5 Hay Hazards

As natural grazers, horses spend a majority of their free time eating. Therefore, it is imperative to feed horses safe, clean, and healthy hay. Feeding questionable hay can result in digestive issues, nutrient deficiency issues, and even possible death. By taking the proper steps to ensure that the hay is safe, you also work to ensure that your horse is safe.


Regardless of the type of hay, the quality of it is of the utmost importance. Eastern Hay Corporation specialists put it simply, “If it feels bad in your hands, just think how bad it will feel in your horse’s mouth.” Be sure to look at the hay, smell it, and feel it. Depending on the kind being purchased, know what to expect. Eastern Hay also suggests that, “The best precautions to take are to purchase hay from a trusted, reputable dealer and use your eyes. Be sure to scan every bale of hay you open in order to be certain it looks good enough to feed.” The biggest hazard that is associated with hay quality is colic. Colic is one of the biggest horse killers out there, so keeping a healthy diet is key. Coarse hay tends to be more likely to obstruct the intestinal system, according to veterinarian Grant Myhre. “A chronic collicer gets a finer grass with ample water in it. More water is always good, the more you soak the hay, the more you’re going to get into the horse.” It is important to consult with a veterinarian if you are unsure if your horse is getting all of his nutrients from his hay to avoid issues with nutrient deficiency.


One of the steps to having healthy hay is to know how to avoid moldy hay. Mold is created when moisture is stored in an enclosed space. According to Myhre, moldy hay’s biggest concern is dust. When a horse breathes in the dust that accumulates around moldy hay, “he’s acquiring a lot of those spores and inhaling those spores so the mold will then cause a reaction in the lungs, which then creates this chronic obstructive lung disease.” Myhre suggests to first, not feed horses moldy hay, but if it is a bit on the dusty side or the horse is sensitive to dust, steam or soak it. He also suggests looking at each flake, because “it only takes one time to cause a problem.”

In the case of hay, mold can grow in a few ways. One is improper storage. Ever notice how hay is more often than not stored in a hayloft or somewhere indoors and off the ground? This is to avoid any moisture from the elements finding its way into the hay. Consider this too when looking at hay, if it is stored in a dry place, the risk of mold after baling is reduced. However, if the hay is being left uncovered on grass, moisture and mold may have already seeped in. Brianna Randow, Quality Assurance expert at Standlee Forage stated, “The preferred way to store hay is in an enclosed barn or building with proper ventilation. If an enclosed facility is unavail – able, hay should be tarped for protection. If there is a possibility of moisture transfer – ring from the floor to the hay, there should be a barrier for protection.” Keeping hay out of the elements is key for not only preventing mold and pests, but also to be sure the nutrient quality does not drop. Overexposure to sun, rain, and snow can deteriorate the nutrients in the hay.

As for inspecting the hay for mold, the more methods used, the better. Once again, it is important to rely on our senses. When the bale is pulled apart, if a white dust cloud appears, this usually means that the bale was once wet, and has now dried out, suggesting mold may be present. The smell is another giveaway. If a bale smells like mildew or has any sort of odd smell to it, it is best to not pick that bale. Hay should just smell like hay, anything additional could be potentially dangerous to horses. “A chemical analysis identifies mold that cannot be seen or smelled and can also specify the type of mold that is present,” says Dr. Stephen Duren, Equine Nutritionist at Standlee Forage. A veterinarian can suggest places to have the hay tested.

Foreign Objects

When looking for new hay, it’s important to know where it is coming from. Different areas have the potential for different types of foreign matter and pests. “The most commonly overlooked hazard of hay would likely be presence of foreign material,” says Dr. Duren. Objects such as plastic and paper are usually easy to spot in a bale, but not all foreign matter is easily detected by a quick glance. In his time as a veterinarian, Dr. Myhre has seen a lot when it comes to horses consuming foreign matter through hay, such as wire or string that can obstruct the intestinal tract. Baling twine is another that can easily end up in the hay, considering it is what holds the bales together. When foreign objects get into the intestinal tract, it can lead to blockage and the possible need for surgery. Myhre said it’s simple, “Most horses don’t eat those things, but they can inadvertently, therefore you just need to be careful and check your hay.”


Organisms that either lived or died in the hay can release toxins that are harmful to horses. The most common concern among our experts in this regard is botulism. “Botulism is a serious concern if small animals happen to be baled up in the hay,” says Dr. Duren. When an animal such as a mouse dies, it excretes toxins that would go directly into the mouth of the horse, if it were in the hay. “Another (toxin) that is common in Kentucky,” according to Myhre, “is the mare reproductive loss syndrome association with tent caterpillars in their hay.” Each of our experts mentioned blister beetles as another organism that can release toxins that can be potentially life threatening to horses. “Blister beetles are common to certain areas of the country, such as Oklahoma,” says Dr. Duren. “If there is a possibility of blister beetle contamination, it can be controlled through spraying or selecting hay from a different part of the country.”

Dr. Duren also references a pest that most New Englanders deal with in the summer months: ticks. “Ticks in hay may also potentially spread blood borne diseases.” Though usually found in tall grass, ticks can still be a risk even in hay. Eastern Hay experts mention, “hay mites can appear under certain environmental conditions and can bite you, or your horse. Luckily they don’t occur very often and it generally seems to happen with hay that’s been stored for a while.”

Poisonous Plants

This one is a bit harder to detect over the rest of the hay hazards. Each flake must carefully be examined. Our experts all concur, if it doesn’t look like hay, take it out. “The best way to avoid a horse consuming hay with toxic weeds is to not feed it weeds at all. Sort through and visually inspect the hay before feeding,” states Dr. Duren. Removing anything that doesn’t look like hay is the best measure to take.

Eastern Hay experts explain that there is an endless list of harmful plants that can be found mixed in with hay. These include “horse nettles, Canadian thistle, cherry, red maple leaves, black walnut, locoweeds, yew, and milkweed.” Though most hay is properly cured, it is still important to properly examine it at each feeding time.

The most important part of preventing hazardous hay is to examine it, especially right before giving it to the horse. Although the initial inspection is, of course, important, keep in mind that pests and mold may cause issues after purchase. Consider this the cost of a questionable bale is preferred over the vet bills and discomfort of a horse suffering from hazardous hay. If it doesn’t look, smell, or feel right, don’t risk feeding it to your horse. If any other factors are still a concern, consider having the hay professionally tested through your feed company. Also, your veterinarian is a tremendous asset to evaluate the hay for abnormalities.

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