RESULTS OF VACCINATING PIGS AGAINST ACTINOBACILLUS PLEUROPNEUMONIAE FROM CLEAN AND INFECTED HERDS AND CHALLENGED WITH A MIXTURE OF PATHOGENIC REFERENCE STRAINS - Mendoza, SE, González, D, Trujillo, D, Vargas, A, Garcia, A, Hernández-Baumgarten, E, Tórtora, J, Ciprián, A (International Pig Veterinary Society Congress, 2006)