title: A field trial to evaluate a Mycoplasma hyopneumoniae vaccine: effects on lung lesions and growth rates in swine.
abstract: A killed Mycoplasma hyopneumoniae vaccine was evaluated in a single swine herd in which the farrowing barn and weaner rooms were on one Mycoplasma-free farm, while the growing and finishing barn was on a separate farm on which Mycoplasma was present. The study was carried out in a cohort of pigs born in a 12-week period. Pigs born in 6 of the 12 wk were vaccinated and the rest were left as controls. The vaccine was administered twice at approximately 3 and 6 wk of age. Carcass characteristics, lung lesions, and growth rates were recorded on 893, 390, and 220 pigs, respectively. The vaccine reduced the prevalence of pneumonic lesions in slaughter hogs from 69% to 36% (P < 0.001). It also appeared to reduce the prevalence of pleuritis from 20% to 13%, but the difference was only statistically significant at P = 0.07. The vaccine had no effects on carcass characteristics except that carcasses of vaccinated pigs were, on average, 1 kg heavier than those of nonvaccinated pigs, and a smaller percentage of vaccinated pigs were shipped "light" (carcass weight < 70 kg). Two methods were used to estimate the effect of the vaccine on growth rates (as measured by days to 80 kg carcass weight) resulting in estimates of 11 and 2 d reduction attributable to vaccination, respectively. The latter estimate was probably an underestimate for reasons discussed in the paper.
authors.affiliation: Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown.
authors.forename: I R
authors.initials: IR
authors.lastname: Dohoo
authors.forename: M E
authors.initials: ME
authors.lastname: Montgomery
mesh_terms: D000818:Animals; D001428:Bacterial Vaccines / Q000008:administration & dosage*; D001835:Body Weight / Q000502:physiology*; D008168:Lung / Q000473:pathology*; D009174:Mycoplasma / Q000276:immunology*; D045729:Pneumonia of Swine, Mycoplasmal / Q000503:physiopathology / Q000517:prevention & control / Q000662:veterinary*; D013552:Swine; D013553:Swine Diseases / Q000517:prevention & control*
chemical_list: D001428:Bacterial Vaccines