Introduction

Rain on hay is one of the most frustrating experiences for farmers.
You’ve cut at the perfect time, the weather looked clear — then a surprise shower hits.

The big question becomes:

➡️ Is the hay still worth baling, or should you skip it?

This guide explains how rain affects hay nutrition, colour, drying time and safety — and gives you a practical checklist to decide whether to bale or walk away.

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1. What Rain Actually Does to Hay

Hay quality losses depend on:

• when it rains
• how long it rains
• how much it rains
• crop type (grass vs legume)
• temperature and drying weather afterward

Rain can reduce the value of hay by 5% to 80%, depending on timing.

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2. If Rain Falls Right After Cutting

This is the least damaging scenario.

Effects:

• slow initial drying
• minor sugar loss
• little colour damage

The crop is still in wide swath form, so losses are low.

Good news:
Almost always still worth baling with proper tedding.

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3. If Rain Falls After the Hay Has Dried to 40–60% Moisture

This is worse — the hay has wilted but not yet ready to bale.

Effects:

• sugar leaching
• leaf loss increases
• drying time resets partly
• risk of mould if left too long

Grass hay usually recovers well.
Alfalfa/clover suffer significant leaf loss when re-tedded.

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4. If Rain Falls When Hay Is Almost Ready to Bale (Below 20% Moisture)

This is the most damaging scenario.

Effects:

• major colour loss
• heavy nutrient washing
• leaves shatter easily
• high chance of mould
• must be re-dried fully
• bale density becomes unpredictable

You may need to:

• re-ted aggressively
• fluff windrows
• widen swaths
• allow extra drying time

In many cases, quality drops dramatically, especially for premium horse hay.

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5. How Much Rain Fell? It Matters

Light rain (0–3 mm):

• minimal damage
• mostly cosmetic
• still baleable

Moderate rain (3–10 mm):

• nutrient leaching begins
• tedding required
• avoid baling until moisture resets

Heavy rain (10–25 mm):

• big leaf losses
• high mould risk
• significant colour change
• may not be suitable for premium markets

Torrential rain (25+ mm):

• stripping of sugars
• severe nutrient loss
• lodging and soil contamination
• often better left on the ground

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6. How Rain Affects Nutrition

Rain leaches soluble components of hay:

Nutrients lost:

• sugars (WSC)
• vitamins (esp. vitamin A)
• minerals
• soluble proteins

Nutrients NOT lost:

• fibre (ADF/NDF) — may even increase
• structural proteins

This means rain-damaged hay often becomes:

• more fibrous
• less digestible
• lower energy
• lower palatability

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7. How to Check if Rain-Damaged Hay Is Still Safe

Use this checklist to evaluate hay after rain.

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1. Smell Test

Good hay smells:

• fresh
• clean
• slightly sweet

Rain-damaged hay may smell:

• musty
• sour
• burnt/caramelised (if it overheated)

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2. Colour Inspection

Rain damage shows as:

• brown/black patches
• bleached yellow sides
• uneven colour when splitting the bale

Colour loss alone doesn’t always make hay bad — but it lowers value.

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3. Leaf Content

Legume leaves (alfalfa/clover) shatter heavily after rain.

If the bale is mostly stems → quality is low.

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4. Moisture Check

Use a moisture meter to ensure:

• Small squares: 16–18%
• Round bales: 12–15%
• Large squares: 12–14%

Moisture pockets = high heating risk.

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5. Break Open the Bale

Look for:

• mould
• heat pockets
• caramel or sour smell
• dust clouds
• slimy stems

If any of these appear → do not feed to horses.

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8. When You Should Still Bale Rain-Damaged Hay

Rain-damaged hay can still be valuable for:

• beef cattle
• sheep
• goats
• dry cows
• overwinter maintenance feed
• bedding material
• mulch or compost

If nutrition isn’t critical, rain-damaged hay can still be economical.

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9. When You Should NOT Bale It

Never bale or feed rain-damaged hay if:

• mould is visible
• bale is heating (over 45°C / 113°F)
• it’s for horses
• hay smells musty or sour
• leaves have completely shattered
• stems feel slimy
• hay dried unevenly and repicked moisture

This hay is unsafe and should be composted or used as bedding only.

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10. Should You Bale or Walk Away? (Quick Decision Guide)

YES – Bale It If:

✔ minimal leaf loss
✔ smells fresh
✔ colour loss is mild
✔ moisture dries back to safe levels
✔ no mould inside windrows
✔ you have a market for lower-grade hay

NO – Skip It If:

✘ heavy rain washed nutrients
✘ mould spotted
✘ heating occurred
✘ hay is blackened or slimy
✘ horse hay market requires premium quality

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Conclusion

Rain doesn’t automatically ruin hay — but it changes everything about quality, value and safety.
By evaluating leaf loss, smell, moisture, colour and internal bale condition, you can confidently decide whether to bale the crop or leave it in the field.

At PremiumHaySupply.com, we assess every field carefully to guarantee clean, safe and consistent hay for our customers.