Location: Poultry Research
2021 Annual Report
Objectives
1. Compare and characterize the transmissibility of Mycoplasma gallisepticum (MG) (virulent and attenuated vaccine strains) between birds in different commercial types of housing systems.
2. Identify the genetic and phenotypic differences between virulent and attenuated vaccine strains which may aid in developing an assay that will allow the differentiation of infection from vaccination.
3. Investigate the efficacy of in ovo vaccination strategies to protect against disease caused by MG.
Approach
To determine the transmissibility of Mycoplasma gallisepticum (MG) under varying conditions relevant to commercial poultry industries, layer chickens will be challenged with virulent and attenuated MG strains and then will be placed among naïve poultry. Transmissibility will be assessed by detection the MG among non-challenged poultry. To determine the impact of housing system on the transmission rates both conventional cage and non-cage systems will be investigated. Further, among conventional cage systems, the ventilation systems will include both still air and tunnel ventilation. Among the non-cage systems, experiments will be designed to compare poultry housed over open pit, deep pit, and flush tank systems to determine any effects on MG transmissibility. To compare genetic and phenotypic differences between virulent and attenuated strains of MG, MG strains will be sequenced and their genome assembled. Further, comparative proteomics will be performed, and all associated findings will be analyzed to elucidate differences which may be applied to future means of MG control. To develop an MG in ovo vaccination protocol and test its’ potential for application towards protection of commercial flocks from MG challenge, experiments will be initially be performed to determine appropriate dosage levels. The effects of the various doses of the MG vaccine on the 18 d embryo will be determined and findings will be applied to the development of a commercially applicable high throughput automated protocol. In addition, chicks derived from the vaccinated eggs will be hatched and assessed for afforded protection.
Progress Report
This is the final report for this project and will be replaced by a bridging project pending completion of research review. To date, research associated with this project has resulted in the sequenced, assembled, and annotated genomes of previously uncharacterized MG strains, including commercial vaccine strains. This data was utilized for the accurate determination of protein fragments via mass spectrometry which identified significant differences in membrane-associated lipoproteins and uncharacterized hypothetical proteins. Research identified more than 140 proteins that are conserved between the eight sequenced strains. Correlation of the genomic and proteomic data identified expression of 100 of these proteins. Most of these proteins are components required for normal cellular operations, are internal to the cell, and are not exposed to the host immune response. However, 16 of the 100 conserved and expressed proteins are potentially exposed on the cell surface and accessible to the host immune response. Separately, the in ovo-based delivery protocols for vaccination of 18-day-of-incubation chicken eggs with live attenuated MG vaccines were developed for two commercially available MG vaccines and applied to high-throughput systems automated systems for commercial poultry industries. In addition, in stakeholder-initiated lighting research, the effect of a newly developed high-frequency photo-stimulation strategy in laying hens was determined to have very little impact on egg size distribution and production, bird stress, and feed efficiency.
Accomplishments
1. In-ovo vaccination for Mycoplasma gallisepticum. ARS researchers at Mississippi State, Mississippi, developed a new high-throughput delivery protocol for in-ovo delivery of live attenuated Mycoplasma
gallisepticum vaccines. These in ovo-based vaccinations will provide for effective application of these MG vaccines while reducing stress and labor requirement associated with eye-drop and spray vaccination methods.
2. Photo stimulation of egg laying hens. ARS researchers at Mississippi State, Mississippi, developed a photo simulation of egg laying hens. The USDA-ARS researchers also demonstrated that a newly developed high-frequency photo-stimulation strategy had little impact on egg size distribution and production, bird stress, and feed efficiency in commercial laying hens.
Review Publications
Nuthalapati, N., Evans, J.D., Taylor, R.L., Branton, S.L., Nanduri, B., Pharr, G.T. 2019. Transcriptomic analysis of early B-cell development in the chicken embryo. Poultry Science. 0:1-13. https://doi.org/10.3382/ps/pez354.
Peebles, E.D., Elliott, K., Branton, S.L., Evans, J.D., Leigh, S.A., Kim, E.J., Olanrewaju, H.A., Pharr, G.T., Pavlidis, H.O., Gerard, P.D. 2020. Effects of dietary Original XPC™ on selected blood variables in layer pullets challenged 3 with Mycoplasma gallisepticum. Poultry Science. 99:4373-4383. https://doi.org/10.1016/j.psj.2020.06.005.
Elliott, K., Branton, S.L., Evans, J.D., Peebles, E.D. 2020. Evaluation of the potential influence of the disinfection cycle on the efficacy of strain F Mycoplasma gallisepticum vaccine administered by in ovo injection to layer hatching eggs. Journal of Applied Poultry Research. 29(3):673-683. https://doi.org/10.1016/j.japr.2020.05.001.
