When it comes to the changes in diet at different life stages, we can't overlook the importance of pregnancy. In order to keep the expecting mother and her puppies healthy, you'll need to provide her with a special diet. Pregnant dogs gain about 20 to 50 percent of their normal weight during pregnancy, but this weight gain usually doesn't begin until the fourth week. So, that's around the time you should start feeding her more food than usual. Keep in mind that if she's carrying a big litter, there'll be less room for food, so this will require more frequent, smaller meals to keep up with her needs. Specifically, she'll need about a third more food than usual at the fourth week [source: Olson]. Meanwhile, as the pregnancy progresses, the amount of food she needs will only increase.
One of the most important elements of the dog's pregnancy diet is high-quality protein -- that is, protein that is easily digestible and provides the right amounts of all the essential amino acids. If you use dry dog food, it should contain around 27 percent protein (because it has water, the equivalent for canned is only 8 percent) [source: Rice]. This protein will work toward forming healthy, strong tissue in the developing puppies while in utero. Some experts recommend vitamin and mineral supplements during pregnancy, but you should talk to your vet before starting these.
The special dietary needs don't end with birth. Remember that a lactating dog still has to provide all the nutrients to her young puppies outside of the womb for about four to six weeks. In fact, she may need even more food than when she was pregnant. The best diet is one rich in animal protein and fat. These will help her with milk production.