Trace minerals and the cow’s immune system

To optimize the growth and production of animals, we have long realized good nutrition is key. Trace mineral supplementation has been simplified to strictly meeting the parts-per-million requirements set out in the nutrient requirement tables, with little attention given to the form in which the mineral is provided. Recently, there has been more interest and research on the influence trace minerals have on the immune system, with specific interest given to mineral form (organic or inorganic).

The minerals most commonly associated with the immune system are zinc, copper, iron, manganese and selenium. These minerals are also involved in nutrient metabolism and structural components of the body. And it isn’t just a deficiency of any single mineral that leads to a compromised immune system; toxicities can also result. It might seem like there could be an easily defined relationship between trace minerals and the immune system, but it is actually quite complicated.

Zinc is most likely the trace mineral that has received the greatest attention with regards to supplementation forms in the last few years. Aspects of the immune system influenced by zinc are T-helper cell function, lymphocyte production and activity, production of antibodies for T-dependent antigens, activity of killer cells, and production macrophages and neutrophils. Researchers in 1995 reported decreased morbidity from BRD in weaned steers fed higher levels of zinc in the diet. More recently, in 2014 researchers showed improved colostrum IgG levels and reduced somatic cell count (SCC) when cows received a form of zinc that had better bioavailability. In 2004, researchers demonstrated greater antibody titers in cattle when a more highly available organic zinc source was provided compared to an inorganic source.

Copper has received less attention than zinc with regard to immunity, but it most likely plays a role as significant as zinc. Copper has influence on the activity of Cu/Zn superoxide dismutase. The use of a more available copper was shown to reduce morbidity in steers. While the actual link between immune response and copper has been variable in livestock research, researchers in 2000 showed a reduced peripheral-blood lymphocyte response in steers stimulated with T-cell mitogens following weaning and IBRV challenge. The low levels of copper supplementation, and thus animal status, could be a reason for the lack of a clear mechanism.

Selenium has received lots of attention in recent years with the development of greater bioavailable sources and feeding level restrictions. Its key role in glutathione peroxidase is one of the most recognized functions of selenium. The mechanism by which selenium influences other aspects of the immune system has yet to be elucidated. Research has indicated selenium could have a substantial influence on neutrophil migration and the subsequent inflammation response.

Manganese has been linked with the immune system. The actual biological ties have been difficult to determine. One proposed hypothesis is that rather than manganese playing a direct role with immunity, it is more the antibody target to sequester it from tissues surrounding an infection site, thus starving the infecting agent from manganese necessary for its biological growth. The same study also proposed similar mechanisms for the influence of iron on the immune system.

The immune system within the body is a complex series of reactions and responses to internal and external stimuli. Trace minerals are believed (and in some cases known) to play a key role in how the immune system functions and protects the body. Simply overfeeding these trace minerals is not a solution for optimization. Overfeeding of trace minerals can create subacute toxicity levels that could be just as bad as subacute deficiency conditions. More consideration should be given to the bioavailability of the source of the mineral to most accurately meet the needs of the animal and keep its immune system functioning properly.