|Cheng, Heng wei|
Submitted to: Journal of Psychoneuroendocrinology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/24/2002
Publication Date: 6/1/2004
Citation: Cheng, H., Chen, Y., Singleton, P.B., Muir, W.M. 2004. Chronic social stress differentially regulates neuroendocrine responses in laying hens: II. Genetic basis of adrenal responses under three different social conditions. Journal of Psychoneuroendocrinology. 97:961-971. Interpretive Summary: Enhancement of productivity and survivability of livestock is a major goal of husbandry management strategies. One approach to reach this goal is to reduce stress and increase in adequate adaptation to stressors through genetic selection. Two genetically selected chicken lines were used as animal models in the present study, which were selected for high and low productivity and survivability in the colony cages without beak trimming. The present data showed that there is a genetic basis for different regulation of hormonal responses among the lines. The differences could contribute to each line's unique behavioral pattern and productivity in response to different stimuli. The results suggest that the changes of stress hormone, such as corticosterone, could be used by producers and scientists to evaluate animal well-being and coping capability of poultry.
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 lines may have been due to differential regulation of adrenal function in response to social stress. The chickens from both HGPS and LGPS line were housed in three different social treatments, i.e., 10-hen, 2-hen and single-hen cages. In the 2-hen treatment, the hens from each of the lines were paired with the hens from the Dekable XL, commercial hens with high aggressive behaviors. At 24 week of age, the HGPS had less plasma corticosterone concentrations than those of the LGPS hens in 2-hen treatment but not in both 10- and single-hen treatments (P<0.05, and P>0.05 respectively). However, compared to the levels from the 10-hen treatment, the corticosterone concentrations were less in both HGPS and LGPS hens under the single-hen treatment (P<0.05, respectively). In addition, no differences in the adrenal gland weights were found among the HGPS hens from the three treatments. However, the adrenal glands became heavier in the LGPS hens under both 10- and 2-hen treatments compared to those at the single-hen treatment (P<0.05, respectively). These results indicate that genetic selection differently alters the chickens' adrenal system in response to social stress, and based on the stressor, changes of corticosterone concentrations could be used as an indicator to evaluate animal well-being.