Effects of 6/85-strain Mycoplasma gallisepticum inoculation alone at ten weeks of age or in conjunction with F-strain Mycoplasma gallisepticum inoculation overlays at twenty-two or forty-five weeks of age on the performance of commercial egg-laying hens.

The effects of 6/85-strain Mycoplasma gallisepticum (6/85MG) inoculation alone or in conjunction with a F-strain M. gallisepticum (FMG) overlay and its timing on the performance of commercial egg-laying hens were investigated. Control birds received sham inoculations at 10 wk of age. A second treated group of birds was inoculated with 6/85MG at 10 wk of age, a third treatment group of birds was inoculated with 6/85MG at 10 wk and received an overlay of FMG at 22 wk, and a fourth treatment group was inoculated with 6/85MG at 10 wk followed by a 45-wk overlay inoculation of FMG. Parameters investigated between 20 and 55 wk of age included BW, mortality, weekly and total egg production, egg weight, relative eggshell conductance, eggshell weight per unit of surface area, percentage shell weight, yolk/albumen ratio, and egg shape index. Hen age effects were reported for BW, egg weight, yolk/albumen ratio, and egg production. No treatment effects or hen age x treatment interactions were noted for those parameters except for yolk/albumen ratio, and no significant effects of any kind were noted for the remaining parameters examined. At wk 47, a significant treatment effect for yolk/albumen ratio was noted. The yolk/albumen ratio in the group of birds that received 6/85MG at 10 wk followed by an overlay of FMG at 22 wk was significantly lower than the sham control birds and those that were inoculated with 6/85MG at 10 wk followed by a 45-wk overlay inoculation of FMG. Prelay 6/85MG inoculations may be a suitable substitute for prelay FMG inoculations, and FMG overlays during lay on prelay 6/85MG inoculations may provide continual protection without eliciting any subsequent suppressive effects on performance.