Short communication: Survey of hepatic copper concentrations in Midwest dairy cows.

Previous research from our laboratory and others indicates that liver copper concentrations in dairy cattle are commonly well above those recognized as adequate for the nutritional needs of the animal. It has also been speculated that hepatic copper concentrations have been increasing in recent years. Unlike other species, the threshold at which elevated liver copper concentrations becomes deleterious to hepatocytes is not known for cattle. Therefore, the objectives of this study were 3-fold: (1) to delineate differences in the range and mean dry matter hepatic copper concentration for dairy cattle in a retrospective analysis (January 1, 2007, to December 31, 2015), (2) to investigate hepatic copper concentrations in Midwest cull dairy cattle, and (3) to evaluate histologic changes in hepatocellular morphology in the context of copper concentration in cull cows. Furthermore, microscopic changes in hepatocellular morphology or architecture were examined and scored for evidence of inflammation, fibrosis, necrosis, and abundance of rhodanine-stained granules using hematoxylin and eosin and rhodanine staining. The retrospective analysis found copper concentrations within a range of 3 to 1,963 µg/g, with a mean of 473 µg/g. Hepatic copper concentrations in our retrospective study did not increase with time. In our abattoir analysis, copper concentrations ranged from 15 to 978 μg/g, with a mean of 390 μg/g. This study found that the range and mean hepatic copper concentrations were comparatively less in the current abattoir study than copper concentrations in our retrospective analysis. There was no evidence for hepatocellular changes associated with increased copper burdens in this study population.