Location: Poultry Research
2023 Annual Report
Objectives
1. Investigate the efficacy of different strategies to displace virulent or moderately pathogenic strains of Mycoplasma gallisepticum (MG) with safer or less pathogenic, including vaccine strains, of MG as a means to reduce economic impacts to egg laying facilities.
2. Evaluate the effects of commercial-scale poultry management practices on transmission and microbial ecology of Mycoplasma.
3. Investigate the long-term 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 nonchallenged 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 impact of sampling schedule on the in vivo Mycoplasma gallisepticum (MG) populations within the choanal cleft, trachea, and cloaca were compared and the optimal schedule for downstream studies was identified. In addition, the impact of sampling on other bacteria at these sites was initiated (e.g., E.coli). The production of the autogenous and electron-beam killed bacterin vaccines were completed through a collaboration with USDA-ARS Fayetteville and Texas A&M University. A secondary electron-beam vaccine is currently being produced to allow for a more precise determination of its associated protection utilizing newly acquired technology at USDA-ARS Fayetteville. A study was initiated and completed to investigate the impact of various ventilation rates on breeder chickens and offspring. Stakeholder requested research was also initiated and completed to develop an in ovo vaccination protocol for a poultry Salmonella vaccine. A cooperative agreement with Zoetis Animal Health was also developed to aide in ovo-based research at the USDA-ARS Poultry Research Unit.
Accomplishments
1. Commercial layer chickens are commonly infected with the avian pathogen Mycoplasma gallisepticum (MG). To date, no holistic means of control is available to limit losses associated with medication costs, carcass condemnations, and egg production losses and therefore efforts are being made to optimize available means of control. In ovo delivery of live attenuated MG vaccines may extend the protection afforded by the vaccine. To manage the effects of MG, commercial layer chickens are vaccinated with an MG vaccine usually by a spray or eyedrop route of administration between 9-15 weeks of age. ARS researchers in Starkville, Mississippi, in collaboration with the Poultry Science Department at Mississippi State University and Zoetis Animal Health investigated in ovo vaccination of MG as an alternative method of vaccination that utilizes less vaccine and is less labor-intensive than handling every bird. Attenuated MG vaccine strains (strains ts-11 and 6/85) were delivered via in ovo technologies to embryos at 18 days of age. Of these vaccines, strain 6/85 was applicable to this delivery method while strain ts-11 was not. In ovo delivered had minimal impact on hatchability and resulted in a measurable immune response.
2. Mycoplasma gallisepticum (MG) is an economically important pathogen in chickens. Routine detection of MG is performed via swabbing of the trachea or choanal cleft. However, prior to application of in ovo MG populations as a metric for determination of treatment effects, the impact of repeated sampling events must be determined. ARS researchers in Starkville, Mississippi, infected layer pullets with MG and housed in one of 4 identical rooms. Post-infection, birds were sampled on 2, 4, 8, or 16 d intervals at 3 distinct sites. At each sampling event, the birds were swabbed and sample-associated MG populations were quantified. Results indicated significant variation among MG populations at individual sampling events and there was no evidence of any difference in trend over time of microbial abundance due to different sampling schedules. However, the choanal cleft demonstrated the greatest MG population among sampled sites. These findings were applied to further research to determine investigating novel MG means of control.
Review Publications
Lindsey, L.L., Collins Elliott, K.E., Fatemi, S.A., Gerard, P.D., Peebles, E.D. 2023. Utilizing in ovo telemetry to examine the effects of reduced incubation temperature on broiler embryo temperature and subsequent hatchability. Poultry Science. 102:102506. https://doi.org/10.1016/j.psj.2023.102506.
Felfoldi, B., Wang, H., Nuthalapati, N., Taylor, R.L., Evans, J.D., Branton, S.L., Pharr, G.T. 2021. Expression of chicken leukocyte cell-derived chemotaxin 2 in the embryonic bursa of Fabricius. International Journal of Poultry Science. 20:43-47. https://doi.org/=ijps.2021.43.47.
Collins Elliott, K.E., Branton, S.L., Evans, J.D., Magee, C.L., Peebles, E.D. 2022. Onset of the humoral immune response of layer chicks vaccinated in ovo with strain F Mycoplasma gallisepticum vaccine and evidence of male-biased mortality. Poultry Science. 101:101761. https://doi.org/10.1016/j.psj.2022.101761.
Leigh, S.A., Evans, J.D. 2023. Whole-Genome sequencing of three M. gallisepticum isolates similar to the 6/85 vaccine strain. Microbiology Resource Announcements. https://doi.org/10.1128/mra.00339-23.
Alqhtani, A.H., Fatemi, S.A., Collins Elliott, K.E., Branton, S.L., Evans, J.D., Peebles, E.D. 2023. Effects of the in ovo administration of the 6/85 Mycoplasma gallisepticum vaccine on layer chicken embryo hatchability and early posthatch performance. Animals. 13(7):1228. https://doi.org/10.3390/ani13071228.
Mousstaaid, A., Fatemi, S.A., Collins Elliott, K.E., Levy, A.W., Miller, W.W., Olanrewaju, H.A., Purswell, J.L., Gerard, P.D., Peebles, E.D. 2023. Effects of the In Ovo administration of L-ascorbic acid on the performance and incidence of corneal erosion in Ross 708 broilers subjected to elevated levels of atmospheric ammonia. Animals. 13(3):399. https://doi.org/10.3390/ani13030399.
Fatemi, S.A., Collins Elliott, K.E., Macklin, K.S., Bello, A., Peebles, E.D. 2022. Effects of the in ovo injection of vitamin D3 and 25-hydroxyvitamin D3 in Ross 708 broilers subsequently challenged with coccidiosis: II. Immunological and inflammatory responses, and small intestine histomorphology. Animals. 12(8):1020. https://doi.org/10.3390/ani12081027.
Mousstaaid, A., Fatemi, S.A., Collins Elliott, K.E., Alqhtani, A.H., Peebles, E.D. 2022. Effects of the In Ovo injection of L-Ascorbic acid on broiler hatching performance. Animals. 12(8):1020. https://doi.org/10.3390/ani12081020.
