The most reliable method for comparing cat foods is learning how to read the nutrition labels. Cats have specific nutritional requirements, such as needing certain percentages of protein, fat, amino acids and carbohydrates. Therefore, comparing what each cat food offers in terms of those needs provides an effective comparison tool.
A kitten needs 30 percent protein and 20 percent fat, while an adult cat needs 25 to 30 percent protein and 15 to 20 percent fat. Linoleic and arachidonic acids as well as omega-6 and omega-3 fatty acids are also necessary requirements in feline nutrition. All of these are listed on nutrition labels.
Reading the level for protein and fat percentages does not give the whole story, as those are based on dry matter. Cat foods, on the other hand, have varying levels of moisture that affect those percentages. For instance, most canned foods contain up to 80 percent moisture, and most kibble has 10 percent. In order to determine how much actual protein or fat a serving contains requires some basic math: If a canned food is 80 percent moisture, it has 20 percent dry matter. That 20 percent gets divided by the protein or fat percentage to give a more accurate count.
Therefore, when comparing cat foods, compare their moisture levels as labeled under "guaranteed analysis" in addition to their nutrition contents. Do the math to get an accurate understanding of which brand offers better nutrition.