Tibetan Yak Research Articles

RESEARCH PROGRESS ON MAJOR DISEASES OF PIGS AND YAKS ON THE QINGHAI-TIBET PLATEAU: A COMPREHENSIVE REVIEW FROM 1990 TO 2023

The increased prevalence of diseases in Tibetan pigs and yaks has significantly hampered the cultivation industry, leading to substantial socioeconomic losses and adversely affecting both Tibetan pig production and the livelihoods of surrounding nomads. To conduct a comprehensive analysis, relevant articles on epidemics affecting Tibetan pigs and yaks from 1990 to 2023 were collected from five databases: CNKI, Google, PubMed, Science Direct, and Web of Science. The study findings, covering the period 1990 to 2023, revealed that Tibetan pigs faced primarily challenges from the porcine epidemic diarrhea virus (PEDV), Swine flu, Cysticercus tenuicollis, diarrheagenic Escherichia coli (DEC) and Enterococci. Zoonotic diseases such as Trichinosis, Swine flu, Hepatitis E virus (HEV), Toxoplasma gondii, Cystic echinococcosis (CE), and Japanese encephalitis virus were prevalent in the Tibetan pig area. Meanwhile, the yaks experienced severe outbreaks caused by bovine coronavirus (BCoV), bovine rotavirus A (BRVA), Echinococcus granulosus, Neosporosis IgM, Theileria spp. and Anaplasma spp., significantly impacting their quality of life. Primary risk factors for diseases in Tibetan pigs and yaks included age, housing conditions, frequency of deworming and vaccinations, and environmental factors on the plateaus. This review aims to improve regional breeding practices for Tibetan pigs and yaks by addressing these risk factors, thus reducing the prevalence of various diseases in the future. Achieving these objectives will not only elevate the local socioeconomic status, but also establish the Tibetan pig and yak industry as an independent and flourishing sector. Keywords: Tibetan pigs; Yaks; Epidemics; Zoonotic diseases; Risk factors

Multi-omics revealed the formation mechanism of characteristic volatiles in Tibetan yak cheese induced by different altitudes

The variation in volatiles, bacteria and metabolites of Tibetan yak cheese (TYC) from different altitudes were characterized with multi-omics to reveal the formation mechanism of characteristic volatile compounds (C-VOCs) in TYC induced by altitudes. 22C-VOCs (odor activity value, OAV > 1) were identified in TYCs, and hexanal, dodecanol, 2,3-butanediol, butyl isobutyate, etc., C-VOCs were confirmed induced by altitude. Lactobacillus, Kocuria, etc., bacteria and benzyl thiocyanate, trehalose, sarcosine, etc., metabolites were screened as the variable bacteria and metabolites for TYCs regulated by altitude, respectively. Pediococcus and carbonhydrates maybe the main contributors for the formation of C-VOCs in TYCs induced by altitudes. The formation of dodecanol, 2,3-butanediol and hexanal maybe derived from sarcosine and EPA, and the generation of butyl isobutyrates maybe originated from 1,6-DP-fructose and threonic acid facilitating by Pediococcus. This research will help us gain insight into the contribution of altitude to the formation of volatiles in TYCs.

Whole-genome resequencing reveals genetic diversity, differentiation, and selection signatures of yak breeds/populations in southwestern China.

