Social stress induced different alterations of dopamine concentrations and adrenal function in geneti - cally selected

Dopamine (DA) and corticosterone (CORT) are involved in regulating animals’ response to stress. The objective of this study was to examine whether alterations of DA concentrations and adrenal function are associated with behavioral response to social stress in two strains of White leghorns hens that were selected for high (HGPS) and low (LGPS) group productivity and survivability resulting from cannibalism and flightiness in multiple-hen cages. At 17-wk of age, hens were randomly assigned into single and 2-hen cages. The 2-hen cages contained one hen from HGPS or LGPS line and one from a commercial Dekalb XL line that was used as standardized genetic competitors. At 24-wk of age, seventy hens were bled (10 hens from 3 genetic line, 2 replicates, plus 10 extra testers). Plasma concentrations of DA were measured using HPLC. Changes of the adrenal function were indicated by plasma concentrations of CORT, and hypertrophy of the adrenal gland indicated as a percentage of adrenal gland weight/body weight (AW/BW). In singlehen cages, HGPS hens had heavier adrenal glands indicated as a greater AW/BW ratio (P < 0.05). However, LGPS hens tended to have greater plasma concentrations of DA (P = 0.07). In 2-hen cages, there were no difference in AW/BW ratio between HGPS and LGPS hens (P > 0.1). However, both plasma concentrations of CORT and DA were greater in LGPS hens (P < 0.05 and P < 0.0 1, respectively). The results suggest that social stress induced an up regulation of DA and adrenal function in LGPS hens but not in HGPS hens. The data was consisted with the previously findings that HGPS hens adapted better to social competition. Some of the parameters, such as concentrations of DA and CORT, could be used as an indicator of chicken well-being.