Most pet owners have come to realize that there is a science to reading the labels of the food they buy for their pets.
Although some loose rules are set out by regulators mandating the information that must be included on a label, these rules don’t really result in consumer-friendly information for the pet-food purchaser. Furthermore, most pet owners do not know these rules, and manufacturers can manipulate them to present their products in the best light. It is possible, however, to learn a few of the most common tricks about labeling, to allow the best choice of foods. Veterinarians can serve as an excellent source for this information if they understand the basic principles themselves.
Dry Matter Basis:
It is important to understand the concept of “dry matter basis” (DMB) to make any sense of pet-food labels. DMB means the amount of a particular ingredient expressed as a percent of the total solids in the can or bag, if the food’s moisture is removed.
Understanding DMB allows comparison of dry and canned foods, with their very different moisture content, in a fair way. It allows the pet-food shopper to compare apples to apples, so to speak.
Dry kibble has about 10 percent moisture. This means that the rest of the ingredients constitute 90 percent of the food. To remove the moisture and reduce the contents to only the dry matter in the food, we perform a simple calculation.
If the protein listed on the kibble label is 25 percent, we divide that 25 percent by .9 (the mathematical equivalent of 90 percent), to get 27.8 percent. So, a dry kibble with 10 percent moisture and 25 percent protein has 27.8 percent protein on a dry matter basis. You can perform this calculation on all of the nutrients listed on the label.
Canned, pouched and homemade wet foods have about 75 percent moisture, and the rest of the ingredients constitute 25 percent of the food. To remove the moisture and reduce the contents to only the dry matter in the food, perform the same calculation.
If a canned food has 10 percent protein and we divide the 10 percent by .25 (the mathematical equivalent of 25 percent), we get 40 percent protein on a dry matter basis.
Notice that in these two hypothetical foods, it appears before we reduce the foods to their dry matter basis that the dry food has a lot more protein in it than the canned food (25 percent compared to 10 percent).
When we do the calculation to make these foods actually comparable, it is apparent that the canned food has much more protein than the dry kibble.
All in the Name
The name of a pet food tells a good deal about what’s inside, if you know how to translate. According to the rules of the Association of American Feed Control Officials, “beef food” must have at least 95 percent beef on a dry matter basis. If the food has the name “beef entrée” or “beef feast,” “beef dinner,” etc., then it need only have 25 percent of ingredients from the named species, in this case, beef.
If the name includes the word “with,” as in “cat food with chicken,” the food only needs to have 3 percent ingredients from the named species, in this case, chicken. The animal source ingredients specified by name in all these examples may not be the only animal source ingredients in the food, however.
Many foods with a meat named on the front of the label will have other animal proteins, usually from fish, not listed on the label. This becomes very important if a patient is or might be allergic to certain meats. You will want to read labels closely, rather than just choose a food based on the meat source specified in the name.
Also remember that label-listed ingredients need not track precisely with the actual formulation in the bag or can. The Food and Drug Administration and Association of American Feed Control Officials allow a lot of time for a company to update its labels when it changes a formula to include or delete ingredients.
Tricky Ingredient Lists
Pet-food labeling rules require that ingredients be listed by decreasing weight, or predominance, in the food. For example, if a food lists as ingredients “water, beef, liver, meat by-products, corn grits, corn flour, corn gluten meal, chicken fat, vitamins and minerals,” we know that water is the most predominant ingredient, with beef, liver, etc., following in decreasing amounts.
This particular label illustrates one of the tricks some companies use to disguise the actual amount of a certain class of ingredients. In this case, corn grits, corn flour and corn gluten meal, although basically just fractions of the same ingredient, corn, have been separated to allow corn to be listed behind the meat ingredients.
In some foods, corn may actually be the predominant ingredient after water, but because it has been split into several corn-type ingredients, the individual fractions dropped to a lower place on the label. You will see this labeling practice applied to other cereals as well.
Sometimes you will see a dry food with “chicken” or “beef” as the first ingredient. The defined ingredients known as “chicken” and “beef” have high-moisture content, and have to be dehydrated, or reduced to chicken or beef meal during the mixing and extrusion process.
If such ingredients were listed as “chicken meal” or “beef meal” on the label, however, they would not have had their moist weight, and would have dropped lower on the ingredient list. For example, a dry food listing “chicken, corn flour, chicken fat, soy protein …” probably doesn’t have more chicken than corn flour by weight in the finished kibble, but listing the chicken before it reached its dry form allowed it to be listed first legally.
