News & Advice

Don’t get caught on the back foot, prioritise your herd’s trace element testing

May 1, 2023 | Dairy, Minerals

Rebecca Smith, Veterinarian, Anexa Vets Morrinsville

Autumn has rolled around again, and trace element planning is in full swing. This season we have been fortunate enough to have a “green summer” and there are many good-looking animals around. It is important to be proactive with trace element testing and planning, for the coming winter to help pave the foundation for a good next season – a little investment now will see greater returns next season.

When I approach the trace element conversation with clients, they often have questions. Below are some of the common ones:

 

Why are trace elements important?

The main trace elements we worry about in dairy cattle are copper and selenium. Animals can suffer from deficiency (too little) or toxicity (too much) of both elements.

Copper is an essential component of many enzymes required for tissue generation. When we understand this, it makes sense that animals with clinical copper deficiency can demonstrate bone abnormalities and fractures, muscle and tendon abnormalities, compromised growth, compromised milk production and reproductive performance.

Selenium is essential as an antioxidant, protecting the body from the biproducts of aerobic metabolism. Selenium is also required for the generation of certain types of white blood cells (immune cells). Cows with selenium deficiency are at increased risk having retained membranes and developing uterine infections such as endometritis post calving, they have an increased risk of developing mastitis and have reduced reproductive performance at mating.

 

My animals look great; they don’t show any of those signs. What benefit will I get from testing them?

Many farms already supplement copper and selenium in some way, so we may not see the more dramatic signs of deficiency described above. More commonly, we find sub-optimal performance. In some cases, the poor production isn’t really appreciated until animals show an improvement…. after the deficiency is detected and corrected.

If you are already supplementing your herd with copper and selenium and haven’t checked their trace element status, it’s important to understand that both copper and selenium are toxic when overdosed or over supplemented. Continually supplementing animals with optimal or high selenium or copper levels may result in cumulative toxicity over time. Understanding the trace element status of your herd through routine testing will reduce this risk and save money that would be spent on unnecessary supplements.

 

What does trace element testing involve?

At this time of year liver biopsies are best. As copper is mainly stored in the liver, liver biopsies are the best way to accurately measure the copper status of your herd. Selenium levels can also be measured in liver samples.

Blood samples are good for assessing the selenium, B12 and magnesium levels in your herd but unless your herd is facing dire copper deficiency, low copper levels will not be picked up. Because liver samples demonstrate the level of copper stored, they allow us to know if an animal is not currently deficient, but likely to become deficient in the winter. This is particularly important knowledge to have for spring calving cows going into winter who are likely to have reduced dry matter intake and increased nutritional demand due to late gestation pregnancy. On the flip side, liver biopsies demonstrating high levels of stored copper could provide you with the peace of mind that copper supplementation over winter is not required.

Liver biopsies are a routine procedure, and our vets are well trained to perform them efficiently and in a way that minimises any potential discomfort experienced by the animal being tested.

Samples from cull cows at the meat works are an option, but these should be a last resort. It is important to bear in mind that cull cows are often cull for a reason, this means that they will potentially have a different trace element profile to the rest of the herd. In addition to this identification of samples through the meat works can be difficult, so if you chose this option, it is important to understand that you may not know which cow had the abnormal result.

 

What about my youngstock? Do we need to test their trace elements too?

Yes, absolutely. Youngstock are the future of your herd, sub-optimal trace element levels in your youngstock will impair their growth rates and potentially lifetime production. Unfortunately, they are often overlooked in the herd trace element testing and supplementation planning. Make sure that your youngstock are included in your plan this season.

 

How much does trace element testing cost?

Not as much as you would think. There are a variety of liver and blood testing packages available. Your vet will be able to go through the different options with you and discuss the cost/benefit of each option.

If you have any other questions about trace element testing, please get in touch with your vet who will be happy to talk through the best options for your farm. Otherwise, contact your local clinic to book in trace element testing today.

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