Copper can equally be a problem in deficient as in excess

It accumulates in the liver and so liver testing is the definitive test for copper.

Copper levels in feed need monitored if the liver levels are high.

Jerseys and crosses are more prone to accumulating copper and hence toxicity issues.

PKE is very high in copper.

Deficiency effects:

fertility, growth rates and can lead to bone fractures.

it also effects red blood cells, cell health and the immune system.

Levels in the liver >2.09 mol/kg are high and heading to or risking toxicity 

Cows can be in the toxicity range but not have any problems until a sudden stress.

This might be calving, dry off, diet change, bad weather or trucking or a combination of the above.

Symptoms of toxicity are:

Depressed, jaundice ( yellow gums, eyes, vagina membranes).

Dark red urine ( hemaglobinuria) and sudden death.

Treatment is non successful.

The only option is to alleviate stress on the mob. 

Diagnosis in sick cows on top of signs and history include blood testing for raised liver enzymes and raised blood copper levels.

PM look for elevated copper in both liver and kidney.