Ceruloplasmin as an indicator of copper status in cattle and sheep.

The relationship between ceruloplasmin, a metalloenzyme with oxidase activity, and copper was investigated in cattle and sheep. The oxidase activity of ceruloplasmin correlated closely with the serum or plasma copper concentrations in cattle. The respective correlation coefficients were 0.83 and 0.60. In sheep serum, a correlation coefficient of 0.92 was obtained. In each instance, the relationship remained linear from the deficient to the high normal ranges of copper. Comparison of the linear regression relationships indicated the ceruloplasmin activity in bovine serum was statistically lower than the activity in bovine plasma (P less than 0.0001), through the intercepts from the regression lines of the two relationships were similar (P = 0.412). Comparisons of ovine and bovine serum-ceruloplasmin relationships indicated that a significant species difference was present. Ovine ceruloplasmin activity increased more rapidly as compared to the corresponding bovine activity over the range of copper concentrations investigated (P less than 0.0001). The intercept from the ovine regression relationship was also lower (P less than 0.0001). A correlation coefficient of 0.35 was observed between the serum ceruloplasmin activity and hepatic copper concentrations in cattle indicating that the mathematical relationship was not as well defined. Ceruloplasmin activity appears to correlate more closely with serum or plasma copper concentrations as compared to corresponding liver copper concentrations.