Cattle in tall pasture

Trace Element Monitoring

Scott Hawkins

Written by Scott Hawkins

Scott is a mixed animal vet
based in Vetlife Twizel.

Monitoring trace elements in your livestock through liver biopsies and blood sampling, is the best way to assess your herd’s status, giving you critical information to help tailor your supplementation programmes. Some of the key trace elements worth monitoring in the autumn are copper and selenium. 


Copper is required for the function of enzymes that play integral roles in growth, bone and tissue development, skin and hair pigmentation, immune function, and production of red blood cells, so it is critical that we ensure stock have sufficient levels to keep them healthy and maximise production. 

Autumn is an important time to monitor your animals’ copper levels, as copper availability from feed declines over winter, especially if stock are grazing crops and/or going away from their usual water source with in-line mineral supplementation. Therefore it is important to check your stock have sufficient copper stores to get them through to spring. Copper is stored in the liver, hence the method of choice for monitoring copper levels is a liver biopsy. Liver biopsies are simple and safe procedures that can be performed by your veterinarian with animals restrained in a crush/head bail. 

Why do we need to sample the liver rather than just take a blood test?

The reason is to assess how much copper the animals have stored, rather than just measure how much they have present in their bloodstream on the day of sampling. You can think of the animal’s liver as the storage tank for copper (like the water tank at the top of the hill), and the blood is the pipe running from the tank. 

Water will remain in the pipe whether the tank is completely full or almost empty, and we cannot tell if the tank is empty until there is no longer any water in the pipe. The same goes for copper in the bloodstream; we could take blood samples to measure copper, but this only tells us what copper is present in the blood at the time of sampling while telling us nothing about how much the liver (tank) has stored. 

If the copper stores in the liver have been depleted, we can see this as low copper in the blood, however if there is just a small amount of copper left in the liver, the copper levels in the blood will remain adequate. Therefore, blood testing for copper is adequate for diagnosing deficiency, but if the tank is empty, it is not useful for ensuring sufficient copper stores are present. 


Selenium is required for normal growth and fertility, and for the prevention of many health disorders. Generally, there is a direct correlation between the levels of selenium in the soil, plant and animal. Selenium is not stored in the animal to any real degree, so animals’ selenium levels correlate to their recent selenium intake; hence a blood test is sufficient for measuring selenium levels. A blood test performed at the same time as liver biopsy in the autumn can be useful to ensure selenium supplementation is adequate, and this gives you time to make any adjustments required to your trace element supplementation programme prior to winter. We can also monitor other important trace element and mineral levels with this blood test, such as cobalt (vitamin B12), iodine and magnesium. 

Different species and stock classes have varying requirements for trace element supplementation. Talk to your local Vetlife veterinarian today about a trace element supplementation and monitoring plan to suit your needs.