Hay is the foundation of most horses’ diets, but “hay” is not automatically safe. The biggest risks are toxic plants mixed into a bale, mold or poor storage, unfamiliar forage introduced too quickly, and cut grass clippings. If a horse has eaten questionable forage and is showing colic signs, diarrhea, weakness, neurologic changes, breathing trouble, or difficulty standing, remove access and call a veterinarian promptly.
Hay and forage hazards horse owners should know
Do not rely on a plant name alone to decide whether a bale is safe. Risk varies with species, growth stage, weather damage, endophytes or other toxins, contamination, and the amount eaten. A local extension forage specialist or equine nutritionist can help identify unfamiliar plants.
Moldy, dusty, or heated hay
Musty-smelling, visibly moldy, damp, or unusually warm hay should not be fed. Mold and dust can aggravate respiratory disease, while heating in a damp bale can signal spoilage and create a fire hazard. Do not assume that shaking out a bale makes moldy forage safe; discard questionable sections and ask your veterinarian or hay professional for advice.
Forage containing toxic weeds
Some weeds and grasses can injure horses under particular conditions. Examples include sorghum-family forage when it has been stressed or improperly managed, certain endophyte-infected grasses, and plants contaminated with ergot or other toxins. Foxtail-type forage can irritate the mouth when mature seed heads are present. Because identification is difficult from a generic web list, photograph the plant, retain a hay sample, and contact a veterinarian or county extension office rather than guessing.
Fresh lawn clippings
Never feed a horse a pile of lawn clippings. Clippings can be eaten rapidly, ferment in a dense mass, contribute to choke or digestive upset, and contain herbicides, pesticides, poisonous weeds, or other debris. Let cut grass dry naturally in the field and use only forage that has been properly harvested and evaluated for horses.
How to inspect a bale before feeding it
- Open a bale and inspect the interior, not just the outside.
- Reject hay with a musty, sour, chemical, or unusually hot smell.
- Look for visible mold, excessive dust, wet spots, insects, foreign objects, and unfamiliar seed heads.
- Ask how the hay was cured and stored. Hay should be protected from precipitation but have appropriate ventilation.
- Keep a representative sample if illness occurs; it can help a veterinarian or laboratory investigate.
- For horses with metabolic, respiratory, or other diet-related conditions, have forage analyzed and follow a nutrition plan rather than choosing by color alone.
Safer feeding practices
Introduce a new lot of hay gradually when possible, and keep clean water available. Feed from a clean, well-drained area that reduces contamination with soil and manure. If dust is a concern, discuss soaking or steaming with your veterinarian; soaking can also change nutrient content and should not replace a balanced ration. Horses with insulin dysregulation, recurrent airway obstruction, or a history of forage-related illness need individualized guidance.
Feed changes, weight loss, repeated loose manure, coughing, nasal discharge, mouth sores, stumbling, or unusual behavior deserve attention. Do not wait for a dramatic reaction before investigating a questionable bale. For practical guidance on forage quantities and body condition, see how much land a horse needs, how the equine digestive system works, how to budget for essential horse care, and emergency planning for horses.
Frequently asked questions
What is the most dangerous hay for horses?
There is no single universally dangerous hay because risk depends on plant identity, contamination, curing, storage, and the horse. Moldy or contaminated hay should be treated as unsafe, and unfamiliar forage should be identified before feeding.
Can horses eat lawn clippings?
No. Fresh lawn clippings can be consumed too quickly, may ferment, and can contain chemicals or toxic weeds. Keep horses away from piles of cut grass.
How can I tell if hay is moldy?
Look and smell for visible mold, dampness, dust, clumping, discoloration, or a musty or sour odor. Open the bale and inspect the center. When in doubt, do not feed it and seek professional advice.
What should I do if my horse eats questionable hay?
Remove access, save a sample or photograph of the forage, observe the horse, and call your veterinarian. Seek urgent help for colic, weakness, neurologic signs, breathing difficulty, severe diarrhea, or trouble standing.