Exosome microRNAs are vital for gene transcription and expression, influencing target genes. They may play direct and indirect roles in pregnancy across animal models and humans. The objective of this research was to comprehensively explore the expression profiles of plasma exosomal miRNAs during the early pregnancy stage in sheep. This study specifically delved into the differences in the expression of plasma exosomal miRNAs between Chinese Merino and Suffolk sheep. The primary focus was on clearly elucidating the changes in plasma exosomal miRNAs, pinpointing potential biomarkers that might exert an impact on early pregnancy, and thoroughly exploring their biological functions as well as the possible underlying molecular mechanisms. Chinese Merino and Suffolk sheep were divided into two groups of 20 for artificial insemination. Blood samples were collected at various pregnancy stages (day 0, day 14, and day 30), Ultrasound diagnosis was carried out five weeks following artificial insemination. Three pregnant sheep from each group were selected for isolating extracellular vesicle-derived miRNAs from plasma. High-throughput sequencing identified differentially expressed miRNAs, and their target genes were analyzed using bioinformatics methods. In plasma exosomal samples derived from all sheep of both breeds at various time points during the early pregnancy stage, a cumulative total of 80 known miRNAs and 182 novel miRNAs were successfully identified. Compared to day 0 gestation controls, both sheep breeds showed differential expression of six known miRNAs: four were up- regulated and two down- regulated. Pathway analysis linked these miRNAs to biological processes such as ECM receptor interactions, growth hormone synthesis, carbohydrate digestion, adrenergic signaling in cardiomyocytes, and MAPK signaling regulation. Notably, Oar-mir-27a differed between the two groups at various time points. In summary, this research meticulously carried out a profiling analysis of the expression of plasma exosomal miRNAs in Chinese Merino and Suffolk sheep. Through this analysis, several exosomal miRNAs were identified, which display distinct abundance levels during the early pregnancy period. These
