Sure you can! I plan on doing it myself. The horse gets use to it pretty quickly, many don't even pay attention to the actual name, just the syllables and the tone of it. If the horse is registered, you contact the registry and you fill out a form. You have to pay a small amount for the processing fee and they eventually send new registration papers with the new name on it. If the horse is not registered, just register the horse with the new name. Good luck!