Swine
respiratory diseases induce severe economic losses in the swine industry worldwide. Several methods have been developed and applied to control these diseases. However, there are still problems of disease control in the swine industry. Recently, egg yolk
antibodies have been found to offer several advantages for disease control in animals and humans. In a previous study (24),
antibodies to several causative pathogens of swine
respiratory diseases were developed. However, several problems remained, especially in terms of reduced laying rates. Therefore, experimental
vaccines were reformulated with various
bacterial antigens of the swine
respiratory diseases. After immunizing hens with the
antigens, antibody profiles and other effects including laying rates were investigated and compared to those of the previous study. Profiles of antibody titers were very similar with those of the previous study. However, side effects, such as depression, weakness, reduction of laying rates and mortality, were dramatically lowered and laying rates were increased in hens injected with certain experimental
vaccines. In particular, laying rates of hens injected with
vaccines against
atrophic rhinitis were increased up to 84% by injecting a
vaccine composed of only the DNTs of B. bronchiseptica and P. multocida D:4. Efficacies of the
vaccines against swine
pneumonic pasteurellosis and
pleuropneumonia were very similar with those of the previous study. These results suggest that new
vaccines could be effective in the production of egg yolk
antibodies against the causative agents of swine
respiratory diseases.