Circulating microRNAs on Day 60 of pregnancy

Poor reproductive performance remains a major issue in the dairy industry, with extremely low calving rates (34 %) affecting milk production, profitability and the economy in general. Early pregnancy detection can help identify non-pregnant animals within three weeks of insemination, minimizing delays and shortening calving intervals. However current pregnancy detection methods are not accurate enough to support such reproductive management programs. MiRNAs have been proposed as non-invasive biomarkers of pregnancy and several reproductive diseases in humans. We previously identified miR-26a as a potential early pregnancy biomarker in cattle. In the current study, using miRNA sequencing, we identified and validated differentially expressed miRNAs on Day 60 of pregnancy compared to Day 0 (non-pregnant), and we investigated the expression of these validated miRNAs in early pregnancy aiming to identify additional early pregnancy biomarker candidates. The expression levels of selected miRNAs which are differentially expressed during pregnancy will also be investigated as part of this study. Overall design: In this experiment a total of 22 bovine plasma samples were analyzed using Illumina miRNA sequencing. These samples were collected at two time-points during pregnancy from each of 11 animals (Day 0, non-pregnant baseline and Day 60 of pregnancy) in a repeated-measures design. Therefore this study included 11 biological replicates for each of the two time-points analyzed.