The Sichuan-Yunnan region is the main production area of yaks in southwestern China, with rich genetic resources of Yaks. Nevertheless, there have been limited study on the genetic characteristics of the entire yak populations in Tibet and southwestern China. In this study, we performed whole-genome resequencing to identify genetic variation information in a total of 198 individuals from six yak breeds (populations) in Sichuan (Muli yak, Jinchuan yak, Changtai yak, Maiwa yak), Yunnan (Zhongdian yak), and Tibet (Tibetan yak). The aim was to investigate the whole-genome genetic diversity, population genetic structure, and genome selection signatures. We observed that all six populations exhibit abundant genetic diversity. Except for Tibetan yaks, which showed low nucleotide diversity (0.00104), the remaining yak populations generally displayed high nucleotide diversity (0.00129-0.00153). Population genetic structure analysis revealed that, among the six yak populations, Muli yak exhibited greater differentiation from other yak populations and formed a distinct cluster independently. The Maiwa yak population displayed a complex genetic structure and exhibited gene exchange with Jinchuan and Changtai yaks. Positive selection signals were detected in candidate genes associated with growth (GNB4, HMGA2, TRPS1, and LTBP1), reproduction (PI4KB, DYNC1I1, and GRIP1), immunity (CD200 and IL1RAP), lactation (SNX13 and CPM), hypoxia adaptation (NDUFB6, PRKN, and MRPS9), hair (KRT24, KRT25, and KRT26), meat quality (SUCLG2), digestion and absorption (CLDN1), and pigment deposition (OCA2) using the integrated Pi and F ST methods. This study provides significant insights into understanding the whole-genome genetic characteristics of yak populations in Tibet and southwestern China.

Physiochemical and Microbial Analysis of Tibetan Yak Milk Yogurt in Comparison to Locally Available Yogurt

Yak yogurt, which is rich in microorganisms, is a naturally fermented dairy product prepared with ancient and modern techniques by Chinese herdsmen in the Qinghai-Tibet Plateau. The objective of this research was to assess the impact of Lactobacillus bulgaricus and Streptococcus thermophilus starter cultures on the quality and shelf life of yak yogurt, as well as the genetic stability across multiple generations, in comparison to commercially available plain yogurt and peach oat flavor yogurt. Following that, the samples were evenly divided into four treatment groups denoted as T1 (treatment 1), T2, T3, and T4, with each group employing a distinct source of yogurt formulation. T1 included L. bulgaricus, T2 comprised S. thermophilus, T3 consisted of plain yogurt, and T4 represented peach oat yogurt flavor. The findings indicate that T1 yogurt consistently presents a lower pH and higher acidity compared to the other three yogurt types throughout the entire generation process. Moreover, the fat content in all generations of the four yogurt types exceeds the national standard of 3.1 g/100 g, while the total solid content shows a tendency to stabilize across generations. The protein content varies significantly among each generation, with T1 and T4 yogurt indicating higher levels compared to the T2 and T3 yogurt groups. In terms of overall quality, T1 and T4 yogurt are superior to T2 and T3 yogurt, with T1 yogurt being the highest in quality among all groups. The findings revealed that the inclusion of L. bulgaricus led to enhanced flavor, texture, and genetic stability in yak yogurt. This study will serve as a valuable source of data, support, and methodology for the development and screening of compound starters to be utilized in milk fermentation in future research and applications.

Herbivore assemblages affect soil microbial communities by altering root biomass and available nutrients in an alpine meadow.

Three different herbivore grazing assemblages, namely, yak grazing (YG), Tibetan sheep grazing (SG) and yak and Tibetan sheep co-grazing (MG), are practiced in alpine meadows on the Qinghai-Tibetan Plateau (QTP), but the effects of the different herbivore assemblages on soil microbes are relatively unknown. The microbial community plays an important role in the functional stability of alpine grassland ecosystems. Therefore, it is important to understand how the microbial community structure of grassland ecosystems changes under different herbivore grazing assemblages to ensure their sustainable development. To fill this gap, a field study was carried out to investigate the effects of YG, SG, and MG on plant communities, soil physico-chemical properties and microbial communities under moderate grazing intensity in alpine meadows. Grazing increased the β-diversity of the bacteria community and decreased the β-diversity of the fungal community. The herbivore assemblage affected the microbial community diversity, but not the plant community diversity. Total phosphorus, soil bulk density, root biomass, and plant α-diversity were correlated with both the bacterial and fungal community composition, available phosphorus and soil moisture were correlated only with the bacterial community composition, while available potassium and above-ground net primary production (ANPP) were correlated only with the fungal community composition. Soil available nitrogen, soil available phosphorus and soil bulk density were highest in SG, while ANPP was highest in MG. It was concluded that MG can improve ANPP and stabilize the soil microbial community, suggesting that MG is an effective method for sustainable use and conservation of alpine meadows on the QTP.

