Using feed additives to enhance immune status

Animal Nutrition Views

Ioannis Mavromichalis, Ph.D., gives his views on poultry, pig and dairy nutrition based on his experience as a nutrition consultant with clients around the world.

There are several commercial products that claim to enhance animal immunity — resistance to pathogens such as viruses and bacteria. One of the latest to be added in this list of additives is algae, or seaweeds. To be more precise, ulvans (polysaccharides from green algae) exert immunomodulating properties by activating expression of some cytokines and chemokines involved in innate and adaptative immune response. The same is true for carrageenans and agar (polysaccharides from red algae). Such effects are of particular interest in diseases where the immune system is impaired or can benefit from a boost. This is the case for example in young animals or during vaccination period. But, I digress.

Any additive with claims on immunity has a major drawback. It lacks strong verification in practice. That is, how to compare the effectiveness of a product that at best case scenario will not "increase" a productivity index. Or, in other words, how can we evaluate the absence of disease? Therefore, in my opinion, the scientific community must address two challenges to enable us to measure the effectiveness of products that enhance the immune system of animals.

  1. The effectiveness of additives with claims on enhancing immunity must be evaluated in disease-challenge trials, involving live farm animals as the ultimate test. This is easier said than done, and this is why most data are obtained using laboratory animals or in vitro test.
  2. We need an effective, accurate and hopefully inexpensive biomarker of immune status. That is, we must be able to measure the resistance of animals to specific diseases at farm level. In this way, we can associate with confidence the enhanced immune status with active resistance to diseases.

At the moment, we have enough indirect information to associate several additives with improved immune status, but we need more data using farm animals. In addition, we lack that effective biomarker that will enable field application of such additives without having to depend on laboratory studies.

Immunity and nutrition is a major field of research that deserves paying close attention to it for the years to come.