Effect of founder allele survival and inbreeding depression on litter sizein a closed line of Large White pigs

An experimental herd of Large White pigs was established in 1931 and mainta ined as a closed population until 1992. The complete pedigree (410 boars an d 916 sows) has been analysed to measure along the succesive cohorts of bre eding animals: the founder representation and allele survival, the evolutio n of coancestry and inbreeding and the components of inbreeding due to each founder. Inferences about genetic and phenotypic parameters and effects of dam and litter inbreeding on litter size were obtained, using Bayesian tec hniques, from 2612 litter records. A significant mean reduction of 0.27 pig lets born and 0.39 live born for each 10% of litter inbreeding was found bu t also evidence of variation among founder lineages in inbreeding depressio n. Alleles contributing to inbreeding depression were descendent from speci fic founder lineages.