An evaluation of the effect of clotting on the recovery of copper from caprine blood

In the goat, diagnosis of copper (Cu) deficiency is often based on measurement of Cu in serum or plasma. Previous research in cattle and sheep has shown that these values are not interchangeable, but data for goats have not been published. Paired serum and heparinised plasma samples taken from 119 goats in eight herds were tested for Cu concentration.Plasma and serum Cu were significantly correlated (r = 0.95). On average serum Cu was 3.5 μmol/L lower than plasma Cu, but this difference was related to Cu status (r = 0.45). Mean serum Cu concentration was 83% of plasma Cu, with the 95% limits of agreement ranging from 66% to 100%. Similar to cattle and sheep, individual variability in Cu loss during clotting is too great for serum Cu to be used as a measure of Cu status in goats.