title: 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.
abstract: 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 < or = 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.
authors.affiliation: USDA, Agricultural Research Service, Poultry Research Unit, Mississippi State, MS 39762, USA. jdevans@msa-msstate.ars.usda.gov
authors.forename: J D
authors.initials: JD
authors.lastname: Evans
authors.forename: S A
authors.initials: SA
authors.lastname: Leigh
authors.forename: S L
authors.initials: SL
authors.lastname: Branton
authors.forename: S D
authors.initials: SD
authors.lastname: Collier
mesh_terms: D000818:Animals; D001428:Bacterial Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D002645:Chickens / Q000097:blood / Q000276:immunology*; D004306:Dose-Response Relationship, Immunologic; D005260:Female; D009175:Mycoplasma Infections / Q000517:prevention & control / Q000662:veterinary*; D045686:Mycoplasma gallisepticum / Q000276:immunology* / Q000472:pathogenicity; D010058:Oviposition; D013997:Time Factors; D014774:Virulence
chemical_list: D001428:Bacterial Vaccines