Because pet owners are now reading labels more closely than ever before, pet food companies use these and other practices to make labels more appealing. Not surprisingly, bending these rules is more misleading in dry kibble, where cereals are such an important ingredient.
The rules of pet food (and human food) labeling call for the manufacturer to list some basic nutrient percentages on the label.
A typical canned food label may have a guaranteed analysis that looks like this:
• CRUDE PROTEIN … Min. 9.5%
• CRUDE FAT … Min 5.0%
• CRUDE FIBER … Max 0.8%
• MOISTURE … Max 75%
• ASH (MINERALS) … Max 2.0%
Notice that there is no listing for carbohydrate, a very important consideration when buying cat food. There is, however, an easy way to find out approximately how much carbohydrate is in such a food.
Simply add all of the listings from protein through ash (do not add any other listed nutrients such as calcium, magnesium and phosphorus as they will simply be part of the ash or the other supplements that are too small to be needed for this calculation).
In this case, we would add 9.5 percent plus 5 percent plus 0.8 percent plus 75 percent plus 2 percent (for a total of 92.3 percent) and then subtract from 100 percent to get the remainder, which is carbohydrates.
Don’t worry that these are maximums and minimums. This addition will get you very close to the true carbohydrate number, allowing a better evaluation of the food than if carbohydrate levels aren’t known.
In the example above, the total of all non-carbohydrate nutrients, including moisture, is about 92.3 percent. When we subtract from 100 percent, we get 7.7 percent carbohydrate, before we convert to DMB. This may not seem like a lot, but it is actually far too much for a canned food.
Many canned foods will have as little as 4 percent or even less carbohydrate on a wet basis. To convert this to a dry matter basis, remember we just take 7.7 percent and divide it by .25 percent (because this canned food is 25 percent dry matter); 7.7 percent divided by .25 gives almost 31 percent carbohydrate on a dry matter basis.
A much better canned food guaranteed analysis would be:
• CRUDE PROTEIN … Min. 11%
• CRUDE FAT … Min. 8.0%
• CRUDE FIBER … Max. 1.5%
• MOISTURE … Max. 75%
• ASH … Max. 2.5%
Adding these, you get 98 percent without carbohydrate, and 100 percent minus 98 percent leaves 2 percent carbohydrate on a wet basis. When we divide 2 percent by 0.25, we get 8 percent carbohydrate on a dry matter basis. This is a far more desirable carbohydrate level than that we calculated above at 31 percent.
Not surprisingly, dry pet foods contain the highest amount of processed carbohydrates (equivalent to breakfast cereal and potato chips).
A typical dry kibbled pet food has a guaranteed analysis like this:
• CRUDE PROTEIN … Min. 24%
• CRUDE FAT … Min. 10%
• CRUDE FIBER … Max. 5%
• MOISTURE … Max. 10%
• ASH … Max. 5%
If we add all of the listed items, we get 54 percent. Subtracting this from 100 percent leaves 46 percent processed carbohydrate. Converting to DMB by dividing 46 percent by .90 we get over 50 percent processed carbohydrate in this kibble.
Imagine if your daily diet contained this much snack food. Is there any wonder our canine and feline patients are so desperately overweight today?
You and your staff and clients will become very skilled at reviewing ingredient lists to determine what is actually in that can, pouch or bag.
Not all commercial wet foods are low in carbohydrates, as we see in the above examples. Both the ingredient list and the carbohydrate calculation from the guaranteed analysis give you valuable tools in deciding what foods to recommend.
All pet food labels carry some kind of AAFCO statement. This statement seems to indicate that the food has been thoroughly tested as good food for the pet. But this statement is available to all foods that either meet the basic minimums of the National Research Council recommendations according to lab testing or have been fed to pets for six months or less without serious harm to the test subjects fed the food.
Veterinarians need to understand that highly processed commercial pet foods, like highly processed human foods, are not all alike, and that some are little more than junk food for pets. Furthermore, because they are intensely processed, even “good” quality foods lack the nutrient vitality of fresh whole foods.
Perhaps it is time for our profession to reconsider its automatic response to a client’s query about what to feed a pet.
Dr. Hodgkins adapted this article from an appendix in her recently published book “Your Cat: Simple New Secrets to a Longer, Stronger Life” (Thomas Dunne Books, 2007). She has a feline practice in Yorba Linda, Calif.