RESUMEN
Mycoplasma hyorhinis (MHR) is a major cause of lameness, arthritis, and polyserositis among growing pigs. Reduced performance and culling due to MHR infection result in economic losses in swine production. We have previously developed an MHR challenge model in seven week-old CDCD pigs using cell-associated challenge material which results in both severe pericarditis and lameness. In this study we sequentially challenged CDCD pigs at seven, ten, thirteen, and sixteen weeks of age. Lameness was observed in >60% of the animals in the first three age groups but only 33% in the oldest age group. The number of animals with arthritis declined from 100% at seven weeks, to 56% at ten weeks and approximately 25% at both thirteen and sixteen weeks of age. Pericarditis was observed in 87% of the seven week challenge group, 28% in the ten week challenge group, 8% in the thirteen week challenge group and 4% in the sixteen week challenge group. All challenged groups showed a reduced average daily gain (ADG) compared to their age-matched non-challenged control groups. The largest disparity in ADG (1.2 lbs/day difference) was noted at thirteen weeks of age. Results of this study demonstrate that these animals were susceptible to MHR-associated lameness through sixteen weeks of age while susceptibility to MHR-associated polyserositis appeared to peak at seven weeks of age.