Impact of Housing Environment on the Immune System in Chickens: A Review

SIMPLE SUMMARY: In poultry production, chickens are confronted with a wide range of potential stressful conditions including restricted movement, long light phases or poor air quality. It is well known that stressors can have negative effects on the immune system. A fully functional immune system is, however, not only essential for chicken health and welfare but also for high productivity and safe animal products. This review summarizes current knowledge about the impact of housing form, light regime, aerial ammonia and hydrogen sulfide concentrations on the immune system in chickens and outlines possible mechanisms and interactions. ABSTRACT: During their lifespan, chickens are confronted with a wide range of acute and chronic stressors in their housing environment that may threaten their welfare and health by modulating the immune system. Especially chronic stressful conditions can exceed the individual’s allostatic load, with negative consequences for immunity. A fully functional immune system is mandatory for health and welfare and, consequently, also for high productivity and safe animal products. This review provides a comprehensive overview of the impact of housing form, light regime as well as aerial ammonia and hydrogen sulfide concentrations on the immune system in chickens. Certain housing conditions are clearly associated with immunological alterations which potentially impair the success of vaccinations or affect disease susceptibility. Such poor conditions counteract sustainable poultry production. This review also outlines current knowledge gaps and provides recommendations for future research.