Effects of oxidative stress and protein S-nitrosylation interactions on mitochondrial pathway apoptosis and tenderness of yak meat during postmortem aging.

To reveal the interaction of oxidative stress and protein S-nitrosylation on mitochondrial pathway apoptosis and tenderness development in postmortem yak meat. Herein, we selected yak longissimus dorsi muscle as the research object and treated hydrogen peroxide (H2O2) with S-nitrosoglutathione agent (GSNO) as well as Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME) in mixed injections with 0.9 % saline as a control group, followed by incubation at 4 °C for 12, 24, 72, 120 and 168 h. Results showed that this interaction significantly increased mitochondrial ROS and NO content (P < 0.05) while weakening the antioxidant capacity of GSH and TRX redox response systems or accelerating the Ca2+ release process, leading to mitochondrial functional impairment and increased apoptosis rate. Notably, the H2O2 + L-NAME group showed more pronounced apoptosis. Hence, we suggest that the interaction between oxidative stress and protein S-nitrosylation could positively regulate yak meat tenderization.

Genomic inbreeding analysis reveals resilience and genetic diversity in Indian yak populations.

The yak (Bos grunniens), renowned for its adaptability to extreme cold and hypoxic conditions, stands as a remarkable domestic animal crucial for sustaining livelihoods in harsh climates. We conducted a comprehensive analysis of the whole genome sequence data from three distinct Indian yak populations: Arunachali yak (n = 10), Himachali yak (n = 10), and Ladakhi yak (n = 10). The genomic data for Indian yaks were meticulously generated by our laboratory and compared with their Chinese counterpart, the Jinchuan yak (n = 8), for a more nuanced understanding. Our investigation revealed a total of 37,437 runs of homozygosity (ROH) segments in 34 animals representing four distinct yak populations. The Jinchuan yak population exhibited the highest proportion, constituting 80.8 % of total ROHs, predominantly as small segments (<0.1 Mb), accounting for 63 % of the overall ROHs. Further analysis uncovered a significantly higher degree of inbreeding in Chinese yaks compared to their Indian counterparts. The Indian yak populations, in contrast, demonstrated relatively lower and consistent levels of inbreeding. Moreover, we identified ROH hotspots that covered at least 60 % of individuals in our study, indicating their pivotal role in environmental adaptation. A total of five hotspot regions were detected, housing genes such as ENSBGRG00000015023 (WNT2), YIPF4, SPAST, TLN2, and DSG4. These genes are associated with traits including hair follicle initiation, nutrient stress response, microtubule assembly, development of cardiac muscle, hair follicle, and coat color. This observation strongly suggests that there is substantial selection acting on these genes, emphasizing their important role in environmental adaptation among yak populations.

Effect of the TGF-ß/BMP Signaling Pathway on the Proliferation of Yak Pulmonary Artery Smooth Muscle Cells under Hypoxic Conditions.

To survive in low-oxygen environments, yaks effectively avoid hypoxia-induced pulmonary arterial hypertension through vascular remodeling. The TGF-ß/BMP signaling pathway plays a key role in maintaining the homeostasis of pulmonary artery smooth muscle cells (PASMCs). However, little is known about the molecular regulatory mechanisms by which the TGF-ß/BMP signaling pathway contributes to the proliferation of yak PASMCs. In this study, yak PASMCs were cultured in vitro, and a hypoxia model was constructed to investigate the effect of TGFß/BMP signaling on yak PASMC proliferation. Hypoxia treatment increased the proliferation of yak PASMCs significantly. As the duration of hypoxia increased, the expression levels of TGF-ß1 and the phosphorylation levels of Smad2/3 were upregulated significantly. The BMP signaling pathway was transiently activated by hypoxia, with increases in BMPR2 expression and Smad1/5 phosphorylation, and these changes were gradually reversed with prolonged hypoxia exposure. In addition, exogenous TGF-ß1 activated the TGF-ß signaling pathway, increased the phosphorylation levels of the downstream proteins Smad2 and Smad3, and increased the proliferation and migration rates of yak PASMCs significantly. Finally, treatment with noggin (an inhibitor of BMP signaling) significantly reduced BMPR2 protein expression levels and Smad1/5 phosphorylation levels and increased yak PASMC proliferation and migration rates. In summary, these results revealed that under hypoxic conditions, the dynamic regulation of the TGF-ß/BMP signaling pathway promotes the proliferation of yak PASMCs.

