Three-week-old pitbull puppies are unweaned, which means that they still depend on their mother's milk for nutrition. However, if the puppies are orphans or the mother is otherwise unable to nurse them, they can be fed a liquid or powder formula for dogs.
When bottle-feeding puppies, use a puppy nursing bottle that holds 2 to 4 ounces of formula. Stir the formula vigorously before giving it to the puppies to ensure that no lumps remain. The puppies can easily choke on these or breathe them into their lungs. Three-week-old puppies typically need to be fed every four to six hours, including during the night.