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Equine Health Resource

Red Maple Leaf Toxicosis

Wilted or dried red maple leaves contain a toxin that causes damage to a horse’s red blood cells, causing rupture of the cells (hemolytic anemia), and an inability of the red blood cell to carry oxygen. It is a life threatening condition. A large percentage of affected horses die from this condition.

Toxicity is a problem primarily when trees or branches have fallen on the ground, especially in the autumn months when the leaves fall. Just a pound or two of wilted or dried leaves can be fatal. The toxicity is probably lessened or lost by the following spring. Other maple species seem to have similar toxins but possibly at a lower concentration and so are not thought to be as dangerous.

Diagnosis is often presumed based on common signs of serious illness including loss of appetite, rapid breathing, pale or reddish gums and high heart rate in a horse that has had access to red maple leaves.

Treatment includes blood transfusion and the use of medications that prevent damage to red blood cells.

PREVENTION

Red maples are common in parts of the United States. Most healthy, well-fed horses do not like to eat red maple, so removal of these trees is usually not necessary.

However, consider taking a few precautions to reduce the likelihood of significant consumption of these toxic leaves. Identify all red maples on your property that are accessible by horses. Pay special attention to horses that have access to red maple, and ensure they are well fed or have plenty of good grazing.

Minimize your horses' access to dried or wilted leaves of the red maple tree whenever possible. Check for and immediately remove fallen limbs and leaves after summer storms. Trim low maple branches back, and clean up leaves and branches that fall to the ground. Avoid planting new maple trees, of any variety, in or near turnout areas or areas where horses are housed. While other maple species may not have as much toxin, they still are best to keep away from horses.   

Do not allow your horse to browse on leaves of species you can't identity while on the trail. Do not tie horses near unknown trees.

Helpful Outside ResourcesCredible Equine Health Information on the Internet

Author: Doug Thal DVM Dipl. ABVP

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