Hormones kick-start lactation in a dog and nursing puppies perpetuate it. Lactation is the result of a lot of cooperation between hormones, body parts and puppies. If puppies are missing from the equation, a dog's milk eventually will dry up on its own.
Milk Production and Letdown
A dog's milk production is a complicated process, involving hormones, glandular tissue and demand for milk. In the final days of a dog's pregnancy, it's normal for her to begin to produce a small amount of milk. Estrogen, produced by her ovaries and secreted by the puppy placentas, alerts her mammary tissue about her pregnancy. Other hormones affecting milk production include:
- Progesterone, from the ovaries
- Prolactin, secreted by the pituitary gland and potentially uterine tissue and placentas
- Relaxin, produced by the placentas
When a dog delivers her pups, prolactin and the hormone oxytocin are responsible for milk letdown, or the release of milk for nursing. During delivery, the puppy closest to the mother's cervix stimulates the release of prolactin, which gets her milk going and stimulates maternal behavior. Nursing puppies further stimulate the release of hormones to keep up the milk production and letdown.
Because of the way her hormones are functioning, a dog may lactate before her puppies are born, often about a week or two before her delivery date. Around six weeks into her pregnancy, her nipples grow and darken, often secreting milky fluid as she approaches her due date. If all goes well, when she delivers her puppies the rest of her mammary system kicks in and begins the lactation process.
Healthy puppies generally nurse for six or seven weeks, putting their peak demand on their mother approximately three weeks after delivery. As they begin to eat puppy food and rely less on their mother, her body responds naturally and in most cases, her milk dries up on its own.
No Puppies to Nurse
If something is wrong with a dog's puppies and they are born dead or die during the normal nursing period, her milk should dry up on its own. Lactation is a supply and demand proposition in dogs; when there is nothing to stimulate additional milk production after delivery, her body will respond as it would to weaned puppies.
You can promote drying up your dog's milk by changing her feeding schedule. Decrease her food intake based on this schedule:
- Withhold food and water for 24 hours.
- Day Two: Offer her 1/4 of her normal daily serving.
- Day Three: Offer her 1/2 of her normal daily serving.
- Day Four: Offer her 3/4 of her normal daily serving.
After the fourth day, feed your dog her adult food according to her regular serving schedule. If your dog's milk isn't drying up, discuss the situation with your vet who may use a medication such as bromocriptine to dry up her milk.
- PetPlace.com: Structure and Function of the Mammary System in Dogs
- University of Illinois -- Urbana-Champagne Department of Animal Sciences: Comparative Lactation -- Cats and Dogs
- Dog Owner's Veterinary Handbook, Debra M. Eldredge, DVM, et al
- Vet West Animal Hospitals: Breeding -- Growing, Lactation, Weaning
- PetMD: Signs Your Dog is Pregnant