Yak meat is valued for its unique flavor and nutrition, but refrigerated storage packaging affects its flavor quality. This study focuses on longissimus thoracis et lumborum (LTL) of yaks and compares the regulatory effects of tray packaging (aerobic environment) and vacuum packaging (low oxygen environment) on the taste and metabolic characteristics of meat products at 3 days (mid-term of short-term storage) and 7 days (end of short-term storage, upper limit of conventional shelf life) under 4 degrees C refrigeration conditions. The relevant mechanisms are analyzed by combining gas chromatography-ion mobility spectrometry (GC-IMS) and gas chromatography-mass spectrometry (GC-MS) techniques. The results showed that GC-IMS detection revealed that tray packaging had significantly higher fresh flavor compounds (alcohols, aldehydes, esters) than vacuum at 3 days, better retaining initial aroma. However, when storage was extended to 7 days, substances imparting undesirable flavors (2-methylbutanal-D, 1-hydroxy-2-propanone, 2-propanethiol, and 2-ethylfuran) accumulated significantly in tray packaging meat, while vacuum packaging effectively inhibited the formation of such substances. GC-MS analysis indicated that the contents of fumaric acid and glutamine in the vacuum packaging groups (3/7 days) were consistently higher than those in tray packaging groups. After 7 days of storage, the content of free amino acids (L-cysteine, L-lysine) in vacuum packaging meat was significantly increased. Furthermore, glyceraldehyde 3phosphate, formamide, and 1-methoxy-2-methylprop-1-en-1-ol were identified as the key differential metabolites between the two packaging methods. KEGG pathway enrichment analysis showed that amino acid metabolism was the core driving pathway for changes in the composition of flavor compounds during the oxidation of yak meat under chilled storage. The selection of yak meat packaging should be adjusted according to storage duration: tray packaging is more suitable for short-term storage (within 3 days) to retain fresh flavor, while vacuum packaging can more effectively maintain meat flavor quality during long-term storage (7 days) by inhibiting oxidative reactions and regulating umami-related metabolism. The results of this study provide experimental support for the targeted optimization of fresh yak meat packaging schemes and the extension of its flavor shelf life.

Chilled yak meat is becoming more and more popular with the improvement in living standards, and the flavor of chilled meat is closely related to storage time. The effect of storage time on the flavor of chilled yak meat was explored in this study. We used GC-MS, HS-GC-IMS, and LC-MS/MS to detect changes in the metabolites in yak meat during storage at 4 °C and constructed storage time-dependent metabolite fingerprints of the yak meat. The results showed that low-temperature storage promoted the degradation of proteins and lipids, nucleotide release, and the production of the volatile compounds heptanal, octanal, n-nonanal, benzaldehyde, 2,3-pentanedione, 3-hydroxy-2-butanone, and 2-butanone. With an increase in the chilled storage time of yak meat, the total volatile basic nitrogen and total viable count of the meat were significantly increased. The short-term storage time of yak meat at 4 °C should not exceed 5 days.

Short-read RNA sequencing has been used to sequence the transcriptome of the skeletal muscle of yak and cattle-yak; however, full-length transcripts cannot be obtained and alternative splicing (AS) events cannot be inferred using this sequencing approach. Here, we used Oxford Nanopore Technologies (ONT) full-length sequencing to sequence the transcriptome of the longissimus dorsi of yak and cattle-yak. A total of 20,323 novel genes and 172,870 novel transcripts were identified, and 159,700 novel transcripts were successfully annotated. A total of 157,812 AS events, 58,073 simple sequence repeats, 57,468 complete open reading frames, 2296 transcription factors, and 20,404 lncRNAs were detected. Differentially expressed transcripts (DETs) in the longissimus dorsi muscle of yak and cattle-yak were involved in the MAPK and JAK-STAT signaling pathways related to muscle development and growth. Protein-protein interaction analysis of DETs suggested that TNNI2 might make a major contribution to differences in muscle growth and meat quality traits between yak and cattle-yak. The results have enriched the transcriptome data of dorsal muscles, providing new ideas for the study of transcriptional regulation processes, and also providing useful information for the production of higher yields of yak meat.

