A 100-sow farrow-to-feeder farm with an outdoor gestation lot had a 4-year history of ring-like skin lesions in lactating sows. On average, 90% of sows in each 5-week batch developed lesions within a week of entering the farrowing house. Lesions beginning as 2to 3-cm circles of dark, crusty skin coalesced into larger areas on the back, sides, and ventral abdomen. No etiologic agent was identifi...
