|Cheng, Heng Wei|
Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2009
Publication Date: 10/1/2009
Citation: Fahey, A.G., Cheng, H. 2009. Effects of Repeated Social Disruption on the Serotonergic and Dopaminergic Systems in two Genetic Lines of White Leghorn Layers. Poultry Science. 88:2018-2025. Interpretive Summary: Mixing unfamiliar chickens is a common management practice carried out today in many poultry farms for production, which may result in social stress in birds and impact their well-being. The aim of this project was to determine genetic basis of variations of birds’ serotonergic and dopaminergic systems in response to the social stress and to develop stress indicators. Results from this study suggest that selection for docile behaviors and productivity in poultry alters hens’ chemical messengers in the brain in response to social stress. These changes are consistent with the hen's unique behavioral characteristics and capability to cope with their housing environments reported previously. The data from the present study can be used by farmers in management practices and other scientists when planning or interpreting their studies.
Technical Abstract: The study was designed to examine whether there are genetic differences in response to repeated social disruption (RSD). Two genetic strains of White Leghorn hens were used in the study; i.e., HGPS (the line selected for high group production and survivability), and DXL (DeKalb XL commercial line). When the hens were at 50 wks of age, RSD was created by increasing group size from 4-hens (control) to 8-hens (experimental) per cage and moving 2 hens once a week among the cages within the same line (experimental birds only). At 58 wks of age, a 15 mL blood sample and brain were randomly collected from one hen per cage (n=10 per treatment). Whole blood was used for analyzing peripheral tryptophan (TRY) and serotonin (5-HT) by high performance liquid chromatography (HPLC). Plasma was analyzed for peripheral norepinephrine (NE), epinephrine (EPI), and dopamine (DA) by using HPLC. The Raphe nuclei and the hypothalamus were dissected and analyzed by HPLC to quantify central concentrations of NE, EPI, DA, DOPAC (dihydroxyphenylacetic acid), HVA (homovanillic acid), 5-HIAA (5-hydroxyindoleacetic acid), and 5-HT. The results indicate that there were no genetic basis of variations in the concentrations of peripheral TRY, 5-HT, EPI, NE, and DA in response to RSD (P>0.10). However, these endogenous neuronal transmitters were regulated differently in the different central nuclei (the Raphe nucleus and the hypothalamus) between the lines. In the Raphe nuclei, HGPS controls tended to have a higher 5-HIAA/5-HT ratio than the DXL controls (P=0.8), indicating the HGPS hens may have a higher 5-HT turnover. In the hypothalamus, compared with its relative controls, there were no significant differences in the concentrations of 5-HT (P<0.05) while the levels of 5-HIAA were reduced (P<0.01) following RSD in the birds regardless of genetic lines, indicating RSD led to a lower 5-HT turnover in the hypothalamus. In the Raphe nuclei, the concentrations of EPI was increased in the DXL birds (P<0.01), while the HGPS hens had decreased DOPAC (P<0.05) and DA turnover (DOPAC/DA, P<0.01) post RSD. The data suggest that selection for docile behaviors and productivity in poultry, such as the hens of the HGPS line, alters hens’ serotonergic and catecholamine homeostasis in the central nervous system in response to RSD. These changes are consistent with line’s unique behavioral characteristics and capability to cope with their housing environments.