Effects of vaccination with F-strain Mycoplasma gallisepticum on egg production and quality parameters of commercial layer hens previously vaccinated with 6/85-strain Mycoplasma gallisepticum.

This study was conducted to determine the effect of overlaying (revaccinating) F-strain Mycoplasma gallisepticum at 22 or 45 wk of age on commercial leghorn hens previously vaccinated with 6/85-strain M. gallisepticum at 10 wk of age. The treatment groups included unvaccinated hens (group 1), hens receiving 6/85-strain M. gallisepticum only (group 2), and hens receiving 6/85-strain M. gallisepticum followed by F-strain M. gallisepticum at either 22 (group 3) or 45 (group 4) wk of age. There was no significant effect on egg production or egg size distribution between any of the treatment groups, unlike previous studies looking at F-strain vaccination only. Egg quality parameters, including eggshell strength, Haugh unit score, and blood-meat spot were similar between the different treatment groups. There was a difference in the rate of pimpling at postpeak production for the treatment group receiving F-strain M. gallisepticum at 22 wk of age, consistent with previously published results. This work suggests that hens previously vaccinated with 6/85-strain M. gallisepticum can be safely revaccinated with F-strain M. gallisepticum to increase protection from field strains while ameliorating the adverse effects associated with F-strain M. gallisepticum vaccination in layers post onset of lay.