During the postnatal stages, skeletal muscle development undergoes a series of meticulously regulated alterations in gene expression. However, limited studies have employed chromatin accessibility to unravel the underlying molecular mechanisms governing muscle development in yak species. Therefore, we conducted an analysis of both gene expression levels and chromatin accessibility to comprehensively characterize the dynamic genome-wide chromatin accessibility during muscle growth and development in the Tianzhu white yak, thereby elucidating the features of accessible chromatin regions throughout this process. Initially, we compared the differences in chromatin accessibility between two groups and observed that calves exhibited higher levels of chromatin accessibility compared to adult cattle, particularly within ±2 kb of the transcription start site (TSS). In order to investigate the correlation between alterations in chromatin accessible regions and variations in gene expression levels, we employed a combination of ATAC-seq and RNA-seq techniques, leading to the identification of 18 central transcriptional factors (TFs) and 110 key genes with significant effects. Through further analysis, we successfully identified several TFs, including Sp1, YY1, MyoG, MEF2A and MEF2C, as well as a number of candidate genes (ANKRD2, ANKRD1, BTG2 and LMOD3) which may be closely associated with muscle growth and development. Moreover, we constructed an interactive network program encompassing hub TFs and key genes related to muscle growth and development. This innovative approach provided valuable insights into the molecular mechanism underlying skeletal muscle development in the postnatal stages of Tianzhu white yaks while also establishing a solid theoretical foundation for future research on yak muscle development.

A hybrid offspring of Gannan yak and Jersey cattle, the Jeryak exhibits apparent hybrid advantages over the Gannan yak in terms of production performance and other factors. The small non-coding RNAs known as miRNAs post-transcriptionally exert a significant regulatory influence on gene expression. However, the regulatory mechanism of miRNA associated with muscle development in Jeryak remains elusive. To elucidate the regulatory role of miRNAs in orchestrating skeletal muscle development in Jeryak, we selected longissimus dorsi muscle tissues from Gannan yak and Jeryak for transcriptome sequencing analysis. A total of 230 (DE) miRNAs were identified in the longissimus dorsi muscle of Gannan yak and Jeryak. The functional enrichment analysis revealed a significant enrichment of target genes from differentially expressed (DE)miRNAs in signaling pathways associated with muscle growth, such as the Ras signaling pathway and the MAPK signaling pathway. The network of interactions between miRNA and mRNA suggest that some (DE)miRNAs, including miR-2478-z, miR-339-x, novel-m0036-3p, and novel-m0037-3p, played a pivotal role in facilitating muscle development. These findings help us to deepen our understanding of the hybrid dominance of Jeryaks and provide a theoretical basis for further research on the regulatory mechanisms of miRNAs associated with Jeryak muscle growth and development.

Differences in skin and hair phenotypes between the scapular and ventral regions of yaks (Bos grunniens) are obvious and become more prominent with age. However, the genetic mechanism that causes differences in yak skin at different ages has not been reported. In this study, we investigated the transcriptomic profile of yak skin across different ages (0.5 years, 2.5 years, and 4.5 years) and body sites (scapular and ventral regions). Differential gene expression analysis was initially conducted to explore the transcriptomic differences in skin at different ages and different body sites. Subsequently, weighted gene co-expression network analysis (WGCNA) was employed to analyze the transcriptomic data comprehensively. The results showed that, among all comparison groups, the Y2.5_S vs. Y2.5_V group (regional comparison) exhibited the highest number of DEGs, with 491 genes (179 upregulated and 312 downregulated), followed by the Y2.5_V vs. Y0.5_V group (age comparison), which had 370 DEGs (103 upregulated and 267 downregulated). DEGs such as IGF2BP3, ADCY8, FOSL1, and S100A8 were found in all comparison groups of different ages, and multiple members of the HOX gene family including HOXC10, HOXA9, HOXA6, HOXB9, and HOXB6 were differentially expressed in comparison groups at different sites. Functional enrichment analysis showed that there were more obvious differences in immune function between different ages of skin and more obvious differences in endocrine function between different parts of skin. WGCNA revealed that genes related with immunity such as GLYATL2, ACSL5, and SPDEF were the core genes of the co-expression module associated with the scapula region, and multiple genes related to hair follicle development such as FOXN1, OVOL1, DLX3, HOXC13, and TCHH were found to be the hub genes of the co-expression module associated with the ventral region. Overall, our study provides valuable insights into the transcriptomic complexity of yak skin across different ages and body sites. The differential gene expression patterns and co-expression network modules identified in this study lay the foundation for further research on skin biology and adaptation mechanisms in yaks.

