The effects of vaccinating pigs for mycoplasmal pneumonia in a swine herd affected by enzootic pneumonia

We compared weight gain, feed disappearance, coughing prevalence, and lung lesion scores among pigs vaccinated against Mycoplasma hyopneumoniae (treatments I and 2) and nonvaccinated controls. Pigs in both vaccinated treatment groups gained significantly more weight (0.14 Ib per day, P < .05) during the finishing phase when grow-finish data were pooled and compared to the control group. Pigs in both vaccinated treatments consumed significantly more feed (0.49 and 0.41 Ib,respectively) versus the control (P < .05) during the finishing phase. We recorded significantly fewer coughs by treatment 2 (vaccinated at 6 and 8 weeks of age) pigs than by treatment I (vaccinated at 2 and 3 weeks of age) and control pigs (P < .05). Coughing frequency was highest when pigs were 4-5 Yzmonths of age. Severity of lung lesions detected at slaughter in both groups I and 2 were reduced significantly (6% and 4% respectively) compared to the control group (12%, P < .05). All other feed and growth parameters during the growing, finishing, and combined phases between both treatment groups and the controls were not significant (P > .05). The prevalence of lung lesions was similar for all three groups. These results indicate that an M. hyopneumoniae vaccine can significantly reduce the severity of lung lesions of enzootic pneumonia detected at slaughter, significantly increase feed disappearance during the finishing phase, and significantly increases average daily gain during the finishing phase. It did not improve feed efficiency in this trial, however.