Hypoxia-Inducible Factor 1α Affects Yak Oocyte Maturation and Early Embryonic Development by Regulating Autophagy.

In animal assisted reproductive technology, the production of high-quality oocytes is crucial. The yak, having lived in the Qinghai-Tibet Plateau for an extended period, has reproductive cells that are regulated by hypoxia-inducible factor 1α (HIF-1α). This study aimed to investigate the impact of HIF-1α on yak oocyte maturation and early embryonic development in vitro through the regulation of autophagy. The in vitro maturation process of yak oocytes involved the addition of the HIF-1α inducer DFOM and the inhibitor LW6 to examine their effects on yak oocyte maturation, early embryonic development, cell autophagy, cytochrome P450s (CYP450s) enzyme expression, and cumulus diffusion factors. The findings revealed that DFOM significantly upregulated the expression of HIF-1α, resulting in increased the cumulus diffusion area, elevated first polar body expulsion rate of oocytes, enhanced mitochondrial and actin levels, decreased ROS production, and reduced early apoptosis levels of oocytes. Moreover, DFOM promoted the expression of autophagy-related proteins, CYP450s enzymes, and cumulus diffusion factors, thereby enhancing oocyte maturation and early embryonic development. Conversely, LW6 exhibited opposite effects. The inhibition of autophagy levels with 3-MA during DFOM treatment yielded similar outcomes. Furthermore, reducing autophagy led to increased apoptosis levels at all stages of early embryonic development, as well as a significant decrease in total cell number and ICM/TE ratio of blastocysts. Studies have shown that during the in vitro maturation of yak oocytes, HIF-1α can affect the cumulus expansion area of oocytes by regulating autophagy, the first polar body excretion rate, mitochondrial level, actin level, ROS and early apoptosis level, the CYP450s enzyme, and the expression of cumulus expansion factors, thereby improving the in vitro maturation and early embryonic development of yak oocytes. These findings offer valuable insights into the reproductive regulation mechanism of yaks in hypoxic environments and suggest potential strategies for the advancement of yak assisted reproductive technology.

Comprehensive cognition of yak (Bos grunniens) AIFM2 gene and its anti-ferroptosis role in bisphenol A-induced fetal fibroblast model.

Apoptosis-inducing factor mitochondrion-associated 2 (AIFM2) has been identified as a gene with anti-ferroptosis properties. To explore whether AIFM2 exerts anti-ferroptosis role in yaks (Bos grunniens), we cloned yak AIFM2 gene and analyzed its biological characteristics. The coding region of AIFM2 had 1122 bp and encoded 373 amino acids, which was conserved in mammals. Next, RT-qPCR results showed an extensive expression of AIMF2 in yak tissues. Furthermore, we isolated yak skin fibroblasts (YSFs) and established a bisphenol A (BPA)-induced ferroptosis model to further investigate the role of AIFM2. BPA elevated oxidative stress (reactive oxygen species, ROS) and lipid peroxidation (malondialdehyde, MDA and BODIPY), and reduced cell viability and antioxidant capacity (glutathione, GSH), with the severity depending on the dosage. Of note, a supplement of Ferrostatin-1 (Fer), an inhibitor of ferroptosis, restored the previously mentioned indicators. Subsequently, we constructed an AIFM2 overexpression vector and designed AIFM2 specific interfering siRNAs, which were transfected into YSFs. The results showed that overexpressing AIFM2 alleviated ferroptosis, characterizing by significant changes of cell viability, ROS, BODIPY, MDA and GSH. Meanwhile, interfering AIFM2 aggravated ferroptosis, demonstrating the critical anti-ferroptosis role of the yak AIFM2 gene. This study shed light on further exploring the molecular mechanism of AIFM2 in plateau adaptability.

Gut Microbial Adaptation to Varied Altitudes and Temperatures in Tibetan Plateau Yaks.

