Chronic stress and environmental enrichment as opposite factors affecting the immune response in Japanese quail (Coturnix coturnix japonica)

Abstract

Procedures in the commercial production of animals involve stressful situations which lessen the animal's welfare. This study on Japanese quail evaluated whether an environmental enrichment manipulation can affect avian immune responses and if combined with a chronic stressor exposure can help to counteract the negative effects of stress on the immune system. Potential gender effects were also considered. After hatch, half of the birds were housed in non-enriched boxes and half were housed in environmentally enriched boxes. From day 33 to 42 of age, all birds within half of the non-enriched and enriched boxes remained undisturbed while the other half were daily exposed to a 15 min restraint stressor (chronic stressor). The inflammatory response (lymphoproliferation after phytohemagglutinin-p), percentage of lymphocytes, heterophil/lymphocyte (H/L) ratio and primary antibody response against sheep red blood cells were assessed. The chronic stressor application and the enrichment procedure, respectively, either increased or reduced the four immunological parameters evaluated and always in opposite directions. Males consistently showed lower antibody titres than females and presented the highest H/L ratio in response to the stressor when reared in the non-enriched environment. The findings indicate that submitting these animals to an enriched environment can be effectively used to improve their immune response and to reduce the detrimental effects of a stressor exposure.

Keywords::

• Antibody response
• chronic stress
• environmental enrichment
• heterophil/lymphocyte ratio
• immune response
• Japanese quail

Acknowledgements

This research was supported by grants from Fondo para Investigación Científica y Tecnológica (FONCYT) (Project 34157), Secretaría de Ciencia y Técnica, Universidad Nacional de Córdoba (SECyT, UNC) and Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) Argentina. FNN holds a research fellowship from the latter institution. RHM is a Career Member of CONICET, Argentina. The authors wish to thank Dr R.B. Jones for his comments during the planning of this study and Dario C. Arbelo for his technical assistance.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.