At the individual level, the presence of M. hyopneumoniae in the BAL fluid or being serologically positive for M.hyopneumoniae at different ages were not significantly
associated with the presence or severity of pneumonia lesions at slaughter (P < 0.05) except for the correlation between the number of organisms at slaughter and both
the presence and severity of pneumonia lesions (r = 0.305 and r = 0.321 respectively; P < 0.05). Also at herd level, no significant correlations were demonstrated.