The decision follows more than three years of research and discussions initiated by a February 2021 article in the Journal of the American Veterinary Medical Association (JAVMA), which questioned the existing Association of American Feed Control Officials (AAFCO) nutritional guidelines for copper (Cu) in dog foods and suggested they should be re-examined.
There is no upper limit in the US regulation for Cu inclusion levels in dog food.
The authors of the JAVMA article wrote: “We suspect that copper contents of many commercial dog foods are greater than the biologic requirement of dogs and exceed the tolerance limit for some of them.”
To address those concerns, AAFCO assembled an expert panel to review veterinary literature and assess the feasibility of setting a safe upper limit for copper in dog food. Although the panel found insufficient data to establish a maximum tolerance, they proposed voluntary language for a ‘controlled copper’ claim.
Further scrutiny came from a copper claim workgroup, which evaluated the proposed claim language and additional guidelines considering concerns from pet owners and veterinarians.
On May 30, 2024, the AAFCO pet food committee reviewed the findings from both the expert panel and the copper claim workgroup, along with feedback from veterinarians, animal nutritionists, consumer groups, and the public. Despite these extensive evaluations, the committee could not reach a consensus and ultimately voted ‘no’ on the voluntary controlled copper level in dog food.
A spokesperson for Mars Petcare told us it is in alignment with the Pet Food Institute (PFI) that any decisions regarding product claims and established limits for trace nutrients must be science-based. "Currently, there is insufficient research to establish such a limit for copper."
Leading consumers to believe that low levels of copper are beneficial for all dogs could result in dietary deficiencies, which could lead to a range of health complications such as skeletal and muscular issues, skin and coat problems, reduced growth rate, and anemia, claimed the PFI.
AAFCO says it will continue to monitor emerging scientific literature and may revisit the issue in the future if new data justifies another review.
Increasing copper content in canine livers
The JAVMA 2021 study maintained that Cu content in dogs’ livers has been increasing over the past two decades. The authors claimed that both the digestibility and the amount of ingredients, other than copper oxide, used to supplement copper into dog foods have caused the copper content in the liver of dogs to steadily increase over time to where the copper content of canine livers is now significantly greater than it was prior to some reference time point within the last 10 to 25 years.
However, AAFCO questioned then whether the increase resulted from a change in the methods used to quantify liver Cu concentrations or from other factors unrelated to dog food and said it was reluctant to make regulatory recommendations based on implications or associations without definitive proof of cause and effect.
Instead it convened the expert panel to assess whether it is necessary to revise the AAFCO copper guidelines,
After an extensive review of relevant veterinary literature, most of those experts determined there was “insufficient empirical data to establish a safe upper limit or maximum tolerable level in normal dogs.”
But it was not a unanimous decision. Two of the expert panel members felt an upper Cu limit in dog food should be established, regardless. The EU has set a legal maximum for the content of element (Cu) in mg/kg of complete feed for dogs with a moisture content of 12% at 25 mg/kg, equivalent to 28,4mg/kg DM in complete feed. This maximum applies to the total copper content of the complete feed but only when copper is added as an additive. The European Pet Food Industry Federation, FEDIAF, has incorporated that upper limit into its nutrient profiles.
Future research
Many questions remain regarding copper metabolism and diet formulation for dogs, according to a paper published in January this year in Translation Animal Science.
A critical challenge for proper copper nutrition in dogs is the known genetic predispositions of some breeds for copper storage and excretion abnormalities, said the authors.
It is imperative that veterinarians, nutritionists, and pet food manufacturers collaborate with the shared goal of providing dog food options that supply the essential nutrients at adequate concentrations to support an active and healthy life for dogs.
“Future research efforts should focus on discovering reliable, non-invasive methods for evaluating canine copper status, a deeper understanding of genetic predispositions of certain breeds, increased knowledge of copper contributions from various ingredients, and the role of unpredictable physiological stressors on copper metabolism,” they highlighted.