The Yushu yak is one of China’s distinctive yak breeds, primarily distributed in the Yushu Tibetan Autonomous Prefecture of Qinghai Province and its surrounding areas. Yushu yaks are not only economically and culturally significant but also play a crucial role in protecting the ecosystem of the Qinghai-Tibet Plateau and promoting sustainable development. However, there are no clear records regarding the ancestry, population structure, and unique traits of Yushu yaks. Therefore, this study conducted an analysis of genetic diversity, population structure, and selection signals in Yushu yak populations, aiming to provide references for the conservation and utilization of the breed genetic resources. The results of the analysis showed that the Yushu yak population has high genetic diversity and low inbreeding coefficients, indicating a stable genetic structure. Population structure analysis revealed that the Yushu yak lineage is unique, with limited gene flow between domestic and wild yaks. Functional enrichment analysis of positively selected genes in Yushu yaks indicated prominent selection features related to growth and development as well as energy metabolism. Additionally, we classified the Yushu yak breeding bulls into family lineages based on kinship, which is essential for improving the efficiency of utilizing genetic resources and scientifically managing the population.

The yak is a classic grazing livestock species on the Qinghai–Tibet Plateau, and fat deposition is indispensable for its survival and metabolism. Coding and non-coding RNAs (ncRNAs) play an important role in regulating fat deposition in livestock. In this study, the expression of mRNAs, lncRNAs, miRNAs, and circRNAs in the subcutaneous fat of yaks under grazing and stall feeding was measured using whole-transcriptome sequencing technology. A total of 677 differentially expressed (DE) mRNAs, 120 DE lncRNAs, 2216 DE circRNAs, and 15 DE miRNAs were identified, and their biological function was explored using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. Co-expression RNA (ceRNA) networks between DE ncRNAs and DE mRNAs were further constructed, and the crucial RNAs and signal pathways regulating fat deposition in yaks were obtained. The effect of mRNAs and ncRNAs on fat deposition in yaks mainly depended on the PPAR, PI3K–Akt, and cAMP signaling pathways, and the regulatory pathways TCONS00042948, TCONS00012083/bta-miR-2316/MCAT, and NR4A3 may be critical in this process. This study provides some theoretical basis for breeding yak species and promotes improvements in yak production.

Oocyte maturation requires close cooperation among multiple kinases and growth factors. However, the proteome landscape during yak oocyte maturation has not yet been characterized. Here, 4D-DIA (data independent acquisition) technology was used to sequence the proteome of yak oocytes at four stages, germinal vesicle (GV), germinal vesicle breakdown (GVBD), meiosis I (MI), and meiosis II (MII), and 5851 proteins were identified. During the transition from GV to GVBD, more proteins are activated to stimulate germinal vesicle breakdown. From MI to MII, the expression of most proteins was down-regulated. Bioinformatics analysis showed that GV oocytes contained a large number of proteins related to energy metabolism. The proteins in GVBD oocytes were mainly related to the activity of enzyme inhibitors. MII oocytes contained keratin family members and proteins involved in cell cycle regulation. In addition, it was found that the expression of phosphorylation modification enzymes and ubiquitination modification enzymes change dynamically during oocyte maturation. Parallel reaction monitoring (PRM) validated the expression of key differentially expressed proteins. These results provide important information for enhancing the understanding of the molecular mechanism of oocyte maturation and improving the efficiency of the in vitro maturation of yak oocytes, which are critically important for enhancing the reproductive efficiency of yak.

