Dogs automatically lose weight after giving birth to puppies. A nursing dog's energy requirements can double or even triple (depending on the size of the litter of puppies) in order for the dog's body to produce enough milk to feed the pups. That can make it pretty difficult for the mother dog to put on any weight at all. You have to carefully choose food for your nursing dog in order to help her gain weight healthfully while still providing proper nutrition to her puppies. The good news is that this can be done by changing the feeding guidelines you normally follow and by switching out a few foods in your dog's diet.
Feed your dog a diet with extra nutrients, such as puppy food. Puppy food also provides added calories, since puppies need the extra energy while they grow. Feeding your nursing dog puppy food helps her gain weight and provide adequate nutrition for her young.
Feed your dog weight-increasing treats to increase her fat and caloric intake in a healthful way. Check the Resources section of this article for a link to weight-increasing dog treat recipes you can make at home.
Increase the number of meals your dog eats in a day. If your dog already eats two meals, increase the count to three or four. Make sure, however, not to increase the amount of food you feed at each meal.
Allow your dog to "free choice" feed. This means that you allow your nursing dog unlimited access to a dish of puppy chow throughout the day. Your dog will automatically eat more and gain weight.