Early post-hatch survival and humoral immune response of layer chickens when in ovo vaccinated with strain F Mycoplasma gallisepticum

Authors: ELLIOTT, K. E. C. - Mississippi State University; Branton, Scott; Evans, Jeffrey - Jeff; PEEBLES, E - Mississippi State University

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/2018
Publication Date: 12/11/2019
Citation: Elliott, K., Branton, S.L., Evans, J.D., Peebles, E.D. 2019. Early post-hatch survival and humoral immune response of layer chickens when in ovo vaccinated with strain F Mycoplasma gallisepticum. Poultry Science. 97(11):3860-3869. https://doi.org/10.3382/ps/pey282.
DOI: https://doi.org/10.3382/ps/pey282

Interpretive Summary: Layer chickens are typically vaccinated with the F strain of Mycoplasma gallisepticum (FMG) at 9-10 weeks of age (woa) but it can be labor intensive and requires a significant amount of time to vaccinate a house of 50,000 chickens. In an effort to determine whether in ovo FMG vaccination would be effective, layer chicken embryos were vaccinated at 18 days of incubation with varying dosages of FMG vaccine. Hatch rate decreased in only the treatment with the high dose; however, the first two week post-hatch mortality experienced mortality less than 12% while all other treatments exhibited mortality in excess of 50%. The lowest FMG dose tested was found to be the most practical resulting in the least mortality, least weight loss, and a humoral (antibody) immune response in the majority of chickens.

Technical Abstract: Commercial layer hens reared on multi-age hen complexes are vaccinated during pullet rearing to combat production losses due to the bacteria, Mycoplasma gallisepticum (MG). In this study, the potential to in ovo vaccinate layer chickens against MG was investigated. Layer embryos were administered a dosage of a live attenuated strain F MG (FMG) vaccine at 18 days of incubation and raised for 6 wk for initial post-hatch evaluation in two replicate trials. Treatments included control non-injected eggs, eggs injected with diluent, a 1X high dosage, a 10-2 medium dilution, a 10-4 low dilution, and a 10-6 very low dilution. A subset of chicks were swabbed for detection of FMG in the trachea at hatch. At 6 wk of age, birds were swabbed again for FMG detection and a blood sample was tested for MG antibody production. Hatch was depressed only in the high dose group (P < 0.0001). Strain F Mycoplasma gallisepticum was detected at hatch in the trachea in each FMG injection treatment, with decreasing numbers of positive chicks in the lower dosage groups. The first 2 wk post-hatch mortality was 3.5% (trial 1) and 11.7% (trial 2) in the very low dose treatment with all other FMG treatments experiencing a high rate of mortality (> 50%). In ovo-vaccinated FMG birds had detectable FMG and antibody production at 6 wk. There were no differences in percentage positive birds between FMG treatments (P > 0.3 for all tests) or ELISA titers between the FMG treatments (P = 0.079). Body weights at 6 wk of age were diminished with increasing FMG dose (P < 0.0001). The lowest dose tested was found to be the most practical causing the least mortality, least weight loss, and a humoral immune response in the majority of the birds. Further work is needed to evaluate how this in ovo vaccine, promoting immunity earlier in life, would compare to standard post-hatch vaccination against an MG challenge scenario through a lay cycle.