Vaccination with F-strain Mycoplasma gallisepticum to reduce production losses in layer chickens.

The effect of Mycoplasma gallisepticum (MG) infection or vaccination of Conn. F-strain MG on 45 weeks of egg production was analyzed using production records from 132 flocks of commercial layer hens. The flocks were located in Pennsylvania, and the data were collected for two years. On the average, layers maintained free from infection with MG laid 15.7 more eggs/hen housed than the MG-infected layers; figures were adjusted for layer-strain effect. This adjusted advantage decreased to 8.7 eggs/hen housed when uninfected flocks were compared with vaccinated flocks. Adjusted average production of vaccinated flocks was 7.0 eggs/hens housed more than production of MG-infected flocks. Egg production of four layer strains was observed with respect to vaccination or natural infection with MG. The four strains responded similarly whether vaccinated or infected. Route of vaccination and age of layer at time of vaccination influenced egg production of vaccinated birds. The adjusted average production/hen housed was 4.9 eggs greater for birds vaccinated via drinking water than for birds vaccinated via spray. The adjusted average was 10.3 eggs/hen housed greater for birds vaccinated between 8 and 18 weeks of age than for birds vaccinated after 18 weeks.