Tree bark trimming

This woodlot caught my attention as I took a wrong turn out in the country. The trees have been peeled of bark to an even height all within a space enclosed by electrified wire. It wasn't until after I stopped and began clicking away that I noticed three very large horses to one side eating hay. Their shaggy winter coats and shy demeanor gave them a mysterious appearance. I could not get a proper capture since they were off to the back. I hope to try again.
They are the reason the trees are nickered... I believe that is the term. They do not seem to have any other shelter than the trees.