Puppies should remain with the mother and the rest of litter until at least 8 weeks of age. Once a puppy reaches the 2-month mark, it can completely wean from the mother's milk and begin eating solid food.
Puppies nurse for the first month of their life and begin eating a combination of solid food and mother's milk in the second month. Puppies removed from the mother before weaning will need a mother's milk alternative. Only a veterinarian can recommend the best alternative to a female canine's milk as regular cow's milk is bad for puppies.
Puppies removed too early can exhibit poor behaviors, including aggression, hyperactivity or extreme fear. Most breeders and private sellers will not sell a puppy younger than 8 weeks old.