Natural Worming for Pigs: diatamaceous earth, garlic and rosemary. We mix diatamaceous earth into their feed bag so the pigs get the advantage of a continuous natural dewormer or 2 tablespoons to food a day for a large pig. Then once a month add 2 tablespoons of minced garlic to their feed once a day for seven days. Mince garlic. Can add some rosemary too.