Submitted to: Poultry Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/14/2008
Publication Date: 2/24/2009
Citation: Viscione, K.A., Branton, S.L., Vance, A.M., Gerard, P.D., Whitmarsh, S.K., Peebles, E.D. 2009. Effects of 6/85-strain Mycoplasma gallisepticum Vaccination Alone at Ten Weeks of Age or in Conjunction with F-strain M. gallisepticum Inoculation Overlays at 22 or 45 Weeks of Age on the Reproductive and Digestive....Hens.. Poultry Science 88:567-570. Interpretive Summary: There are three live Mycoplasma gallisepticum (MG) vaccines currently available for use by the commercial table egg industry. One vaccine termed the Fstrain MG vaccine (FMG) causes production drops of approximately 6% when hens are vaccinated as late as the beginning of the third trimester of lay (45 weeks of age [WOA]). However, it is the preferred MG vaccine when field or wild strains of MG are endemic as FMG is the only MG vaccine that has been shown to be capable of displacing field strains. Often layer complexes begin using one of the other two live MG vaccine strains and at some point a field strain gains entry into the layer complex. When this happens, use of FMG is often desirable. The objective of this study was to determine the effect of overlaying FMG to 45 WOA hens that had been previously vaccinated with 6/85 strain MG at 10 WOA. Results of this study demonstrate that prelay 6/85 MG vaccination may be a suitable substitute for prelay FMG inoculation and FMG vaccination overlay at 45 WOA may provide continual protection against field-strain MG infections without eliciting subsequent suppressive affects on performance.
Technical Abstract: Two trials were conducted to determine the effects of a prelay 6/85-strain M. gallisepticum (6/85MG) vaccination alone or in conjunction with time specific F-strain M. gallisepticum (FMG) inoculation overlays on the gross reproductive and digestive organ characteristics of commercial egg-laying hens. In each trial, the following 4 treatments were applied: 1) sham vaccination at 10 wk of age; 2) vaccination of 6/85MG at 10 wk; 3) 6/85MG at 10 wk overlaid by FMG inoculation at 22 wk; and 4) 6/85MG at 10 wk overlaid by FMG at 45 wk. Two birds per isolation pen (experimental replicate unit) were necropsied at the end of both trials to observe the effects of treatment on liver weight, liver lipid and moisture concentrations, incidence of fatty liver hemorrhagic syndrome, ovary weight, mature ovarian follicle numbers, and the total and segmental weights, lengths, and histologies of the oviduct and small intestine. The applied treatments affected only liver moisture. Liver moisture content was higher in birds vaccinated with 6/85MG at 10 wk alone or in conjunction with FMG at 45 wk in comparison to sham vaccinated controls and birds that received a 6/85MG vaccination at 10 wk overlaid by an FMG inoculation at 22 wk. Prelay 6/85MG vaccinations may be a suitable substitute for prelay FMG inoculations, and FMG overlays during lay on prelay 6/85MG vaccinations may also provide continual protection against field-strain MG infections without eliciting any subsequent suppressive affects on performance, as noted in an earlier study.