Every once in awhile I get to work with really, really cool people who do really, really cool work. This is one of those times. About a year ago I received a message from Dr. Stephanie Valberg, a Professor over at the University of Minnesota’s Equine Center. It seems that she was interested in looking at a deadly disease called Seasonal Pasture Myopathy which she thought might have something to do with horses ingesting maple leaves. Specifically, at the time she contacted me, she thought that this disease might be associated with horses ingesting tar spot, a common disease that maples get. Seasonal Pasture Myopathy is a particularly nasty disease because it is fatal in over 90% of cases, and the death is far from painless.
After doing site visits to many farms where this disease was found, she discovered something very important: Every farm had box elders in a location where horses could feed on the seed when they got hungry. And for most of the farms, horses were also dealing with scant pickings in terms of food. They usually had sparse pastures and not much supplemental hay. So, in these conditions, the horses might find box elder seed attractive, or at least palatable.
After a literature search, Dr. Valberg discovered an old article showing that box elder seeds could very well contain a toxin, hypoglycin A, which might cause this disease if they were eaten. After testing the seeds for the presence of this toxin (Done by a friend of mine, Adrian Hegeman, located here in the University of Minnesota’s Department of Horticultural Science) it was established that, Yep, box elder seeds have this toxin, and if your horse eats them, it might be in trouble. You can find out more here.
Right now more work is going on to see if this toxin is more or less present in box elder trees that are under stress, if it is present in other parts of the tree besides the seeds, and at what time of year the toxin might be most present in the seeds. It also looks as though some other maples may have this toxin in their seeds, most notably sycamore maple.
All in all, having the opportunity to watch this work unfold has been one of the highlights of my career. It was like watching an episode of House unfold in real life. And the great part is that this work has the potential to save the lives of dozens, if not hundreds or thousands, of animals. So if you have horses, and box elder or sycamore maples in your pasture, be careful!
3 thoughts on “A Note To Horse Owners”
Wow. What a discovery. I have friends and relatives who have horses. I will pass this information on to them.
Do you know of any resource that will tell other maples that have this toxin? The word is out among horse owners in our area that red maples (Acer rubrum) are poisonous to horses, and it would be nice to know one way or the other if there is any truth to this.
I can’t say anything for sure, but I believe that red maple seed is not likely to have the toxin.