Efficacy of commercial Mycoplasma gallisepticum bacterin (MG-Bac) in preventing air-sac lesions in chickens.

One-week-old chickens were vaccinated with commercial Mycoplasma gallisepticum bacterin subcutaneously and challenged with the S6 strain by the intra-air-sac route 3 weeks later. Significantly fewer vaccinated chickens had air-sac lesions than controls.