Horse Feed Storage and Preservation

Buy quality hay and grain and store it in cool, dry places to preserve nutrient content and prevent spoilage.

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To prevent feed degradation, mold growth, or contamination, owners should obtain and preserve the safest product

feed storage
Store grain in secure containers and avoid leaving bags open or unsealed to prevent vermin from coming in contact with horses’ feed. | Photo: Alexandra Beckstett/The Horse

Poised on a Peruvian hillside sits a cavelike construction that once held a cache of food to supply an entire village. The steady cool temperature and darkness preserved it from rapid decomposition—a practice of storing food that developed over millennia. But in today’s world, on a moment’s whim, we find what we need at the supermarket, the farmer’s market, or in our backyard garden, with little need to keep substantial quantities of food on hand. When it comes to stocking up on feedstuffs for our horses, however, we still rely on storage and preservation lessons learned through history and science.

Ideally, owners should obtain the safest product and preserve it for feeding throughout the year, preventing feed degradation, mold growth, or contamination that could harm their horses.

Hay Storage

In much of the United States hay only grows during temperate months. The best quality is obtained and the best prices achieved by putting up a supply that will last until the next harvest. To keep stored hay as fresh and palatable as possible, focus on preventing mold development, heat buildup and combustion, and nutrient deterioration.

Proper hay harvesting and drying is important to control “respiration,” a naturally occurring process that produces heat and bacterial growth. Michael Collins, PhD, former professor of agronomy at the University of Kentucky, describes some of the science behind hay production: “Hay crops generally contain around 80% moisture at the time of cutting; field curing reduces moisture to levels (at which hay) can be safely stored. Hay cured to less than 16-20% moisture stores well with minimal problems of heating or mold growth. However, if baled with too much moisture (25-35%), microbial activity generates significant amounts of heat. In extreme cases, hay can reach spontaneous combustion temperatures.” Hay heated to 150-175°F has the potential to burst into flames, posing great danger to a horse facility.

In the initial weeks following baling, moisture and heat combine to maximize combustion risk. Thus, Kathleen Crandell, PhD, of Kentucky Equine Research, advises horse owners to monitor moisture levels (keeping them below 14%) and heat for two weeks after stacking new hay. They can achieve this by inserting an electronic probe (Delmhorst, for example, to measure moisture) and a temperature probe into bales to ensure temperatures remain below 120°F. If you come across hotter bales, remove them from the stack and spread them out in an area protected from rain to allow drying.

After buying properly cured hay, store it in a building separate from the barn with a leak-free roof. And, to thwart wicking of ground moisture into bales, Collins says to place bales on a layer of loose straw, crushed gravel, or wooden pallets. Otherwise, condensation forming beneath bales sitting directly on dirt or concrete can lead to mold growth and spoilage.

Crandell recommends stacking hay so air can circulate freely to evaporate moisture. “Stack square bales on edge, leaving narrow gaps between rows, alternating bale orientation in each layer and stacking no more than four or five bales high,” she suggests.

More horse farms are using round bales as an economical, less labor-intensive way to feed hay. Crandell suggests these bales be well-dried before stacking, as well.

Ventilation and air circulation also are essential in lofts, where hay is particularly prone to hazards of heat and spontaneous combustion. Follow Crandell’s recommended stacking regimen, refraining from stacking bales tightly or all the way to the ceiling. Lofts also tend to accumulate dust, which can build up on hay and cause respiratory problems for horses.

Protect hay stacks stored outdoors with well-secured waterproof tarps or other coverings that will withstand wind, rain, sun, and snow. Canvas tarps are superior to plastic covers, which are prone to punctures and leaks. Exposure to air (causing oxidation), sunlight, and weather extremes also subjects hay to nutrient loss. “Vitamin deterioration is inevitable, beginning the minute forage is cut in the field,” says Crandell. “As much as 75% of carotenes (vitamin A) diminish in the first 24 hours. Even under ideal storage conditions, more than 5% of vitamins are lost each month, possibly necessitating supplementation with a vitamin/mineral mix, ration balancer, or commercial concentrate.” Perform a hay and/or pasture nutrient analysis to determine supplement needs.

