Effects of prelay ts11-strain Mycoplasma gallisepticum inoculation and time-specific F-Strain M. gallisepticum inoculation overlays on internal egg and eggshell characteristics of commercial laying hens.

Mycoplasma infections are pandemic in multiage layer chicken flocks, with Mycoplasma gallisepticum being the species of greatest concern to commercial egg producers. Live M. gallisepticum vaccines are presently being used to help control M. gallisepticum outbreaks. However, vaccination of layers with F-strain M. gallisepticum may adversely affect egg production. In the present study, 2 trials were conducted to compare the effects of 2 currently available live Mycoplasma vaccines (the ts11- and F-strains), used in conjunction, on internal egg and eggshell characteristics. The following 4 inoculation treatments were used: 1) sham at 10 wk of age (control), 2) ts11 at 10 wk, 3) ts11 at 10 wk overlaid by F at 22 wk, and 4) ts11 at 10 wk overlaid by F at 45 wk. In each trial at various ages between 23 and 57 wk of age, percentage of yolk weight, percentage of yolk moisture, percentage of yolk lipid, percentage of albumen weight, Haugh unit scores, and percentage of shell weight of eggs were assessed. At wk 32, percentage of yolk lipid was increased in eggs belonging to the ts11 at 10 wk and ts11 at 10 wk overlaid by F at 22 wk treatment groups in comparison with controls. There was also a significant decrease in percentage of albumen weight in eggs in the treatment with ts11 at 10 wk overlaid by F at 22 wk, as well as a decrease in Haugh unit scores in the ts11 at 10 wk treatment in comparison with controls during post-peak lay. Percentage of yolk moisture, percentage of egg yolk weight, and percentage of eggshell weight in layers were not significantly affected by a 10-wk ts11 inoculation alone or in conjunction with subsequent overlay inoculations of F during lay. It is suggested that a 10-wk inoculation of commercial layers with ts11-strain M. gallisepticum may reduce the negative impacts of a prelay F-strain M. gallisepticum inoculation on performance while providing protection against subsequent field strain M. gallisepticum infections.