wrap the tree in horse fencing, the no climb kind or chicken wire... as the tree grows you need to expand it though, or the tree will just grow right through it... the other thing is to put 3 or 4 stakes about a foot out from the tree all around it and wrap around the tree using the posts to wrap around... trim up the tree so the mule can not get to it, you can also make sure they horse has the right mineral mix, as they are usually looking for copper, at least that is what I was told by a couple different people...
-- My horses love their track system~ http://picasaweb.google.com/dakota.charm/TrackSystem The Soul of a Horse ~ has touched my soul, may it touch yours too! ~ thesoulofahorse.com ~
