Hay Storage for Horse Farms: 7 Tips to Save Money & Keep Your Horse Safe

Proper hay storage is critical for maintaining the quality, safety, and nutritional value of your horse’s forage. Whether you’re managing a large equine facility or a small hobby farm, knowing how to store hay correctly can prevent mold, spoilage, and costly waste.

Without proper ventilation, correct stacking, or moisture control, hay can spoil quickly, leading to mold growth and pest infestations that can compromise its nutritional value and potentially harm your horses.

Horses that consume improperly stored hay are at risk of respiratory allergies, gastrointestinal issues, and even mycotoxin poisoning. Additionally, improper hay storage can increase the risk of barn fires, further threatening your horses’ safety.

In this guide, we review the considerations for indoor and outdoor hay storage, how to protect hay from moisture and pests, and offer our expert tips to keep your feed fresh year-round. By following these hay storage techniques, you can ensure your horses receive clean, high-quality forage while minimizing losses.

Proper Hay Storage for Horses

Hay is a cornerstone of the equine diet, offering vital nutrients such as fiber, protein, vitamins, and minerals. Horses should consume between 1.5 – 2.5% of their body weight in hay (dry matter) and other forages per day.

Given this, poor hay hygiene can significantly impact the overall health and well-being of your horse.

Improper hay storage can result in mold, mildew, and nutrient degradation, which can pose health risks to horses including:

• Respiratory issues
• Colic
• Laminitis
• Toxicosis (poisoning)

Proper storage helps preserve the nutritional integrity of hay while preventing contamination from pests, rodents, and moisture.

Types of Hay Storage

There are various methods for storing hay on horse farms, each with its own advantages and disadvantages. The choice of storage method depends on the size of the farm, available space, and budget.

Indoor Storage

Indoor storage is often considered the best option for keeping hay dry and protected from the elements. When stored in a barn or shed, hay is shielded from rain, snow, and direct sunlight, all of which can cause it to degrade more quickly.

Advantages of indoor storage include: ^[1][2]

• Provides protection from extreme weather and precipitation
• Improves temperature and humidity control
• Reduces exposure to pests and wildlife

However, indoor storage also has some disadvantages, including: ^[1][2]

• Requires dedicated space
• Higher construction costs, especially in regions with heavy snow load

To maximize the benefits of indoor storage, certain best practices should be kept in mind, including: ^[1][2]

• Stacking hay on raised flooring: this prevents contact with the ground and reduces moisture absorption
• Maintaining ventilation: minimizes the risk of mold growth, as fungus thrives in stagnant, humid conditions

Outdoor Storage

Outdoor storage options, such as stacked round bales or hay bale rows, are common on farms that don’t have a barn or otherwise have limited space.

The main advantages of outdoor storage include: ^[1][2]

• Cost-effective, especially for large-scale operations
• Provides easy access

However, outdoor storage exposes hay to the elements, and increases the risk of rodent and other pest infestations. When hay is kept outside, losses can be significant. More than 40% of hay stored outdoors may be damaged compared to only about 5% loss when stored indoors. In round bales left outside without protection, the spoiled layer can extend 4 to 8 inches deep into the bale, reducing both hay quality and the amount of usable hay that horses can consume. ^[3]

Reducing contact between hay and soil is the best way to protect hay that is stored outdoors. Ideally, raise the bales off the ground using pallets or large poles. This prevents moisture from soaking in from the soil below. If you don’t have pallets or poles, place the bales on a well‑drained surface, such as crushed stone or sandy soil, to help reduce nutrient loss.

How you organize hay bales outside also contributes to the risk of damage from outdoor storage. Key strategies to minimize waste include:

• Line them up correctly: Place the flat ends of round bales tightly together, but don’t let the curved sides touch.
• Choose the right spot: Store bales in sunny, open areas so they dry quickly after rain. Large, open areas with lots of wind are ideal. Avoid shady spots under trees, which block wind and sunlight that help with bale drying.
• Leave space for airflow: Keep 1 m (3 -4 ft) between rows of bales to let air move freely. This allows for quicker drying after rain.

