An oil-emulsion, betapropiolacton inactivated bacterin of Myco plasma gallisepticum was prepared. The vaccine was inoculated twice in Meat-type parent flock. Egg production was insignifican tly increased but birds were protected aganist transient sever egg production drop. Mycoplasma isolation from incubated eggs was greatly reduced in vaccinated birds.
Hatchability rate was also increased. Haemagglutination inhibation titer in vaccinated birds was greatly higher than in non vaccinat ed birds.