Effects of time-specific F-strain Mycoplasma gallisepticum inoculation overlays on prelay ts11-strain Mycoplasma gallisepticum inoculation on performance characteristics of commercial laying hens.

Mycoplasma bacteria are virtually ubiquitous in layer chicken flocks, and Mycoplasma gallisepticum is the species of greatest concern to commercial egg producers. Live M. gallisepticum vaccines were initially approved by the USDA for use in commercial layers in 1988 to help control M. gallisepticum outbreaks. In the present study, 2 trials were conducted to determine the effects of 2 currently available live Mycoplasma vaccines (the ts11-and F-strains) when used together. The following 4 inoculation treatments were used: 1) sham inoculation at 10 wk of age, 2) ts11 at 10 wk, 3) ts11 at 10 wk overlaid by the F-strain at 22 wk, and 4) ts11 at 10 wk overlaid by the F-strain at 45 wk. In each trial, at various ages between 18 and 57 wk of age, hen mortality; BW; egg weight; egg production; eggshell breaking strength; incidences of egg blood spots, egg meat spots, and eggshell pimpling; and eggshell weight per unit of surface area were assessed. The effects of inoculation treatment on egg weight at 27, 37, and 38 wk were inconsistent and variable. Eggshell pimpling and egg blood spot incidences at 56 wk were highest in eggs belonging to the ts11 at 10 wk/F-strain at 45 wk group. Despite increases in pimpling and blood spot incidences very late in production because of the ts11 at 10 wk/F-strain at 45 wk treatment, performance in layers was not adversely affected by a 10-wk ts11 inoculation alone or in conjunction with subsequent overlay inoculations of the F-strain during lay. It is therefore suggested that the 10-wk inoculation of commercial layers with ts11 may reduce the negative impacts of a prelay F-strain inoculation on performance, as reported in earlier studies, while providing protection against subsequent field strain M. gallisepticum infections. Furthermore, the ts11- and F-strain M. gallisepticum treatment combinations may overcome some of the inadequacies that prelay ts11- or F-strain M. gallisepticum vaccines may have when given independently.