Yak Population Research Articles

Genetic structure analysis of yak breeds and their response to adaptive evolution

Yaks are crucial genetic resources in the Tibetan Plateau and surrounding regions. Throughout the long process of domestication, natural and artificial selection pressures have enabled yaks to demonstrate adaptive characteristics to the environment in terms of physiological structure and genetic molecules, but no systematic cell analysis has been carried out on this phenomenon of yaks. Here, the population structure and genetic diversity of yak were studied by WGRS, and the genes related to yak adaptability were excavated. Combined with scRNA-seq method, the transcription map of yak lung tissue and skin tissue was constructed, which provided a new comprehensive insight into yak adaptability. The analysis of yak population structure showed that there was obvious genetic differentiation between TZ _ yak and other seven yak populations, while there was significant genetic exchange between PL _ yak and SB _ yak at high altitude. WGRS and scRNA-seq analysis revealed that the gene HIF1A related to high altitude adaptation was expressed in various cell types, while EPAS1 was predominantly expressed in epithelial and endothelial cells of yak lung tissue. Endothelial cells play a critical role in hypoxia-adapted VEGF signaling, which correlates closely with the high expression of KDR and VEGFA genes in endothelial cells and monocytes. Furthermore, in the selection signal of High _ yak vs Low _ yak, 19.8 % of the genes overlapped with the genes screened by skin scRNA-seq, including genes related to coat color such as RORA, BNC2, and KIT. Notably, BNC2 is a gene associated with melanin deposition and shows high expression levels in HS cells. Additionally, GRN in melanocytes and SORT1 in IRS play an important role in cell communication between melanocytes and IRS. These findings offer new insights into the natural polymorphism of yaks and provide a valuable reference for future research on high-altitude mammals, and potentially even human genetics.

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.

Integrative analysis of Iso-Seq and RNA-seq data reveals transcriptome complexity and differential isoform in skin tissues of different hair length Yak

BackgroundThe hair follicle development process is regulated by sophisticated genes and signaling networks, and the hair grows from the hair follicle. The Tianzhu white yak population exhibits differences in hair length, especially on the forehead and shoulder region. However, the genetic mechanism is still unclear. Isoform sequencing (Iso-seq) technology with advantages in long reads sequencing. Hence, we combined the Iso-seq and RNA-seq methods to investigate the transcript complexity and difference between long-haired yak (LHY) and normal-haired yak (NHY).ResultsThe hair length measurement result showed a significant difference between LHY and NHY on the forehead and the shoulder (P-value < 0.001). The skin samples from the forehead and the shoulder of LHY and NHY were pooled for isoform sequencing (Iso-seq). We obtained numerous long transcripts, including novel isoforms, long non-coding RNA, alternative splicing events, and alternative polyadenylation events. Combined with RNA-seq data, we performed differential isoforms (DEIs) analysis between LHY and NHY. We found that some hair follicle and skin development-related DEIs, like BMP4, KRT2, IGF2R, and COL1A2 in the forehead skin; BMP1, KRT1, FGF5, COL2A1, and IGFBP5 in the shoulder skin. Enrichment analysis revealed that DEIs in both two comparable groups significantly participated in skin and hair follicle development-related pathways, like ECM-receptor interaction, focal adhesion, and PI3K-Akt signaling pathways. The results indicated that the hair follicle development of Tianzhu white yak may influence the hair length difference. Besides, the protein-protein interaction (PPI) network of DEIs showed COL2A1 and COL3A1 exhibited a high degree of centrality, and these two genes were suggested as potential candidates for the hair length growth of Tianzhu white yak.ConclusionsThe results provided a comprehensive analysis of the transcriptome complexity and identified differential transcripts that enhance our understanding of the molecular mechanisms underlying the variation in hair length growth in Tianzhu white yak.