The yak (Bos grunniens) exhibits exceptional regional adaptability, enabling it to thrive in the distinctive ecological niches of the Qinghai-Tibet Plateau. Its survival relies on the intricate balance of its intestinal microbiome, essential for adapting to harsh environmental conditions. Despite the documented significance of bacteria and fungi in maintaining intestinal homeostasis and supporting immune functions, there is still a substantial gap in understanding how the composition and functionality of yak gut microbiota vary along altitude-temperature gradients. This study aims to fill this gap by employing 16S rRNA and ITS amplicon sequencing techniques to analyze and compare the intestinal microbiome of yaks residing at different elevations and exposed to varying temperatures. The findings demonstrate subtle variations in the diversity of intestinal bacteria and fungi, accompanied by significant changes in taxonomic composition across various altitudes and temperature gradients. Notably, Firmicutes, Actinobacteriota, and Bacteroidota emerged as the dominant phyla across all groups, with Actinobacteriota exhibiting the highest proportion (35.77%) in the LZF group. Functional prediction analysis revealed significant associations between the LZF group and metabolic pathways related to amino acid metabolism and biosynthesis. This suggests a potential role for actinomycetes in enhancing nutrient absorption and metabolism in yaks. Furthermore, our findings suggest that the microbiota of yaks may enhance energy metabolism and catabolism by modulating the Firmicutes-to-Bacteroidota ratio, potentially mitigating the effects of temperature variations. Variations in gut bacterial and fungal communities among three distinct groups were analyzed using metagenomic techniques. Our findings indicate that microbial genera exhibiting significant increases in yaks at lower altitudes are largely beneficial. To sum up, our research investigated the changes in gut bacterial and fungal populations of yaks residing across diverse altitude and temperature ranges. Moreover, these results enhance comprehension of gut microbial makeup and variability, offering perspectives on the environmental resilience of dry lot feeding yaks from a microbial angle.

FSH induces apoptosis in follicular granulosa cells of Tianzhu white yak and regulates the expression of Fas/FasL mRNA.

The Tianzhu white yak, a globally rare species, holds immense value as a source for yak materials. While the Fas/FasL pathway is pivotal in granulosa cells apoptosis, its precise molecular workings remain enigmatic. This study endeavours to decipher the role of follicle-stimulating hormone (FSH) in suppressing ovarian granulosa cells (GC) apoptosis in the Tianzhu white yak. Utilizing advanced cell culture techniques, we employed the MTT method, flow cytometry, fluorescence labelling and RT-PCR to investigate the apoptotic effects of FSH on yak GCs. Our results reveal that FSH's inhibitory effect on GC apoptosis follows a normal distribution pattern, peaking at an FSH concentration of 100 ng/mL with an apoptosis inhibition rate of 89.31%. When serum was withdrawn, an FSH concentration of 2 × 106 ng/mL reduced apoptosis by 72.84%. Annexin V-FITC staining revealed membrane invaginations, bubble and protrusion formation on the cell surface, and alterations in membrane structure and cell morphology. Flow cytometry analysis further demonstrated that FSH administration prior to early granulosa cell apoptosis had a more profound effect than during gradual apoptosis, both showing a suppressive effect on early follicular granulosa cell apoptosis. A transcription-level analysis conducted 3 h prior to serum withdrawal, with the addition of 100 ng/mL FSH, revealed intricate regulations in the expression of Fas/FasL. Notably, we observed a gradual increase in FasL expression over time, yet the presence of FSH effectively down-regulated FasL expression to baseline levels, without notable changes in Fas expression. Immunocytochemical analysis further confirmed the presence of both Fas and FasL on the cell membrane, nucleus and cytoplasm, with varying intensities depending on the duration of FSH treatment. Our findings suggest that FSH may suppress the apoptotic pathway in follicular primarily by down-regulating FasL expression, indicating that Fas-regulated mitochondrial pathways play a more prominent role compared to death receptor pathways. This study offers a fresh perspective on the mechanism underlying follicular atresia in Tianzhu white yaks and lays a solid theoretical foundation for the expansion of this endangered species' population.

Understanding Consumer Preferences for Attributes of Yak Meat: Implications for Economic Growth and Resource Efficiency in Pastoral Areas.

Realizing the market value of grassland resources is of great significance to finding a balance between ecological protection and economic development. As a unique livestock animal that is native to the Qinghai-Xizang Plateau, the yak plays an important role in maintaining ecosystem stability, ensuring the livelihoods of herdsmen, promoting socio-economic development, and preserving ethnic cultural traditions. However, given its small market share, little is known about the factors that drive Chinese consumer preferences for yak meat. This study aimed to investigate consumer preferences for yak meat by means of an online survey involving a sample of 2999 respondents from five cities in China. The best-worst scaling method was employed to measure the relative importance of different attributes of yak meat by using a purchasing scenario. The results indicated that quality-safety certification, freshness, and production sustainability were regarded as the most preferred attributes, whereas animal welfare, brand, and the purchasing channel were found to be the least preferred. In addition, significant heterogeneity was detected in consumer preferences. Consumers were divided into three classes, namely 'Price Sensitive Consumers,' 'Environmentally Friendly Consumers,' and 'Yak Meat Inclined Consumers,' respectively. Our findings might be helpful for policymakers and yak meat producers to develop targeted strategies to facilitate the sale of yak meat and then restore degraded grasslands.

