Genetic parameters of tail and ear damage

As pigs are kept in groups during production, it is essential to consider the effects of their social interactions when making breeding decisions. However, behaviour is difficult to measure on a scale needed for breeding. Damage measured on the victims of harmful behaviour can be used as a proxy for the behaviour. In this work, tail and ear damage scores were provided by Topigs Norsvin. These traits were analysed on the original scale and in binary and combined versions of the original traits. The genetic parameters were estimated with an animal model for all traits in ASReml-R. Accuracies for estimated breeding values (EBVs) were calculated based on the standard errors of the estimates. Accuracies and biases of the EBVs were also calculated with cross-validation with 100 replicates. The heritability of the damage traits ranged from 0.04 to 0.06. Ear and tail damage are moderately correlated (0.4), meaning that these two traits indicate different victims. The genetic correlations between ear damage and the summed traits were higher than the correlation with tail damage. (0.83 and 0.72, respectively). The accuracy based on standard errors of the EBVs ranged from 0.45 to 0.49. The accuracy calculated from cross-validation ranged from 0.52 to 0.68. These results suggest that the genetic predisposition to being the victim of harmful behaviour can be predicted moderately accurately. The estimated bias was around 1.7, meaning the EBVs were systematically underestimated. Our study laid the groundwork necessary to reduce harmful behaviour by genetic improvement.