Circulating microRNA profiles during the bovine oestrous cycle

Up to 50% of ovulations go undetected in modern dairy herds due to attenuated oestrus behavior and a lack of high-accuracy methods for detection of fertile oestrus. This significantly reduces overall herd productivity and constitutes a high economic burden to the dairy industry. MicroRNAs (miRNAs) are ubiquitous regulators of gene expression during both health and disease and they have been shown to regulate different reproductive processes. Extracellular miRNAs are stable and can provide useful biomarkers of tissue function; changes in circulating miRNA profiles have been reported during menstrual cycles. This study sought to establish the potential of circulating miRNAs as biomarkers of oestrus in cattle using Illumina small-RNA sequencing. Overall design: In this experiment a total of 24 bovine plasma samples were analysed using Illumina miRNA sequencing. These samples were collected at three time-points during a normal oestrous cycle from each of 8 animals (Day 0, Day 8 and Day 16 after oestrus) in a repeated-measures design. Therefore this study included 8 biological replicates for each of the three time-points analysed.