Retrospective analysis of hepatic copper concentrations in an internal feeding colony of dogs fed a broad range of foods.

Objective: To examine the effects of age, sex, year of death/sample collection, and liver histopathology on liver copper concentrations in dogs fed a wide variety of commercial dog foods throughout their lives.

Methods: This study utilized all bioarchived liver samples collected during necropsy at time of death from 2006 to 2022 from dogs housed in a closed feeding colony. Liver samples were analyzed on a dry matter basis for copper concentration by inductively coupled plasma-optical emission spectrometry and did not require specific criteria for selection. The effects of animal age, year of death/collection, sex, and liver histopathology on liver copper concentrations were assessed.

Results: Liver samples were analyzed from 296 dogs. Age and sex had no effect on liver copper concentrations, which increased linearly over time by an average of 3.41 ppm per year but remained within the normal reference range. Quantile regression indicated that the lowest 5% and highest 5% of liver copper concentrations analyzed were not changing and only a slight increase (3.7 ppm per year) was observed in the lower 25th quantile. The mean copper concentration of abnormal liver histopathology samples was not different from the mean copper concentration of normal liver histopathology samples.

Conclusions: Histopathologic findings or animal demographic did not impact liver copper concentrations over a 16-year period. Liver copper concentration increased linearly but remained within the normal reference range.

Clinical relevance: Mean liver copper concentrations for each year remained within normal limits. Studies assessing the impact of specific nutrient profiles and sources in various populations are warranted.