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This study aimed to estimate genetic parameters for the mortality causes stillborn, weak at birth, starvation, crushing, and miscellaneous in crossbred piglets produced by crossbred dams. Data were collected in a single Danish commercial herd from October 2006 to July 2008 and consisted of 34,194 piglets (2,152 litters), which originated from 195 Danish Duroc sires and 955 crossbreds between Danish Landrace and Danish Yorkshire dams. Of the 34,194 piglets born, 11.5% were stillborn, 4.2% were crushed by the sow, 2.7% died due to starvation, 2.3% were weak at birth, and 2.2% died of miscellaneous causes before weaning. The first 4 mentioned causes were analyzed multivariately using a generalized linear mixed model with a probit link function, including the genetic effect of both sire and dam. Heritabilities based on the sire component ranged between 0.08 for stillborn and 0.21 for starvation whereas heritabilities based on the dam component ranged between 0.01 for miscellaneous and 0.24 for stillborn, indicating that reducing piglet mortality through genetic selection is possible. The expected observed responses to selection would, however, be low. The genetic correlations between mortality traits based on the sire component ranged from -0.05 between stillborn and starvation to 0.35 between stillborn and weak at birth whereas genetic correlations based on the dam component ranged from -0.11 between weak at birth and starvation to 0.76 between crushing and starvation. There seemed to be a favorable relationship between the 2 traits stillborn and weak at birth and between crushing and starvation, implying that care should be taken with correct recordings of mortality causes. The genetic correlation precision was rather low, and if nonadditive effects are not accounted for, there may be unexpected correlated responses among the different mortality causes in the crossbred mortalities.
Strange et al. (Thu,) studied this question.