Effects of different drying methods on physicochemical, textural, flavor, and sensory characteristics of yak jerky.

The work aimed to study the effect of four drying methods, namely constant temperature hot air drying (HD), microwave drying (MD), hot air microwave drying (HMD), and gradient hot air drying (GHD), on quality characteristics of dried yak meat. The analyses of physicochemical, textural, flavor, and sensory characteristics were carried out based on these four drying methods. The results revealed that microwave dried yak jerky exhibited better color and received the highest sensory score. Hardness of samples were affected by the drying methods, which showed significant differences. There were 21 free amino acids (FAAs) detected in dried yak samples. The samples treated by microwave drying showed the highest total free amino acid content (73.30 mg/100 g) and the EUC value was significantly higher than other methods, indicating the sample displayed greater flavor. A total of 153 volatile compounds were identified in dried yak meat samples, primarily including aldehydes, ketones, and esters. Moreover, the sensory evaluation indicated that the drying methods could significantly affect on color, flavor, and overall acceptability of different samples. Microwave drying samples scored higher than other drying methods. Overall, considering aspects of quality, time savings, and energy efficiency, microwave drying of yak jerky emerges as a more satisfactory option. This study could provide important theoretical support for the application of drying methods to improve the quality of yak jerky and enhance production efficiency.

Evaluation of the application potential of Bdellovibrio sp. YBD-1 isolated from Yak faeces.

Studies on Bdellovibrio and like organisms (BALOs), obligate predatory bacteria, have highlighted the possibility of regulating bacteria and biofilms; however, yak-derived BALOs are yet to be reported. We aimed to characterize the BALOs isolated and identified from yak (Bos grunniens) feces and examine application potential. BALOs were isolated from healthy yak fecal samples, with Escherichia coli (ATCC 25922) as prey using the double-layer agar method, identified by transmission electron microscopy (TEM), and the specific 16S rDNA sequencing analysis. Sequencing of the 16S rDNA gene indicated that this isolate was 91% similar to the Bdellovibrio sp. NC01 reference strain and was named YBD-1. Proportion of YBD-1 lysed bacteria is 12/13. The YBD-1 showed best growth at 25-40°C, 0-0.25% (w/v) NaCl, and pH 6.5-7.5. YBD-1 significantly reduced the planktonic cells and biofilms of E.coli in co-culture compared to the E.coli group. Additionally, SEM analysis indicated that YBD-1 significantly reduced biofilm formation in E. coli. Furthermore, quantitative Real Time-polymerase chain reaction (qRT-PCR) showed that the expression of the virulence genes fim and iroN and the genes pgaABC involved in biofilm formation went down significantly. We concluded that YBD-1 may have the potential to control bacterial growth and biofilm-associated bacterial illnesses.

Protein Lactylation Profiles Provide Insights into Molecular Mechanisms Underlying Metabolism in Yak.

Protein lysine lactylation, a recently discovered post-translational modification (PTM), is prevalent across tissues and cells of diverse species, serving as a regulator of glycolytic flux and biological metabolism. The yak (Bos grunniens), a species that has inhabited the Qinghai-Tibetan Plateau for millennia, has evolved intricate adaptive mechanisms to cope with the region's unique geographical and climatic conditions, exhibiting remarkable energy utilization and metabolic efficiency. Nonetheless, the specific landscape of lysine lactylation in yaks remains poorly understood. Herein, we present the first comprehensive lactylome profile of the yak, effectively identifying 421, 308, and 650 lactylated proteins in the heart, muscles, and liver, respectively. These lactylated proteins are involved in glycolysis/gluconeogenesis, the tricarboxylic acid cycle, oxidative phosphorylation, and metabolic process encompassing carbohydrates, lipids, and proteins during both anaerobic and aerobic glucose bio-oxidation, implying their crucial role in material and energy metabolism, as well as in maintaining homeostasis in yaks.

Polymorphisms of ITGA9 Gene and Their Correlation with Milk Quality Traits in Yak (Bos grunniens).

