My observation regarding wood chewing is it’s a pain response. Often the horse will chew wood because he has pain issues and this is an expression that he’s feeling pain. It might help the horse to get massaged or chiropractic care. It could be his joints hurt, or muscles are tight. Once the pain is under control then he will probably stop chewing wood. Along this same line, cribbing can be an expression of a mineral deficiency. I hope this viewpoint is helpful so the owners look deeper at possibilities rather than just painting boards with bad-tasting products.