Seroepidemiology of Neosporosis in Various Animals in the Qinghai-Tibetan Plateau.

Neosporosis is a worldwide infectious disease caused by intracellular parasite Neospora caninum that is a major pathogen of abortion in cattle and neurological disorders in other hosts. However, limited data are available on animals exposed to N. caninum in the Qinghai-Tibetan Plateau Area (QTPA), and little is known about whether animals in the plateau area play an important role in the epidemiology of N. caninum. Therefore, indirect ELISAs based on a combination of NcSAG1 and NcGRA7 antigens were developed to examine both N. caninum-specific IgG and IgM antibodies in Tibetan sheep, yak, cow, pig, cattle, horse, chicken, camel, and donkey from the QTPA in this study. The results showed that all current species present- IgG and IgM-positive animals, and that the overall seroprevalence of N. caninum were 18.6 (703/3,782) and 48.1% (1,820/3,782) for the IgG and IgM antibodies, respectively. Further analysis found significant differences from different altitudes in IgG in Tibetan sheep and IgM in the yak. Hence, the present serological results indicate that the tested animal populations in the QTPA are suffering from N. caninum infections or have become carriers of N. caninum antibodies. To the best of our knowledge, this is the first report on current N. caninum-infected animals in the QTPA, the first epidemiology of neosporosis in cow and camel in China, and the first record of N. caninum IgM antibodies in all the surveyed animals in China. This study provides the latest valuable data on the epidemiology of neosporosis in China and in plateau areas of the world.

Effect of Grazing Treatments on Phenotypic and Reproductive Plasticity of Kobresia humilis in Alpine Meadows of the Qinghai-Tibet Plateau

Plant phenotypic and reproductive plasticity is strongly influenced by long-term grazing activities. It is important to understand the life history of dominant plant species, such as Kobresia humilis of alpine meadow, for the stability and sustainable grazing administration meadow on the Qinghai-Tibetan Plateau (QTP). We compared the effects of different grazing treatments (grazing yak, Y; grazing Tibetan sheep, S; and grazing Tibetan sheep and yak, S+Y) on the reproductive and phenotypic plasticity of K. humilis in an alpine meadows on the northeastern margin of the Qilian Mountains in China. The results showed that different grazing treatments had significantly effects on the K. humilis phenotype and reproductive plasticity. The Y treatment significantly reduced the plant height, crown width and K. humilis biomass, but increased the density, which was 1.27 and 1.53 times higher than that in the S+Y and S treatments, respectively. Further, the S+Y treatment significantly increased the crown width, biomass, and future life expectancy of K. humilis. Whereas the S treatment increased the height of K. humilis significantly, which was 1.57 and 1.10 times higher than that in the Y and S+Y treatments, respectively. Both Y and S treatments significantly increased the sexual reproduction efficacy of K. humilis but reduced the storage efficacy. The storage efficacy at S+Y treatment was highest among these treatments. Further, grazing treatments did not change the resource allocation strategy of K. humilis, while the sexual reproductive efficacy was significantly higher than the vegetative reproduction efficacy. The storage efficacy was significantly higher than the growth efficacy among the different grazing treatments. The increase of Cyperaceae indicates the degradation of Cyperaceae—Poaceae meadows. This study showed that grazing Tibetan sheep is a more sustainable grazing method in cold season pastures of alpine meadows on the QTP.

