Copper nutritional status of free-ranging wild ruminants in southern Africa

To assess the copper nutritional status of southern African free-ranging wild ruminants, liver copper concentrations from more than 1000 animals representing 14 species were evaluated. Hepatic copper concentrations closely reflect copper intake levels in ruminants, and are widely accepted as the most reliable biomarker of copper status in ruminants, including in cases of environmental copper pollution. The liver serves as the primary copper storage organ in ruminants, maintaining copper supply until hepatic reserves are depleted, with plasma levels only declining once liver concentrations fall below approximately 20 mg/kg dry matter (DM). However, diagnostic thresholds for copper status vary among laboratories: some classify liver concentrations of 20–90 mg copper/kg DM as marginally deficient, whereas others consider concentrations of <20 mg/kg DM indicative of marginal to clinical deficiency. The latter criterion was adopted in this study. If the 20–90 mg/kg DM criterion had been applied, about 40% of the animals sampled would have been classified as marginally deficient; however, in this study a range of 20–500 mg copper/kg DM was interpreted as adequate. Most animals fell within this range, with a small proportion below the deficiency threshold, notably among grazers foraging on floodplains as well as in the southern Kruger National Park, and in the eastern Free State and Mpumalanga provinces. Although interspecies comparisons are confounded by dietary differences, mixed feeders (consuming grass and browse) often exhibited higher liver copper concentrations than grazers occupying the same areas, suggesting either species-specific differences in copper metabolism and/or higher copper concentrations in browse than in grass. (Submitted 02 October 2025; Accepted 20 January 2026; Published 12 March 2026)