If bales aren’t covered, don’t stack them. Rainwater can run off the top bales and soak into the ones below

Covering bales with a tarp can reduce storage losses by more than 75%. ^[4] However, waterproof tarps can also trap moisture between the bales and the tarps so they have to be used with care.

Consideration for storing covered bales include:

• Stack square and round bales in a pyramid shape with small gaps for ventilation. Leave the ends of the stack open to allow wind to travel betwen the bales.
• When tarping rows, don’t let the tarp hang past the widest curve of the bale. This way, rain sheds off the top while air can still circulate along the sides.
• If tarps aren’t an option, using more twine during baling can help. Denser twine wrapping improves water shedding and reduces spoilage.

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Wrapped hay

Wrapped hay (also called baleage) is forage sealed tightly in durable plastic, allowing farms of all sizes to store it outdoors while protecting forage from rain, sun and the elements. This method also allows farmers to harvest forage under a wider range of weather conditions, especially when rain prevents hay from fully drying before bailing.

For optimal storage, it’s best to keep wrapped hay in a dry location with good drainage and even, flat ground. Avoid storing the bales in areas with lots of rocks, sticks and brush, as sharp objects can damage the plastic wrap.

Research shows the best moisture range for making wrapped hay is when forage has an internal moisture content of 45% to 55%. ^[5] At this moisture level, the bale can undergo a fermentation process that helps preserve the forage for long-term storage.

During fermentation, beneficial bacteria on the forages convert plant sugars into acids, lowering the pH of the bales. This low pH environment minimizes growth of undesirable bacteria, helping prevent spoilage while preserving nutrient quality. However, the bales must be fully sealed to prevent oxygen from disrupting this fermentation process.

It’s important to note not all fermentation is beneficial. If hay is wrapped at too high a moisture level, proper fermentation cannot occur and the pH fails to drop as it should. Excess moisture and elevated pH creates conditions where harmful bacteria from the Clostridia family can grow. Bacteria from this class produce toxins, including botulin, which can be fatal to horses. ^[6]

To reduce this risk, it’s essential to ensure hay is not too wet before storage, that bales are properly wrapped to exclude oxygen, and horses are vaccinated against botulism.

When wrapping bales, it’s important to minimize internal air within the bale by tightly compacting the bales and applying sufficient plastic wrap. Current guidelines recommend a total plastic thickness of at least 6 mm to prevent air infiltration after wrapping. ^[5]

Additionally, bales should be wrapped within 24 hours of bailing to avoid internal heat buildup that can degrade quality. Some studies even indicate that wrapping within 12 hours may be preferable, depending on factors like moisture content and forage type. ^[5][7]

7 Tips to Optimize Hay Storage

The decision to store hay inside or outdoors depends on many factors, including available space, climate, and number of horses on the farm. Regardless of where the hay is stored, follow these seven tips to maximize your hay use by keeping your horse’s feed fresh and safe all year long.

1) Monitor Internal Bale Temperature After Harvest

One of the biggest risks in hay storage is spontaneous combustion, primarily caused by storing hay with excessive moisture. ^[8]

Hay has natural insulating properties, which means internal heat cannot dissipate easily. When hay bales with more than 22% moisture are stored, microbial activity generates heat. If internal hay temperatures exceed 55 °C (131 °F), flammable gases can form, increasing the risk of ignition. Large stacks of hay are particularly vulnerable due to reduced air flow, which limits dissipation of heat and gases. ^[8]

All baled hay is expected to have a slight rise in temperature immediately after baling due to plant respiration and microbial processes within the bale. ^[9] Temperature and moisture levels are expected to equilibrate independently of each other within 40 days, which underscores the importance of taking routine measurements during the first four weeks of hay storage. ^[9]

Most hay fires occur within the first six weeks after baling. During this period, even hay with moisture levels as low as 15% may have rising temperatures. ^[8]

Figure 1. Baled hay temperatures, internal biological processes, and fire hazards ^[9]

Implementing the following preventive strategies can significantly reduce the risk of barn fires due to hay storage: ^[10]

• Thoroughly dry hay before baling. If hay was not given time to adequately dry, use a moisture probe to monitor the bales or conduct a hay test.
• If hays were not harvested at an ideal moisture, regularly monitor hay stack temperatures for the first four weeks after harvest. Use a long combost thermometer to detect early signs of heat buildup. The probe must be long enough to reach the middle of the bale.
• If a bale reaches an internal temperature over 55 °C (131 °F), remove it immediately from the barn, away from other structures or hay bales. Continue monitoring these bales by checking temperatures twice per day.
• Ensure ample clearance between hay stacks and light fixtures.
• Replace hydrogen or halogen lighting with LED alternatives to reduce heat output and lower fire risks.

