Effect of Acer species (red and Freeman maple) and horse characteristics, management, and location on the in vitro oxidation of equine erythrocytes.
Wickizer LF, Burk SV, Lehman JS
Plant Toxicology
Freeman maples are planted in millions of suburban yards and parks as ornamental shade trees, and if one overhangs a paddock or trail, it poses a measurably higher poisoning risk to horses than red maple — a danger most owners don't even know to look for.
Researchers tested whether two common maple trees — red maple and Freeman maple (a popular hybrid often used in landscaping) — were equally dangerous to horses. They soaked leaf extracts with horse blood cells and measured the damage. Freeman maple turned out to be significantly more harmful, destroying about 65% more blood cells than red maple, suggesting it may be the more dangerous tree for horses to graze near.
Key Findings
Freeman maple leaf extracts produced 64% more methemoglobin and 67% more hemolysis than red maple extracts in horse blood cell tests (n=120 horses).
Barn location (site) was the largest single factor explaining differences in blood cell oxidation between individual horses, outweighing age, breed, and body condition.
Regression models explained 22–89% of variation, with age and time of sample collection as minor additional contributors for red maple, while only barn site remained significant for Freeman maple.
chevron_right Technical Summary
Both red maple and Freeman maple leaves are toxic to horses, but Freeman maple — a popular landscaping hybrid — caused roughly 65% more blood cell damage in lab tests than red maple. Horse owners and property managers near pastures should treat Freeman maple as an equal or greater hazard than red maple.
Abstract Preview
Red maple toxicosis arises when horses consume wilted maple leaves, resulting in methemoglobinemia and hemolytic anemia due to oxidative damage to erythrocytes. The objective of this study was to d...
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