Why Would a Mother Dog Reject a Newborn Puppy?

A mother will reject a puppy if he is ill, whether due to a bacterial or viral infection, a congenital birth defect or another type of disease like anemia. When a puppy fails to thrive -- a condition known as fading puppy syndrome -- mom will stop feeding him or warming him because she may not feel he can survive. If mom has pushed any puppies to the side, it's imperative that you get them to the vet immediately.

Young, inexperienced mother dogs and pups who give birth via caesarean section tend to lack maternal instinct necessary to care for their puppies. One of the reasons for this is a lack of the hormone oxytocin in the mother's system after birth, which encourages maternal behavior, according to the petMD website. Without the hormonal desire to care for her puppies, she'll reject them. Such mothers may even harm their young, so it's best to separate mom and pups if you notice aggressive behavior by mom toward the little ones. Hand-feed them instead, using canine milk replacement formula. Keep the babies warm with a heating pad set to low and covered with a thick towel.

If a mother dog's suffering from an illness, she'll reject the pups simply because she won't have the strength to care for them. Some nursing mother dogs can suffer from a condition known as mastitis. Mastitis is an infection of the mammary glands that can arise when your pooch nurses her little ones. She may suffer from post-birth complications like a bacterial infection of the uterus called metritis, causing her to neglect her pups, the Merck Veterinary Manual warns. If mom appears lethargic, won't eat, has a fever or exudes a puslike discharge from her vagina or teats, get her to the vet right away for treatment -- along with the puppies, who may also need supportive care.

Sometimes a mother will reject one or some of her pups because she has too many to care for. If mom seems overwhelmed by her babies, provide supplemental bottle feedings for rejected ones yourself. Keep the mother in a quiet, isolated spot with her pups; a stressed-out mother is more likely to reject babies. Feed the mother puppy food, which contains more fat and protein than regular dog food. It will provide her with extra calories she needs to care for her babies.

Some breeders recommend allowing a mother's culling to determine a puppy's fate, but rejected pups are usually not hard to save except in cases of congenital malformation or severe illness. Ann Seranne, author of "The Joy of Breeding Your Own Show Dog," recommends letting rejected puppies perish naturally before removing them from the mother's nest. It's a contested argument, though. In the case a rejected newborn's expiration isn't imminent, he can easily become hypothermic and hypoglycemic without vet care -- simple intervention would save him; otherwise the death is slow and cruel for no good reason. Have your vet euthanize rejected puppies too ill to save so they don't needlessly suffer.