Introduction
Hay doesn’t have an official “expiry date,” but it absolutely changes in quality as it ages.
Even hay that was baled perfectly will lose nutrients, vitamins, colour and palatability over time — and poor storage accelerates the process.
This post explains:
- how long hay stays good
- what nutrients are lost first
- how to identify spoiled or unsafe hay
- how to store hay correctly to slow deterioration
- when old hay is still usable (and when it’s not)
Does Hay Lose Quality Over Time? Yes — Here’s How
Hay is a preserved forage, but it’s still a biological product.
Over months, several natural processes slowly reduce quality.
Vitamins — especially vitamin A (beta-carotene) — are extremely fragile.
Expected vitamin loss:
- 1 month: 20–30% loss
- 6 months: up to 50% loss
- 12 months: up to 80% loss
This matters most for horses, dairy cows and growing animals.
2. Colour Fades Due to Sunlight & Oxidation
Even perfectly stored hay will fade from bright green to:
- yellow-green
- light brown
- dusty tan
Colour loss doesn’t always reduce nutrition — but it signals oxidation, which means nutrient loss is happening.
3. Dry Matter Loss Reduces Feed Value
Dry matter is the “actual feed” portion of hay.
Stored hay loses:
- 3–10% over 6–12 months
- Up to 20% if stored outdoors
This means one-year-old hay provides less true feed per bale, even if it looks okay.
4. Protein Declines Slowly Over Time
Protein is relatively stable, but still declines:
- 5–10% loss over the first year
- More in poor storage conditions
Hay with many leaves (alfalfa, clover) loses protein faster than grass hay if mishandled.
5. Fibre Increases as Hay Ages
As hay oxidises:
- NDF and ADF rise (fibre that reduces digestibility)
- Energy drops
- Palatability decreases
Old hay is harder for animals to digest and produces more waste.
How Storage Conditions Impact Hay Quality
Hay stored properly can last 1–2 years and still feed well.
Hay stored poorly can deteriorate in weeks.
Best Storage Conditions
✔ Indoors
- Dry barn or shed
- Off the ground (pallets or rails)
- Good ventilation
- No roof leaks
- Away from manure moisture
- Stack loosely to avoid trapped humidity
✔ Outdoors (if necessary)
- Use net-wrapped round bales
- Place on gravel or pallets
- Cover with breathable tarp
- Maintain drainage
Outdoor storage increases spoilage by up to 25–35%.
Signs Your Hay Has Gone Bad
Even old hay can be usable — unless it shows these warning signs.
1. Mould (white, grey or black spots)
Unsafe for:
- horses
- small ruminants
- high-performance animals
May cause colic, respiratory issues, abortions or reduced milk yield.
2. Heating or Burned-Smell Hay
Indicates:
- baled too wet
- internal spoilage
- possible caramelisation
If hay smells smoky, burnt or sour, discard immediately.
3. Dust Clouds When You Handle It
Dust may be:
- mould
- soil
- broken leaf particles
Excess dust makes hay unsafe for horses.
4. Slimy or Wet Patches
Usually caused by:
- leaks
- condensation
- sweating bales
This hay should not be fed.
5. Rodent or Bird Contamination
Old hay stored improperly may contain:
- droppings
- urine
- nesting areas
This makes hay unsuitable for all livestock.
How Long Does Hay Stay Good? (General Guide)
High-quality indoor-stored hay:
✔ 12 months — still very good
✔ 18 months — usable, vitamin loss
✔ 24 months — quality significantly reduced
✘ Over 2 years — mostly bedding value
Outdoor-stored round bales:
✔ 6 months — moderate loss
✔ 12 months — outer spoilage likely
✘ 18+ months — generally low-feed value
✘ 2 years — usually bedding or compost at best
Can You Feed Old Hay?
Safe to feed IF:
- no mould
- no heating damage
- not overly dusty
- animals are maintenance-level (dry cows, beef cattle, goats)
- you supplement vitamins or minerals if needed
Not safe for:
- horses with respiratory sensitivity
- lactating dairy cows
- pregnant animals
- high-performance horses
- young growing animals
When in doubt, do a forage test.
External resource:
Forage testing labs – https://www.foragetesting.org
Conclusion
Hay does get worse over time — but proper storage can preserve quality for over a year.
Understanding nutrient loss, spoilage warning signs and storage strategies helps ensure your animals receive safe, nutritious feed.
Does Hay Get Worse Over Time? How Storage Duration Affects Quality.
Introduction
Hay doesn’t have an official “expiry date,” but it absolutely changes in quality as it ages.
Even hay that was baled perfectly will lose nutrients, vitamins, colour and palatability over time — and poor storage accelerates the process.
This post explains:
Does Hay Lose Quality Over Time? Yes — Here’s How
Hay is a preserved forage, but it’s still a biological product.
Over months, several natural processes slowly reduce quality.
1. Vitamin Loss Begins Immediately
Vitamins — especially vitamin A (beta-carotene) — are extremely fragile.
Expected vitamin loss:
This matters most for horses, dairy cows and growing animals.
2. Colour Fades Due to Sunlight & Oxidation
Even perfectly stored hay will fade from bright green to:
Colour loss doesn’t always reduce nutrition — but it signals oxidation, which means nutrient loss is happening.
3. Dry Matter Loss Reduces Feed Value
Dry matter is the “actual feed” portion of hay.
Stored hay loses:
This means one-year-old hay provides less true feed per bale, even if it looks okay.
4. Protein Declines Slowly Over Time
Protein is relatively stable, but still declines:
Hay with many leaves (alfalfa, clover) loses protein faster than grass hay if mishandled.
5. Fibre Increases as Hay Ages
As hay oxidises:
Old hay is harder for animals to digest and produces more waste.
How Storage Conditions Impact Hay Quality
Hay stored properly can last 1–2 years and still feed well.
Hay stored poorly can deteriorate in weeks.
Best Storage Conditions
✔ Indoors
✔ Outdoors (if necessary)
Outdoor storage increases spoilage by up to 25–35%.
Signs Your Hay Has Gone Bad
Even old hay can be usable — unless it shows these warning signs.
1. Mould (white, grey or black spots)
Unsafe for:
May cause colic, respiratory issues, abortions or reduced milk yield.
2. Heating or Burned-Smell Hay
Indicates:
If hay smells smoky, burnt or sour, discard immediately.
3. Dust Clouds When You Handle It
Dust may be:
Excess dust makes hay unsafe for horses.
4. Slimy or Wet Patches
Usually caused by:
This hay should not be fed.
5. Rodent or Bird Contamination
Old hay stored improperly may contain:
This makes hay unsuitable for all livestock.
How Long Does Hay Stay Good? (General Guide)
High-quality indoor-stored hay:
✔ 12 months — still very good
✔ 18 months — usable, vitamin loss
✔ 24 months — quality significantly reduced
✘ Over 2 years — mostly bedding value
Outdoor-stored round bales:
✔ 6 months — moderate loss
✔ 12 months — outer spoilage likely
✘ 18+ months — generally low-feed value
✘ 2 years — usually bedding or compost at best
Can You Feed Old Hay?
Safe to feed IF:
Not safe for:
When in doubt, do a forage test.
External resource:
Forage testing labs – https://www.foragetesting.org
Conclusion
Hay does get worse over time — but proper storage can preserve quality for over a year.
Understanding nutrient loss, spoilage warning signs and storage strategies helps ensure your animals receive safe, nutritious feed.
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