Species: Cattle, sheep, deer, goats, alpaca
Specimens: Serum, whole blood (EDTA or heparin) or liver.
Number of animals to test for mob/herd/flock deficiency: 10 (serum, whole blood) and >10 (liver).
General information about the test:
Copper is stored in the liver so measurement of plasma, ferroxidase or serum copper do not give an estimation of the liver reserves until they are very low < 4.5 umol/L (serum or plasma) or ferroxidase <7 U/L. However if more than two serum coppers are low in a group then the liver coppers of all animals in the group will also be low.
Ferroxidase is a copper containing enzyme which deteriorates over time so using old or haemolysed serum samples can affect results. However it does correlate with serum copper if fresh samples are used.
Reference ranges for copper were established using plasma samples whereas most samples taken are serum. In cattle a significant amount of copper is sequestered during the clotting process which is not currently accounted for with the current reference ranges and could lead to misdiagnoses of copper deficiency.
Although plasma copper also measures the copper which would have been retained in the clot if serum copper had been measured there appears to be no clinical advantage in using plasma copper over serum copper as the reference ranges have been adjusted and both are equally poor indicators of liver stores but can give an indication if copper deficiency is the cause of the current problem.
Serum (live animal) and kidney (dead animal) are the samples to test for copper toxicity. Serum copper >40 umol/L and and a kidney copper >150 umol/kg indicate toxicity. Liver coppers >4000 umol/kg in liver biopsies or liver taken at slaughter plants from normal cattle indicate the potential for copper toxicity.
Reference interval (serum Cu):
- Cattle – Adequate >7 umol/L
- Sheep – Adequate >8 umol/L
- Deer – Adequate >8 umol/L
- Goat – Adequate >11 umol/L
- Alpaca – Adequate >5 umol/L
Reference interval (plasma Cu):
- Cattle – Adequate >9 umol/L
Reference interval (ferroxidase):
- Cattle – Adequate >14 IU/L
Reference interval (liver Cu):
- Cattle – Adequate >95 umol/kg
- Sheep – Adequate >65 umol/kg
- Deer – Adequate >100 umol/kg