Comparison of the immune responses against Salmonella enterica serovar Gallinarum infection between naked neck chickens and a commercial chicken line.

The immune responses of indigenous naked neck (NaNa and Nana) and normally feathered (nana) chickens against a Salmonella Gallinarum (SG) infection were evaluated and compared with those of a commercial line (B-380). Groups of 28-day-old chickens (NaNa, Nana, nana, and B-380) were immunized orally and subcutaneously with 50 microg of SG antigens. Control non-immunized animals were inoculated with sterile saline solution. All chickens were challenged with 1 LD(50) of SG and mortality was recorded daily for 20 days. Antibodies to SG were measured in sera before immunization, before the challenge, 10 days after the challenge, and at sacrifice. Peripheral blood lymphocyte proliferation assays were performed using concanavalin A and SG antigens. Results showed that non-immunized Nana chickens exhibited the best natural resistance to Salmonella infection, since only 30% of them died. In contrast, all control B-380 chickens died by the 13th day. Immunization with SG induced immunity in chickens of all genotypes. Indigenous naked neck and normally feathered chickens showed a higher survival rate when compared with B-380 chickens. Immunized Nana chickens showed the highest antibody titres (P<0.05) as well as the highest thymidine incorporation in peripheral blood lymphocytes stimulated with con A or SG antigens (P<0.05). The results show that Nana chickens are the most resistant to SG infection and the best responders to vaccination with SG antigens.