This study aimed to investigate the growth performance and dynamic changes in rumen microbiota of yaks during cold season under house feeding fattening. Eight male yaks of 18 months of age, with similar body weights and good health conditions, were selected for a housed fattening experiment. The pre-trial period was 10 days and the formal trial period was 90 days. The formal trial period was divided into three fattening stages: 0~30 days was the early fattening stage (group D1), 31~60 days (group D2) was the middle fattening stage, and 61~90 days (group D3) was the late fattening stage. The results showed that the body weight of the groups D2 and D3 was significantly higher than that of the group D1 (P<0.05). The average daily feed intake of the group D2 was significantly higher than that of the groups D1 and D3 (P<0.05), while the average daily gain of the group D1 was significantly higher than that of groups D2 and D3 (P<0.05). 16S rDNA sequencing revealed that with the progression of the fattening period, the Ace, Chao1, Shannon, and Sob indices of the rumen microbiota showed an increasing trend (P>0.05). The relative abundance of Bacteroidetes in the group D1 was significantly higher than that in the groups D2 and D3 (P<0.05), while the relative abundance of Firmicutes was significantly lower than that in the groups D2 and D3 (P<0.05). The relative abundance of Euryarchaeota and Actinobacteriota in group D2 was significantly higher than that in group D1 (P<0.05), and the relative abundance of Verrucomicrobia in the group D2 was significantly lower than that in the group D1 (P<0.05). The relative abundance of Spirochaetota in the group D3 was significantly lower than that in the groups D1 and D2 (P<0.05). Compared with the group D1, the relative abundance of Prevotella in the group D3 was significantly decreased (P<0.05), while the relative abundance of the Christensenellaceae_R-7 group was significantly increased (P<0.05). In the group D2, the relative abundance of Methanobrevibacter was significantly increased (P<0.05). The relative abundance of signal transduction pathways was significantly higher in the group D2 than in the group D1 (P<0.05), while the relative abundance of immune disease pathway was significantly lower (P<0.05). The study shows that house feeding fattening in the cold season can effectively improve the weight of yak, increase the relative abundance of dominant phyla and genera, and enhance the metabolic activity of microbiota and immune regulation ability of the body.

The hybridization of yak with cattle is an effective means to improve the yak’s production performance. The fatty trait greatly affects the meat quality, the growth and development, and the reproduction of bovine. In this study, the thickness of subcutaneous fat in cattle-yaks and yaks was measured, and fatty acid composition was detected by a gas chromatograph-mass spectrometer (GC-MS); the transcriptome and metabolome in fat were detected by mRNA-Sequencing (mRNA-Seq) and an ultra-high performance liquid chromatography-mass spectrometry technique (UHPLC-MS/MS), respectively. The results revealed that the thickness of subcutaneous fat in yaks was greater than the value in cattle-yaks; the content of saturated fatty acids (SFAs), polyunsaturated fatty acids (PUFAs), and Σn-3 PUFAs in cattle-yaks’ fat were higher than the values in yaks’ fat, whereas the unsaturated fatty acids (UFAs) and monounsaturated fatty acids (MUFAs) content in cattle-yaks’ fat were lower. Furthermore, the expression of the SREBF1 gene in the fat deposition of the two bovines was affected by PI3K-Akt and AMPK signal pathways, which led to the expression change of downstream VLDLR, INSIG1, ACACA, LIPE, SLC2A4, CPT1C, SCD, and DGAT2 genes. Therefore, fatty acid synthesis, glucose and lipid transport, and lipid synthesis differed in fat depositions between the two bovines, ultimately leading to differences in the fat quantity in the two bovines. Moreover, the expression of VLDLR, CPT1C, LEP, SCD, and CEBPE genes was closely related to the differences in fatty acid composition between the fat tissues of two bovines. The results can provide some theoretical basis for yak breeding and can also promote the improvement of yak production.

The epididymis is essential for sperm maturation. During sperm maturation, markable alterations of the payload of small noncoding RNAs are observed in the epididymis, which indicated the role of epigenetic alterations in sperm maturation. However, the N6-Methyladenosine (m6A) modification profile of the epididymis remains unelucidated. Therefore, in this study, we assessed the m6A modification levels in the caput, corpus, and cauda of the yak epididymis using a combination of methylated RNA immunoprecipitation and RNA sequencing. The m6A levels were significantly increased in the corpus of the epididymis. Functional enrichment analysis of differentially methylated RNA (DMR) between the corpus and caput group revealed the significant enrichment of DMRs in the gap junction, ErbB signaling pathway, and mTOR signaling pathway, which participate in cell communication and sperm maturation. In addition, the DMRs of cauda-vs-corpus group were enriched in apoptosis, the FoxO signaling pathway, the PI3K-Akt signaling pathway, and the tumor necrosis factor signaling pathway that were associated with sperm autophagy, oxidative stress, and sperm maturation. Furthermore, we identified the key genes exhibiting significant changes in m6A levels but with no differences in RNA levels, including YY1-associated factor 2, forkhead box J2, and forkhead box O1. This finding indicated that m6A modifications affect these genes during translation, thereby participating in sperm maturation. In summary, we generated the m6A profile of the yak epididymis, which will aid in further elucidating the maturation process of sperm and reveal more information related to male infertility.

