Identifying the Genetic Basis of Fetal Loss in Cows and Heifers Through a Genome-Wide Association Analysis.

Fetal loss, the spontaneous termination of pregnancy between day 42 and 260 of gestation, is poorly understood. Impacts of fetal loss include loss of production, increased health risk, and economic loss. The aims of this study were to identify loci associated with fetal loss in Holstein heifers and primiparous cows to facilitate the selection of reproductively efficient cattle and identify the genetic causes of fetal loss. A genome-wide association analysis (GWAA) compared 5714 heifers that calved at term (controls) to 416 heifers that experienced fetal loss (cases), and for primiparous cows, 2519 controls were compared to 273 cases. The efficient mixed-model association eXpedited approach in the SNP and Variation Suite (v 9.1) statistical software was used with additive, dominant, and recessive inheritance models for the GWAA. In heifers, 16 loci were associated (FDR < 0.05) with fetal loss in the recessive model. In primiparous cows, there were 44 loci associated (FDR < 0.05) with fetal loss in the recessive model. No loci associated with fetal loss were shared between cows and heifers or in the additive and dominant models. These results improve the characterization of genetic factors contributing to fetal loss in Holstein heifers and primiparous cows and provide targets for genomic selection.