My mare was a chewer before she was diagnosed with ulcers. It didn’t matter what we put on the walls she would eat them. Once we got her ulcers under control (we use u-guard) and gave natural licorice treats the chewing miraculously stopped! We tried the stall ball and everything, but nothing worked. The vet told us horses with ulcers must have some kind of fiber in their system almost continuously, he recommended a slow feed hay bag or box of free choice hay, In addition to her supplements. It’s been 15 years and she no longer wood chews, and we haven’t had issues since!