Yak Herding as the Main Source of Livelihood: Examining Challenges and Opportunities of Highlanders in Bhutan

Yak farming is the mainstays of nomadic herders’ economy in Bhutan. However, it has declined over the years despite diverse government interventions. Rapid socio-economic development and access to economic opportunities further hindered yak farming culture rather than helping to maintain highlanders’ livelihood. The study was carried out in four gewogs, Chhoekhor, Sephu, Merak and Sakteng, that depends on yaks for their living. Questionnaire based semi-structured interview was conducted to identify the main challenges and opportunities of yak herding within the different regions and examined the cost-benefit of herding yaks within the premises of nomadic herder’s livelihood sustenance. The study revealed that yak farming generates sufficient income to support the herders’ livelihood even though the profit margin was minimal. Around 90% of herders earned cash income from yaks. Dry cheese was the main revenue generator of Chhoekhor and Sephu, while fermented cheese earnt the highest income in Merak and Sephu. Yaks not only serve as the primary source of livelihood but also acts as a catalyst to generate additional income by gaining access to natural resources such as Cordyceps and herbal medicines. However, increased wildlife depredation on yaks and inadequate pastureland coupled with poor modern amenities threatened yak farming. The findings showed a declining trend in total yak population and number of yak-owning households particularly in Chhoekhor and Sephu compared to Merak and Sakteng. The future of yak farming in Bhutan is uncertain, but there is potential to address the challenges and ensure its continued importance to Bhutanese highlanders.

Can the Bhutan Yak Federation Revitalize Waning Yak Herders’ Enthusiasm and Rejuvenate the Declining Yak Farming in Bhutan

Yaks, native to Bhutan and other Himalayan regions, play a crucial role in the livelihoods of highlanders, serving as a sources of milk products, meat, transportation, fiber, and even dung used as fuelwood for cooking. Concerned about the perceived decline in the country’s yak population, the Bhutan Yak Federation (BYF) was established in 2019 to support highlanders. Presently, the BYF consists of 268 males and 203 females, representing 1067 yak rearing households. Its primary objectives include advocating for policy and investment support and promoting yak farming as a vibrant and sustainable enterprise. To gain a deeper understating of BYF’s roles and functions, this study focused on the Lingshi and Sephu yak cooperatives under the Thimphu and Wangduephodrang districts, conducting phone interviews with 40 cooperative members. The study revealed that highlanders primarily generate income through the sale of cordyceps, followed by yak products, portering services, and medicinal plants collection.

Whole-genome resequencing reveals the uniqueness of Subei yak.

Subei yak is an essential local yak in the Gansu Province, which genetic resource has recently been discovered. It is a meat-milk dual-purpose variety with high fecundity and relatively stable population genetic structure. However, its population genetic structure and genetic diversity are yet to be reported. Therefore, this study aimed to identify molecular markers of Subei yak genome by whole-genome resequencing, and to analyze the population structure and genetic diversity of Subei yak. This study screened 12,079,496 single nucleotide polymorphism (SNP) molecular markers in the 20 Subei yaks genome using whole-genome resequencing technology. Of these SNPs, 32.09% were located in the intronic region of the genome. Principal component analysis, phylogenetic analysis, and population structure analysis revealed that the Subei yak belonged to an independent group in the domestic yak population. A selective clearance analysis was carried out on Subei yak and other domestic yaks, and the genes under positive selection were annotated. The functional enrichment analysis showed that Subei yak possessed prominent selection characteristics in terms of external environment perception, hypoxia adaptation, and muscle development. Furthermore, Subei yak showed excellent muscle fat deposition and meat quality traits. Thus, this study will serve as a reference for discovering population structure, genetic evolution, and other unique traits of Subei yak and for expanding the genetic variation catalog of yaks.

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.

Indicators of production use and yaks immunity of the Central Ciscaucasia

The purpose of the research is to study the main production indicators and immunological status of the breeding stock of yaks of the Sarlyk breed living in the Central Ciscaucasia. The object of the investigation was the animals of LLC «Mountain-Alpine», LLC «Garant A», LLC «Selskie Dary», and LLC «Business Group», located in Chereksky district of the Kabardino-Balkarian Republic. The breeding population of yaks in the region is more than 7,500 heads, of which 4,123 are yak-cows. The share of breeding sires is accounted of 217 heads, which is 2.9% more than the total yak population. Milk production of yak-cows is fluctuated on approximately the same level on farms and amount to 179-184 kg. For every 100 yak-cows in analyzed organizations were obtained at least 88 calves, and more than 98% of young animals were preserved for weaning. Species from all farms were distinguished by the optimal duration of the calving intervals, which made it possible to produce one calf per year from them within 12-13 months. More preferable values for the period between calving were observed among representatives from LLC Garant A (358 days) for all other things being equal. It was established that cows were eliminated from the herds at the age of 3.2-3.8 calving, and they were used longer by 0.4-0.6 calving in LLC «Selskie Dary» and LLC «Garant A» regardless of organizational affiliation. The most common reasons for attrition were injuries and diseases of the limbs. Yak -cows of all breeding reproducers were characterized by high humoral and cellular immunity.

