The drought in Missouri has caused an early leaf change in
our trees this year at the research center.
As I got into my truck this morning, there were fallen leaves from the
huge silver maple that sits next to my driveway stuck in my windshield wipers
and it got me to thinking about the dangers dead maple leaves can pose to
horses and I decided to write a blog post about it.
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Red maple tree just beginning to show its’ fall colors –
Photo by K. Williamson
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Red maple trees (Acer
rubrum) are absolutely gorgeous in the fall when their leaves turn bright
flame red, which is one reason why they are among the most popular ornamental
trees in the United States. However, red
maples can pose a serious health risk to horses. The dried or wilted leaves of the red maple
contain an unknown oxidant toxin or combination of toxins which cause damage to
red blood cells leading to a condition known as acute hemolytic anemia and/or
increased formation or abnormal accumulation of methemoglobin (an abnormal form
of hemoglobin that is not capable of carrying oxygen). Horses are more susceptible and commonly
affected by RMT than other species. Red
maple toxicity may occur throughout the growing season but cases are more
common during the late summer and fall.
The seasonal increase in cases of RMT appears to be due to 2 main
factors: First, the toxic principle(s)
in the leaves appear to increase later in the growing season and are especially
abundant in the fall. Second, horses
have more access to the toxic leaves during the fall months when the trees are
shedding their leaves which may fall or be blown into pastures. Consumption of as little as 1 gram of red
maples leaves per kilogram body weight can result in fatality.
