Cats will eat dog food (and vice versa), and it’s not uncommon in homes with both dogs and cats for an owner to let the dog and cat both eat dog food. Probably one incentive to do this is that dog food is generally cheaper than cat food. While it won’t hurt the cat to eat dog food now and then, making a regular diet of it is bad news. Remember that cats are carnivores while dogs are omnivores, and their foods are formulated accordingly. Dog food, even the canned variety, usually has a fair amount of cereal in it—ﬁne for dogs, who need plant matter in the diet, but not adequate nutrition for your meat-loving cat.