AAFCO reaffirms guideline on copper levels in dog food

The Association of American Feed Control Officials (AAFCO) reaffirmed its guidelines for copper concentration in commercial dog foods after an expert panel concluded there is currently a lack of definitive evidence linking copper-associated hepatitis in dogs and the copper content in dog foods. 

The AAFCO is the organization that sets standards for both animal feeds and pet foods in the United States.

“At this time AAFCO does not see the need to restrict the use of other sources of (copper) in dog foods beyond any restrictions already imposed in their definitions or approvals,” AAFCO CEO Austin Therrell wrote in March. “Until such time as science definitively shows additional controls or restrictions are needed, AAFCO feels that recommendations for (copper) concentration in foods for normal dogs are appropriately and sufficiently regulated at present.”

The AAFCO convened an expert panel shortly after the publication of a February 15, 2021, JAVMA Viewpoint article, “Is it time to reconsider current guidelines for copper content in commercial dog foods?” warning about potentially harmful concentrations of copper, or Cu, in dog foods.

Dry dog food in a bowl and a scoop

An expert panel convened by the Association of American Feed Control Officials (AAFCO) recommended, among other things, that the AAFCO not establish a maximum for the overall copper content of dog foods within the AAFCO Dog Food Nutrient Profiles.

“Over the past 15 to 20 years, we have seen what we believe to be an increased incidence of copper-associated hepatopathy in dogs. The onset of this increase appears to have coincided with a change in the type of copper used in premixes added to commercial dog foods,” the article’s authors wrote.

They called on AAFCO to reestablish a maximum concentration for copper in its Dog Food Nutrient Profiles, which are the nutritional standards established by AAFCO. The authors also requested the AAFCO set the recommended content for copper in the profiles to a range from 0.9 mg Cu/1000 kcal of metabolizable energy (ME) to a maximum of 1.1 mg Cu/1000 kcal ME, and prohibit the use in dog foods of all supplemental sources of copper except copper oxide.

The AAFCO’s 13-member panel was led by Dr. William Burkholder, a diplomate of the American College of Veterinary Nutrition who works at the Food and Drug Administration (FDA) Center for Veterinary Medicine (CVM). Members met four times between May 2021 and July 2022, and issued a report to AAFCO on August 1, 2022.

As to the matter of restricting the source for adding copper to dog foods to copper oxide (cupric oxide), “the majority of the panel expressed opposition to such a restriction, noting that the bioavailability of cupric oxide was essentially zero and thus would add nothing of value to the dietary formula,” according to the report.

Some discussion occurred concerning adding a footnote to the AAFCO Dog Food Nutrient Profiles to suggest that sources of chelated copper be restricted to approximately 25% of the added copper in diets with the remaining added copper being supplied from inorganic mineral salts. However, the panel did not express a strong position that such a footnote was needed.

The panel had previously rejected decreasing the recommended amount of copper to 3.6 mg Cu/kg DM as this amount of copper is less than the amounts for adequate intake or recommended allowances for any life stage of dog established by the National Academies of Sciences’ 2006 Nutrient Requirements of Dogs and Cats Expert Subcommittee.

Additionally, the panel struggled with setting a maximum amount of copper in the AAFCO Dog Food Nutrient Profiles for several reasons. Among those cited in the report was a determination by the NAS subcommittee that there is insufficient empirical data to establish a safe upper limit or maximum tolerable level in normal dogs.

“Arbitrarily setting some value as a maximum for copper implies that diets containing less than, or equal to, the maximum are safe for dogs and that diets containing more than the maximum amount are unsafe, with neither condition having been demonstrated to be true,” the panel wrote.

This was not a majority opinion, however, as two panel members believed that “some maximum amount should be set.”

The panel concluded its report with the recommendations that the AAFCO not pursue a restriction for allowing only copper oxide as the form of copper allowed for copper supplementation of dog foods; not establish a maximum for the overall copper content of dog foods within the AAFCO Dog Food Nutrient Profiles; and explore adding a “Low Copper” claim to the descriptive term in model regulations for dog food.

A version of this article appears in the June 2023 print issue of JAVMA.