There is a narrow range when supplementing with copper meaning getting it to optimum levels are essential. Sampling can be difficult as blood can be difficult to interpret and liver samples are the premium method of doing this.
Remember low copper can be an issue but also over-supplementation (toxicity) is a big problem on some farms.
It has been associated with swayback and changes in hair coat and wool. It can also when low effect immunity and may cause infertility. As it is involved in glucose metabolism.
While we can get copper deficiencies due to low copper they are rare. They usually occur because of complex interactions or are locked up by other minerals.
The key minerals involved in this are iron, sulphur and molybdenum. This begins with simple interactions in the rumen and then the blood that locks up copper making it not freely available for use within the body. These form substances called thiomolybdates which will give the appearance of deficiency but can be due to lock up.
These animals will not be low in copper in their diet but because it is locked up may not be freely available.
In calves and lambs, they digest copper through their intestine. With copper toxicity or oversupply we can see animals getting weak, listless and experience a haemolytic crisis. This haemoglobin is broken down and excreted in plasma and urine.
There are a number of ways of measuring copper in the blood, but liver sampling (major reserves) are the premium animal-based tests for copper. This can be done by liver biopsy or checking livers from culled animals in the factory.
When measuring copper on a farm like other minerals you must look at all potential sources.