Ceruloplasmin as an indicator of copper reserves in wild ruminants at high latitudes

Northern ungulates must establish trace mineral reserves when forage is available in spring and summer to sustain biochemical activities through the long winter. Copper (Cu), zinc (Zn) and iron (Fe) reserves were measured in the serum, digestive tract, liver, and kidney of six male caribou and reindeer (Rangifer tarandus) fed a complete pelleted ration. Dr matter content and absolute amounts of Cu, Zn and Fe were highest in the liver. Digesta contents of Cu and Zn were greatest in the rumen but dry matter concentrations were greatest ill the cecum reflecting the high levels of Cu and Zn in the diet. Serum ceruloplasmin (an oxidase containing Cu) activity was related to liver copper in captive reindeer and caribou (P < 0.05, r(2) = 0.82) during spring and winter but not during the nit. Michaelis-Menten kinetics of ceruloplasmin were measured in sera from captive reindeer, muskox (Ovibos moschatus) and moose (Alces alces) (n = 3/species). Maximum velocities (V-MAX) were 42, 20 and 9 (IU.L-1): k(M) were 0.38, 0.55 and 0.62 (mM) for muskox, reindeer and moose respectively. Wild caribou (n = 3) from the Teshekpuk herd and moose (n = 3) from the Colville River had lower V-MAX (7 IU.L-1) and higher k(M) (1.9 mM) than their captive conspecifics. These kinetic parameters probably reflect differences in ceruloplasmin structure between species as well as differences in tissue reserves between populations within each species. Serum ceruloplasmin activity and kinetics carl protide a non-lethal alternative to direct measures of hepatic Cu reserves in wild and captive populations. However. the method requires validation for the effects of sex, season, development and disease in each species.