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Title: Effects of live and killed vaccines against Mycoplasma gallisepticum on the performance characteristics of commercial layer chickens

Author
item JACOB, R - Mississippi State University
item Branton, Scott
item Evans, Jeffrey - Jeff
item Leigh, Spencer
item PEEBLES, E - Mississippi State University

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/27/2014
Publication Date: 6/2/2014
Citation: Jacob, R., Branton, S.L., Evans, J.D., Leigh, S.A., Peebles, E.D. 2014. Effects of live and killed vaccines against Mycoplasma gallisepticum on the performance characteristics of commercial layer chickens. Poultry Science. 93:1403-1409.

Interpretive Summary: The bacterial organism Mycoplasma gallisepticum (MG) affects the reproductive efficiency of 95% of the nation’s table egg laying chickens which in turn costs producers over $140 million annually. Vaccines developed over the past 25 years ameliorate the infection but much variation exists among the vaccines in application, timing of vaccination relative to chicken age, and even whether the vaccines are permitted to be used in specific states. In this study, 2 trials were conducted wherein live or killed MG vaccines were administered either singly or in combination to commercial layer chickens either pre-lay or at 45 weeks of age (woa) in order to investigate the effects of the vaccines on performance characteristics. Results of the study showed that a pre-lay vaccination with a killed MG vaccine did not prevent a drop in egg production in response to a live MG vaccine given to the same hens at 45 woa; however, when a live MG vaccine was given at pre-lay followed by subsequent vaccination with a different live MG vaccine at 45 woa, no reduction in egg production occurred. Thus, when hens are vaccinated initially with a live MG vaccine followed at a later date with a different live MG vaccine, the birds were protected.

Technical Abstract: Mycoplasma gallisepticum (MG) is a major and economically significant pathogen of avian species. Different strains of MG have been used as vaccines in multiple-age commercial layer farms in an effort to protect the birds against more virulent field strains. The lower level of protection afforded by the low virulent MG strain vaccines provides an opportunity to the use of an overlay (revaccination) with an F-strain of MG (FMG) later in their production cycles. In the present study, 2 trials were conducted to investigate the effects of pre-lay vaccinations of a live and killed MG vaccine or their combination, in conjunction with an FMG vaccine overlay after peak egg production (EP), on the performance characteristics of commercial layers. The following treatments were utilized at 10 wk of age (woa): 1) Control (no vaccinations); 2) ts-11 strain MG vaccine; 3) MG-Bacterin vaccine; and 4) ts-11 MG and MG-Bacterin vaccines combination. At 45 woa, half of the birds were overlaid with an FMG vaccine. In each trial, performance parameters including hen mortality, BW, egg weight, percentage hen-day EP, egg blood spots, and egg meat spots, were determined at various time periods between 18 and 52 woa. During interval II (46 to 52 woa), the control birds along with the MG Bacterin-vaccinated birds overlaid with the FMG vaccine had a significantly lower EP compared to all other treatment groups. This shows that a prelay vaccination with MG-Bacterin did not prevent the drop in EP in response to the FMG overlay at 45 woa. The treatments applied also showed a significant effect on the BW of the birds during interval II. Despite the effect on BW and EP, no differences were observed for egg blood and/or meat spots among the various treatments. Therefore, it is suggested that vaccination of commercial layers with a ts-11 MG vaccine in conjunction with a subsequent overlay vaccination with FMG, may reduce the negative impacts of an FMG vaccination. In conclusion, these results establish the potentially effective prelay use of the ts-11 MG vaccine in combination with an FMG overlay for the provision of continual protection against field strain MG infections, without eliciting any subsequent suppressive effects on the performance of commercial layers.