Objective: To document the maternal transfer of IgG antibodies from Blue and Gold Macaw hens to chicks via the egg; to measure serum IgG half-life in macaw chicks; and to measure the ability of 2- to 10-week-old macaw chicks to generate primary and secondary IgG responses.
Procedure: 4 adult Blue and Gold Macaw hens were inoculated with 200 micrograms of bovine serum albumin (BSA) every 21 days throughout the breeding season. Eggs laid by these hens were incubator hatched to eliminate the possibility of antibody transfer through crop secretions during feeding. Anti-BSA titer was measured just prior to each inoculation in hens and in chicks from 14 to 42 days of age. 1 chick from each of 5 macaw clutches hatched to nonimmunized hens was assigned to 1 of 2 experimental groups. Group-1 chicks were inoculated with 200 micrograms of BSA at 2 and 6 weeks of age. Group-2 chicks were inoculated with 200 micrograms of BSA at 6 and 10 weeks of age. Anti-BSA titer was measured weekly for 8 weeks after primary inoculation. Blood samples were centrifuged, and serum was harvested and frozen at -85 C until analyzed. Anti-BSA IgG titer were measured by ELISA. In the maternal transfer experiment, an exponential decay model was used to calculate the half-life of BSA antibodies in chicks. In the BSA antibody response experiment, comparison of primary and secondary anti-BSA responses of 2- and 6-week-old chicks was performed, using a two-way repeated measures ANOVA, with significance set at P < 0.05.
Results: Hens maintained high anti-BSA titer throughout the breeding season. Maternal transfer of anti-BSA IgG antibodies was documented in all 7 chicks. Anti-BSA titer in chicks decreased in exponential fashion with an average serum IgG half-life of 3.85 days. By 42 days of age, antibodies to BSA were virtually undetectable in all chicks. The primary antibody response of 6-week-old chicks was significantly higher than that of 2-week-old chicks (P = 0.016). No significant difference was observed in the magnitude of the secondary antibody responses between these age groups. Peak anti-BSA IgG antibody responses were reached by 14 days after primary and secondary immunization. Chicks of both age groups generated lower anti-BSA IgG titer than did adult Blue and Gold Macaws.
Conclusions: Blue and Gold Macaw hens transfer IgG antibodies to their chicks through the egg. The half-life of IgG in newly hatched chicks is approximately 3.85 days. 6-week-old chicks develop higher anti-BSA titers than do 2-week-old chicks, but significantly lower titers than do adult macaws.
Clinical relevance: Information on the nondomestic avian immune system will be useful in the development of vaccination and other preventive health programs for psittacine birds.