Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 26, 2006
Publication Date: December 1, 2006
Citation: Dennis, R., Zhang, H.M., Cheng, H.W. 2006. Effect of selection for resistance and susceptibility to viral diseases on concentrations of dopamine and immunological parameters in six-week-old chickens. Poultry Science. 85:2135-2140. Interpretive Summary: Genes determine functions of the neuroendocrine and immunological systems that affect an animal's ability to cope with stress, resistance to disease, and productivity. As a strategy to enhance resistance to disease, chickens have been selected for the phenotypic characteristics associated with resistance (line 63) or susceptibility (lines 72 and 15I5) to Marek's disease and lymphoid leukosis (Bacon, 2002). The differences in disease resistance among the lines may be related to differences in expression of genes controlling the neuroendocrine system and immunity. The present study demonstrated that genetic selection for avian disease-resistance in chickens affected the regulation of the neuroendocrine and immune systems in their inbred offspring. There were line differences for blood concentrations of DA, IgG, and percentage of CD4+ cells, CD8+ cells, and B cells between the disease resistant and susceptible lines. These differences might be associated with the unique characteristics of lines in disease resistance. The unique homeostatic characteristics of each selected line may provide a useful animal model for investigation of the molecular and cellular mechanisms of disease resistance in poultry. The results suggest that changes of neurochemical concentrations could be used as stress indicators in evaluating animal well-being. These results can be used by producers and scientists for evaluation of animal well-being and coping ability of their social environments.
Technical Abstract: White Leghorn chickens were inbred respectively from their parent lines, which were diversely selected for resistance (line 63) or susceptibility (lines 72 and 15I5) to Marek's disease and lymphoid leukosis. The differences in disease resistance may have been due to differential regulations of immune and neuroendocrine homeostasis. At 5 wk of age, chickens from each line were randomly assigned to cages at 4 birds per cage. Blood samples were collected from the chickens at 6 wk of age (n = 10/line). Subsets of T lymphocytes (CD4+ and CD8+) and B cells were measured using flow cytometry. Concentrations of plasma IgG and dopamine were quantified with ELISA and HPLC assays, respectively. Line 63 chickens had a higher percentage of CD8+ cells but not CD4+ cells than the chickens of the lines 72 and 15I5 (P < 0.01). In contrast, both lines 72 and 15I5 had greater percentage of B cells (P < 0.01). The concentrations of plasma IgG and dopamine were also different among the lines, both were in an order of 72>15I5>63 (P < 0.05, and 0.01, respectively). These results suggested that genetic selection for disease resistance also directly or indirectly altered the corresponding genetic components that govern or co-govern the immune and neuroendocrine systems of the lines. The genetic lines of chickens may be used as animal models for investigation of the cellular mechanisms of genetic-environmental interactions on disease resistance.