You have to be careful with everything that you use around horses. Especailly if it is not labeled for them. But I will tell you this. My horses live in a would barn that was painted for over 10 years and they would periodically chew on the window frames and other parts of the barn and never got sick, BUT that is not saying that your horses wont. Our new place is steel fencing and a steel barn (easier up keep for our area). My best advice is call your vet and speak with them. What affects one horse one way can affect another a different way, so be careful.

Hope this helps.