Chewing on wood can lead to cribbing, but it doesn't necessarily lead to cribbing, I don't think it even often leads to cribbing. I've had a butt-load of horses that would chew on wood, but never had a cribber. Get some No Chew and spray it on everything.

It probably will improve when he's got more to do and more room to do it.

If you're told about vampires, it's a good thing to be told about stakes at the same time.- Terry Pratchett