Abstract: In this study, density-gradient centrifugation was used to extract bovine milk exosomes, and the small non-coding RNA (sRNA) in the exosomes were sequenced by Illumina sequencing technology to explore the expression profile of bovine milk microRNAs (miRNAs). Through quality control of the original sequence, a total of 3 899 629 pure sRNA sequences were obtained, and their length was concentrated at 28 nt. By comparison with the database, 61 known miRNAs and 346 novel miRNAs were identified. The results of gene ontology enrichment analysis showed that miRNAs from bovine milk exosomes played a critical role in various biological processes such as cell process, single organism process and metabolic process. It mainly consisted of cells and organelles and was mainly involved in molecular functions such as binding, catalytic activity and transporter activity. The results of Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis showed that the known miRNAs and the new miRNA target genes were significantly enriched in pertussis (ko05133), chemokine signal pathway (ko04062), endocytosis (ko04144), lysosome (ko04142) and other pathways, and bovine milk exosome miRNAs played an important role in specific signaling pathways.

Key words: bovine milk exosomes; Illumina sequencing; miRNA