Molecular Cloning and Functional Characterization of the 5′ Regulatory Region of the SLC11A1 Gene from Yaks

The solute transport protein family 11 A1 (SLC11A1), also recognized as natural resistance-associated macrophage protein 1 (NRAMP1), represents a transmembrane protein encoded by the SLC11A1 gene. A variety of prior investigations have illuminated its involvement in conferring resistance or susceptibility to bacterial agents, positioning it as a promising candidate gene for breeding disease-resistant animals. Yaks (Bos grunniens), renowned inhabitants of the Qinghai-Tibet Plateau in China, stand as robust ruminants distinguished by their adaptability and formidable disease resistance. Notwithstanding these unique traits, there is scant literature on the SLC11A1 gene in the yak population. Our inquiry commences with the cloning of the 5′ regulatory region sequence of the Zhongdian yak SLC11A1 gene. We employ bioinformatics tools to identify transcription factor binding sites, delineating pivotal elements like enhancers and cis-acting elements. To ascertain the promoter activity of this region, we amplify four distinct promoter fragments within the 5′ regulatory region of the yak SLC11A1 gene. Subsequently, we design a luciferase reporter gene vector containing four site-specific deletion mutations and perform transient transfection experiments. Through these experiments, we measure and compare the activity of disparate gene fragments located within the 5′ regulatory region, revealing regions bearing promoter functionality and discerning key regulatory elements. Our findings validate the promoter functionality of the 5′ regulatory region, offering preliminary insights into the core and principal regulatory segments of this promoter. Notably, we identified single nucleotide polymorphisms (SNPs) that may be associated with important regulatory elements such as NF-1 and NF-1/L. This study provides a theoretical framework for in-depth research on the function and expression regulation mechanism of the yak SLC11A1 gene.

Characterization of a unique Sikkimese yak population of India: a multivariate approach

Native Sikkimese yak in Sikkim state of India is a pastoral treasure being raised through centuries-old transhumance practices and has evolved in response to natural and man-made selection. Currently, the population of Sikkimese yak is at risk with about five thousand total headcounts. Characterization is essential for taking appropriate decisions for conservation of any endangered population. In an attempt to phenotypically characterize the Sikkimese yaks, this study recorded phenotypic morphometric traits information, viz., body length (LG), height at withers (HT), heart girth (HG), paunch girth (PG), horn length (HL), horn circumference (HC), distance between horns (DbH), ear length (EL), face length (FL), face width (FW), and tail length with switch (TL), on 2154 yaks of both sexes. Multiple correlation estimation highlighted that HG and PG, DbH and FW, and EL and FW were highly correlated. Using principal component analysis, LG, HT, HG, PG, and HL were found to be the most important traits for phenotypic characterization of Sikkimese yak animals. Discriminant analysis based on different locations of Sikkim hinted at the existence of two separate clusters, however, broadly, phenotypic uniformity could be observed. Subsequent genetic characterization can offer greater insights and can pave the way for future breed registration and conservation of the population.

The Novel Structural Variation in the GHR Gene Is Associated with Growth Traits in Yaks (Bos grunniens)

The growth hormone receptor (GHR) is a member of the cytokine/hematopoietic factor receptor superfamily, which plays an important role in the growth and development, immunity, and metabolism of animals. This study identified a 246 bp deletion variant in the intronic region of the GHR gene, and three genotypes, including type II, type ID, and type DD, were observed. Genotype analysis of structural variation (SV) was performed on 585 individuals from 14 yak breeds, and it was found that 246 bp deletion was present in each breed. The II genotype was dominant in all yak breeds except for SB yak. The association analysis of gene polymorphisms and growth traits in the ASD yak population showed that the 246 bp SV was significantly associated with body length at 6 months (p < 0.05). GHR messenger RNA (mRNA) was expressed in all the tested tissues, with significantly higher levels in the liver, muscle, and fat than in other organs. The results of transcription activity showed that the luciferase activity of the pGL4.10-DD vector was significantly higher than that of the pGL4.10-II vector (p < 0.05). Additionally, the transcription-factor binding prediction results showed that the SV in the runt-related transcription factor 1 (Runx1) transcription-factor binding site may affect the transcriptional activity of the GHR gene, regulating yak growth and development. This study showed that the novel SV of the GHR gene could be used as a candidate molecular marker for the selection of the early growth trait in ASD yak.

