One of the benefits of a vet business our size is the amount of data we collect on animal performance. How can this help me I hear you ask? Recently we reviewed the serum selenium and liver copper results in cattle that have been tested through all the Anexa clinics over the past 10 years! That is 30,880 pieces of data! 

The key messages from this analysis for you and your stock are:

• Selenium deficiency is relatively uncommon with <5% of animals sampled having levels which are considered truly deficient indicating that supplementation plans are mostly working. We just need to keep monitoring to make sure we identify the ones that aren’t. 
• Heifers <15 months old have lower levels of selenium than older animals, which means testing your yearlings pre-mating should be part of your trace element plan. 
• 30% of heifers (mostly sampled on arrival home from grazing) had liver copper levels that were deficient (<95), which was 2 X as common than it was in the mature cows. Therefore, doing liver biopsies on arrival home is a must. 
• There has been a general increase in liver copper levels over the past 10 years; however from season to season there is still variation in copper levels, so without measuring you cannot be certain your current supplementation plan is working. 

What are trace elements and why are they important?

Trace elements are essential micronutrients such as copper, selenium, cobalt and iodine. As the term essential implies, animals which are deficient in these elements have compromised health and production. The two main trace elements of concern in dairy cows are copper and selenium. Deficiency can present in different ways and can be hard to pinpoint without lab testing. Sub-optimal levels can lead to reduced milk production, poorer reproduction, reduced growth rates in young stock as well as a range of other health problems due to immune suppression. 

Why bother testing? Why not just supplement?

Supplementing at incorrect levels (either too much or too little) costs you money without achieving the desired results. If you are not giving enough to correct the deficit, then you won’t see the production (and reproduction) benefits you expect. If you are giving too much, you run the risk of toxicity in the herd. Trying to save money by not testing is false economy in the long run! To ensure you get the levels right, we recommend testing a sample of your herd prior to supplementation to assess their trace element status. This is particularly important for herds experiencing a change in diet such as removal or addition of PKE, which is quite high in copper. 

When is my herd at most risk of being deficient? When should I test and how?

Copper is stored in the liver and is released into the blood as needed. Consequently, copper levels do not show up as low in the blood until the liver reserves are exhausted. Copper storage levels deplete over the winter due to reduced pasture copper levels, reduced feed intake and increased copper requirements of the cow in late gestation. Because of this, we advise that liver biopsies are taken in autumn to check that cows have enough copper storage to get them through winter. Blood samples can then be taken in pre-mating to screen for copper deficiency.

The procedure for taking liver biopsies in cows is quite straightforward and is far less invasive than you might think. While livers from cull cows can be tested at the works for copper, these results often don’t reflect an accurate picture of the true copper status of your herd as many of these cows are empty cows or low producers due to underlying illness, which will affect their liver copper levels.

Herd selenium levels are best assessed from blood samples; these can be taken at the same time at the liver biopsies in autumn.