Preserving the value of dry stored hay
What you need to know
Bale hay at 15 to 20 percent moisture (wet basis).
If stored uncovered, use bales harvested early in the season first, and try to sell or feed all bales before the following spring.
If stored outside, place bales on a well-drained surface, such as gravel, old tires or pallets rather than directly on the ground.
Consider investing in tarps or storage buildings.
The way you store hay after baling can have a big effect on hay quantity and quality losses, so it’s worth investing additional resources – money, labor and equipment – in hay storage.
This preserves the value of the hay and ensures a good return on your initial investment to bale the hay. Baling uses a large amount of resources, including land, labor, seed, fuel, fertilizer and equipment.
On this webpage, you’ll find hay storage research findings and best practices for preserving the value of your baled hay.
Factors affecting losses
Most dry matter and quality losses that occur during storage are due to molds and bacteria that consume hay’s nutrients. These microorganisms generate heat that causes chemical reactions and additional nutrient loss.
In extreme cases, the heat generated by molds and bacteria can cause fires, destroying the hay and the surrounding structures. Molds and bacteria grow and reproduce faster if hay is warm and moist. The more time they have to work, the more damage they can do.
In general, microorganism-caused losses are lower at lower temperatures and moisture levels and shorter storage periods. Because most hay is stored outdoors or in structures that aren’t heated or cooled, storage temperature follows outdoor temperature and is beyond your control.
We have little control over hay storage temperature, plus livestock feeders and hay processors usually need to store hay for year-round use. This means controlling moisture is probably your best strategy for limiting storage losses.
Hay harvested late in the season and consumed during the winter is stored for a relatively short time at relatively low temperatures and should have minimal losses. Hay harvested early in the season and stored into winter will be subject to some warm temperatures before winter arrives and is likely to have greater losses.
Expect the greatest losses with hay that’s stored through winter and into the following spring and summer. According to research by Oklahoma State University, losses after 12 to 18 months of storage are twice as great as losses after nine months of storage.
Baling: Recommended moisture content
Timing of baling is critical to maximize the hay’s value. Optimum moisture for baling is between 15 to 20 percent moisture (wet basis), which is low enough to prevent mold activity.
Baling at lower than 15 percent moisture will result in greater harvesting losses, especially for alfalfa, because leaf loss increases as moisture decreases.
Large hay packages, especially large rectangular bales, don’t lose much moisture after baling. This is why it’s important to bale at the proper moisture, instead of baling at a higher moisture and counting on some natural drying in storage.
Baling at higher moistures
If you must bale at higher moisture, here are some options:
- Bale at a slightly higher moisture (20 to 30 percent) and apply a preservative that inhibits mold growth in storage.
- Bale at a higher moisture (20 to 35 percent) and artificially dry the bales.
- Bale at a much higher moisture (50 to 65 percent) and ensile the bales by storing them sealed in plastic.
Storage: Recommended moisture content
After baling, hay should continue to be at moisture contents below 20 percent for storage. Storing hay at moisture contents above 20 percent will result in:
Some molding and heating.
Dry matter and nutrient loss.
Study: Impact of storage moisture
A study of small rectangular bales stored in a barn at the U.S. Dairy Forage Research Center in Madison, Wis. showed that dry matter loss increased with storage moisture (Table 1). Quality loss was also greater in the wetter bales.
Table 1: Dry matter and quality loss
|Storage moisture||Dry matter loss||Digestible dry matter loss||Crude protein loss|
|11 to 20%||4.50%||6.20%||6.00%|
|20 to 25%||7.90%||11.80%||8.80%|
|25 to 34%||10.90%||13.50%||7.50%|
Protecting bales in storage
If you store dry hay outside, find ways to prevent direct contact between the ground and the bales’ bottom layer. Bales resting on the ground will absorb enough moisture to grow mold.
Research studies and farmer experience show that placing hay bales on layers of coarse gravel, old tires or wood pallets is an effective way to prevent rewetting the hay via soil moisture. Studies in other states indicate storage losses are about 5 percent less for hay stored on gravel, tires or pallets compared to hay stored directly on the ground.
Research: Hay storage in Minnesota
To better understand expected losses, the University of Minnesota West Central Research and Outreach Center in Morris studied different hay storage methods in Minnesota conditions.
Hay for the study was third-cutting alfalfa baled at about 18 percent moisture in September 1996. Researchers baled half the hay as large, round bales, measuring 5 feet in diameter by 6 feet long. The other half was baled as large rectangular bales that were 3 feet by 4 feet by 8 feet.
How bales were stored
Researchers stored the bales in four ways:
- Uncovered, directly on the ground (on pasture or sod).
- Uncovered, on gravel.
- Covered with a tarp, on gravel.
- In a shed with an earthen floor and an enclosed north side.
Round bales were stored on their sides, pyramid style, in piles of 12 bales. The bottom layer was three bales wide by two bales long, the middle layer was two by two and the top layer was one bale wide by two bales long.
Rectangular bales were stored in piles of 11 bales, all oriented the same direction, and resting on their four-foot-wide sides. Researchers stacked nine rectangular bales three wide and three high, and placed two bales on the top over the cracks between bales in the lower layers.
