Relevance of intersexuality to breeding and reproductive biotechnology programs ; XX sex reversal in pigs

In pigs, the frequency of intersexuality ranges from 0.1 to 0.6%. Economic losses are significant and result from sterility, urogenital infections and downgrading of carcasses because of boar taint. To elucidate the genetic aetiology of pig sex reversion, 50 intersexes from a closed breeding herd were analysed. The majority have a 38,XX karyotype without Y chromosome sequences. Phenotypically, the animals range from true hermaphrodites to XX males with or without genital ambiguities. Analysis of crosses between parents of intersexes showed that the trait is inherited and caused by the same mutation in the Large White breed. Investigations are currently being carried out to isolate a genetic marker linked to intersexuality using genetic map of the porcine genome. Such a marker will be useful in eradicating the mutation in pig breeding herds and in permitting the isolation of the gene responsible.