So, what trace elements are important and why?
Selenium: selenium is essential for a wide range of functions relating to growth, immunity and fertility. This is because it is a component in a large number of proteins and enzymes responsible for physiological functions within the body. Selenium deficiencies can present in a wide range of ways such as ill thrift, poor immunity, poor fertility performance (including both cyclicity and issues post calving) or even white muscle disease (weak calves that fail to thrive).
Iodine: Iodine is essential for thyroid function and, similarly to selenium, is needed for a variety of bodily functions. Low levels can cause calves to be stillborn, along with fertility issues (including poor heat expression), poor growth and reduced milk production.
Cobalt: Also known as B12, cobalt is needed by micoroorganisms in the rumen to break down cellulose; ie. So that the rumen bacteria can fully utilise the diet they are presented with. Low levels can cause issues with growth.
Zinc: Similarly to most of the trace elements mentioned zinc is involved in a wide range of functions and low levels can be associated with poor growth and production, fertility, immunity and hoof growth.
Copper: In the UK we often find issues with over supplementation as opposed to under. Copper issues may be associated with poor fertility, ill thrift and can be identified by animals with pigmentation issues (spectacles).
Assessing mineral status
The easiest method of assessing mineral status is through blood samples, looking at circulating levels. However, minerals such as copper and cobalt are stored in the liver and so circulating levels can appear normal, whilst the actual levels in the body may not. In this case, liver biopsies can prove more useful and give a true assessment of an animal’s status.