This is a very common problem that as been addressed by many. It goes way back.

I believe with some horses it is simply a matter of being bored. Some times a toy of some sort hanging from the ceiling will help. I had one mare that played with a teather ball. It stopped her chewing the boards.

The idea of a spicy mix spread on the boards will work with many.

Other times it may be something lacking in their diet. Maybe place a small protein lick in the feeders.

And, finally, I have seen some horses that no matter what they do, the horse still eats down the stall.

Good luck.

If you change the boards don't use woanized or treated lumber. They treat them with a petrolium based solution that could make an animal real sick.

I try to feed my animals as low as I can. Since they are grazeing animals they were ment to eat with their heads down. When they eat by lifting their heads all the hay dust and seeds has a tendancy to get in their eyes and cause problems.

I also get the coursest hay I can find. If it ain't mouldy I feed feeder hay when I can get it. We have a mule that is 30YO and never had to have his teeth floated. I lay it to feeding good course ruffage.

I keep some rough hay hanging in front of them at all times.

gives them something to do and chew on besides my facilites.

Now I buy bottom bale that most horse folk would not touch with a ten foot pole. Have been buying them for years for the cattle.

when i got the equines I started them on the same hay and they have done well.

I use hay nets and hang it high and the little bit of gunk from being on the ground falls into the stall as they pull on the bales.

since I switched to hay nets and keep hay up my chewing problems have gone away.

Go down to your local supermarket and visit the spice rack.Get you a bag of bulk chillie powder. Mix it with water to a thick past and paint it on their favorite chew spots with a paint brush. It will flat change their minds about chewing.