We have a herd of seven horses of various breeds. We live on approximately one hundred wooded acres. We partially cleared approximately ten acres for horses leaving it heavily wooded. We supplement with year round hay and they receive grain each day that is prepared by a livestock/equine nutrition expert that is a family member. They are in good condition. We use them primarily for trail riding and my daughter gives some riding lessons in the summer. She went to college for equine management and training. None of our contacts have seen this behavior either. These horses have been eating the bark off the trees. They have completely killed an area of three acres. The stripped these trees up to approximately twenty feet. They loosen the bark and peel it up until it breaks. I'm stumped. Any suggestions?
It can be very frustrating to deal with behaviors that not only seem to have no cause but also are so damaging to your property! It sounds like your horses are displaying a form of the stereotypy wood-chewing. A stereotypy is a repeatitive behavior with no apparent cause. However when you start to look at stereotypic behaviors, we see that they often have a cause. In the case of wood-chewing, some behaviorists theorize that the horses are missing nutrients. Other times, the horses are frustrated and that causes stress that comes out in the form of stereotypies. Since your property is heavily wooded, I'm going to guess there's not a lot of available grass. If you are supplementing with square bales instead of round bales or if your round bales are not good quality, your horses may be frustrated because they don't have forage available 24/7. Horses are made to eat throughout the day, and when they can't sometimes they turn to wood-chewing to deal with their frustration.
I have a wood-chewer, and he does much better when he has constant access to either grass or hay (in the form of a round bale), and when he's in a stall he also does better if he has a mineral block to chew on. You might try those two things and see if they help. Unfortunately, sometimes once horses start chewing wood, they are reluctant to stop - even once you've given them alternatives. At that point, you either have to let them kill off your trees or restrict their access to the trees by wrapping tree trunks in chicken wire or covering the tree trunks in something like "Chew Stop" or a similar product.