As long as you are feeding healthy rodents to your snake, then there is no need to dust the rodents at all. They are whole prey items therefore they are nutritionally complete. It won't hurt to dust your snakes food once in a while, but it isn't necessary either. Some people may dust their rodents if they are feeding them to breeding females, but other than that it isn't a common practice. Vitamin and mineral supplements are best left to the herbivores, omnivores, and insectivores