Genome-wide Prediction of Pleiotropic Regions that Influence Age at Puberty and Reproductive Longevity in Sows

Traditional selection for sow reproductive longevity has not been very effective due to low heritability and late expression of the trait. Employment of DNA markers in selection programs represents a potentially more efficient approach than mass selection for improving lifetime reproductive longevity. Using approximately 1,030 crossbred gilts, we analyzed pleiotropic sources of variation for age at puberty and reproductive longevity.  The genetic variance explained by 1 Mb windows across the swine genome, compared across traits, uncovered regions on multiple chromosomes including SSC5, SSC8, and SSC12 that influence both age at puberty and lifetime number of parities. Combined analysis of allelic variants from multiple loci exhibited additive effects and indicated that an increase in the number of favorable alleles decreased age at puberty and increased the lifetime number of parities produced. The identified pleiotropic region on SSC5 harbors non-synonymous alleles in the arginine vasopressin receptor 1A (AVPR1A) gene, a G-protein coupled receptor associated with social and reproductive behaviors in humans and voles, and is a positional candidate for the observed effects. This region is characterized by high levels of linkage disequilibrium in unrelated commercial lines that could be exploited in selection programs across populations using marker-assisted selection to increase sow reproductive longevity.