Location: Poultry Research
2019 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
The effect of a newly developed high-frequency photostimulation strategy in laying hens was assessed in 2 trials of which trial I has been completed and trial II is nearing completion. The hens were maintained through 30 wks of age and egg production, egg size distribution, bird stress, and feed efficiency were compared to hens on a traditional light emitting diode (LED) layer lighting program. Results showed a shift toward earlier egg production and larger eggs among birds under the new lighting strategy which would be beneficial to the layer egg industry.
Mycoplasma gallisepticum (MG) vaccine strain 6/85 is licensed for fine spray application while the TS-11 MG strain is licensed for eye-drop application and both application techniques tend to limit the use of these products due to facility limitations, labor availability and associated costs. A study which entailed the use of both the 6/85 and the TS-11 strains was performed to assess the applicability of in ovo application of these MG vaccines which are less pathogenic than the F strain of MG. The study was successful. In ovo application of both the 6/85 and TS-11 MG vaccine strains which may ultimately lead to pre-hatch delivery of these vaccines on a commercial scale and may offer producers a means of delivery which has nominal associated labor costs, is accurate and efficient, and reduces stress associated with handling of the birds during vaccination.
Finally, proteomic analysis of three MG vaccines strains and two virulent strains has identified many significant differences in protein expression between the various strains. In addition to the differences previously identified through genetic comparisons, differences in vlhA gene expression were identified between the strains. Most expression differences were found to be hypothetical proteins. This research has identified targets for further study, both to identify potential targets for inclusion in future vaccines, but also potential targets for differential diagnosis of vaccine strains versus virulent strains.
Accomplishments