Stored Forage-Related Health Concerns

It is also important to consider potential dangers lurking in the hay and other stored forages themselves. Consuming as few as three to six blister beetles in legume hay (such as alfalfa or clover) can kill a horse. These insects often reside in hayfields and can be killed and baled during harvest. “(Owners are) less likely to encounter blister beetle problems in spring or early summer first-cutting hay since they are attracted to flowering plants that often coincide with late summer cuts of alfalfa,” says Collins. “Pre-bloom cut hay is less likely to be infested.”

Blister beetles might be more prevalent during years with bumper crops of grasshoppers, since they also feed on grasshopper larvae.

Hay poses another health threat: Horses might ingest spores of the botulism bacterium, Clostridium botulinum. “While not as common in hay as with ensiled feeds (i.e., haylage), botulism is usually associated with the presence of dead animals caught up in hay during baling,” explains Crandell. “It also occurs from ingestion of contaminated soil baled with trampled forage. An environment conducive to C. botulinum also promotes mold growth, yet another reason not to feed moldy hay.”

Haylage is high-moisture hay that has been compressed and encased in plastic within hours of harvesting. This processing environment couples high moisture and anaerobic (not requiring oxygen) fermentation, which can encourage proliferation of C. botulinum. “Moldy or discolored haylage should not be fed,” says Crandell.

She recommends inspecting hay and haylage carefully before feeding and disposing of suspect material. “Inspection can be difficult with round bales, but with availability of adequate forage, horses tend to eat around bad hay due to poor palatability,” she says.

Grain and Supplement Storage

Moisture is the enemy when storing forage or grain-based feeds, as well. To decrease the risks of decomposition and mold development, Crandell counsels owners to keep feed in cool, dry environments, with containers tightly closed to seal out moisture, insects, or rodents. Just as with forage, oxidation affects short-lived vitamins, particularly B-vitamins such as biotin.

Exposing cereal grains (oats, barley, and corn, for example) to high humidity or moisture can lead to mycotoxin production, which can have dangerous health consequences for horses. “Various mycotoxins are produced from fungi present at grain harvest that proliferate in the presence of moisture or humidity during storage,” Crandell explains. “Very small amounts of mycotoxins won’t usually affect a horse. A recent survey found these present in over 80% of grains. With (consumption of) significant mycotoxin levels, reduction in feed intake may be the first sign of a problem.”

Often, fungi are neither visible to the eye nor with a black light. “Some describe a pinkish, reddish hue to some corn kernels,” Crandell adds. “The only way to accurately test is to submit the sample to a lab. Moldy-looking feed may or may not be contaminated (with mycotoxins) but should not be fed to horses under any circumstance.”

A horse consuming moldy corn is at risk of developing liver failure and a serious neurologic condition called equine leukoencephalomalacia (ELEM, or moldy corn poisoning) caused by the mycotoxin fumonisin. Conditions that favor fumonisin growth on corn include a humid climate and a dry summer, followed by wet weather at harvest time. “During years of questionable corn harvests,” explains Crandell, “safe recommendations limit corn concentrations (in feed recipes) to less than 20% along with heating of corn through steaming, pelleting, or extrusion.”

All grains—not just corn—are subject to mold and mycotoxin development. Crandell reports that Aspergillus fungi produce alfatoxins in cereal grains; at high levels, these too are detrimental to horse health.

Stored Grain Longevity

Crandell explains that feed companies generally designate expiration dates within 30 to 60 days after grain product manufacture. If owners maintain feed under ideal circumstances, it might remain safe for four to six months, with straight whole grains (unprocessed, uncrimped) potentially lasting years, she says. Feed should contain few broken kernels, be kept in low-moisture (less than 13%) conditions, and safeguarded from insects and rodents. Humidity and temperature of storage facilities, degree of rodent or insect infestation, and exposure to air impact shelf life. “Store bags on pallets and try not to stack them more than five high, especially in humid climates,” says Crandell. “Sealed bags last longer than open bags. Once a bag is open, the clock starts ticking with quality of feed subject to degradation from exposure to air, humidity, and heat.”

