Health Disorders and Growth Performance at a Swedish Pig Progeny Testing Station

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Abstract
Information on health disturbances recorded clinically as well as post mortem, together with growth data for different parts of the test period was analysed for pigs at the Hallsberg pig progeny testing station. The data comprised information on 1486 Landrace, 1036 Yorkshire, 92 Hampshire and 132 Duroc pigs slaughtered between January 1982 and June 1984. Yorkshire pigs had significantly higher incidence of lung lesions compared with Landrace pigs. Enteric diseases were more common among Hampshire and Duroc pigs compared with Landrace and Yorkshire. Castrates had a significantly higher burden of respiratory diseases than gilts. The influence of elite herd and batch of test on health status as well as on growth rate was considerable. The influence of within litter weight relation at the start of the test on growth rate during the test was analysed. A lower weight of the castrate compared with the gilt at the start of the test minimized the effect of sex on the slaughter order within litter. The growth depression occurring when one single pig is left alone in the pen was demonstrated. For the Landrace, this growth depression was significantly higher if the castrate was left alone than if the gilt was the last to be slaughtered. Clinically recorded diseases reduced growth rate in spite of appropriate medical treatments. Pigs which showed clinical signs of enteric diseases had a reduced growth rate during the first weeks of the test period, whereas pigs which were recorded as having extensive lesions due to respiratory diseases at slaughter had grown slower during the last part of the test period. The heritability estimates for the diseases recorded post mortem were around or below 0.2. It was concluded that an indirect selection against disease already takes place, since a disease which reduces growth rate will cause a somewhat lowered estimate of breeding value for growth rate.