Epidemiological and genetical studies in Norwegian pig herds. IV. Breed effects, recurrence of disease, and relationship between disease and some performance traits.

Individual health records collected from 1984 to 1986 in 70 swine-herds in the south-eastern part of Norway were analysed by epidemiological methods. The incidence rate for most of the reported diseases was less than 1% per farrowing, and a majority of disease recordings concerned 6 frequently-occurring conditions. The incidence of several diseases was lower in crossbred sows compared to purebred Norwegian landrace sows. The risk of most diseases increased in sows that had been ill previously, and also in litters from sows that had previously had diseased litters. Disease risk in piglets also increased if the sow became ill during the first few days after farrowing. The reduced performance associated with most of the common diseases impacts adversely on economic returns.