Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2020
Publication Date: 4/9/2020
Citation: Oliver, K.F., Geary, T.W., Kiser, J.N., Galliou, J.M., Van Emon, M.L., Seabury, C.M., Spencer, T.E., Neibergs, H.L. 2020. Brief report: Loci associated with conception rate in crossbred beef heifers. PLoS One. 15(4):e0230422. https://doi.org/10.1371/journal.pone.0230422.
DOI: https://doi.org/10.1371/journal.pone.0230422

Interpretive Summary: Pregnancy failure is a major cost in cattle production. Pregnancy loss is especially high among dairy cattle and most loss occurs in the first month of pregnancy. Cows that lose pregnancies have lower production and economic efficiency. The goal of this study was to identify genetic markers related to fertility in cattle. This would allow producers to identify heifer calves that are best suited for herd replacements. Thus, producers would be able to identify and develop only the most fertile heifers for their herd. Beef heifers were bred by AI before exposure to fertile bulls for 50 days. Pregnancy and fetal age were determined by ultrasound. Heifer DNA was compared to pregnancy results. Eleven genes or genetic markers were related to fertility. This research allows producers to use genomic selection for cattle with greater fertility. More fertile cows will reduce costs associated with beef production.

Technical Abstract: The inability of beef cattle to maintain full term pregnancies has become an economic concern for the beef industry. Herd management and nutritional improvements have alleviated environmental impacts on embryonic and fetal loss, yet additional gains can be made through genomic selection. The objectives of this study were to identify loci and gene-sets in crossbred beef heifers associated with the number of services required to become pregnant (TBRD) and heifer conception rate at first service (HCR1). Heifers (n = 709) from a commercial beef operation underwent one round of artificial insemination, before exposure to bulls for natural service for 50 days. Pregnancy and time of conception was determined by ultrasound 35 days after the conclusion of the breeding season. Heifers were genotyped using the GeneSeek (Lincoln, NE) Bovine GGP50K BeadChip prior to genome-wide association analyses (GWAA) conducted using EIGENSTRAT to identify loci associated (P < 1 x 10-5) with TBRD and HCR1. One locus was associated (P = 8.97 × 10-6) with TBRD on BTA19 and included the positional candidate gene ASIC2, which is differentially expressed in the endometrium of fertility classified heifers, and the positional candidate gene, SPACA3. Gene-set enrichment analyses using SNP (GSEA-SNP) data, was performed and identified one gene-set, oxidoreductase activity, acting on paired donors, with incorporation or reduction of molecular oxygen as enriched (NES = 3.15) with TBRD and contained nine leading edge genes. The enriched gene-set is involved in catalyzing oxidation-reduction reactions. Imbalances in oxidation-reduction reactions has been associated with oxidative stressors impacting pregnancy success. No loci were associated or gene-sets enriched with HCR1. Identification of loci, positional candidate genes, gene-sets and leading edge genes enriched for fertility facilitates genomic selection that allows producers to select for reproductively superior cattle, reduce costs associated with fertility, and increase percent calf crop.