- 40–50%: Moderate; appropriate for most livestock
- 50–60%: Higher fill; typical for grass hays
- Above 65%: Very high fill; animals physically can't eat enough of this to meet high energy demands
Total Digestible Nutrients (TDN %)
A composite energy measure — the percentage of the hay's dry matter that provides digestible energy. Calculated from ADF. Higher TDN = more energy per pound of hay.
- 60%+ TDN: High energy; premium hay
- 55–60%: Good energy; typical for quality grass hay
- 50–55%: Moderate; adequate for maintenance
- Below 50%: Low energy; marginal for most production purposes
Relative Feed Value (RFV)
A single index number combining digestibility (ADF) and intake potential (NDF) into one score. An RFV of 100 is defined as full-bloom alfalfa — the NFTA reference standard. Higher RFV = better overall feeding value.
- RFV 150+: Prime; dairy-quality hay
- RFV 125–150: Good; appropriate for performance horses, dairy, late gestation
- RFV 103–125: Fair; adequate for horses and beef cattle at maintenance
- RFV 87–103: Utility grade; appropriate for dry cows, beef at maintenance
- Below 87: Poor; limited use cases
Calcium (Ca) and Phosphorus (P)
The Ca:P ratio matters more than absolute levels for most species. The ideal ratio is 1.5–2:1 calcium to phosphorus. Imbalance — especially inverted P:Ca ratio (more P than Ca) — is associated with metabolic bone disease in horses and urinary calculi in wethers and bucks. Alfalfa is high in calcium (1.2–1.8%); grass hays are lower (0.3–0.5%). Most horses on grain-based diets have adequate phosphorus; calcium supplementation is more often needed.
| Metric | Horses (maintenance) | Beef Cattle (maintenance) | Dairy Goats (production) |
|---|---|---|---|
| CP | 8–10% | 7–9% | 14–18% |
| ADF | 35–40% | 38–44% | 28–34% |
| NDF | 55–65% | 58–68% | 40–52% |
| TDN | 52–58% | 50–56% | 58–65% |
| RFV | 90–115 | 85–110 | 120–150+ |