The most important part about selecting any diet is what it consists of. The label on the container of food will list the ingredients from largest to smallest amount of each in the food. The analysis will list the minimum level of Protein, Fat, Crude Fiber and moisture. Cats are carnivores and dogs are obligate carnivores, both require high protein diets with minimal carbohydrates. The general rule is on dry or wet food analysis is that the fat content be a % have of that of the %of protein. The average dry food has 10% moisture content and canned or raw food contains 70 to 80% moisture. When calculating protein on a dry bases, you divide the % of protein on the label by decimal % of the dry matter. . IE label reads 24 % on a bag of dry dog or cat food and he moisture % is 10%. ( This means that their is 90% dry matter) 24 divided by 0.9 = 26.6% . If it were canned food the protein analysis may say 13 % with a moisture content of 75%. 30% divided by 0.25 (decimal of % dry matter content) = 52 %. Now you can accurately know how much the food actually contains and what is in it. Under ingredients make sure their is NO by-products, artificial preservatives, flavoring or coloring, and human grade or organic products. Their are hundreds of commercial diets to choose from. You need to check that they meet all of the previous requirements mentioned. You also have the option of making your own home made diets. Here is a book to how to make your own diets Dr. Becker’s REAL FOOD for Healthy Dogs and Cats Simple homemade food by Beth Taylor and Karen Shaw Becker, DVM
Paleo DOG by Jean Hofve, DCM and Celeste Yarnall, PhD See Spot Live Longer by Steve Brown and Beth Taylor
Here is a link to commercial RAW food diets and how to make your own homemade diets.