Loci Associated with Spontaneous Abortion in Primiparous Holstein Cattle

Emaly M Suarez¹Victoria Kelson¹Jennifer N Kiser^1,2Kimberly M Davenport¹Brenda M Murdoch³Allison L Herrick¹Holly Louise Neibergs^1*

• ¹Department of Animal Sciences, College of Agricultural, Human, and Natural Resource Sciences, Washington State University, Pullman, Washington, United States
• ²Animal Disease Diagnostic Laboratory, College of Veterinary Medicine, Washington State University, Pullman, Washington, United States
• ³Department of Animal, Veterinary and Food Sciences, College of Agricultural and Life Sciences, University of Idaho, Moscow, Idaho, United States

Spontaneous abortion (SA) in cattle consists of a pregnancy loss between days 42 and 260 of gestation. SA is costly, inefficient, and often leads to premature culling of cows. This study aimed to identify loci associated with SA in primiparous Holstein cows by completing a genome-wide association analysis of cows bred by artificial insemination (AI; 679 controls and 69 cases that aborted) or that were embryo transfer (ET) recipients (236 controls and 41 cases) from a single dairy. In AI bred cows, 86 loci (413 single nucleotide polymorphisms or SNPs) and 168 positional candidate genes were associated (FDR < 0.05) with SA, and in ET recipients, 4 loci (10 SNPs) and 16 positional candidate genes were associated (FDR < 0.05) with SA. No SA associated loci were shared between AI bred or ET recipient cows, but 9 associated loci (FDR < 0.05) in AI bred cows were shared with AI bred heifers. The difference in loci associated in AI bred and ET recipient cattle may be due to differences in mechanisms associated with the maintenance of pregnancy between in vivo and in vitro derived embryos, or a larger sample size was needed to identify additional shared loci. Identifying loci associated with SA in AI bred and ET recipient cows provides an opportunity to enhance selection for reproductive efficiency in Holstein cattle.