Cattle–yak, a hybrid of yak and cattle, exhibits significant heterosis but male infertility, hindering heterosis fixation. Although extensive research has been conducted on transcriptional mechanisms in the testes of cattle–yak, the understanding of their translational landscape remains limited. In this study, we characterized the translational landscape of yak and cattle–yak based on Ribo-seq technology integrated with RNA-seq data. The results revealed that gene expression was not fully concordant between transcriptional and translational levels, whereas cattle–yak testes exhibited a stronger correlation across these two regulatory layers. Notably, genes that were differentially expressed at the translational level only (MEIOB, MEI1, and SMC1B) were mainly involved in meiosis. A total of 4,236 genes with different translation efficiencies (TEs) were identified, and the TEs of most of the genes gradually decreased as the mRNA expression level increased. Further research revealed that genes with higher TE had a shorter coding sequence (CDS) length, lower GC content, and higher normalized minimum free energy in the testes of yaks, but this characteristic was not found in cattle–yaks. We also identified upstream open reading frames (uORFs) in yak and cattle–yak testes, and the sequence characteristics of translated uORFs and untranslated uORFs were markedly different. In addition, we identified several short polypeptides that may play potential roles in spermatogenesis. In summary, our study uncovers distinct translational dysregulations in cattle–yak testes, particularly affecting meiosis, which provides novel insights into the mechanisms of spermatogenesis and male infertility in hybrids.

Translation regulation plays a crucial role in testicular development and spermatogenesis, but its dynamic mechanism has not yet been elucidated. This study integrated transcriptome data through ribosomal sequencing (Ribo-seq) to analyze the translation landscape of yak (Bos grunniens) testes at 6 months (Y6M), 18 months (Y18M), and 4 years (Y4Y) of age. The results revealed that the ribosome footprint characteristics of yaks were consistent with those of other mammals. The differentially translated genes during sexual maturity are significantly enriched in the meiotic cell cycle, PI3K Akt, and Notch signaling pathways. From Y6M to Y18M, most of the TE altered genes showed inverse transcription-translation efficiency trends, potentially involved in protein ubiquitination modification. From 18 M to 4Y, translationally altered genes lacked transcriptional changes but associated with acetyltransferase and phosphotransferase activity. PPI analysis identified stage-specific regulatory genes: COL1A2/MEIOB/SYCP3 (6 M-18 M) and STAT1/ITGB5/ERBB2 (18 M-4Y). Additionally, we identified 106 predicted translatable small open reading frames (sORFs), which included annotations for 58 known coding proteins and 1 long non-coding RNA. Sequence feature analysis revealed that higher translation efficiency correlates with longer uORF length, lower GC content, shorter CDS length, and higher NMEF. In conclusion, the results provide new insights into the dynamic regulation of gene translation during testicular development and spermatogenesis, which is highly significant for enhancing yak reproductive performance.

Translation, plays a critical regulatory role in follicular development, ovulation, and corpus luteum formation and degeneration in the ovaries. To better understand the molecular mechanisms of reproductive regulation at the translation level in yaks, the present study analyzed gene expression changes in the ovarian tissues of yaks in different reproductive stages by using ribosome profiling and integrating RNA sequencing data. The small open reading frames (sORFs) of the ovarian tissue were characterized, and the effect of the translation efficiency of the targeted genes on their sequence features was determined. The results showed that over 80% of genes in the two groups exhibited inconsistent changes in their expression at the transcription and translation levels; this finding indicated that the changes in gene expression at both levels were not merely synergistic. The pathway enrichment analysis revealed that these differentially expressed genes were enriched in various pathways, including PI3K-Akt, MAPK, calcium signaling, and ovarian steroidogenesis. Further investigations showed that some genes related to ovarian function displayed inconsistent changes in their expression at both transcription and translation levels and exhibited dynamic changes in translation activity, including PALB2, BMP7, PIK3R2, and WNT2B. Additionally, we identified 66 predicted translatable sORFs and assessed the impact of upstream ORFs on the translation efficiency of downstream major ORFs. The present study systematically revealed the characteristics of gene expression at the translational level in yak ovarian tissues in different reproductive stages for the first time and provided a new perspective for in-depth understanding of the physiological mechanisms of yak reproduction.

