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Simple Summary: Yaks are a major economic source for people in the Tibetan Plateau region. Yaks are rich in nutrients, but their low fat content is not conducive to the large-scale promotion of yak meat, so the study of the mechanism of yak lipid deposition is beneficial to the marketing of yak meat. In this paper, the results of transcriptome sequencing analysis of yak liver showed that it could be determined that the expression levels of genes associated with partial lipid deposition were significantly up-regulated during yak fattening. In addition, this study found that the tenderness of yak meat improved during this process. Fattening significantly affects fat deposition in yaks, which may be realized through its effects on lipid metabolic pathways. Therefore, studying the mechanism of lipid deposition in yaks and fattening yaks will improve the quality of yak meat. Yak meat is nutritionally superior to beef cattle but has a low fat content and is slow-growing. The liver plays a crucial role in lipid metabolism, and in order to determine whether different feeding modes affect lipid metabolism in yaks and how it is regulated, we employed RNA sequencing (RNA-seq) technology to analyze the genome-wide differential gene expression in the liver of yaks maintained under different raising systems. A total of 1663 differentially expressed genes (DEGs) were identified (|log2FC| ≥ 0 and p-value ≤ 0.05), including 698 down-regulated and 965 up-regulated genes. According to gene ontology (GO) and KEGG enrichment analyses, these DEGs were significantly enriched in 13 GO terms and 26 pathways (p < 0.05). Some DEGs were enriched in fatty acid degradation, PPAR, PI3K-Akt, and ECM receptor pathways, which are associated with lipid metabolism. A total of 16 genes are well known to be related to lipid metabolism (e.g., APOA1, FABP1, EHHADH, FADS2, SLC27A5, ACADM, CPT1B, ACOX2, HMGCS2, PLIN5, ACAA1, IGF1, FGFR4, ALDH9A1, ECHS1, LAMA2). A total of 11 of the above genes were significantly enriched in the PPAR signaling pathway. The reliability of the transcriptomic data was verified using qRT-PCR. Our findings provide new insights into the mechanisms regulating yak meat quality. It shows that fattening improves the expression of genes that regulate lipid deposition in yaks and enhances meat quality. This finding will contribute to a better understanding of the various factors that determine yak meat quality and help develop strategies to improve yield and quality. [ABSTRACT FROM AUTHOR]

Background: Yaks (Bos grunniens), prized for their ability to thrive in high-altitude environments, are indispensable livestock in the plateau region. Modifying their feeding systems holds significant promise for improving their growth and meat quality. Tenderness, a key determinant of yak meat quality and consumer appeal, is demonstrably influenced by dietary regimen. Indoor feeding regimes have been shown to enhance tenderness by lowering shear stress and optimizing pH values. CircRNAs, well-known modulators of circulatory function, also play a crucial role in skeletal muscle development across various animal species. However, their functional significance in yak skeletal muscle remains largely unexplored. Results: In this study, we identified a total of 5,534 circRNAs within the longissimus dorsi muscle, and we found 51 differentially expressed circRNAs (20 up-regulated and 31 down-regulated) between the two feeding groups. Constructing a comprehensive ceRNA network illuminated intricate regulatory mechanisms, with PGP and circRNA_0617 converging on bta-miR-2285q, mirrored by KLF15/circRNA_0345/bta-miR-20b and CTSF/circRNA_0348/bta-miR-146a. These findings shed light on the potential of circRNAs to influence yak muscle development and meat quality, offering valuable insights for future research. Conclusions: This investigation unraveled a complex interaction network between circRNAs、mRNAs and miRNAs in yak skeletal muscle. We further elucidated the target genes regulated by these target genes within the network, offering valuable insights into the potential regulatory mechanisms governing muscle development and meat quality-related traits in yaks. [ABSTRACT FROM AUTHOR]

AbstractYak is an important dominant livestock species at high altitude, and the growth performance of yak has obvious differences under different feeding methods. This experiment was conducted to compare the effects of different feeding practices on growth performance and meat quality of yaks through combined transcriptomic and metabolomic analyses. In terms of yak growth performance, compared with traditional grazing, in-house feeding can significantly improve the average daily weight gain, carcass weight and net meat weight of yaks; in terms of yak meat quality, in-house feeding can effectively improve the quality of yak meat. A combined transcriptomic and metabolomic analysis revealed 31 co-enriched pathways, among which arginine metabolism, proline metabolism and glycerophospholipid metabolism may be involved in the development of the longissimus dorsi muscle of yak and the regulation of meat quality-related traits. The experimental results increased our understanding of yak meat quality and provided data materials for subsequent deep excavation of the mechanism of yak meat quality. [ABSTRACT FROM AUTHOR]

Yaks (Bos grunniens) are a critical livestock breed in the plateau region, and changing the feeding system of yaks can significantly improve their growth performance. The effects of different feeding regimes on the growth performance and meat quality of yaks were comprehensively compared here. The transcriptome and proteome of the Longissimus dorsi muscle were determined using RNA-seq and Tandem Mass Tag (TMT) techniques. Indoor feeding significantly improved the growth performance (such as the average daily gain and carcass weight) and meat quality characteristics compared with traditional grazing feeding. In the grazing (Group G) vs. in-house fed group (Group HF) comparison, 40 differentially expressed genes/differentially abundant proteins exhibited the same mRNA and protein expression trends. These genes were associated with collagen binding, the lipoxygenase pathway, and the arachidonic acid metabolic process. Parallel reaction monitoring verified whether the TMT results were reliable. Moreover, some pathways, such as the AMPK signaling pathway, FoxO signaling pathway, PPAR signaling pathway, and fatty acid metabolism, were significantly enriched. These results expand our knowledge about meat quality in yaks and provide practical information and more evidence for further insight into the biological mechanisms underlying meat quality traits. [ABSTRACT FROM AUTHOR]

Mammalian skeletal muscle is composed of various muscle fibers that exhibit different physiological and metabolic features. Muscle fiber type composition has significant influences on the meat quality of livestock. In this study, we comprehensively analyzed the whole transcriptome profiles of the oxidative muscle biceps femoris (BF) and the glycolytic muscle obliquus externus abdominis (OEA) of yak. A total of 1436 mRNAs, 1172 lncRNAs, and 218 circRNAs were differentially expressed in the oxidative muscles compared with the glycolytic muscles. KEGG annotation showed that differentially expressed mRNAs regulated by lncRNA and circRNA were mainly involved in PPAR signaling pathway, citrate cycle (TCA cycle), and PI3K-Akt signaling pathway, which reflect the different metabolic properties between oxidative and glycolytic muscles. In addition, regulatory networks associated with muscle fiber type conversion and mitochondria energy metabolism in muscles were constructed. Our study provides new evidence for a better understanding of the molecular mechanisms underlying skeletal muscle fiber determination and meat quality traits of yak. • We explored metabolic differences between oxidative and glycolytic skeletal muscles of yak. • Oxidative and glycolytic skeletal muscles showed distinct transcriptome profiles. • Numerous ncRNAs were closely related to distinct metabolic features between oxidative and glycolytic skeletal muscles. • Several signaling pathways related to skeletal muscle energy metabolism and meat quality traits were identified. • The result revealed possible candidate genes and ncRNAs for improvement of meat quality of yak. [ABSTRACT FROM AUTHOR]