Comparison of immunoglobulin Y antibody production in new and spent laying hens.

Background and Aim: Immunoglobulin (Ig)Y, a specific type of Ig found in chicken eggs, has potential use in the diagnosis of human and animal diseases. This study assessed the feasibility of using spent laying hens to produce IgY. In addition, the effects of antigen injection on egg and antibody production in new and spent laying hens were compared. Materials and Methods: Hens were intramuscularly injected with three booster shots of antigens. IgY was extracted from egg yolks using polyethylene glycol 6000 precipitation followed by dialysis. Results: Spent laying hens (83 weeks) consistently showed lower egg production than new laying hens (27 weeks) throughout the study. Post-immunization, a further decline in egg production was observed in spent laying hens, and egg production stopped after the second antigen injection. Eggs from spent laying hens were less dense than eggs from new hens. Despite lower IgY levels in eggs from spent laying hens, the heavy-to-light chain ratio remained consistent in both groups. Notably, IgY from spent and new laying hens demonstrated effective hemagglutination against cat erythrocytes in the A blood group. Conclusions: This study demonstrated the potential of using spent laying hens to produce IgY, with significant implications for future research, immunotherapy, and diagnostic applications, despite the observed reduction in egg production compared with new laying hens.