​Dominant-genotype Frequency Analysis of Economic Traits Related to SNP Candidate Markers in Three Yak Populations

Background: Yak as a unique domestic animal that has extremely important social value and influence on the local culture and economy in the Qinghai-Tibet Plateau. The current study aimed to evaluate the genotype distribution of a series of economic traits (growth, meat quality and lactation) related to single nucleotide polymorphisms (SNP) in three Tibetan yak populations. Methods: A total of 238 yaks from three populations [Sibu (SB), Chawula (CWL) and Jiali (JL) yaks] including 34 SB, 104 JL and 100 CWL yak individuals were collected. All samples were genotyped for 12 SNP markers by using SNaPshot technology. Result: All loci had abundant polymorphisms in the three populations, except for the Hesx1_G618C locus. The dominant growth-related genotype was MyoD1_C1710T (C/T), which had the highest frequency in the three Tibetan yak populations. However, the growth-related dominant genotypes at UCP2_T1499C (C/T) and CYP4A11_G4806A (G/A) loci were rare genotypes in the three Tibetan yak populations. Results of Hardy-Weinberg equilibrium (HWE) analysis showed that all sites did not deviate from the HWE within the population. This finding indicated that these populations belonged to a natural one without having been subjected to artificial selection on economic traits. Overall, this study provided valuable reference for the future molecular breeding of yak based on the genotype distribution of economic-trait candidate markers in three yak populations in Tibet.

Pyrolysis of Tibetan Yak Dung for Producing Biochar Pertinent to Agro-environmental Application

ABSTRACT The study was investigated the influence of pyrolysis conditions on the yield and nutrient properties of yak dung-based biochar and its potential of agro-environmental applications. A series of biochars were made by hydrothermal carbonization (HTC) under the different atmospheres, such as Nitrogen (N2) and carbon dioxide (CO2), processing temperatures (200-300 °C) and residence times (1-2 h). The results showed the yield of yak dung-based biochar ranges from 35.33 wt% to 58.29 wt%. The concentration of nitrogen (N), phosphorus (P) and potassium (K) in biochar varied from 28.18 mg·g−1 to 15.54 mg·g−1, 16.23 mg·g−1 to 25.31 mg·g−1 and 0.59 mg·g−1 to 1.02 mg·g−1, respectively. And the contents of micronutrients Zn and Fe varied from 4.6 mg·g−1 to 17.42 mg·g−1, and 15.28 mg·g−1 to 29.22 mg·g−1, respectively. The yield, total carbon (C), N, hydrogen (H) and oxygen (O) content of biochar decreased with increasing processing temperature, while the total P and K content, pH and Brunauer-Emmett-Teller (BET) surface area increased; moreover, the P and K content of biochar produced in N2 increased more compared with CO2. The heavy metal contents of copper (Cu), cadmium (Cd), chromium (Cr), platinum (Pb) and arsenic (As) all were lower in yak dung-based biochar compare with other manures or sewage sludge-based biochar. Biochar produced in N2 had higher nutrient content indicating the potential of application for fertilizer compared with it in CO2; while the biochar produced in CO2 with larger surface area characteristic and more abundant functional groups showing higher potential of application for the soil amendments and nutrient control materials. Our study provides some new insights for biochar production according to its application.

Antioxidant properties of lactic acid bacteria isolated from traditional fermented yak milk and their probiotic effects on the oxidative senescence of Caenorhabditis elegans.

The objectives of the current study were to screen antioxidant lactic acid bacteria (LAB) strains isolated from traditionally fermented Tibetan yak milk, and to evaluate their probiotic effects on the oxidative senescence of Caenorhabditis elegans (C. elegans). A total of 10 LAB isolates were assessed for their antioxidant activity by in vitro assays, and three strains with high activity were selected for an investigation of their probiotic functions in C. elegans. The results indicated that Lactobacillus plantarum As21 showed high anti-oxidant capacity and had a high survival rate (64%) in a simulated gastrointestinal tract. The lifespan of C. elegans treated with As21 was increased by 34.5% compared to the control group. Strain As21 also showed improved motility and enhanced resistance to heat stress and H2O2 stimulation in C. elegans. Moreover, treatment with As21 reduced the production of age-related reactive oxygen species (ROS) and malondialdehyde (MDA) damage and promoted the production of the antioxidants superoxide dismutase (SOD), catalase (CAT) and glutathione GSH. These results suggest that Lactobacillus plantarum strain As21 could be a potential probiotic strain for retarding ageing and could be used in functional foods.

