Question: “I read in Equus about the dangers of withered Red Maple leaves for horses. Is it true that just eating a few of these leaves can sicken or kill a horse? I have always let our horses graze in my back yard, surrounded by various maples and oaks. Should I stop? Are there times of year that are more or less risky? As far as I know, none of my horses have ever been sickened by this. Thanks for your advice.”

The question is excellent. Every year horses suffer from Red Maple Leaf Toxicosis.

Last fall, I was covering emergency “on call” for a local colleague. I received a page from a client of hers. The client reported that she had taken her young Haflinger out for an afternoon trail ride. On the ride, she noticed that her horse was not acting like “himself”. During the ride, the Haflinger stopped and urinated and the urine was a red wine color. Alarmed, she jumped off of him, brought him back to the barn, and called me. In the barn, he urinated a second time and again the urine was dark red wine in color.

After listening to the client, I asked her if there was any possibility that her horse had eaten withered red maple leaves. She did not know. I told her that it was imperative that she get her horse on a trailer and get him to a hospital for evaluation and emergency treatment. She did so quickly. We found out later that there had been red maple leaves, wilted, in the bale of hay fed to the horse that morning. If it had not been for the client’s quick actions, noticing the urine, taking the horse immediately to a referral hospital, the horse may not have survived.

From June through October wilted, or partially wilted, leaves of the Red Maple tree are deadly to horses. The older, drier leaves cause faster poisoning than the early summer leaves. The leaves remain toxic and deadly for three plus weeks once they dry and wilt on the ground. Horses that ingest even just small amounts of these leaves often die from a profound anemia that is caused by the destruction of the red blood cells in the horse’s system. Horses may die within as little as 18 to 24 hours due to a lack of oxygen delivered to vital organs.

Not all maples are Red Maples and we do not know the affects of all maple leaves red in color on our horses. However, because of the profound effects of Red Maple Leaf Toxicosis, and to be on the safe side, I would absolutely recommend avoiding the exposure of any horse to red colored maple leaves. If your horses have access to leaves from a Red Maple tree I would recommend:

• Simply do not allow your horse access to Red Maple leaves. Ensure that fallen leaves and branches are not allowed into horse areas. Fence off Red Maple leaf areas.

• It may sound extreme, but consider cutting down any Red Maple tree that could “contaminate” your property. Ensure the stumps are completely dead so that they do not sprout leaves and shoots.

Red Maple leaves can be toxic at just 1.5 pounds per 1,000 pound horse. Red Maple leaves can be lethal at just 3 pounds per 1,000 pound horse! Why risk any amount of red maple leaf ingestion?

Great question and rethink allowing your horses out in this area from late spring through the fall.

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