During the first 36 hours after whelping, mothers produce a special type of milk that is high in vitamins, minerals, and protein. This is the colostrum, or first milk of the dam. Colostrum also contains antibodies and other immune substances (primarily IgG) that provide protection against infectious diseases. Dams vaccinated one month before breeding have antibody levels high enough to protect puppies from distemper, parvovirus, and other infectious diseases for up to 16 weeks. Some veterinarians do not believe it is necessary to give the dam this booster shot; they believe she will have adequate immunity to pass on to her puppies as long as she is current on her vaccinations.
Newborn puppies nurse vigorously and compete for nipples. Puppies often nurse six to eight times a day, with suckling sessions lasting up to 30 minutes. Frequent nursing is essential to survival, because at this stage the energy for heat and metabolism is supplied principally through mother’s milk.
Neonatal puppies have little subcutaneous fat, and reserve energy is supplied almost entirely by glycogen in the liver. The liver is the last organ to grow, while the brain is the organ that consumes the most energy, so a puppy with a brain too large in proportion to his liver rapidly runs out of energy. Accordingly, the weight of the liver at birth should be at least one and a half times the weight of the brain. It’s even better if the liver is twice or three times the size of the brain. But even with a large liver–brain ratio, energy reserves are limited. Therefore, the potential for low blood sugar must be offset by frequent feeding. A puppy who does not nurse frequently, for whatever reason, is headed for trouble.