Effect of a live Mycoplasma synoviae vaccine on the production of eggshell apex abnormalities induced by a M. synoviae infection preceded by an infection with infectious bronchitis virus D1466.

An experimental study was conducted to assess the effect of a live Mycoplasma synoviae vaccine (Vaxsafe MS; Bioproperties Pty Ltd, Ringwood, Victoria, Australia) on M. synoviae-induced eggshell apex abnormalities (EAA). Four experimental groups of specified-pathogen-free white laying hens were made. All groups were inoculated with infectious bronchitis virus D1466 at 18 weeks of age. One group did not receive further treatment (non-vaccinated non-challenged (NVNC)). Two groups were vaccinated at 14 weeks of age against M. synoviae, and one of these groups was also challenged with an EAA-inducing M. synoviae strain 5 days after infectious bronchitis virus challenge (vaccinated non-challenged (VNC) and vaccinated challenged group (VC), respectively). The fourth group was not vaccinated but was challenged with M. synoviae (non-vaccinated challenged (NVC)). Eggs with EAA eggs were produced only in the NVC and VC groups. However, the proportion of eggs with EAA and the mean daily production of eggs with EAA per chicken was significantly lower (P<0.05) in the VC group (88/741 (11.9%) and 0.09+/-0.01 eggs per hen) compared with the NVC group (148/646 (22.9%) and 0.14+/-0.01 eggs per hen). The mean daily egg production per chicken was significantly lower in the NVC group (0.48+/-0.03 eggs) compared with that of the NVNC group (0.60+/-0.03 eggs), but not significantly different from other groups. The eggshell strength of eggs with EAA (22.8 N) was significantly lower (P<0.05) than non-affected eggs from the other groups (33.7 to 39.5 N). Furthermore, the eggshell strength of non-affected eggs in the NVC group was significantly lower (P<0.05) compared with that of non-affected eggs from the flock of origin (33.7 versus 41.2 N), but not different from the other groups. It can be concluded from the present study that vaccination with a live M. synoviae vaccine reduces the occurrence of M. synoviae-induced EAA significantly.