M. hyopneumoniae DNA concentrations in TBLF at day 0 and day 17–18 showed increases from the pre-challenge concentration in Beaufort and Hillcrest groups, with numerically higher (but not statistically different,P > 0.05) mean concentrations in Hillcrest-challenged compared with Beaufort-challenged pigs, while control pigs showed no increase in M. hyopneumoniae DNA concentration (Table 5).