Are Acorns Toxic to Horses?

If you happen to own horses, you know what a blessing they can be. You also know it takes a lot of work to give them the care they need. Since they spend most of their time outdoors, it’s important to know what may be toxic to horses. There is a long list of trees that can make horses sick, such as the red maple, chokecherry, buckeye/ horse chestnut, black locust, black walnut, and oaks. When eaten in large quantities, acorns are toxic to horses.

According to Tufts University, “The parts of the tree that can cause trouble are the immature leaves that appear in the spring, and green unripe acorns, which have the highest level of toxins. The leaves and acorns that fall in the autumn are not as toxic and horses tend to stay away from them.” Tannins found in acorns are also toxic to humans but boiling them until the water runs clear removes the tannins, making them safe for human consumption. Tannins and gallotannins are what make acorns, flower buds, and oak leaves toxic for horses. Researchers believe there may be more toxins in oaks that have yet to be discovered.

A horse would have to consistently consume the acorns, flower buds, and/or leaves over days or weeks to experience oak toxicity. Even though this is rare, it does happen if a horse is doesn’t have access to the foods they should be eating, or if they’re bored. “Typical symptoms include depression, inappetence, colic, diarrhea, ventral edema, apparent straining to urinate, and red-brown urine. The rare horse with oak toxicity often needs sustained fluid therapy for kidney damage, as well as supportive care for the colic or diarrhea caused by the oak toxins.”

You don’t have to cut down oak trees in areas where horses graze. To avoid toxicity from happening to your horses, keep the grazing area clean and make sure they have plenty of grain and hay to eat. Collecting acorns is quick and easy with a Bag-A-Nut Acorn Picker. You should also keep branches trimmed so the horses can’t reach them. If necessary, build fences around young oaks for protection. Taking these precautions and educating yourself are the best ways to keep your horses healthy.

Further Reading

The Truth About Acorn Toxicity and Horses | Cummings School of Veterinary Medicine (tufts.edu)

Plants Toxic to Horses (psu.edu)

Trees in Horse Pastures (psu.edu)

Oak buds and green acorns can harm horses (umn.edu)