Table 1. Internal hay temperature risk guidelines ^[8][10]

2) Intervene in Extreme Heat

Although controlling outside temperatures is difficult, extreme heat can have a significant impact on hay quality. In regions such as Arizona and Texas, where summer days routinely exceed 100°F (38°C), it’s especially important to pay attention to how hay is stored.

Excessive heat can reduce the amount of protein available in hay through a chemical process known as the Maillard reaction. This reaction binds proteins to sugars, creating an indigestible compound that reduces protein availability of the hay. ^[11]

In addition to protein loss, excessively hot and dry conditions can cause hay bales to become overly dry and brittle. When hay reaches this state, it easily breaks into fine particles during handling or feeding, which increases waste and can irritate respiratory issues for sensitive horses.

To reduce the risk of hay becoming too brittle, losing protein availability, and decreasing fiber digestibility, it is recommended to store hay in areas with routinely high temperatures under a roof. Roofed structures with open or closed siding are preferable to tarps, since tarps can trap heat and raise bale temperatures compared to leaving them uncovered. ^[11]

3) Ensure Adequate Ventilation

Proper ventilation is important for maintaining hay quality during storage. Adequate air circulation helps prevent moisture buildup, which is one of the primary causes of mold and mildew growth. When air is stagnant, humidity levels can rise, creating an ideal environment for microbial activity.

Robust ventilation ensures that any moisture released by hay, particularly newly baled or slightly damp hay, can dissipate quickly. To provide adequate ventilation, hay storage structures should be equipped with sufficient vents or windows to allow consistent air flow.

When storing hay under a roof, it’s important to leave about 0.5 – 1 m of space between the top of the highest bale and the roof. This headspace allows air to circulate, helping moisture escape from the bales. Small gaps between stacks of hay also improve ventilation, giving newly stored hay a chance to dry more evenly. ^[12]

Striking a balance between protecting hay from external elements and allowing natural ventilation is key to maintaining hay quality.

4) Perform Routine Maintenance

Maintaining hay storage systems is just as important as the initial setup. Regular inspection, cleaning, and maintenance are essential for ensuring that hay remains safe and nutritious for horses.

Routine maintenance in hay storage areas includes:

• Regular inspections: Frequent inspections of hay storage areas can help identify early signs of mold, pests, or moisture damage. Early detection assures that issues can be addressed promptly to prevent contamination
• Cleaning hay storage areas: Cleanliness helps control dust and debris accumulation over time, which discourages pest infestation and bacterial growth in the storage area
• Equipment maintenance: In indoor storage areas, make sure electrical equipment like lighting or fans are well-maintained and functional. It’s also important to check any ventilation outlets like ducts and windows to ensure they are clear and allowing appropriate exchange of air

5) Control Mold & Dust

Mold and dust are the two primary irritants commonly found in hay. Mold thrives in damp, poorly ventilated environments where hay is exposed to excess moisture or high humidity. Dust is an unavoidable aspect of feeding hay as the dried fibers break into microscopic particles as the hay is handled and moved around.

Many species of mold produce mycotoxins, which can lead to signs of toxicity when ingested by horses. Signs of mycotoxin poisoning in horses include: ^[13][14][15]

• Diarrhea
• Colic
• Lethargy
• Loss of appetite

Dust particles are easily inhaled by the horse while feeding, which may be particularly irritating for horses with pre-existing respiratory conditions like heaves or equine asthma.