Remains of the Baikal yak (Poehpagus mutus baikalensis N. Verestchagin, 1954) from Late Pleistocene localities of Southern Siberia

136 bones of the postcranial skeleton and a part of the skull of a female Baikal yak (Poephagus mutus baikalensis N. Verestcthagin, 1954), originating from 18 cave locations and open-type Paleolithic sites in Altai-Sayan, Transbaikalia and Central Mongolia were examined. The material includes 38 metacarpals and 9 metatarsals of the yak. Morphometric differences in the structure of the postcranial skeleton of the yak and the bison (Bison priscus Bojanus, 1827) were revealed. The body size of the Baikal yak significantly exceeded that of the wild Tibetan yak (Poephagus mutus Przewalski, 1883). The largest representatives of P. m. baikalensis inhabited the Altai Mountains. In most of the sites, located in the mid-mountain landscapes of Southern Siberia (with absolute heights of 500–700 m), only a few remains of the Baikal yak were found, accounting for 0.01% to 1–2% of the number of megafauna remains. Most likely, herds of yaks did not live here permanently, but appeared only sporadically, during seasonal migrations. In higher mountainous areas (from 1000–1500 m) of Gorny Altai and Khangai Mountains in Central Mongolia, the proportion of the remains of the Baikal yak increases significantly – up to 16–22%. Like the contemporary P. mutus, the Pleistocene yak found its ecological optimum in the high-mountainous parts of ridges and mountain plateaus, dominated by cold, dry mountain-steppe landscapes with herb-grass vegetation and a small amount of snow. During the periods of cryochrones, the area of P. m. baikalensis apparently expanded significantly, incorporating the adjacent foothill territories. During the periods of thermochrones, it was most likely limited to the high-mountainous areas of the mountain uplifts of Southern Siberia.

Effect of Simulated Tibetan Sheep and Yak Trampling at Different Periods on the Reproductive Characteristics, Underground Morphology, and Carbohydrate Content of Kobresia humilis

Studying the effects of trampling at different stages on plant reproduction is necessary to provide the basis for grassland management. However, the changes in forage growth characteristics are still unclear under the action of livestock trampling from soil thawing to regreening stage of alpine meadows.We studied the changes of growth, reproduction, and storage characteristics of Kobresia humilis in the alpine meadow of Tianzhu, Gansu Province, after 2 yr of simulated Tibetan sheep and yak trampling at five periods (prophase, initial, and middle period of thawing, initial regreening, and regreening period).Trampling period had the highest influence on K. humilis phenotypic traits, followed by livestock species. Considering the same trampling period, the negative effects of Tibetan sheep trampling on the sexual reproduction, different modular biomass, and root growth of K. humilis were lower than those of yak trampling. Sexual reproduction effort and storage growth effort were higher in Tibetan sheep trampling conditions, and vegetative reproductive effort was lower in sheep compared with yak trampling treatment conditions.There was a trade-off of resource allocation between K. humilis reproductive organs and storage organs. For the average of each indicator under different combination treatments, the vegetative reproductive effort was 11.1 times that of sexual reproduction effort. The comprehensive evaluation of K. humilis phenotypic traits showed that the trampling treatments could be divided into excellent (prophase period of thawing), good (middle period of thawing), general (initial period of thawing), and inferior (initial regreening to regreening period) grades of Tibetan sheep and yak trampling.We suggest that the actual grazing process in the cold-season pastures of this alpine meadow should be fully used at the prophase of soil thawing, implement rest-grazing for grassland and confinement from initial period of soil thawing to the forage regreening period, and appropriately increase the proportion of Tibetan sheep and reduce the number of yaks to avoid the high-intensity trampling of grassland. This will not only make optimum use of the limited grassland resources but also promote their recuperation.

