It may be an underlying problem. But I have tried every supplement for wood chewing, including Pennwoods Blue, without any success. My horses have regular visits with their chiropractor. My horses have plenty of turnout in wonderful fields and unlimited hay when they have to come in. Since my problem was with a mother and daughter, I think this may have been a learned problem from the mother. I have since cured them of their chewing habit with a bit of pepper paste.