Pet and sporting dog owners often think they know a lot about protein content in pet foods.

The fact is, most know very little about the subject and issue opinions based upon protein content on labels and hearsay about animal performance.

An excellent article on the subject was just published, written by veterinarians Rebecca Remillard and Michelle Evason, both of whom have extraordinary small-animal nutritional credentials. You can find their piece here at this shortened web link, which requires a free account to sign in:

The authors point out five important things to know about protein, an essential part of a dog or cat diet, as it is prepared in pet food.

First, the “crude protein” value printed on a pet food label is a calculated estimate. It should not be used to compare foods directly.

Proteins are about 16 percent nitrogen. The so-called protein number is based on the lab determining the total nitrogen content of the ration, which is then divided by 16. Not all nitrogen in rations is in the form of protein. There is nonprotein nitrogen in other nutrients, too, such as carbohydrates, fats, fiber and supplements.

Do you remember the pet food that was adulterated with melamine from China in 2007? Melamine is a small, nitrogen-containing molecule (67 percent by weight) with a number of industrial uses. Its nitrogen content was used to spoof the pet food tests and bump up the appearance of proteins, which allowed the sale at a higher price to manufacturers.

Second, animals require essential amino acids, not protein itself, from their diet. Amino acids are the components from which proteins are built. Some are essential, meaning the animal or person has to have them or will eventually suffer.

“Specific essential amino acids (not dietary protein) are required by each species to support growth, maintenance, gestation, and lactation and to avoid disease,” explain the authors. “The crude protein number on the pet food label does not provide any information regarding concentration, ratio, or digestibility of the essential amino acids in the product.”

Third, protein adequacy can only be assured through standardized feeding trials or nutritional review. Such trials measure the bioavailability of proteins in the ration. A food fed for 6 months as the sole diet to adult dogs (and with certain biologic criteria met) is allowed the legal claim of “nutritionally complete and balanced as substantiated by feeding studies.” Always look for that wording on packaging.

Fourth, pet food protein recommendations are suggested ranges, not absolutes. The “numbers” people refer to are recommended by NRC and AAFCO (see sidebar). Those ranges “include a margin of safety to account for known negative ingredient interactions, losses and bioavailability uncertainties across the variety of ingredients used by manufacturers.

“Neither NRC nor AAFCO values should be mistaken as the minimum requirement for an animal, nor should they be interpreted as optimal.”

Last, the authors advise that, “Protein recommendations for dogs and cats with various medical concerns differ. The decision to adjust dietary protein concentration should be based on current protein intake.”

That means for things like kidney or liver disease, get your veterinarian involved and be sure both of you understand the amount of protein given to an animal based on how much it is getting now and making adjustments accordingly.

Charlie Powell is the public information officer for the Washington State University College of Veterinary Medicine, which provides this column as a community service. For questions or concerns about animals you’d like to read about, email

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