our horses do the same thing. What we do is supply them with wood they are allowed to chew on i.e. some old logs and make the fence posts harder to get to and less appealing by bad tasting stuff and chicken wire. I find its way better than trying to get them to stop altogether.
When I bestride him, I soar, I am a hawk: he trots the air; the earth sings when he touches it; the basest horn of his hoof is more musical than the pipe of Hermes. ~William Shakespeare