Influence of environmental stress on immunity of swine

Abstract

SummaryThis paper deals with pigs kept in environments, where they are exposed to a high number of pathogenic microbes and have reduced feed intake and growth, even when no obvious acute illness exists. According to the presented article this chronic drain on production is called immunologic stress. Sentinel immune cells (e.g. macrophages) supervise the diverse microbial environment by detecting pathogen -associated molecular patterns (PAMPs), which are molecules associated with groups of pathogens. The immune sentinels detect PAMPs mainly with Toll -like receptors (TLRs). Stimulation of macrophages through their TLRs leads to the synthesis and secretion of pro-inflammatory cytokines and prostaglandins, initiating the inflammatory response that recruits both immune molecules and circulating immune cells. Pro-inflammatory cytokines enable the immune system to communicate with other physiological systems. They rearrange the animal's metabolic priorities, resulting in re-partitioning of nutrients away from productive processes towards responses that support the immune system. Thus, the immune system, through detection of PAMPs and production of proinflammatory cytokines, is the critical chain link connecting the pathogenic environment to productivity. The evaluation indicates, that at maintenance a healthy animal uses about 0.5-2% of the body's lysine for leucocytes, antibodies and acute phase proteins. In the situation of contamination by pathogens of the environment the immune response is estimated to account for about 9% of the body's lysine. Providing additional lysine in the diet does not improve the reduced growth of the pig, caused by immunologic stress as the result of contamination of the pig environment by pathogenic or facultatively pathogenic microorganisms. Thus, minimizing exposure to pathogenic microorganisms and providing sound environmental management practices is a high priority.