Hay storage strategies to minimize mold and dust include:

• Maintaining ventilation: Store hay in a well-ventilated area to promote airflow and prevent moisture buildup. Use fans or open-sided structures to reduce humidity
• Stacking strategically: Arrange hay in a crisscross or pyramid pattern to improve air circulation and dissipate moisture, which prevents heat build up and mold growth
• Elevating hay: Store bales on wooden pallets, rubber mats, or gravel to prevent moisture absorption from the floor
• Controlling humidity: Keep hay storage areas dry and well-ventilated to regulate moisture levels
• Covering hay: Use breathable tarps or hay covers to protect outdoor hay while allowing airflow. If using impermeable plastic tarps, stack bales in a pyramid structure to allow for air movement between bales
• Performing regular inspections: Check hay frequently for signs of mold, dust buildup, or overheating, and remove any affected bales immediately
• Handling and feeding effectively: Shake out and dampen excessively dusty hay before feeding, or consider soaking hay to reduce airborne dust and improve palatability

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6) Control Rodents & Other Pests

Rodents, insects, and other pest infestations can lead to hay damage and contamination. Mice, rats, and squirrels are particularly drawn to hay due to its fibrous texture and potential as a food source. Insects, including ants, beetles, and moths, can infest hay, causing damage to bales and introducing droppings or larvae that further contaminate the hay.

These pests not only degrade hay quality but can also introduce harmful bacteria or parasites that jeopardize horse health. To mitigate these risks, horse owners can implement several strategies, including: ^[16]

• Set traps: Trapping is the most effective method for controlling rodent populations. Snap traps, live traps, and electronic traps can capture or repel rodents. Traps should be placed around the perimeter of the hay storage area or near points where pests are likely to enter. Traps should be easy to access so trapped pests can be quickly removed from storage area.
• Perform regular inspections: Regularly check for signs of pest activity, such as droppings, chewed bales, or visible insects. Early detection of pest problems allows for prompt action, preventing significant damage to the hay.
• Maintain cleanliness: Rodents are attracted to clutter and debris, and many insect populations arise on decaying organic matter like spoiled hay. Keeping the storage area clean and tidy, ensuring grain and other feed are kept in rodent-proof containers, and disposing of any spoilage promptly can all minimize pest infestation.

In addition, many farms keep barn cats, which can be an effective deterrent against rodents and other small mammals.

Some owners may consider using rodenticides (bait) to deter pests, but this approach is not safe for feed storage areas. Rodenticides can cause severe and potentially life-threatening toxicosis in both horses and other animals.

Any product with one or a combination of these ingredients is not safe for feed storage areas: ^[17]

• Anticoagulants
• Bromethalin
• Cholecalciferol
• Phosphides
• Sodium fluoroacetate

These chemicals are highly toxic and can lead to symptoms such as bleeding, organ failure, seizures, and even death if ingested. It’s crucial to avoid using these substances in or around hay storage areas where horses could have access. If rodenticide exposure is suspected, immediate veterinary attention is required. ^[17]

7) Manage Inventory

Implementing an inventory management system is one of the simplest and most effective ways to prevent hay spoilage and reduce the risk of spontaneous combustion.

By keeping track of which bales were most recently made, you can routinely check the newer hay to ensure it is curing safely. At the same time, knowing which bales are oldest allows you to follow the “first‑in, first‑out” (FIFO) principle to minimize spoilage.

While well‑stored hay can remain in good condition for many years, it is still best practice to use older inventory first, especially when hay is stored outdoors. This approach minimizes waste, ensures that hay more likely to lose quality over time is fed before it spoils, and helps maintain the best possible nutrition for your horses while protecting against unexpected losses.

Frequently Asked Questions

Here are some frequently asked questions about storing hay for horses:

Summary

Proper hay storage in equine facilities is important for preserving the nutritional quality of forage and ensuring the overall health and well-being of horses.

• Indoor hay storage offers the best protection from the elements, but requires additional space that may not be available on all farms
• Outdoor storage requires less space but hay is more exposed to the elements
• Maintaining clean, well-managed hay inventory is key to preventing barn fires and hay spoilage
• Adequate ventilation and frequent monitoring are cornerstones of controlling mold and pest infestation
• Proper hay storage is an investment in both the health of horses and the sustainability of the farm's feeding practices