She notes that adding molasses and/or oil to grain mixes increases moisture levels and can also affect shelf life. And high-fat feeds are more prone to rapid spoilage from the oxidation that degrades fats and fat-soluble vitamins (and causes them to go rancid). “Manufacturers add preservatives to slow oxidation, mold, and bacterial growth, but this doesn’t prevent deterioration, which is determined by storage conditions,” Crandell says. With rising temperatures and humidity during summer months, a feed’s shelf life decreases. Thus, Crandell advises keeping on hand only as much grain as can be fed within three to six weeks, or, if purchasing large volumes at one time, installing air conditioning in storage rooms.

Pelleted feeds’ shelf life might be longer not only because of lower moisture content but also due to heat treatment associated with pelleting. “Textured feeds usually include pellets containing the ‘loose’ particles (protein source, minerals, vitamins, yeast),” Crandell observes. While pellets generally last longer, other ingredients in a feed mix can shorten the shelf life. “Pellets are mixed with grains, beet pulp, and molasses—moisture differences and quality of all constituents affect shelf life,” she says.

Pest Protection

Fewer moisture-related problems arise when storing feed in breathable paper bags or wooden bins; however, these are not necessarily pest proof. Metal or hard plastic containers with secure lids reduce losses and spoilage, as well as prevent contamination with pathogens that pests can introduce such as Sarcocystis neurona (which causes equine protozoal myeloencephalitis, or EPM) or leptospires (causing leptospirosis). Horses can develop EPM from ingesting feed containing opossum feces. They contract leptospirosis by ingesting feed contaminated with infected mammals’ urine. Discard forage or grain that has been soiled with pest urine or feces. The best prevention is to store feed where rodents or other varmints can’t access it.

Plug rodent-sized holes in a feed room with steel wool or mesh to discourage mice; scattering sheets of fabric softener around the area also can achieve this. Use a feed storage container made of a material that rodents can’t chew their way into, and seal it securely with a lid that raccoons and other dexterous critters can’t open. “Galvanized metal trash cans effectively deter rodents,” says Crandell. “Since warm air hitting cold metal causes condensation inside that increases the chance of mold, these work best when kept in a temperature-controlled room.” She notes that metal-lined wood bins might also prevent rodent damage; however, wood does little to discourage insect intrusion or prevent spoilage from air exposure.

Moisture encourages not only mold growth but also insect proliferation within grain kernels. “Insects (weevils, grain mites, or beetles) eat grain from the inside out, removing nutrients,” says Crandell. “As with broken grain kernels, insect breakdown opens up grains to oxidation and mold growth, leading to a stale smell and significant decrease in palatability.”

Pest protection isn’t the only critical element of animal-proof feed storage: It is important to secure grain and supplement containers in a locked room or bin that can’t be accessed by a horse that has escaped from his stall or paddock. Unhindered access to feed can mean a very sick horse. Also to that end, on horse farms with small animals, chickens, ducks, or other livestock, take additional precautions to lock their feed supplies away from horse access.

Take-Home Message

Storing forage and grain properly helps maintain nutrient content and feed palatability. Critical aspects of safe storage include keeping feed in cool, dry locations to avoid moisture accumulation. Also remember that starting with a quality feed contributes to your feed stores’ longevity and nutritional impact.


Written by:

Nancy S. Loving, DVM, owns Loving Equine Clinic in Boulder, Colorado, and has a special interest in managing the care of sport horses. Her book, All Horse Systems Go, is a comprehensive veterinary care and conditioning resource in full color that covers all facets of horse care. She has also authored the books Go the Distance as a resource for endurance horse owners, Conformation and Performance, and First Aid for Horse and Rider in addition to many veterinary articles for both horse owner and professional audiences.

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