Pet Food Nutrients
Finding the name of a specific meat at the top of the ingredients list on your natural cat food doesn't guarantee a truly natural meat-based product.
If you combine all of the non-meat ingredients following it, even if they are pesticide-free and naturally preserved, you may very well find that they outweigh the meat content. Thus, what you have is a grain-based cat food, which would be considerably unhealthy, and flagrantly 'un-natural' for a feline.
The source of the nutrient, especially that all-important protein, also determines how much of the nutrient your pet is really getting from the food.
Many sources of protein are poorly digested. You might do a comparison of the crude protein analysis and find that two products have essentially the same amount of protein. Good enough? Not quite. An ingredient such as beef byproduct may contain things like hair and hooves, so a product with beef byproduct as the primary source of its 28% protein is really providing much less protein to your dog's nutrition than the product with beef, or even beef meal.
Pet Food Processing
Processing methods can also contribute to (or detract from) a pet food's digestibility and nutrient retention. Rendering at extremely high temperatures significantly depletes many nutrients, while baking is less destructive. With taurine, an extremely important part of a cat's nutrition and found only in animal tissues, baking and boiling reduces the amount by an average of 52 and 79 percent respectively.
Many manufacturers promote their dry baked dog food and dog treats as being healthier than canned food for these reasons. However, some of the individual ingredients within those final baked products may have been extruded and rendered at high temperatures prior to the final baking.
Many people recommend feeding unprocessed raw foods only, and there are several products in specialty pet supplies stores that meet this demand for those without the time to prepare their own.