The study aims to investigate the skin microbiome composition of Yaks and the effects of different dietary nutrient levels on the skin microbiome diversity and metabolites. A total of 19 healthy Tianzhu White Yaks at two age stages (2.5 and 4.5 years old) were selected and fed either a high-energy diet (n = 9) or a low-energy diet (n = 10). After 90 days of feeding, skin microbiota and skin tissue metabolites were detected using 16S rRNA sequencing and LC-MS/MS untargeted metabolomics, respectively. The results showed: (1) the phyla Firmicutes, Actinobacteriota, Proteobacteria, and Bacteroidetes exhibited relatively high abundances in the skin of yaks, and the total abundance of these four phyla reached as high as 99.3%. Alpha diversity analysis indicated that the alpha diversity index of yak skin microbiota was significantly higher (p < 0.05) in the low-energy nutritional level group than in the high-energy nutritional level group in yaks of both 2.5 and 4.5 years of age. Principal coordinate analysis (PCoA) revealed a distinct separation of all skin microbiota samples into two clusters: the high-energy (H) and low-energy (L) groups. (2) A total of 114 differentially expressed metabolites were screened across both groups, significantly enriched (p < 0.05) in pathways including synaptic vesicle trafficking and glycerophospholipid metabolism; (3) Correlation analysis between microbiota and metabolites revealed significant positive correlations (p < 0.01) between Psychrobacter and choline, and between Corynebacterium and palmitic acid. In conclusion, A low-energy diet increases skin microbial diversity, which is beneficial for maintaining community stability; In contrast, a high-energy diet enriches bacterial genera such as Corynebacterium and Psychrobacter, enhancing functions related to antibacterial activity and barrier protection.

(1) Background: Hair growth can function as an indicator of an animal’s health and nutritional status, furnishing a valuable means for early diagnosis and timely modifications to management practices, and is influenced by hormones, the immune system, and the levels of minerals within the animal’s body. (2) Methods: In this study, a total of 81 yaks were selected and divided into three groups according to their ages (1–2 years, 3–4 years, 5–6 years), and the concentrations of melatonin, dihydrotestosterone, IgA, IgG, and IgM in their blood serum and the levels of Ca, Mg, Zn, Fe, and P in both their blood serum and hair were detected. (3) Results: The levels of melatonin and dihydrotestosterone in yaks aged 1–2 years were significantly higher than those of other age groups (p < 0.001). In addition, the concentration of melatonin in male yaks was markedly greater than that in female yaks (p < 0.05). When it came to immunoglobulins, the IgA level in 1–2-year-old yaks was strikingly higher than those in yaks aged 3–4 years and 5–6 years (p < 0.05). In terms of mineral elements, the concentrations of calcium, magnesium, zinc, and iron in the blood serum of 1–2-year-old and 5–6-year-old yaks were significantly elevated compared to those in 3–4-year-old yaks. However, there was no notable difference between the 1–2-year-old and 5–6-year-old groups. The correlation analysis showed that there was a significant correlation between DHT and the levels of melatonin and IgA in yaks. Additionally, a significant correlation was observed between IgA and IgG, as well as between IgA and the levels of Fe, Mg, and Ca. It is likely that they jointly regulate the hair growth and immune processes of yaks. (4) Conclusions: There are positive correlations among melatonin, dihydrotestosterone, and IgA in the blood serum and the content of Fe and Mg in the hair to varying degrees, implying these indicators may jointly regulate yak hair growth and immune status. These research findings provide data support for applied research into evaluating the overall health status of yaks through the growth status of hair or by measuring the mineral content in hair in a non-invasive way.