Effect of genetic selection for group productivity and longevity on immunological and hematological parameters of chickens

A line of White Leghorn chickens was selected for high group productivity a nd longevity resulting in improved survival and feather score as well as re duced cannibalism and flightiness. Improvements in survival might have also been due to improved immunity. The present study was designed to test the hypothesis that selection for high (HGPS) and low (LGPS) group productivity and survivability also altered immune and hematological parameters. The LG PS line was an intense reverse selected line of the HGPS line at the eighth generation of development. Hens were randomly assigned to individual cages at 17 wk of age. Blood samples were collected from the hens at 21 wk of ag e. Subsets of T lymphocytes (CD4(+), CD8(+), and gamma delta cells) were me asured using flow cytometry. Concentrations of plasma IgG were quantified w ith western blot analysis and immunoprecipitation assay. Hematological para meters were collected from blood smears. The HGPS hens had significantly higher percentages of blood lymphocytes and CD4(+):CD8(+) ratios of circulating T cells (P < 0.01) and tended to have more, but not significantly, gamma delta T cells (P = 0.07) than the LGPS h ens. In contrast, the LGPS hens exhibited eosinophilia and heterophilia and greater heterophil:lymphocyte ratios (P < 0.01). The concentrations of pla sma IgG were also significantly higher in the LGPS hens (P < 0.01). These r esults suggest that genetic selection for group productivity and longevity also alters the immunological and hematological systems of hens. The line d ifference in regulation of T cells, leukocytes, and production of IgG may s uggest that different genes or modes of gene action are involved.