Comparison of vaccination protocols of broiler breeder hens for Pasteurella multocida utilizing enzyme-linked...

A commercial enzyme-linked immunosorbent assay (ELISA) to detect serological response to vaccination and virulent challenge with type 1 (X-73) Pasteurella multocida was used to determine the best vaccination protocol for broiler breeders against fowl cholera. Birds vaccinated twice, at 10 and 19 weeks of age, with the avirulent Clemson University (CU) strain both times, with a commercial bacterin first and the CU strain second, or with the CU strain first and bacterin second had the highest survival rates (98-100%) following challenge at 25 weeks. The two groups that received the CU strain and bacterin also produced the highest mean ELISA antibody titers (greater than 10,000). Birds vaccinated once, at 10 weeks, with the CU strain had the same survival rate as birds vaccinated twice with bacterin (90 and 91%). Under the conditions of this experiment, an ELISA titer greater than or equal to 1000 resulted in at least a 92% survival rate after virulent challenge (23% survival in nonvaccinates).