This study unveils the unique origins, evolution, and genetic variations of the Yangba cattle, an endangered breed in China, through a comparative genomic analysis involving 202 individuals from 21 domestic and international breeds. Genetic component analysis revealed that the Yangba cattle comprise four ancestral lineages: Eurasian taurine (18%), East Asian taurine (26%), Chinese indicine (39%), and Indian indicine (17%). Their high genetic diversity and low inbreeding coefficient set them apart significantly from mainstream commercial breeds. Gene introgression analysis indicated that the influx of genetic material from East Asian taurine has enhanced the Yangba cattle’s adaptability to environmental stress, while the introgression from Chinese indicine has endowed them with unique advantages in muscle development and tissue repair. A genome-wide selection scan identified strong positive selection signals for genes such as ABCC2, which is involved in immune regulation, and NCOA3, which plays a role in growth regulation, in the Yangba cattle. This study systematically elucidates, for the first time, the composite ancestral composition and mechanisms of adaptive evolution in Yangba cattle. These findings offer critical insights into the conservation and sustainable utilization of endangered cattle resources and underscore the importance of implementing effective breeding programs.

The aim of this study is to determine the effects of a high-concentrate diet on growth performance, serum biochemical indexes, and rumen microbiota in house-fed yaks. Sixteen male yaks (body weight, 151.73 ± 14.11 kg; 18 months) were randomly allocated into two dietary treatments: a group with a low level of concentrate (n = 8, LC, concentrate–forage = 40:60) and a group with a high level of concentrate (n = 8, HC, concentrate–forage = 60:40). We found that compared with the LC group, the average daily feed intake (ADFI), the average daily gain (ADG), and the serum albumin (ALB) concentration in the HC group were significantly increased (p < 0.05). The rumen bacterial compositions also differed significantly between the groups, as indicated by principal coordinate analysis (p < 0.05). Firmicutes and Bacteroidota were the main dominant phyla of rumen bacteria in yaks. Compared with the LC group, the relative abundance of Firmicutes in the HC group was significantly increased (p < 0.05) and the relative abundance of Bacteroidota was significantly decreased (p < 0.05). At the genus level, Rikenellaceae_RC9_gut_group, Succiniclasticum, Prevotella, Christensenellaceae_R-7_group, and NK4A214_group had the highest relative abundance. The relative abundance of Christensenellaceae_R-7_group in the HC group was significantly higher than that in the LC group (p < 0.05). The PICRUSt 2 results showed a significant enrichment in glycosaminoglycan degradation, apoptosis, and ECM–receptor interaction in HC relative to LC (p < 0.05). In conclusion, high-concentrate diets can enhance growth performance and alter the compositions and functions of ruminal bacterial communities in yaks.

Milk lipids greatly affect the volatile flavor of milk, and the relationship between lipids and volatile flavor in yak milk was explored in this study. The volatile flavor compounds (VFCs), lipids profile, fatty acids in yak ordinary milk and colostrum were detected with HP/SPME-GC-MS, the semiquantitative lipidomics based on LC-MS/MS, GC-MS, respectively. The VFCs differences in yak milk were closely related to 1-((1 s,3ar,4r,7 s,7as)-4-hydroxy-7-isopropyl-4-methyloctahloctahydro-1h-inden-1-Yl)-ethanone,2,6,6-trimethyl-2,4-cycloheptadien-1-one, pentanal, 2-phenylethyl propionate, octanoic acid methyl ester, diphosphoric acid diisooctyl ester, (Z)-3,4,4-trimethyl-5-oxo-2-hexenoic acid and acetic acid. The volatile flavor in yak milk was well correlated with milk lipids, and TG(4:0_12:3_18:1), TG(6:0_8:0_18:1), TG(4:0_12:3_18:1), TG(12:0_18:2_18:3) and TG(16:0e_18:1_22:5) were the crucial lipid molecules affecting volatile flavor. The degeneration of above lipids by hydrolysis produced some fatty acids and alcohol, then these compounds were further derived into other VFCs especially above crucial 8 molecules. This study provided a theoretical basis for improving the volatile flavor by controlling lipids in yak milk.