Bales were stored until mid-June 1997 (about eight months) and then reweighed, resampled and sold.
In the Morris study, researchers found the bottom bales stored uncovered on sod were rewet. This was true for both round and rectangular bales.
Moisture content went from 18 to about 32 percent, high enough to cause significant spoilage by mid-June. Spoilage would’ve been worse if they left bales in place through the summer.
The percentage of the total volume of bottom bales that appeared to be spoiled was about the same (22 to 23 percent) for both round and rectangular bales. By comparison, 1 to 8 percent of bottom bales spoiled if they were stored on gravel or in the barn.
If you’ll process the hay in a hammer mill or other processor that could be damaged by foreign objects, make sure stones don’t adhere to the bales’ bottom layer. Reduce problems with stones by using larger-sized gravel or crushed rock for the base, or by using pallets or tires instead of gravel.
Effects of covering hay
Water from rain and melted snow can also rewet hay to moistures high enough to support mold growth.
Studies at other universities have shown that covering hay can result in up to 10 percent less dry matter loss. In our study at Morris, covering bales reduced dry matter loss by about 6 percent. Average dry matter loss for bales stored covered on gravel was 4.8 percent, compared to 10.9 percent for bales stored uncovered on gravel.
When bales were stored uncovered on sod in Morris, the upper layers of round bales didn’t show any increase in moisture. Rectangular bales’ upper layers were rewet slightly to an average of about 22 percent moisture.
Even though the average moisture absorption in the upper layers was relatively small, the watershed locations (points where water ran off an upper bale onto a lower one) showed greater moisture increase and very obvious mold development, particularly in the large rectangular bales.
Dry matter losses
Dry matter losses caused by the combination of soil moisture and precipitation can be fairly large.
For example, in Oklahoma, researchers found 13.1 percent dry matter loss for uncovered storage on the ground versus a 2 percent loss for covered storage on pallets. Wisconsin researchers found a 10.9 percent loss for uncovered storage on the ground versus 4.6 percent in a barn.
In the Morris study, average dry matter losses in the uncovered piles on sod were 11.2 percent versus 2.3 percent in the barn. It appears that for eight to nine months of storage, keeping bales off wet ground and under cover can offer a 6 to 11 percent advantage.
Besides losing dry matter, uncovered hay also loses quality, as determined by nutritional analysis and appearance. The loss in dry matter reduces weight available for sale and the loss in quality can have a large impact on animal performance and hay value.
For example, in our Morris study, the internal parts of bales stored in the shed had a relative feed value (RFV) of 133, while the bottom six inches of the bales at the bottom of the pile had an RFV of 106. The internal parts of bales stored uncovered, outside on sod had an RFV of 114, while the bales’ external parts had RFVs ranging from 55 to 107.
In just eight months, the differences in hay weight, quality and price resulted in hay stored in the shed being worth about $3,350 more per 100 tons harvested than hay stored outside on sod. These numbers show it’s worth considering an investment in tarps and gravel, or even hay storage sheds.
Round bales vs. rectangular bales
Studies don’t show a clear advantage for one bale type over the other.
For example, despite the tendency for uncovered large rectangular bales to absorb more moisture than large round bales, our Morris study indicated no significant difference in average dry matter loss for the two bale types over an eight-month storage period.
- Greater availability of balers and handling equipment.
- Lower price for balers.
- Greater ability to shed water if bales are stored uncovered.
- Less efficient use of space in hauling and storing bales.
- A tendency for bales to lose their shape during storage.
Strategies for reducing storage losses
Hay waste can occur during both storage and feeding. Research shows outdoor hay storage losses for round bales can range from 5 to 35 percent depending on precipitation, storage site and the bale’s original condition.
For example, the outer 4-inch layer of a 6-foot diameter, round bale contains about 25 percent of the total bale volume and is most likely to be damaged by weather if stored improperly or unprotected.
A number of techniques can minimize outdoor storage losses of round bales:
Create or buy a dense bale. These will sag less and have less surface area in contact with the ground.
Use plastic wrap, net wrap or plastic twine. Research shows that net-wrapped bales reduce grass hay dry matter losses by 32 percent compared to twine bales when stored outside.
Use a good plastic covering (i.e., a tarp) when storing outdoors, which can cut storage losses in half.
Finding a storage area
Store bales on a well-drained surface. A well-drained, 4- to 6-inch coarse rock base will minimize bottom spoilage, as will storing on wood pallets.
Never store bales under trees.
Indoor storage usually reduces storage losses by approximately two-thirds.
Store round bales end-to-end when storing outside. Position round bales as tightly as possible in long lines on a well-drained site. If you need more than one line of bales, space adjacent lines at least 3 feet apart. This will increase air flow and allows sunlight to penetrate the bales. In a South Dakota study, dry matter losses of round bales were 4 percent for round bales stacked individually and less than 1 percent for round bales stacked end-to-end.
When storing round bales outside without cover, never stack round bales in a pyramid. Stacking tends to trap moisture and limits drying action from sunlight and wind. A South Dakota study reported dry matter losses of more than 10 percent after one year of storage for round bales stacked in pyramids.
More efficiently uses space in transport and storage.
Better shape retention during storage.
Greater moisture absorption by bales stored without cover.
Reviewed in 2018