Cute and sensitive as they are, newborn puppies stay mom-dependent for only a matter of a month. Between age 3 weeks and 5 weeks they'll begin to cease nursing and start eating solid food. Weaning can take several weeks, and a mama dog may not lose her milk until a week or so later.
Puppies and Mother's Milk
In the weeks before giving birth to her litter, a mama dog wolfs down a lot more food than usual. That's because her puppies are 100 percent dependent on her milk for sustenance. Mother dogs produce colostrum -- a supercharged, antibody-rich form of milk -- for their puppies immediately after they're born. A day after that, they begin producing normal milk that, while somewhat watered down, is vital for puppy growth, particularly when puppies are about 3 weeks old. At this point they're as large as they've ever been and are still growing, and aren't yet able to eat solid food. During this period, a mama dog and her puppies are practically inseparable.
Nursing and Weaning
Puppies begin eating solid food when they're about 4 weeks old, just as they're becomingbraver and more independent. That's not to say mama dog's not in the picture -- her puppies will continue nursing at her teats for the next few weeks. She'll discipline and encourage them as necessary. As weaning progresses, the mother dog's milk production tapers off. Weaning is usually complete by the time puppies turn 5 or 6 weeks old. Still, don't be surprised if you spot a 5-and-a-half-week old puppy trying to sneak in one last easy meal. Don't be surprised, either, if the mama dog isn't exactly encouraging of this. Her natural instincts tell her nursing time is over. So, too, do her puppies' teeth, which can make nursing quite uncomfortable.
Canine lactation, which gears up right before a litter is born, usually lasts until the puppies are 5 or 6 weeks old. Weaning is a process, though, which means that time table can vary by about a week or so. In terms of milk production, a mama dog usually lactates less and less until her puppies no longer try to feed on her. As such, that means most mama dogs lose their milk right around the time their puppies are 6 weeks old. It can take up to a week for her breast to run dry, though, particularly if any of her puppies are aggressive nursers suddenly stop suckling at her teats.
If a mama dog stops lactating suddenly while her puppies are still dependent on her for mother's milk, you need to take her to a vet as soon as possible. The same is true if her milk looks off-color. It should be watery to milky white -- any discoloration could indicate infection or disease, which a mother dog can pass on to her puppies. In the event a mama dog can't produce milk for her offspring, you may need to supplement their diet with canine milk replacement. If a mama dog continues producing milk after her puppies are fully weaned, she likewise needs to visit a vet. She could be pregnant again or be suffering the primary or secondary effects of one of a multitude of medical conditions.