Effects of age at inoculation and. induced molt on the recovery of mycoplasma gallisepticum from layer chickens

An experiment was conducted to determine the effects of age at inoculation and induced molt on the reisolation of Mycoplasma gallisepticum (MG) from c ommercial leghorn hens that had been eyedrop-inoculated with F strain MG at either 10 or 66 wk of age. Chickens were maintained in biological isolatio n units from 10 wk of age through 78 wk of age. Ar 70 wk of age (premolt), hens were swabbed, cultured for MG, and molted. Swabs were taken both at th e end of molt (postmolt [74 wk]) and again 4 wk later (postmolt+4 [78 wk]). A significant (P less than or equal to 0.05) decrease in MG isolations was observed in the postmolt swabs as compared with the premolt swabs of hens inoculated at either 10 or 66 wk of age. A significant (P less than or equa l to 0.05) increase in isolations was observed in the postmolt+4 swabs as c ompared with the postmolt swabs of hens inoculated at either 10 or 66 wk of age. For the hens inoculated at 10 wk, no significant difference was found in premolt as compared with postmolt+4 MG isolations; however, for hens in oculated at 66 wk, a significant (P less than or equal to 0.05) decrease wa s observed between premolt and postmolt+4 isolations. Significantly (P less than or equal to 0.05) fewer MG isolations were obtained from the premolt swabs of hens inoculated at 10 wk as compared with hens inoculated at 66 wk . No significant difference in MG isolations was observed in either the pos tmolt or postmolt+4 swabs between hens inoculated at either 10 or 66 wk.