Dog food brands are important once you find one that agrees with your dog's system. Shopping by brand works well even when you're going to add some variety to your pet's diet.
Things to consider: Changing dietary needs, how to add variety, and avoiding problems between different types of food.
Food Needs Change - Shop by brand if you have found a dog food that your dog likes, but her dietary needs change. For example, once you find a puppy food at the dog food center that agrees with your dog (and her vet) then when you make the transition to adult food, stick with the same brand and you will both probably have a smoother transition.
Variety - If you want to add some variety into your dog's diet, do not just haphazardly start trying out different dog foods. That could upset her digestive system greatly. Instead, shop by brand and get different flavors (beef, chicken, pork, lamb) of the same brand dog food.
Wet & Dry - If you feed your dog both kibble (or "dry") food and canned (or "wet") food, your dog is more likely to get complete and whole nourishment if you buy the same brand for each kind. To buy a combination of wet and dry foods that have been specifically designed to nutritionally complement one another, shop by brand.
