Effects of rapid inbreeding on sow fertility traits in a closed herd of Swedish Landrace

Abstract

In this study we analyzed the effects of rapid inbreeding, calculated from three generations long pedigrees, on fertility traits of sows. The analysis was based on 72 inbred (ranging from inbreeding coefficient 3.12% to 31.25%) and 89 non-inbred sows of Swedish Landrace and all fertility traits were related to the first litter. The analysis was done by regressing fertility traits on inbreeding coefficients (univariate models). The effect of the age of sow at the first successful conception (fixed) was also included into regression models. The available data did not let us to consider the effects of litter inbreeding. When dependent variable was litter size (total number born and number born alive) and number at weaning, the linear regression model was applied. Dependent variables that were distributed according to Poisson distribution, as it was case for the number born dead, mortality during weaning and total number of inseminations, were analyzed by generalized linear regression models assuming Poisson distribution. Significant inbreeding depression was obtained for total number born (b=-0.103, P<0.001), number born alive (b=-0.0910, P<0.01), number at weaning (b=-0.078, P<0.01) as well as the number born dead (P<0.01). On the other hand, significant inbreeding depression was not present for the total number of inseminations (P=0.867) and mortality during weaning (P=0.068). Thus, it was shown that higher inbreeding of sows leads to the reduced fertility.