In my research on this topic, I am finding a variety of answers. I was prompted to write about this subject because in the best book on wild cats (Wild Cats of the World), at the very beginning, the authors, Mel Sunquist and Fiona Sunquist, state that for a cat to remain healthy, its diet must contain 12% protein by weight for adult cats and 18% for kittens. Domestic cats have the same dietary requirements as wild cat species.
These figures seem low in comparison to those specified in an article written by Jennifer Coates on the petmd.com website. She concludes that most cats should be eating foods that contain at least 30% protein in dry food, supplemented with a 40% to 50% protein in canned (wet) food.
Jennifer states that the least amount of protein allowable in AAFCO-approved cat food to be 26% for adult domestic cat maintenance and 30% for growth and reproduction (e.g. kittens). She argues that this figure is too low.
Another website, thenest.com, states that an adult cat food should contain a minimum 26% crude protein by weight while kittens should be provided with food that contains 30% or more crude protein by weight.
The well-respected website written by veterinarians, peteducation.com concludes that the recommended protein level for adult cats is 25% to 30% and for kittens the figure should be 30%.
The veterinarians who wrote the very popular Cat Owner’s Home Veterinary Handbook state that the ideal natural cat diet, the mouse, is 40% protein, 50% fat and only 3% carbohydrates. They therefore recommend a 40% protein diet. This is more in line with the assessment by Jennifer Coates.
Cats are sometimes called hypercarnivores because they need a much higher level of protein in their food than almost any other mammal.
Percentages on a on a dry matter basis. Best canned cat food 2012!