RESISTANCE OF CHINESE MEISHAN, FENGJING, AND MINZHU PIGS TO THE K88AC(-COLI() STRAIN OF ESCHERICHIA)

The microscopic brush herder membrane adherence assay was used to dete rmine resistance (nonadherence) and susceptibility (adherence) of Chin ese pigs (n = 289) to the K88ac(+) strain of Escherichia coli-mediated disease. This study estimates prevalence of resistance to diarrheal d isease in multiple family lines (no common ancestry for a minimum of 3 generations) for the Chinese Meishan, Fengjing, and Minzhu breeds. Re sults of in vitro assays indicate that pigs of the Meishan breed are h ighly resistant (nonadherent) to K88ac(+) E coli-mediated disease. The gene conferring susceptibility to K88ac(+) E coli-mediated disease ex ists at low frequency in pigs of the Minzhu breed. Minzhu-type (crossb red) pigs of both phenotypes (susceptible and resistant) were identifi ed in ratios consistent with a 1-locus gene model. Given that all susc eptible pigs were from 1 site, frequency of susceptibility within this Minzhu population is estimated at 8%. Inheritance within the Fengjing breed is still unclear because a weakly adherent phenotype, as well a s the resistant. phenotype, was identified. The weakly adherent phenot ype was observed in pigs derived from multiple family lines. Expressio n of the weakly adherent phenotype in terms of susceptibility to disea se is not known at this time.