A single-nucleotide polymorphism (SNP) is a genome-level trait that arises from a variation in a single nucleotide, leading to diversity in DNA sequences. SNP screening is commonly used to provide candidate genes for yak breeding efforts. Integrin Subunit Alpha 9 (ITGA9) is an integrin protein. It plays an important role in cell adhesion, signalling, and other processes. The aim of this study was to discuss the association between genetic polymorphisms in the ITGA9 gene and milk quality traits and to identify potential molecular marker loci for yak breeding quality. We genotyped 162 yaks using an Illumina Yak cGPS 7K liquid chip and identified the presence of polymorphisms at nine SNP loci in the ITGA9 gene of yaks. The results showed that the mutant genotypes in the loci g.285,808T>A, g.306,600T>C, and g.315,413C>T were positively correlated with the contents of casein, protein, total solids (TS), and solid nonfat (SNF) in yak milk. In other loci, heterozygous genotypes had a positive correlation with nutrient content in yak milk. Then, two ITGA9 haplotype blocks were constructed based on linkage disequilibrium, which facilitated a more accurate screening of ITGA9 as a candidate gene for yak milk quality improvement. In conclusion, we identified SNPs and haplotype blocks related to yak milk quality traits and provided genetic resources for marker-assisted selection in yak breeding.

Influence of Varied Environment Conditions on the Gut Microbiota of Yaks.

Despite the crucial role of the gut microbiota in different physiological processes occurring in the animal body, reports regarding the gut microbiota of animals residing in different environmental conditions like high altitude and different climate settings are limited. The Qinghai-Tibetan Plateau is renowned for its extreme climatic conditions that provide an ideal environment for exploring the effects of high altitude and temperature on the microbiota of animals. Yaks have unique oxygen delivery systems and genes related to hypoxic response. Damxung, Nyêmo, and Linzhou counties in Tibet have variable altitudes and temperatures that offer distinct settings for studying yak adaptation to elevated terrains. The results of our study suggest that amplicon sequencing of V3-V4 and internal transcribed spacer 2 (ITS2) regions yielded 13,683 bacterial and 1912 fungal amplicon sequence variants (ASVs). Alpha and beta diversity indicated distinct microbial structures. Dominant bacterial phyla were Firmicutes, Bacteroidota, and Actinobacteriota. Genera UCG-005, Christensenellaceae_R-7_group, and Rikenellaceae_RC9_gut_group were dominant in confined yaks living in Damxung county (DXS) and yaks living in Linzhou county (LZS), whereas UCG-005 prevailed in confined yaks living in Nyêmo county (NMS). The linear discriminant analysis effect size (LEfSe) analysis highlighted genus-level differences. Meta-stat analysis revealed significant shifts in bacterial and fungal community composition in yaks at different high altitudes and temperatures. Bacterial taxonomic analysis revealed that two phyla and 32 genera differed significantly (p < 0.05). Fungal taxonomic analysis revealed that three phyla and four genera differed significantly (p < 0.05). Functional predictions indicated altered metabolic functions, especially in the digestive system of yaks living in NMS. This study reveals significant shifts in yak gut microbiota in response to varying environmental factors, such as altitude and temperature, shedding light on previously unexplored aspects of yak physiology in extreme environments.

Temporal-spatial variability of grazing behaviors of yaks and the drivers of their intake on the eastern Qinghai-Tibetan Plateau.

Introduction: Grassland-livestock balance is an important principle of sustainable development of grassland livestock production and grassland ecosystem health. Grassland degradation becomes more serious at global scales and especially at the area that is sensitive to climate change and human activities. Decreases in pasture biomass and shifts in plant community composition in degraded grasslands can largely affect grazing behaviors of livestock. Up to date, however, it is unclear that whether livestock behaviors change across spatial and temporal scales and what key factors are to shape observed behavioral patterns of livestock. Methods: Here, yak behaviors including grazing, rumination and walking on the eastern Qinghai-Tibetan Plateau (QTP) were monitored by a continuous visual observation, to investigate temporal and spatial variations of grazing behavior of yaks (Bos grunniens); based on the data from public database in the past 18 years, a meta-analysis was conducted to examine the main factors that affect grazing behaviors and intake of yaks. Results: We showed that grazing behaviors of yaks differed significantly within hours, among hours of each day and among days as well as across different observation sites. Intake rate of yaks was higher in the morning than in the afternoon, but walking speed showed an inverse trend compared with intake rate. Resting, altitude, the mean annual precipitation (MAP), the mean annual temperature (MAT), forage ash, yak age and season were the main predictors for yak intake, and forage and yak individual characteristics had direct effects on grazing behaviors and intake of yaks. Discussion: The findings confirm that grazing behaviors of yaks can vary even at small temporal scales and regional scales, which is closely related to the shift in forage quality and biomass caused by environmental changes. The study suggests that multiple factors can be responsible for the variation in livestock behaviors and shifts in behavioral patterns may consequently lead to positive or negative feedback to grassland ecosystems through plant-animal interactions.

