Vaccination of broilers against chronic respiratory disease with the Conn. F strain of Mycoplasma gallisepticum

Abstract

The ocular vaccination of one-day old broilers with the Conn. F strain of Mycoplasma gallisepticum (MG) induced a specific serological response and protection against chronic respiratory disease. The challenge was done at 30 days of age, injecting the R strain of MG into the left thoracic air sac. The vaccinated birds had, before and after the challenge, hemagglutination-inhibition (HI) titers higher than the nonvaccinated ones. The percentages of agglutination in the plate test, before the challenge, were higher among the vaccinated birds. At the end of the challenge, they were practically the same in both treatments. The vaccinated birds had air sac lesions at a lower frequency and intensity than the nonvaccinated ones (P < 0.05). There was a positive relation between groups from different treatments in serological response and protection. However, some individuals with high HI titers had intense air sac lesions and vice-versa. No strong vaccinal reactions were observed, besides occasional sneezing of low intensity.