Clinical Examples of Hypermirroring, Emotionally Gifted Heart Kids

Studying the effects of trampling at different stages on plant reproduction is necessary to provide the basis for grassland management. However, the changes in forage growth characteristics are still unclear under the action of livestock trampling from soil thawing to regreening stage of alpine meadows.We studied the changes of growth, reproduction, and storage characteristics of Kobresia humilis in the alpine meadow of Tianzhu, Gansu Province, after 2 yr of simulated Tibetan sheep and yak trampling at five periods (prophase, initial, and middle period of thawing, initial regreening, and regreening period).Trampling period had the highest influence on K. humilis phenotypic traits, followed by livestock species. Considering the same trampling period, the negative effects of Tibetan sheep trampling on the sexual reproduction, different modular biomass, and root growth of K. humilis were lower than those of yak trampling. Sexual reproduction effort and storage growth effort were higher in Tibetan sheep trampling conditions, and vegetative reproductive effort was lower in sheep compared with yak trampling treatment conditions.There was a trade-off of resource allocation between K. humilis reproductive organs and storage organs. For the average of each indicator under different combination treatments, the vegetative reproductive effort was 11.1 times that of sexual reproduction effort. The comprehensive evaluation of K. humilis phenotypic traits showed that the trampling treatments could be divided into excellent (prophase period of thawing), good (middle period of thawing), general (initial period of thawing), and inferior (initial regreening to regreening period) grades of Tibetan sheep and yak trampling.We suggest that the actual grazing process in the cold-season pastures of this alpine meadow should be fully used at the prophase of soil thawing, implement rest-grazing for grassland and confinement from initial period of soil thawing to the forage regreening period, and appropriately increase the proportion of Tibetan sheep and reduce the number of yaks to avoid the high-intensity trampling of grassland. This will not only make optimum use of the limited grassland resources but also promote their recuperation.

Optical sensing in Tibet Plateau wildlife observation based on tethered balloon

As the third pole of the earth, Qinghai Tibet Plateau breeds many unique species; their population size, living environment and migration process have been observed and studied by many researchers. However, these observations are mainly carried out in summer with UAVs when the temperature is high, while they are hard to work in winter since the harsh environment such as low temperature and strong wind. Here, we used a tethered balloon to observe and monitor Tibetan animals in the winter of Tibet Plateau with a long wave refrigeration infrared camera (resolution is 0.2 m@2 Km). The camera was installed on a two dimensional stable platform and was raised up to 150 m by the tethered balloon. The experiment results show that the camera on the tethered balloon can complete the observation in the harsh environment and obtain better images and videos including the mating process of two Tibetan antelopes. After this experiment, the acquired videos were used for further processing, such as motion detection and animal counting. This method can be used to observe other species occupying similar environment, such as Tibetan yak and Equus kiang.

Characterization and identification of cellulase-producing Enterococcus species isolated from Tibetan yak (Bos grunniens) rumen and their application in various forage silages.

Cellulase-producing Enterococcus species isolated from the rumen of Tibetan yak (Bos grunniens) were characterized, and their combined effects on the silage quality of various forages were studied. The two isolated strains with high cellulolytic potential were identified as Enterococcus faecalis (EF85) and E. faecium (EF83) by 16S rRNA sequencing. Both EF85 and EF83 could grow well at 15-55°C, pH 3·0-6·0 and in 3·0-6·5% NaCl. The cellulase secreted by EF85 and EF83 showed good stability at temperatures from 20 to 45°C and pH from 4·5 to 7·0. A commercial inoculant (CLP), a commercial cellulase (CE) and the two cellulolytic strains (EF85+EF83) were added to whole-crop corn, sweet sorghum and Napier grass ensiling for 120days respectively. In Napier grass silage, all inoculants significantly increased lactic acid content and ratio of lactic to acetic acid and decreased pH, butyric acid and ammonia nitrogen contents. The acid detergent fibre and cellulose contents in EF85+EF83 treatment were significantly lower than those in the other treatments. In whole-crop corn and sweet sorghum silages, all additives had no significant effect on the fermentation quality, while CE and EF85+EF83 markedly enhanced cellulose degradation and increased free sugar content. The combined inoculation of the cellulolytic strain EF85 and EF83 to various forages reduced the fibre content of the resulting silages. Few studies involved inoculation of silage with Enterococcus species in different forage types. The isolated cellulolytic strains of E. faecalis EF85 and E. faecium EF83 could be a great alternative for commercial inoculants and enzymes in silage production.

