That may not sound like what you want for dinner tonight, but that's what Max and Cody eat every day at my house. The label says it's good stuff, and Max's mouth is too full to complain. That may be unappetizing to you and me, but it can be just as nutritious as meat or better for your four-legged friends. Ingredients vary widely depending on the pet food, but the quality of the protein ingredients is most important. A mixture of motor oil and leather can have the recommended amount of fat and protein, but it is completely non-digestible.
Some proteins are more digestible than others.
Evaluating a pet food can be tricky, especially since there are thousands to choose from. In general, dry food will be more economical than wet foods, and cheaper foods may actually be more expensive than you think. That goes back to the quality of ingredients. If the food is poorly digested, you'll have to feed a lot more of it. With a more expensive, premium brand of food, you'll actually feed less because generally these foods are highly digestible.