|Cheng, Heng Wei|
Submitted to: Journal of Psychoneuroendocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2002
Publication Date: 5/1/2003
Citation: CHENG, H., CHEN, Y., SINGLETON, P.B., MUIR, W.M. CHRONIC SOCIAL STRESS DIFFERENTIALLY REGULATES NEUROENDOCRINE RESPONSES IN LAYING HENS: I. GENETIC BASIS OF DOPAMINE RESPONSES UNDER THREE DIFFERENT SOCIAL CONDITIONS. JOURNAL OF PSYCHONEUROENDOCRINOLOGY. 2003. V. 28. P. 597-611. Interpretive Summary: Stress susceptibility in animals is a major problem in modern intensive husbandry, including the poultry industry. Genetic selection strains with specific physiological and behavioral characteristics have become a major tool to combat stress and improve animal well-being. The present data showed that there is a genetic basis for regulation of plasma dopamine concentrations in response to different social stress. The differences could contribute to each line's unique behavioral pattern and productivity in response to different stimuli. The results further suggest that change of dopamine concentrations could be used as a stress indicator by producers and scientists for evaluation of animal well-being and coping ability.
Technical Abstract: Chickens were selected for both high (HGPS) or low (LGPS) group productivity and survivability resulting from cannibalism and flightiness in colony cages, without beak trimming. The hypothesis was tested that the different behavioral patterns and productive capabilities between the two lines may have been due to differential regulation of neuroendocrine hormones in response to social stress. At 24 week of age, data showed that the HGPS had less plasma dopamine concentrations than those of the LGPS hens in all three social treatments, i.e., housed in the 10 hen, 2- hen and single-hen cages (P < 0.05, respectively). The study revealed that dopamine concentrations were regulated differently based on the social treatments, i.e., single-hen > 10-hen > 2-hen treatment. These results indicate that genetic selection for group productivity and survivability altered the chickens' dopaminergic system in response to social stress, and chickens prefer a small social group rather than crowded or being isolated. The data further support our previous mention that changes of dopamine concentrations could be used as a physiological indicator for evaluating animal well-being and an animal's ability to cope with environments created by modern intensive husbandry.