Grain free dog food is becoming a popular type of dog food to feed your dog. Found in both canned and kibble formats, grain free dog foods do not contain any cereal grains, which are usually used as fillers. Cereal grains include corn, wheat, barley, and rice. Instead, grain free dog food is rich in real meat products (not by-products) and protein, as well as easy-to-digest animal fats. Vegetables can also be found in some dog food, such as potatoes or sweet potatoes.