Impact of stress on the functioning of the immune system, swine health, and productivity

Stress can affect many aspects of the body, including the immune response, and stress factors are an inherent element in the life of animals in intensive production, such as pigs. Major pathways involved in these interactions are associated with the sympathetic nervous system (SNS) axis and the hypothalamic–pituitary–adrenal (HPA) axis. This review is focused on the effects of various stress factors described so far on the swine immune system. The literature data presented here indicate that the effect of stress factors depends not only on the duration and severity of stress, but also on the animal’s temper. Stress, through its influence on the immune system, strongly influences the digestive tract of pigs such as response to pathogens, microbiome disturbance and influence on appetite. Thus, long-term stress has negative effects on the animal’s development, including a high rate of morbidity and mortality, an increase in the feed conversion rate (FCR), and, important in intensive production, weight differentiation of the same age groups of pigs. Therefore, the role of stress and the immune system itself in the production of pigs should not be underestimated. Any decrease in animal stress is crucial.