Effects of group selection for productivity and longevity on blood concentrations of serotonin, catecholamines, and corticosterone of laying hens

Selection of a line of White Leghorn chickens for high group productivity a nd longevity resulted in reducing cannibalism and flightiness in multiple-h en cages. Improvements in survival might have been due to changes of physio logical homeostasis. The objective of the present study was to test the hyp othesis that genetic selection for high (HGPS) and low (LGPS) group product ivity and survivability also altered regulation of neuroendocrine homeostas is. Hens were randomly assigned to individual cages at 17 wk of age. At 21 wk of age, blood concentrations of dopamine, epinephrine, norepinephrine, a nd serotonin were measured using HPLC assay. Blood concentrations of cortic osterone were measured using radioimmunoassay. The LGPS hens had greater blood concentrations of dopamine and epinephrine than the HGPS hens (P < 0.01). The blood concentration of norepinephrine wa s not significantly different between the lines, but the ratio of epinephri ne to norepinephrine was greater in the LGPS hens (P < 0.01). The blood con centrations of serotonin were also higher in the LGPS hens compared to thos e in the HGPS hens (P < 0.01). Although the HGPS hens tended to have a high er level of blood corticosterone, the difference was not significant (1.87 +/- 0.19 vs. 1.49 +/- 0.21 ng/mL; P = 0.08). The results suggest that selec tion for group productivity and survivability alters the chickens' neuroend ocrine homeostasis, and these changes may correlate with its line-unique co ping ability to domestic environments and survivability.