My draft gets abscesses. I hear a lot of Perchies that have them. Some of it is due to cracks in the hoofs and bacteria or objects getting into the cracks and creating abscesses.
The best thing you do is feel the hooves regularly for heat so you can tell if one is coming on. Soak it in warm water and Epsom salt, then get a diaper, put some epsom salt in the bottom and wrap it up with duct tape and change it once a day.
My vet says sometimes there doesn't seem to be a specific reason a horse will chronically get them. They just seem more prone.
Is your horse barefoot? Try to make sure that you keep the hooves cleaned very well anytime you walk across gravel/dirt/paved areas.