Mycoplasma gallisepticum vaccination-challenge: an egg-production model

Specific-pathogen-free layer hens in maximum lay were exposed by aerosol to a broth culture of Mycoplasma gallisepticum R' strain. Egg-production loss of greater than 50% was evident 7-14 days following challenge of unvaccinated chickens, with a gradual recovery during the next several days. Various vaccine preparations were tested to determine the effect in the model. All vaccinated chickens exhibited significantly (P < or = 0.05) lower egg-production loss than the unvaccinated controls. The model provides a method for testing treatment effects on egg-production losses resulting from controlled exposure to M. gallisepticum and may be useful in simulating field exposure.