of vaccine dilution per isolator the ms1 concentrations in the final vaccine dilutions were determined by ccu count the chickens were vaccinated with vaccines containing 10 6 ccu ml group a and 10 3 ccu ml group b three weeks post vaccination the vaccinated chickens and unvaccinated controls were challenged with a m synoviae f10 culture containing 10 7 ccu ml at necropsy protection against airsacculitis was observed in both vaccinated groups table 4 a vaccinated at 10 6 ccu ml b vaccinated at 10 3 ccu ml c unvaccinated and challenged d unvaccinated and unchallenged table 4______________________________________airsacculitis score 10 d after f10 challenge a vaccinated at 10 sup 6 ccu ml b vaccinated at 10 sup 3 ccu ml c unvacci nated and challenged d unvaccinated and unchallenged group b 1 10 000 animal a 1 100 vac vac c chall d cont ______________________________________1 2 0 3 0 2 1 2 1 0 3 2 3 3 0 4 2 1 2 0 5 2 2 2 0 6 1 2 3 7 0 1 2 8 1 2 3 9 1 2 10 1 mean 1 3 sup a 1 6 sup b 2 3 0______________________________________ a significantly p lt 0 01 different from unvaccinated challenged control group b p 0 10.