Multi-omics analysis of five species of milk and specific composition links within each species.

The gold standard of milk is human milk, not cow milk. The present study expects to explored the comprehensive nutritional value of different kinds of milk and the differences between them through multi-omics analysis and found functional components that are more similar to human milk. This study employed untargeted LC-MS/MS metabolomics, untargeted LC-MS/MS lipidomics, and 4D label-free proteomics analysis techniques. The findings revealed substantial disparities in metabolites, lipids, and proteins among the five types of milk. Notably, pig milk exhibited a remarkable abundance of N-acetylneuraminic acid (Neu5Ac) and specific polar lipids. Yak milk stood out with significantly elevated levels of creatine and lipoprotein lipase (LPL) compared to other species. Buffalo milk boasted the highest concentrations of L-isoleucine, echinocystic acid, and alkaline phosphatase, tissue-nonspecific isozyme (ALPL). The concentrations of iminostilbene and osteopontin (OPN) were higher in cow milk.

Polymorphisms within the PRKG1 Gene of Gannan Yaks and Their Association with Milk Quality Characteristics.

Yak milk, known as the "liquid gold", is a nutritious food with extensive consumption. Compared with cow milk, yak milk contains higher levels of nutrients such as dry matter, milk fat, and milk protein, which demonstrates great potential for exploitation and utilization. Protein kinase cGMP-dependent 1 (PRKG1) is an important functional molecule in the cGMP signaling pathway, and its significant influence on milk fatty acids has been discovered. The aim of this study is to explore the correlation between single nucleotide polymorphisms (SNPs) in the PRKG1 gene and the quality traits of Gannan yak milk in order to identify candidate molecular markers for Gannan yak breeding. In this study, genotyping was performed on 172 healthy, 4-5-year-old lactating Gannan yaks with similar body types, naturally grazed, and two to three parity. Three SNPs (g.404195C>T, g.404213C>T, and g.760138T>C) were detected in the PRKG1 gene of Gannan yaks, which were uniformly distributed in the yak population. Linkage disequilibrium analysis was conducted, revealing complete linkage disequilibrium between g.404195C>T and g.404213C>T. After conducting a correlation analysis between SNPs in the PRKG1 gene and milk quality in Gannan yaks, we found that PRKG1 SNPs significantly increased the content of casein, protein, and SNFs in yak milk. Among them, the TT homozygous genotype at the PRKG1 g.404195C>T loci exhibited higher casein and protein contents compared to the CC and CT genotypes (p < 0.05). The SNP g.760138T>C locus was associated with casein, protein, SNFs, and TS traits (p < 0.05). The CC genotype had higher casein and protein contents than the TT and TA genotypes (p < 0.05). However, there were no significant differences in milk fat, lactose, and acidity among the three genotypes (p > 0.05). In summary, PRKG1 gene polymorphism can serve as a candidate molecular marker for improving milk quality in Gannan yaks.

Effects of Dietary Protein Level and Rumen-Protected Methionine and Lysine on Growth Performance, Rumen Fermentation and Serum Indexes for Yaks.

This study investigated the effects of the dietary protein level and rumen-protected methionine and lysine (RPML) on the growth performance, rumen fermentation, and serum indexes of yaks. Thirty-six male yaks were randomly assigned to a two by three factorial experiment with two protein levels, 15.05% and 16.51%, and three RPML levels: 0% RPML; 0.05% RPMet and 0.15% RPLys; and 0.1% RPMet and 0.3% RPLys. The trial lasted for sixty days. The results showed that the low-protein diet increased the DMI and feed conversion ratio of yaks. The diet supplemented with RPML increased the activities of IGF1 and INS and nutrient digestibility. The high-protein diet decreased the rumen butyrate concentration and increased the rumen isovalerate concentration. The low-protein diet supplemented with RPML increased the rumen pH and the concentrations of total volatile fatty acids, butyrate and NH3-N; the high-protein diet supplemented with a high level of RPML decreased the rumen pH and the concentrations of isobutyrate, isovalerate, propionate and NH3-N. The low-protein diet supplemented with RPML increased the total antioxidant capacity and glutathione peroxidase activity, along with the concentrations of malondialdehyde and amino acids such as aspartic acid, lysine, cysteine, etc. In conclusion, a low-protein diet supplemented with RPML is beneficial for rumen and body health, physiological response, and metabolic status in yaks.