In order to investigate the composition and differences in volatile organic compounds (VOCs) in yak and cattle-yak meat and determine the key metabolites and metabolic pathways related to flavor formation. In this study, the VOCs and non-volatile metabolites in Longissimus dorsi muscle of two groups of samples were detected and analyzed by gas chromatography-ion migration spectrometry (GC-IMS) and gas chromatography-mass spectrometry (GC-MS). The results showed that 31 VOCs were identified by GC-IMS, including 5 alcohols, 5 ketones, 5 esters, 3 aldehydes, 2 furans, 2 hydrocarbons, 1 amine, 1 acid, 1 thiazole, 1 pyrazine, and 5 others. Most of them were alcohols, ketones, esters, and aldehydes. A total of 75 non-volatile metabolites with significant differences were obtained by GC-MS screening, among which amino acid contents such as serine, glycine, phenylalanine, and aspartic acid were significantly up-regulated in cattle-yak, and glutamic acid and tyrosine were significantly up-regulated in yak. The non-volatile differential metabolites in the two groups were significantly enriched in the metabolic pathways of arginine biosynthesis and oxidative phosphorylation. By combining GC-IMS and GC-MS, this study comprehensively and intuitively reflected the differences in VOCs between yak and cattle-yak meat, and clarified the metabolomic reasons for the differences in VOCs, so as to provide a theoretical basis for meat quality improvement.

Yaks (Bos grunniens) exhibit exceptional adaptation to the challenging high-altitude environment of the Qinghai-Tibetan plateau, making them the sole bovine species capable of thriving in such exreme conditions. Investigating the cellular and molecular characteristics of yak ovaries across different reproductive states is crucial for gaining insight into their ovarian functions. Herein, the cellular atlases of yak ovaries in different reproductive states were depicted by single-cell RNA-sequencing (scRNA-seq). The cellular atlases of the ovaries were established by identifying specific gene expression patterns of various cell types, including granulosa cells, theca cells, stromal cells, smooth muscle cells, endothelial cells, glial cell, macrophages, natural killer cells, and proliferating cells. The cellular compositions of the ovaries vary among different reproductive states. Furthermore, the granulosa cells comprise six cell subtypes, while theca cells consist of eight cell subtypes. The granulosa cells and theca cells exhibit distinct biological functions throughout different reproductive states. The two cell types were aligned along their respective pseudotime trajectories. Moreover, a cell-to-cell communication network was constructed among distinct cell types within the ovary, spanning the three reproductive states. Notably, during the estrus period, the granulosa cells demonstrated more prominent interactions with other cell types compared to the remaining reproductive states.

Alternative splicing is a prevalent phenomenon in testicular tissues. Due to the low assembly accuracy of short-read RNA sequencing technology in analyzing post-transcriptional regulatory events, full-length (FL) transcript sequencing is highly demanded to accurately determine FL splicing variants. In this study, we performed FL transcriptome sequencing of testicular tissues from 0.5, 1.5, 2.5, and 4-year-old yaks and 4-year-old cattle-yaks using Oxford Nanopore Technologies. The obtained sequencing data were predicted to have 47,185 open reading frames (ORFs), including 26,630 complete ORFs, detected 7645 fusion transcripts, 15,355 alternative splicing events, 25,798 simple sequence repeats, 7628 transcription factors, and 35,503 long non-coding RNAs. A total of 40,038 novel transcripts were obtained from the sequencing data, and the proportion was almost close to the number of known transcripts identified. Structural analysis and functional annotation of these novel transcripts resulted in the successful annotation of 9568 transcripts, with the highest and lowest annotation numbers in the NR and KOG databases, respectively. Weighted gene co-expression network analysis revealed the key regulatory pathways and hub genes at various stages of yak testicular development. Our findings enhance our comprehension of transcriptome complexity, contribute to genome annotation refinement, and provide foundational data for further investigations into male sterility in cattle-yaks.