Single-Cell Transcriptomics Reveals That Metabolites Produced by Paenibacillus bovis sp. nov. BD3526 Ameliorate Type 2 Diabetes in GK Rats by Downregulating the Inflammatory Response.

Chronic low-grade inflammation is widely involved in the development and progression of metabolic syndrome, which can lead to type 2 diabetes mellitus (T2DM). Dysregulation of proinflammatory and anti-inflammatory cytokines not only impairs insulin secretion by pancreatic β-cells but also results in systemic complications in late diabetes. In our previous work, metabolites produced by Paenibacillus bovis sp. nov. BD3526, which were isolated from Tibetan yak milk, demonstrated antidiabetic effects in Goto–Kakizaki (GK) rats. In this work, we used single-cell RNA sequencing (scRNA-seq) to further explore the impact of BD3526 metabolites on the intestinal cell composition of GK rats. Oral administration of the metabolites significantly reduced the number of adipocytes in the colon tissue of GK rats. In addition, cluster analysis of immune cells confirmed that the metabolites reduced the expression of interleukin (IL)-1β in macrophages in the colon and increased the numbers of dendritic cells (DCs) and regulatory T (Treg) cells. Further mechanistic studies of DCs confirmed that activation of the WNT/β-catenin pathway in DCs promoted the expression of IL-10 and transforming growth factor (TGF)-β, thereby increasing the number of Treg cells.

PSI-40 Two mitochondrial lineages revealed in North American yak

Abstract Domestic yak (Bos grunniens) are bovids native to the Asian Qinghai-Tibetan Plateau. Studies of Asian yak have revealed that introgression with domestic cattle has contributed to the evolution of the species. When imported to North America (NA), some hybridization with B. taurus did occur. The objective of this study was to use mitochondrial (mt) DNA sequence data to better understand the mtDNA origin of NA yak and their relationship to Asian yak and related species. The complete mtDNA sequence of 14 individuals (12 NA yak, 1 Tibetan yak, 1 Tibetan B. indicus) was generated and compared with sequences of similar species from GeneBank (B. indicus, B. grunniens (Chinese), B. taurus, B. gaurus, B. primigenius, B. frontalis, Bison bison, and Ovis aries). Individuals were aligned to the B. grunniens reference genome (ARS_UNL_BGru_maternal_1.0), which was also included in the analyses. The mtDNA genes were annotated using the ARS-UCD1.2 cattle sequence as a reference. Ten unique NA yak haplotypes were identified, which a haplotype network separated into two clusters. Variation among the NA haplotypes included 93 nonsynonymous single nucleotide polymorphisms. A maximum likelihood tree including all taxa was made using IQtree after the data were partitioned into twenty-two subgroups using PartitionFinder2. Notably, six NA yak haplotypes formed a clade with B. indicus; the other four haplotypes grouped with B. grunniens and fell as a sister clade to bison, gaur and gayal. These data demonstrate two mitochondrial origins of NA yak with genetic variation in protein coding genes. Although these data suggest yak introgression with B. indicus, it appears to date prior to importation into NA. In addition to contributing to our understanding of the species history, these results suggest the two major mtDNA haplotypes in NA yak may functionally differ. Characterization of the impact of these differences on cellular function is currently underway.

Improvement of fermentation quality and cellulose convertibility of Napier grass silage by inoculation of cellulolytic bacteria from Tibetan yak (Bos grunniens).

