Hi there Jessica!
I enjoy your newsletter very much and really like your wise, balanced point of view! I hope that you can answer my question! In a few weeks, my family is going to bring our horses home. On the path to the barn there is a layer of 4-year-old partly decomposed black walnut wood chips. These wood chips also go down into the pasture a ways. I know that black walnut makes horses founder, but is this decomposed stuff a problem? How long does the potency last? Hope to hear from you soon!
Hi Amanda! I don't know the answer to your question, but I'm not sure I'd want to take a chance with black walnut shavings of ANY age, anywhere on a horse property.
It's possible that if you're just walking the horse back and forth, and its feet are in contact with the path for no more than a few moments each day, you might get away with it, especially if you are careful to wash the horse's feet and legs after each contact.
The main problem is that black walnut is so very damaging to horses. As many horse-owners have found to their great sadness, 20% of black walnut in shavings/bedding will bring on laminitis within a day, and bedding containing even 5% is enough to produce clinical signs.
There is something in black walnut that causes the damage, but in spite of the best efforts of a number of scientists, nobody has managed to find out precisely what the toxic element is. The toxicity is obvious - someone did an experiment that involved giving horses 2 (yes, two) grams of heartwood extract via nasogastric tube, and even that tiny amount was enough to produce clinical signs.
I don't think that anyone has tested black walnut shavings over a period of several months to see whether they continue to have the same toxic effect, but here's what would worry me: Since we haven't identified the toxic element, there's no way to test the shavings to see whether the toxic element
In the absence of good information on that subject, I really wouldn't take the chance. If I were you, I'd remove those shavings and replace them with something that isn't dangerous to horses. They might be safe by now, but I don't think there is any way of being sure, other than using your own horses as test subjects, and that just doesn't seem like a very good idea. If the toxic element is still active, and a horse got loose and took a few bites of the shavings, as horses often do when they're curious about something, the results could be very bad.
There are a few things I simply wouldn't accept on a horse property - black walnut tree or shavings, barbed wire, red maples, and yew, for instance. The dangers are simply too great.
This article reprinted by special permission of Dr. Jessica Jahiel, from www.horse-sense.org
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