The effectiveness of simultaneous administration of commercial Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniae
vaccines was tested in an indoor commercial piggery which had experienced continuing respiratory-disease problems confirmed as due to both of these pathogens. Piglets were randomly assigned in equal numbers to vaccination and control groups, and each
vaccine was administered at a separate site to assigned piglets at two and four weeks of age. Live weight of vaccinates immediately prior to slaughter was 2.49 kg higher (p = 0.04) than for controls at equal mean slaughter age of 132 days. Average daily gain (ADG) from 16 weeks to slaughter of vaccinates was also significantly higher (33 g/day) than in controls (p = 0.05). Daily gain was not significantly different in younger age groups. Active enzootic
pneumonia lesions were more likely in control than in vaccinated pigs. There were no significant differences between vaccination groups with regard to severity of
pleurisy or presence of
pleuropneumonia lesions at slaughter. Log-linear modelling was used to test the statistical association between vaccination, enzootic
pneumonia lesions,
pleurisy lesions and
pleuropneumonia lesions. It showed a reduction in the severity of enzootic
pneumonia lesions for vaccinated pigs, and the presence of
pleuropneumonia lesions increased the likelihood of
pleurisy lesions. No other association was significant, and no evidence of synergy between the
vaccines in influencing lesion severity for
pleuropneumonia was detected (within the limitations set by the trial design).