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Effects of Increased Dosages of the Mycoplasma Gallisepticum Vaccine MYCOVAC-L® in Layer Chickens Subsequently Challenged with Virulent M. gallisepticum: Egg Production and Serologic Response

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Ten-week-old Hy-Line Commercial W-36 pullets were spray-vaccinated with MYCOVAC-L® at the manufacturer's recommended dosage (1x) or at 15 times that rate (15x). At 22 or 45 wk of age, subsets of 1x- and 15x-vaccinated pullets were challenged with the virulent Mycoplasma gallisepticum (MG) strain Rlow. Percent hen-day egg production was determined through week 55. Analyses for treatment effects on overall (22-56 wk) percent hen-day egg production revealed no significant differences between nonchallenged 1x and nonchallenged 15x MYCOVAC-L® treatments. Among 1x MYCOVAC-L®-vaccinated groups, Rlow challenge at 45 wk corresponded to significantly (P 0.01) lower overall egg production compared with the unchallenged 1x-vaccinated control (70.88% vs. 79.15%, respectively). Conversely, at the 15x MYCOVAC-L® dosage level, overall egg production was not significantly affected by virulent MG challenge at 45 wk compared with its unchallenged counterpart (84.09% vs. 81.03%, respectively) and could indicate increased protection from virulent MG challenge. Serologic monitoring indicated the virulent MG challenge was consistently (100%) associated with seroconversion. Comparisons among the nonchallenged experimental treatments indicated that vaccinations at the 15x MYCOVAC-L® dosage rate were associated with a greater seroconversion rate at weeks 21, 27, and 44, but not at week 50.
Evans, J.D. , Leigh, S.A. , Branton, S.L. , Collier, S.D.
Includes references
Avian diseases 2007 Dec., v. 51, issue 4
American Association of Avian Pathologists
Journal Articles, USDA Authors, Peer-Reviewed
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