THE ENERGY COST OF ILLNESS IN SWINE

Dirty, less hygienic environments increase the level of immunological stress and depress growth and performance of pigs. In response to challenge by bacterial or viral pathogens, the pig's immune system responds by secreting cytokines. These molecules which promote inflammation were originally described for their ability to orchestrate the immune response against the infectious pathogen. It is now recognized that cytokines also act on other targets outside of the immune system. The cytokines released by activated macrophages have been found to alter the metabolism of carbohydrate, fat and protein substrates, regulate certain endocrine secretions, and reduce food intake. In short, many findings converge to suggest that a major component of the growth inhibition observed in immunologically challenged pigs is mediated by pro-inflammatory cytokines. The goal of this short paper is to provide an integrated view of how immunological stress through the secretion of cytokines depresses growth in pigs