Copper Metabolism in the Koala (Phascolarctos cinereus) as Indicated by a Ceruloplasmin Stimulation Test

Tests to examine the copper status of herbivores were evaluated in lactating cattle (Bos taurus). Serum copper, erythrocyte-copper superoxide dismutase, and serum ceruloplasmin were measured prior to and following an injection of a physiological dose of copper. The change in ceruloplasmin activity 24 h posttreatment was found to be the preferred test and response time. This ceruloplasmin stimulation test was then used to examine the physiological copper status of seven free-living koalas. One koala had a ceruloplasmin stimulation of 125%, while three further koalas had ceruloplasmin stimulations of 18%, 56%, and 63%. In the remaining koalas the ceruloplasmin stimulations at 24 h were all <10%. From these stimulation effects, a reference range for koala serum copper levels was established. Serum copper levels less than 1.5 μmol liter⁻¹ are considered deficient, 1.5-4.5 μmol liter⁻¹ marginal, and greater than 4.5 jtmol liter⁻¹ adequate. Twenty-three healthy koalas from other sites had serum copper levels of...