The Testis is an important reproductive organ in male mammals and the site for spermatogenesis, androgen synthesis, and secretion. Non-coding RNAs (ncRNAs) play an important regulatory role in various biological processes. However, the regulatory role of ncRNAs in the development of yak testes and spermatogenesis remains largely unclear. In this study, we compared the expression profiles of circular RNAs (circRNAs), microRNAs (miRNAs), and messenger RNAs (mRNAs) in yak testicular tissue samples collected at 6 months (Y6M), 18 months (Y18M), and 4 years (Y4Y). Using RNA sequencing (RNA-Seq), we observed a significant difference in the expression patterns of ncRNAs in the samples collected at different testicular development stages. Twenty-two differentially expressed (DE) circRNAs, 69 DE miRNAs, and 64 DE mRNAs were detected in Y6M, Y18M, and Y4Y testicular samples, respectively. The results of gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed that the source genes of DE circRNAs, predicted target genes of DE miRNAs, and DE mRNAs were specifically associated with signaling pathways and GO terms that were related to sperm synthesis, sperm vitality, and testicular development, such as cell cycle, Wnt signaling pathway, MAPK signaling pathway, GnRH signaling pathway, and spermatogenesis. The analysis of the circRNA-miRNA-mRNA network revealed that some DE ncRNAs, including miR-574, miR-449a, CDC42, and CYP11A1, among others, may be involved in testicular spermatogenesis. Concurrently, various circRNA-miRNA interaction pairs were observed. Our findings provide a database of circRNAs, miRNAs, and mRNAs expression profiles in testicular tissue of yaks at different developmental stages and a detailed understanding of the regulatory network of ncRNAs in yak testicular development and provide data that can help elucidate the molecular mechanisms underlying yak testicular development.

This study aims to explore the key metabolites and metabolic pathways related to the formation of flavor in yak meat, laying the foundation for in-depth analysis of the composition of yak meat and improving meat quality. This study selected six healthy 4-year-old male Tianzhu white yaks under the same growth conditions as the research subjects. The metabolites of three groups of longissimi dorsi (LD), triceps brachii (TB), and biceps femoris (BF) were analyzed and identified using gas chromatography–ion mobility spectrometry (GC-IMS), gas chromatography-mass spectrometry (GC-MS), and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results showed that Tianzhu white yak meat contains abundant metabolites, and the VOC levels in BF muscles are higher than those in LD and TB muscles. The levels of 1-penten-3-one and 2-pentone in LD muscle are higher than in BF and TB muscle. The levels of 2-hexanol, 2-hexanol-D, and pyridine in TB muscles are higher than those in LD and BF muscles. The content of benzaldehyde, benzaldehyde D, 3-hydroxy-2-butane-D, 3-hydroxy-2-butanone, and mesitylene in BF muscle is higher than in LD and TB muscle. There is a significant difference in the enrichment degree of the glycolysis or gluconeogenesis pathways between LD muscles and the other two groups (BF and TB muscles). There were significant differences in the enrichment degrees of the D-glutamine and D-glutamate metabolic pathways, the alanine, aspartate, and glutamate metabolic pathways between the TB muscles and the other two groups (BF and LD muscles). There is a significant difference in the enrichment degree of the niacin and nicotinamide metabolic pathways between BF and LD muscles. In addition, there were significant differences in the enrichment degree of the histidine metabolism pathway among the three groups of muscles. This study identified key metabolites related to differences in meat quality and flavor formation in different parts of the muscle tissue of Tianzhu white yak through metabolomics analysis, providing a theoretical basis for exploring the molecular regulatory mechanism and molecular breeding of yak meat flavor formation in the future, and also providing a reference for quality trait breeding in other beef cattle.