ABSTRACT
In the perpetual battle against common poultry pathogens and other environmental antigens, the role of the immune system is an important and ongoing topic of research. With the current trend of reduced reliance on preventative drugs and emphasis on more natural alternatives, the proper functioning of the host defences becomes even more significant. Careful priming and activation of targeted immune responses not only leads to better protection against challenges, but also helps in optimizing the birds’ performance through proper allocation of nutrients towards maintenance and growth. Modulation of immune responses is best exemplified by routine vaccination to build specific immunity against common pathogens and prevent disease development. However, stressors such as subclinical infections that often go undetected pose the most significant threat to profit margins of the poultry industry. Low pathogenic loads, especially in the gastrointestinal tract, frequently lead to diminished performance as they compromise the epithelial lining. By priming local immune elements at mucosal sites (digestive and respiratory), subclinical infections could be averted or suppressed, thus enhancing growth and general health. Among the most commonly used modulators are feed and/or water supplements such as probiotics and prebiotics where much of the recent research focus has been invested. Therefore, this chapter will first review the various elements of the host defence system, and then will provide specific examples on how certain supplements can modulate the immune system and its responses to specific challenges that are common in commercial production.
