News & Advice

It’s trace element testing time

Apr 1, 2024 | Dairy, Dairy Animal Health & Welfare, Minerals

Now that autumn has well and truly arrived, it’s time to ensure that your herd has sufficient trace elements on board, particularly copper and selenium, before winter hits. Being proactive about trace element testing now will reduce the risk of cows becoming deficient in future, with negative effects on milk production, fertility, and general health. Knowing the trace element status of your herd will also allow you to ensure you get the best bang for your buck from supplementation. 


Why worry about copper? 

Copper plays a key role in cow health: supporting growth, milk production, fertility and calf viability. It is stored in the cow’s liver and slowly released into the bloodstream to maintain sufficient levels. However, when the liver stores are exhausted, blood copper levels begin to drop and cows show obvious signs of deficiency.


Ensuring cows have adequate body copper stores heading into winter is important for two key reasons:

  • Winter pasture is often high in molybdenum, sulphur and iron, meaning less copper is available to cows during this period; 
  • In addition, during late pregnancy, the calf creates a large copper demand on the pregnant cow. 

It is also known that copper and zinc compete with each other for uptake in cows, meaning that zinc supplementation for facial eczema prevention will have potentially reduced copper intake over the past few months.

Trace element testing is critical to determine how much copper cows have stored in their liver, and therefore, what level of supplementation is required to maintain their copper levels.

Just as importantly, there is a limit to how much copper a healthy animal should receive. Excessive supplementation can lead to copper toxicity with disastrous consequences. In particular, this can be an issue when copper supplementation is combined with palm kernel feeding, which in itself is high in copper.

The only way to be confident about your copper supplementation is to test your cows’ liver copper storage levels first. 


What about selenium? 

Selenium is another important trace element for cow health, playing a number of roles in the body. It is involved with milk production, reproduction, calf viability, immune function, as well as reduced incidence of disease during the calving period, such as mastitis and retained fetal membranes (cleanings).
Selenium supplementation is highly variable farm to farm and is dependent on soil levels as well as the amount of supplemental feeding. The only way to be sure about selenium supplementation on your farm is to get your cows tested. 


Liver biopsies are best! 

Liver biopsies are the most accurate way to determine copper storage levels in your herd prior to winter. It is also possible to test selenium levels from the same liver sample, meaning two tests from one sample! We recommend liver samples are collected, representing older and younger animals in your herd. These results will enable a tailored trace element supplementation plan to be developed for your farm, or alternatively, prevent unnecessary supplementation in herds whose levels are adequate and are at risk of toxicity.


…but aren’t they quite invasive?

We know that some farmers are concerned about the impact of liver biopsies on their cows. Anexa Vets are trained to perform liver biopsies as painlessly and efficiently as possible. The risk of complications from the biopsy procedure is very low and we believe that the benefits of trace element testing far outweigh the risks.


…but what about cull livers at the works?

While cull livers are still commonly used for copper testing, and there is some merit in doing so when necessary, it is likely that these results are less reliable than if samples are taken from live cows still in your herd. The identities of the cows sampled are rarely known, and the reason for culling, for example, empties or old age, means that these animals may not be representative of your herd.


…could you just test bloods instead?

It is possible to test blood samples for copper and selenium levels, however, the usefulness of those results in making decisions about your herd is questionable. While the results for selenium are useful, the copper results will only tell you what the cow’s blood copper level is on that day. It will not give you any information about the amount of copper a cow truly has stored in her liver. A cow could have adequate blood copper levels and be on the verge of deficiency, with no copper left stored in her liver. Therefore, it is very difficult to make recommendations about copper supplementation from blood copper results alone. 


It’s time to make a trace element testing plan 

Once the busy dry-off period is over, it’s an ideal time to get your trace element testing underway. Speak to your Anexa Vet about the possibility of liver biopsies this year. We are confident you will see the benefit.


Other resources that you may find helpful:


The complications of copper (and other trace elements)

Minerals and Trace Elements

Trace element monitoring and supplementation for optimal results


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