Stress and immunity in the pig.

Abstract One potential indication of decreased welfare in pigs is a greater prevalence of disease as a result of compromised immunity in 'stressed' animals. Various studies have endeavoured to assess the effects of stress on pigs. Stressors included social interactions from crowding or mixing pigs, ambient temperature variations, restraint, transportation, food deprivation, weaning and photoperiod manipulation. Typically, serum cortisol concentrations are used to quantify or confirm whether the animals were stressed; however, several methods were used to examine the influence of stress on immune function. The results of these studies varied in documenting whether the animals were stressed, what the general effects were on the porcine immune system and, in particular, which cells of the adaptive or innate immune systems were affected. This review is intended to provide an overview of previous methods of creating stressful conditions for pigs, techniques to assess immune function and finally, the interactions between stress and measurements of immune function in pigs. Emphasis is laid on the influence of stress on adaptive immunity.