The objective of this study was to evaluate the effect of vaccination of breeder chickens on Salmonella prevalences and loads in breeder and broiler chicken flocks. Chickens housed on six commercial breeder farms were vaccinated with a killed Salmonella vaccine containing
Salmonella Typhimurium, Salmonella Enteritidis, and Salmonella Kentucky. Unvaccinated breeders placed on six additional farms served as controls. Eggs from vaccinated and unvaccinated breeder flocks were kept separately in the hatchery, and the resulting chicks were used
to populate 58 commercial broiler flock houses by using a pair-matched design. Vaccinated breeder flocks had significantly higher Salmonella-specific antibody titers than did the unvaccinated breeder flocks, although they did not differ significantly with respect to environmental Salmonella
prevalences or loads. Broiler flocks that were the progeny of vaccinated breeders had significantly lower Salmonella prevalences and loads than broiler flocks that were the progeny of unvaccinated breeders. After adjusting for sample type and clustering at the farm level, the odds of
detecting Salmonella in samples collected from broiler flocks originating from vaccinated breeders were 62% lower (odds ratio [95% confidence interval] = 0.38 [0.21, 0.68]) than in flocks from unvaccinated breeders. In addition, the mean load of culture-positive samples was lower in
broilers from vaccinated breeders by 0.30 log most probable number per sample (95% confidence interval of −0.51, −0.09; P = 0.004), corresponding to a 50% decrease in Salmonella loads. In summary, vaccination of broiler breeder pullets increased humoral immunity in
the breeders and reduced Salmonella prevalences and loads in their broiler progeny, but did not significantly decrease Salmonella in the breeder farm environment.
Department of Population Health, College of Veterinary Medicine, University of Georgia, 953 College Station Road, Athens, Georgia 30602, USA
Publication date: May 1, 2011
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