Genome-wide association study in Brown Swiss for fertility traits based on sequence data

Fertility in dairy cattle has declined continuously during the last years. In Switzerland low fertility is one of the most important culling reason. Therefore this trait complex is of great economic importance. But fertility traits are functional traits with low heritabilities. We performed GWAS in Brown Swiss and Holstein cattle for the fertility traits: non-return rate after 56 days in heifers (NRH) and cows (NRC); days between first and last insemination in heifers (FLIH) and cows (FLIC); and days to first service (DFS). We used deregressed breeding values as input phenotypes and imputed whole-genome sequence dosages as genotypes. In Holstein (2,336 to 3,257 individuals) we could not identify any significant region for any of the investigated traits. For Brown Swiss cattle (1,392 to 3,278 individuals) however we could identify a QTL on BTA 17 for NRH and FLIH. This locus also showed a suggestive association with NRC and FLIC. The region significantly associated to NRH and FLIH comprises 27 genes. Among the associated variants two non-synonymous variants in the genes GAS2L and ASCC2 could be identified. These two variants could be potentially causative ariants.