To isolate and identify cellulolytic bacteria from yak rumen and further evaluate the effects of the isolates on the silage quality, structural carbohydrates degradation and cellulose convertibility of Napier grass silage. Two out of 218 strains were selected based on their most extensive transparent zone and the highest filter paper disintegration rate. The two isolates (JFL12 and JF85) could grow normally at 15-55°C, pH 3·0-7·0 and NaCl (3·0, 6·5%), and were identified as Enterococcus casseliflavus and Enterococcus faecalis by 16S rDNA sequence analysis, respectively. Napier grass was ensiled with no additive control (C), Lactobacillus plantarum (Lp), JFL12, JF85, JFL12+Lp and JF85+Lp for 3, 5, 7, 14, 30 and 60days. All inoculated silages had higher lactic acid content, lower pH, ammonia nitrogen (NH3 -N) and lignocellulose contents than the control silage. Silages treated with JFL12+Lp and JF85+Lp had the lowest pH and NH3 -N contents, the highest lactic acid content and lignocellulose degradation among all treatments. The isolates with or without Lp significantly (P<0·01) increased water soluble carbohydrates (WSC), glucose, fructose and sucrose contents as compared with the control silage. Silages treated with JFL12+Lp and JF85+Lp had higher glucose yield and cellulose convertibility than the other silages. Therefore, the application of isolates (JFL12 and JF85) with Lp had synergistic effects on accelerating the degradation of structural carbohydrates and improving the silage quality. Napier grass presents difficulty to ensiling due to its low WSC and high structural carbohydrates contents. The screened cellulolytic bacteria could be a candidate strain in improving fermentation quality and structural carbohydrates degradability of ensiled forages.

High-throughput sequencing approach to reveal the bacterial diversity of traditional yak jerky from the Tibetan regions

A high-throughput sequencing approach was used to investigate the bacterial community diversity of traditional Tibetan yak jerky, which was collected from three different regions in Tibet and with different natural drying times. Tibetan yak jerky from different regions had different bacterial communities, which was mainly reflected in the relative abundance levels of unclassified Cyanobacteria, Psychrobacter and Acinetobacter. The unclassified Cyanobacteria was the dominant genus of Qamdo yak jerky, Acinetobacter was the dominant genus of Shigatse yak jerky, and Psychrobacteria was the dominant genus of Nyingchi yak jerky. With increasing natural drying time, the diversity of bacterial communities in yak jerky decreased, and unclassified Cyanobacteria become the dominant genus. Spearman's correlation analysis and canonical correspondence analysis revealed that physicochemical factors (moisture content, water activity, shear force and pH) were significantly correlated with bacterial community. Our results will be beneficial to improve and standardize the safety and quality of traditional Tibetan yak jerky.

Biochar from pyrolyzed Tibetan Yak dung as a novel additive in ensiling sweet sorghum: An alternate to the hazardous use of Yak dung as a fuel in the home

Yak dung is used as fuel in Tibetan homes; however, this use is hazardous to health. An alternative use of the dung that would be profitable and offset the loss as a fuel would be very beneficial. Sweet sorghum silage with yak dung biochar as an additive was compared with a control silage with no additives and three silages with different commercial additives, namely Lactobacillus buchneri, Lactobacillus plantarum and Acremonium cellulase. Biochar-treated silage had a significantly greater concentration of water-soluble carbohydrates than the other silages (76 vs 12.4–45.8 g/kg DM) and a greater crude protein content (75.5 vs 61.4 g/kg DM), lactic acid concentration (40.7 vs 27.7 g/kg DM) and gross energy yield (17.8 vs 17.4 MJ/kg) than the control silage. Biochar-treated and control silages did not differ in in vitro digestibility and in total gas (507 vs 511 L/kg DM) and methane production (57.9 vs 57.1 L/kg DM). Biochar inhibited degradation of protein and water-soluble carbohydrates and enhanced lactic acid production, which improved storability of feed. It was concluded that yak dung biochar is an efficient, cost-effective ensiling additive. The profit could offset the loss of dung as fuel and improve the health of Tibetan people.