News & Advice

Why do I need to test my cattle’s mineral levels?

Mar 23, 2022 | Dairy, Dairy Animal Health & Welfare, Minerals

Knowledge of the copper and selenium levels in your herd is important for making safe and productive trace element supplementation decisions. We recommend testing your herd’s trace element status at least twice per year in autumn and pre-mating. To get the best value from your trace element testing a combination of liver biopsies and blood samples are required. Our large animal vets are highly proficient at liver biopsies, making the process on farm a breeze, while keeping the cow comfortable.


Why do I need to test my animal’s minerals at least twice a year?

Trace element profiles are dynamic and seasonal so they change frequently. Just because your herd was not deficient last year, does not mean it will be the same this year. At the end of the zinc season, it is important to check the copper status of your herd. At the same time the status of selenium and magnesium can be checked. 


How does supplementing with zinc during the facial eczema season affect copper levels?

Animals can become low in copper during the facial eczema season, as zinc and copper compete with each other in the gut for absorption. Copper deficiency does not always produce the typical ‘rough coated’ red tinged appearance. Many copper deficient animals look completely normal, but deficiency in copper can affect bone development and cause significant production losses. There have been an increased number of heifers presenting with broken legs during their first lactation. The causes of this are currently being investigated at Massey University with the aid of vets around the country. One theory being investigated is that copper deficiency is playing a significant role as lack of copper can lead to inadequate bone formation and subsequent weak bones. On the other hand, if animals are not deficient, there is no point supplementing more than a maintenance dose rate. Over supplementation may not only be a waste of your money, but can also be harmful for the animal’s health. The only way to know the true status of your animals is to test them! 


What is the best way to test copper levels in cattle?

The best way to assess the copper status of an animal is to get your vet to take a liver biopsy. The liver is the storage organ for copper, so liver sampling will give an accurate indication of the true status of the animal. A blood sample simply provides a snapshot of the copper levels released into the bloodstream from the liver on a particular day. A deficiency will only be detected in a blood sample if the liver is completely depleted. 


When should I test my cattle’s copper levels?

Liver samples need to be taken from at least 6 animals of mixed ages. Heifers should be treated as a separate mob and sampled separately from the main herd as we know that heifers can have a hugely different mineral profile from their future herd mates. If cull cows are sent to the works, liver samples can be requested from the works. These cull animals may not be representative of the herd since they have underlying issues that cause them to be sent away. It is best to take liver samples from a mixed group of healthy live animals


What other minerals should I test for?

The selenium and magnesium status can be tested in blood samples. At least 10 samples are required for a good overview of the mineral status. For any trace mineral testing the animals need to be randomly picked from different age groups to represent the build-up of the herd. 

Talk to your vet to discuss the best strategy to ensure your animals have the correct trace element levels. 


Other Anexa resources you may find helpful:

Dairy – Minerals


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