Tylan-medicated pigs had significantly lower fecal shedding levels of Lawsonia intracellularis compared to the challenged non-medicated pigs. Tylan-fed pigs also had lower oral fluid levels of L. intracellularis than the challenged control pigs. The subclinical infection in the challenged only pigs resulted in a difference in average daily gain (ADG) and feed efficiency (FE) compared to the challenged control pigs. By controlling subclinical ilietis, the Tylan 100 g/ton followed by 40 g/ton treated group had improved ADG and FE compared to the challenged, non-medicated pigs. Tylan® Soluble followed by Tylan 40 g/ton medicated animals tended to have improved FE compared to the challenged-only pigs.1