Effect of 3-Nitropropionic Acid at Different Doses on In Vitro Rumen Fermentation, Digestibility, and Methane Emissions of Grazing Yak and Cattle.

3-nitropropionic acid (3NPA) has been proposed as an useful modifier to mitigate ruminal enteric methane emissions. However, few studies investigated the effects of 3NPA on ruminal fermentation characteristics of grazing ruminants in vitro. Rumen fluid from grazing yak and cattle were collected and incubated with additions of 0, 8, and 16 mM 3NPA. The total gas production, CH4 production, and dry matter digestibility significantly decreased with increasing 3NPA doses in both ruminant species (p < 0.05) and methane production decreased to almost 100% in cattle at 8 mM NPA but not yak, while H2 accumulation showed an opposite trend. The total fatty acid (TVFA) production, acetate concentration, and propionate concentration in cattle decreased as 3NPA doses increased at 12 and 24 h incubation. For yak, the H2 accumulation reached its apex at 8 mM NPA (p < 0.05). The TVFA in yak decreased significantly with increasing 3NPA doses at 12 and 72 h incubation. Moreover, the acetate concentration and propionate concentration in yak decreased as 3NPA doses increased at 12 and 24 h incubation. Overall, these findings demonstrated that 3NPA could be used as a strategy to mitigate methane emissions; although, it negatively affected the dry matter degradability in vitro.

Yaks Are Dependent on Gut Microbiota for Survival in the Environment of the Qinghai Tibet Plateau.

The yak (Poephagus grunniens) has evolved unique adaptations to survive the harsh environment of the Qinghai-Tibetan Plateau, while their gut microorganisms play a crucial role in maintaining the health of the animal. Gut microbes spread through the animal population not only by horizontal transmission but also vertically, which enhances microbial stability and inheritance between generations of the population. Homogenization of gut microbes in different animal species occurs in the same habitat, promoting interspecies coexistence. Using the yak as a model animal, this paper discusses the adaptive strategies under extreme environments, and how the gut microbes of the yak circulate throughout the Tibetan Plateau system, which not only affects other plateau animals such as plateau pikas, but can also have a profound impact on the health of people. By examining the relationships between yaks and their gut microbiota, this review offers new insights into the adaptation of yaks and their ecological niche on the Qinghai-Tibetan plateau.

Comprehensive analysis of differentially expressed mRNAs, circRNAs, and miRNAs and their ceRNA network in the testis of cattle-yak, yak, and cattle.

Cattle-yak is a hybrid offspring resulting from the crossbreeding of yak and cattle, and it exhibits substantial heterosis in production performance. However, male sterility in cattle-yak remains a concern. Reports suggest that noncoding RNAs are involved in the regulation of spermatogenesis. Therefore, in this study, we comprehensively compared testicular transcription profiles among cattle, yak, and cattle-yak. Numerous differentially expressed genes (DEGs), differentially expressed circRNAs (DECs), and differentially expressed miRNAs (DEMs) were identified in the intersection of two comparison groups, namely cattle versus cattle-yak and yak versus cattle-yak, with the number of DEGs, DECs, and DEMs being 4968, 360, and 59, respectively. The DEGs in cattle-yaks, cattle, and yaks were mainly associated with spermatogenesis, male gamete generation, and sexual reproduction. Concurrently, GO and KEGG analyses indicated that DEC host genes and DEM source genes were involved in the regulation of spermatogenesis. The construction of a potential competing endogenous RNA network revealed that some differentially expressed noncoding RNAs may be involved in regulating the expression of genes related to testicular spermatogenesis, including miR-423-5p, miR-449b, miR-34b/c, and miR-15b, as well as previously unreported miR-6123 and miR-1306, along with various miRNA-circRNA interaction pairs. This study serves as a valuable reference for further investigations into the mechanisms underlying male sterility in cattle-yaks.