Some people think it is a quack medical treatment, but I tried colloidal silver on my mare's feet, because the thrush was so bad that she was very sensitive to any chemical on her frog. Less than a week there is no thrush in her back feet, and the cracks in her frog is regrowing slowly be surely. Her front feet are better but they are the ones with open holes, and thrush is greatly reduced but I am not stopping treatment to prevent further damage. She needs to regrow a whole new frog on her front left.
Plus getting a better farrier that didn't want to keep shoes on her, helped a lot too. We're working on backing up a really long flatten heels, which should help to get more health over all feet.
Colloidal Silver is a tiny bit of silver suspended in pure water if I remember right, believed to be anti bacterial, anti fugal and improve over all health. Bought at health food stores. I don't believe it is a miracle cure like some people, but it seems to help. Put in spray bottle and clean hoofs, spray, go.