Puppies may be tiny, but their appetites aren't, and they need their mother's milk. Newborns don't have fully developed immune systems, which means they're prone to illnesses and infections. The milk their mother produces contains the correct nutrients, proteins and antibodies to keep them healthy.
Typical Nursing Time
Healthy puppies nurse every two to three hours for the first week or so, and then begin nursing every four hours, with intervals between feedings decreasing until they're able to eat solid food. They should nurse for at least three weeks before you begin weaning them, and four to six weeks in total.
At the very least, puppies should nurse for the first twenty-four hours after they're born, if this is at all possible. This is because of colostrum, a substance produced by their mother right after she gives birth. Colostrum contains powerful antibodies that give puppies "passive immunity" for the first few weeks of their lives. Puppies who don't ingest colostrum are at risk for infections and disease.
When it isn't possible for puppies to nurse for at least four weeks, you'll need to step in as a surrogate mama. Very young puppies should be fed a high-quality milk replacement until they transition to solid food -- cow or goat milk alone isn't enough. Their tummies should be round and full after each meal, and you'll need to "burp" them after feeding. Pay close attention to each puppy's weight and appetite. A puppy who doesn't want to eat, or who doesn't gain weight, should see a veterinarian as soon as possible. In fact, it's a good idea to take all the puppies to a vet, just in case.
When puppies are about 3 weeks old, they're ready try semisolid food. Mix high-quality dry or canned food with milk replacement until it has a thin, mushy consistency. Each day, increase the amount of mush the puppies eat. They'll nurse less on their own, since their tummies will be already be full. During week four, gradually increase the ratio of solid to liquid. By the end of week four, they should be eating semisolid mush and be ready to be completely weaned. By week six or seven, they should be ready for regular commercial puppy food.