Grazing-Induced Changes in circRNAs, miRNAs and mRNAs Expression in Tibetan Sheep Biceps Femoris

The present study is aimed at investigating the effects of grazing on the meat quality of Tibetan sheep, as well as the associated molecular mechanisms. A total of ten Tibetan sheep were utilized and equally allocated into two groups: grazing and pen-feeding. To assess the intramuscular fat (IMF) content, Soxhlet extraction was performed on the biceps femoris muscle. Additionally, transcriptome sequencing was carried out to evaluate the expression profiles of RNAs, facilitating the construction of a ceRNA regulatory network. The results demonstrated that the IMF content in the grazing group was significantly higher compared to the pen-feeding group, implying that grazing might foster the formation of Type I muscle fibers, thereby enhancing meat quality. Moreover, the expression levels of circRNAs, such as novel_circ_001331, novel_circ_012918, novel_circ_029843, and novel_circ_059962, were markedly up-regulated in the grazing group. These circRNAs may alleviate the inhibitory effects on genes like COL8A1, MYLK3, and NOX4 by interacting with miR-381-y, miR-7144-x, miR-16-z, miR-8159-x, novel-m0040-3p, novel-m0092-5p, and oar-miR-329a-3p. These circRNAs and miRNAs are predominantly involved in the MAPK, Wnt, and VEGF signaling pathways and could be implicated in biological processes such as muscle fiber type switching and energy metabolism. This research offers valuable insights for improving the meat quality of Tibetan sheep and provides a foundation for exploring the role of circRNA and miRNA in the regulation of meat quality under grazing conditions.