Talk about the role of pet food ingredients in copper-related liver disease has been going on for years. A very small percentage of dogs accumulate excess copper in the liver, resulting in copper storage disease, hepatitis and/or cirrhosis. Various factors have been suggested as causes, including genetics and pet food ingredients. The first observations of copper-storage disease only affected Bedlington Terriers due to an autosomal recessive trait in the dogs’ DNA. However, case reports have emerged involving other breeds, such as Labrador Retrievers. As the number of affected breeds grew, so did the range of proposed causes. A straightforward explanation for these copper storage problems has remained elusive.
A research group with Hill’s Pet Nutrition set out to look for patterns in copper levels over time in dog livers. They used a data store house on records from kennels involved in feeding trials.
“We have a very good bio-archive of samples, because dogs eat a little bit of everything,” Leslie Hancock, DVM, study co-author and director of clinical nutrition research at Hill’s Pet Nutrition, told Petfood Industry. His team published their results in the Journal of the American Veterinary Medical Association.
Data from dogs eating different diets
Dogs in Hill’s feeding trials eat a wide range of recipes during various palatability and digestibility studies. Because of this, the results are less influenced by any particular brand or recipe formulation and supply chain when compared to pet dogs that often eat the same varieties consistently.
“We test Hills products, we test competitors’ products, and we test global products,” he said. “Canned, dry, fresh, the gamut.”
Feeding trial dogs ate a wider range of products and formulations than most dogs in private households. That gave Hancock’s team an unusual opportunity to look for correlations between copper levels in the dogs’ bodies and diets.
“If there’s something endemic with a substance source or levels in dog foods, because dogs get a wide range, maybe we’ll pick up trends in the dogs’ biomarkers,” he said. “If nothing else, it can serve as a baseline.
Previous studies often relied on liver biopsies taken for a specific reason, he said, but data about copper levels in the general population was lacking.
Fluctuations in copper levels but no explanations
After analyzing 336 samples taken during necropsies performed from 2006 to 2022, Hancock’s team did not observe any clear correlation between copper levels in the dogs’ livers and their other’ different diet. Instead, copper concentrations in dog livers decreased from 2006 to 2011, increased in 2012, decreased in 2013, and peaked in 2016, then began a steady decline. However, nothing related to ingredients or manufacturing as the direct cause of those changes.
There was a peak in one year, but it was not clinically relevant, Madison Amundson, associate scientist at Hill’s Pet Nutrition and study co-author, said. Copper levels in dogs never fell outside a normal reference range.
Considering genetics, Labrador Retrievers have lower concentrations of copper in the liver compared to Beagles, while mixed breeds are not significantly different from either pure. However, all of the dog’s copper levels remained within a safe range, Amundson said.
Although there was no explanation for copper storage disease, it blazed a trail to a rich source of data.
“Hill’s bio-archive is a unique thing to have as part of our facility,” said Laura Smith Motsinger, PhD, study co-author and senior scientist at Hill’s. “There’s a lot of potential there. It contains biopsy samples, it contains blood, it contains dog and cat. There’s a lot out there that we haven’t explored yet.”
This paper, which uses liver samples from the bio-archive, will hopefully open the gateway for other ideation projects, he said.
