A mama dog requires at least double the calories she would eat normally and if she has a large hungry litter will often eat 3x as many calories. I have taken that into account with my bitches by feeding them high quality food and also by adding a product called K9 Puppy Gold to her food for the extra calcium needed for a good supply of milk.
This product is a powder and can be mixed with hot water and poured over the food to make a stew or just mixed in dry. My females love the flavor and gobble it up. I have found it keeps their coat shiny and helps them maintain their weight during the stress of nursing.
Once the puppies are changing over to puppy food, I also to mix Puppy Gold with their kibble and keep them on it as a supplement until they leave for their new homes. Fat and fluffy puppies are the result!!