Dear Jessica, I am a new subscriber and enjoy your newsletters. I have a question regarding a subject I haven't seen listed before.
Last winter, I boarded a friend's horse for a short time. My pasture area is not much pasture but there is a lot of open area and there is also a lot of trees, mostly popal and a few maples. Anyhow, I noticed her horse started stripping the bark off all my trees. He literally strips the bark from the top or bottom until the entire trunk (or side of the trunk) is smooth and bare (if it doesn't peel in strips he will chew the remaining chunks off). From what I can tell he doesn't actually eat the bark because I noticed it mostly sitting at the base of the tree, although I'm sure he must digest some of it. I have had one trainer suggest that his diet is deficient of something and another who suggested he is just bored and I should spray my trees (I would have to spray alot of trees) and put out more hay. Eventually, his owner picked him up and took him home but unfortunately my other horses have now picked up this bad habit now. I could care less about my trees, I just worry that my horses' diet is lacking something or that they are digesting the bark and could eventually have some health problems. What is your take on this situation and how would you suggest I handle it? Thank you. Lorie
The danger is probably far greater for the trees than for the horses, especially if they're just stripping and dropping the bark instead of actually eating it. But even if they are eating some of it, I've never heard of popal/aspen trees being toxic to horses. Obviously if some of your trees are toxic to horses (red maple, wild cherry, etc.), you won't want them in or near your pasture anyway, but if your maples are other types of maples - sugar maples, for example - then the real danger will not be to your horses but to the trees.
Trees don't live when their bark is stripped off all the way around. If there are trees that you don't want to keep, you can just plan to cut them down eventually; if you LIKE any of your pasture trees and want to keep them, you'd better put fences around them, far enough from the trees that the horses won't be able to stretch their necks and reach the bark. Do this even if you try some other ways to discourage the horses from bark-stripping, because you may lose more trees during the time you're trying to find a way to make the horses lose interest.
Your trainers are probably right - at least about the initial reason for the horses to start chewing the tree bark. Once they've begun to do it, it can become a habit - and in the spring, long before the grass comes in, the sap may make bark-stripping rewarding by providing something that tastes fresh and sweet (maple syrup comes from maple sap). If horses learn that trees taste good in spring, you will eventually have no trees at all... so no matter what else you do to cure or prevent this behavior, DO fence in your trees for their own protection.
Boredom may well be a factor, so can lack of forage, and so can the lack of salt and/or certain other minerals (ask your vet about copper). You might begin by providing the horses with a salt block and a salt/mineral block (be sure to get ones for horses, not for cattle or deer) in the pasture - in some cases, that's all it takes to cause horses to lose interest in eating pasture trees and fences. Forage is another major factor - do you supplement with hay when your pasture grass is getting low? Horses are hard-wired to nibble all day and all night, and to pull and tear at forage - that's how they graze. If there's insufficient grass - or no grass - in the pasture, they'll need hay, both for nutrition and to keep them busy. You may need to put your horses on a "Southern California grazing" plan - that is, compensate for the lack of natural grazing by providing the horses with free-choice grass hay whenever they're turned out. Horses will eat bark when there's nothing else in the field to eat - investigators for horse rescue organizations often find trees without bark in places where horses have been turned out and left to starve.
I wouldn't advise spraying your trees - as far as I know, no one has yet managed to find a substance that can be sprayed or painted on wood, absolutely prevents wood-chewing (or bark-stripping), AND is non-toxic to both horses and trees! I'm truly not sure what sort of products would be available, let alone effective, if you DID decide to spray the trees. In any case, it seems likely, based on your description, that some trees are already dead or dying, in which case spraying would be pointless.
Salt and forage would be my suggestions - "boredom" in a large field isn't generally a problem for healthy horses, because they spend so much of their time grazing. Providing them with the salt and forage they need will keep them busy walking and "grazing" day and night, and boredom isn't likely to be an issue. But do, by all means, protect your living trees. You say that you don't care about your trees, but your feelings might be different if they all died. You should also consider the financial implications of letting the trees die. First, it takes equipment and time and energy - or money to pay for someone else's equipment and time and energy - to remove dead trees and get rid of stumps. Second, the absence of trees would make your horses entirely dependent on a shed for their windbreak and rain/snow/sun shelter. If your horses don't have a shed, and you've been counting on the trees to provide them with a natural windbreak and protection from rain, snow, wind, and summer sun, you may find that putting protective fencing around your pasture trees costs less than building or buying a three-sided shed that will accommodate all of your horses.
Good luck - I hope you find a way to maintain healthy horses AND healthy trees.
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