Understanding Cat Food Labels

A Formula and Some Important Rules

Photo of a Can of Popular Cat Food
Opening Can of Popular Cat Food. photo © Getty / Tom Kelley Archive

I mentioned in the previous article that the AAFCO uses dry matter values when referring to the recommended breakdown of "key nutrients" for cat food by percentage or weight. Since most food manufacturers do not list their breakdowns in this way on labels, false assumptions may be made by the consumer when comparing canned food to dry food. You will see by using the following formula, that when the moisture content is removed from the equation, the results may be surprising.

Dry Matter Value Formula​

  1. Look at the "Guaranteed Analysis" on a label
  2. Subtract the moisture percentage from 100
  3. Divide the resulting figure into the crude protein figure (disregard decimals when dividing)
  4. The result will be a close approximation of protein by dry matter value

(You can use the same formula to calculate the percentage of fat or fiber by dry matter value.)


Here are figures from three different cat foods I happened to have on hand. They are from three different manufacturers, which shall remain anonymous for purpose of this exercise.

  1. Brand A Premium Canned Food: Protein, 8.5% | Moisture, 78%
  2. Brand B Premium Dry Food: Protein, 32% | Moisture, 10%
  3. Brand C "Supermarket Brand" Canned Food: Protein, 10% | Moisture: 78%

Brand A: Using the formula above, and subtracting the moisture from 100%, we divide the remainder, 22 into the 8.5 protein content for a result of 38.5% protein by dry matter.

Brand B: 100 minus 10 equals 90, divided into 32 gives us 35.5%.

Brand C: 100 minus 78 equals 22 divided into 10 for 45%.

You can see in the example given that the two canned food brands contain more dry matter protein content than Brand B, a dry food, which at first glance seems to contain far more protein.

In fact, by this test alone, one might think that Brand C (the "supermarket" brand) is superior for protein content.

Not so fast!

Actually, the first two listed ingredients on Brand C's label are "meat by-products," and "poultry by-products," which were listed under "What to Avoid" in the first part of this series. The protein quality of this "supermarket" brand simply does not make the cut.

The 95%, 25%, 3% Rules

AAFCO has provided certain other rules for "truth in advertising" in cat foods. Don't let those fancy designations such as "gourmet" or "feast" slip one past you. With these rules you'll know at least the minimum your cat is getting of the advertised ingredient.
Here are the rules:

  • The 95% Rule
    A cat food may not be labeled simply "Chicken for Cats," or "Chicken Cat Food," unless it contains 95% or more chicken by total weight of the product.
  • The 25% Rule
    Foods labeled "Chicken Entre," "Chicken Dinner," "Chicken Feast," or the like, must contain 25% to 95% chicken. Combinations, such as "Chicken and Beef Dinner" must contain a total of 25% to 95% of the combined meats, listed in order of quantity, and the second meat listed must comprise at least 3% of the total weight. (Imagine ordering a "steak and lobster" dinner and finding the "lobster" will barely fill a fork.)
  • The 3% Rule
    A food labelled "Kitty Stew with Chicken" must contain 3% or more chicken. ("With" is the optimum word here.)
  • "Flavor"
    Barely worth mentioning here, but if you see something similar to "chicken flavored," be assured that the product is unlikely to contain any chicken at all, as long as there is a "sufficiently detectable" amount of chicken flavor. Since these "flavors" may be the result of digests or by-products of the named animal, I'd avoid these at all costs.

"FDA Rules"

The FDA (which is the governing authority for pet foods) allows dog and cat food makers to vary ingredients by as much as 25% from what the label says. They are supposed to have the label and ingredients in the bag or can in close agreement at least once every six months (that translates to a requirement of 2 days a year).

The rest of the time, the ingredient variation is okay, as long as nutritional requirements are met. This is a reasonable policy when one understands that these ingredients are perishable (need for preservatives) and simply may randomly become unavailable.

"Human Grade" and "Natural"

Although you will occasionally see "Human Grade" listed on pet food labels, the AAFCO does not recognize nor presently address this form of labeling. However, because of the current trend toward "natural," as well as "organic," the AAFCO is currently working to define at least the former description. In the meantime, caveat emptor with those phrases. If you lean toward cat foods described as one or the other, make sure you completely understand what is meant by the terms.

"Dental Care," "Hairball Formula?"

You will find a number of foods labeled for dental care, hairball control, lite, weight reduction, or senior. At present, AAFCO does not address these definitions, so caveat emptor applies here also. If they seem to work for the stated purpose with your cat, fine, but make sure the essential nutrients are not compromised at the same time. The "complete and balanced" verbiage refers to life-stages only: kitten/lactating queens or adult/maintenance.

Back to the Scavenger Hunt
What is this?

This concludes the series on "what you need to know about cat food labels." The information provided herein is intended to give you a basis for learning more about cat food labels, to help you make better-informed decisions. It is not intended to be a complete analysis of cat food ingredients, nor labeling requirements. Indeed, what we have presented here is just the tip of the iceberg. I encourage readers to continue doing your own research, as there is a wealth of information available. I've listed some excellent references below, to get you started. Happy reading, and good health to your kitties!

Other Suggested Reading:

  • A Consumers' Guide to Pet Food - from the Pet Food Institute, this page also has little label pop-ups where you can mouse-over to read explanations of the various fields on the labels.