Analysis of Copy Number Variation in the Whole Genome of Normal-Haired and Long-Haired Tianzhu White Yaks

Long-haired individuals in the Tianzhu white yak population are a unique genetic resource, and have important landscape value. Copy number variation (CNV) is an important source of phenotypic variation in mammals. In this study, we used resequencing technology to detect the whole genome of 10 long-haired Tianzhu white yaks (LTWY) and 10 normal-haired Tianzhu white yaks (NTWY), and analyzed the differences of CNV in the genome of LTWYs and NTWYs. A total of 110268 CNVs were identified, 2006 CNVRs were defined, and the distribution map of these CNVRs on chromosomes was constructed. The comparison of LTWYs and NTWYs identified 80 differential CNVR-harbored genes, which were enriched in lipid metabolism, cell migration and other functions. Notably, some differential genes were identified as associated with hair growth and hair-follicle development (e.g., ASTN2, ATM, COL22A1, GK5, SLIT3, PM20D1, and SGCZ). In general, we present the first genome-wide analysis of CNV in LTWYs and NTWYs. Our results can provide new insights into the phenotypic variation of different hair lengths in Tianzhu white yaks.

Evolutionary and genomic insights into the long-term colonization of Shigella flexneri in animals

ABSTRACT The enteroinvasive bacterium Shigella flexneri is known as a highly host-adapted human pathogen. There had been no known other reservoirs reported until recently. Here 34 isolates obtained from animals (yaks, dairy cows and beef cattle) from 2016 to 2017 and 268 human S. flexneri isolates from China were sequenced to determine the relationships between animal and human isolates and infer the evolutionary history of animal-associated S. flexneri. The 18 animal isolates (15 yak and 3 beef cattle isolates) in PG1 were separated into 4 lineages, and the 16 animal isolates (1 yak, 5 beef cattle and 10 dairy cow isolates) in PG3 were clustered in 8 lineages. The most recent human isolates from China belonged to PG3 whereas Chinese isolates from the 1950s–1960s belonged to PG1. PG1 S. flexneri may has been transmitted to the yaks during PG1 circulation in the human population in China and has remained in the yak population since, while PG3 S. flexneri in animals were likely recent transmissions from the human population. Increased stability of the large virulence plasmid and acquisition of abundant antimicrobial resistance determinants may have enabled PG3 to expand globally and replaced PG1 in China. Our study confirms that animals may act as a reservoir for S. flexneri. Genomic analysis revealed the evolutionary history of multiple S. flexneri lineages in animals and humans in China. However, further studies are required to determine the public health threat of S. flexneri from animals.

Домашний як и его гибрид в номадном стаде монголов и бурят

Goals. The article aims at characterizing a unique animal of Inner and Central Asian nomads — the domestic yak (sarlyk) and its hybrid (khainak) that have been bred by Mongols and Buryats for hundreds of years. The work provides a first ethnographic insight into statistical data on yak population dynamics in synchronous and diachronous perspectives, reviews adaptive properties of the animal instrumental in surviving in extreme conditions of highlands, its exterior, breeding and behavioral specifics, economic significance. Materials and methods. The article explores literary, field and online sources to employ the methodology of comparative analysis, in particular, the comparative-historical-genetic method. Materials about yak breeding among Turkic peoples are essentially verifying by nature. Results. When it comes to declare the five traditional types of livestock bred, Mongols and Buryats mention no yak, the latter be clustered with cattle. Mongolia’s yak population ranks second worldwide — after China. The post-Socialist era witnessed an increase in yak numbers in Mongolia paralleled by a decrease in Russia. Domestic yaks have unique adaptive properties towards low oxygen partial pressure, extreme cold, and meagre fodder resources. The incomplete domestication of animals is determined by high profitability via such extensive farming techniques. Being meat, dairy and working animals, sarlyks and khainaks were most essential to the traditional economy of nomads. In the 21st century, their products become exotic and environment friendly food items, while skin, hair, wool, undercoat and other components serve as unique raw materials for light industry, pharmacology and cosmetology. Conclusions. The 21st century Mongolia with its vast yak friendly territories witnesses a significant head increase resulting in industrial processing facilities of yak raw materials nationwide. In the 1980s, the Soviets were undertaking active purposeful efforts to develop yak breeding, while the free market period decreased both numbers of animals held by Buryats and their habitat. The situation is due to the lack of demand for yak products and the lack of infrastructure for industrial processing of raw materials. The domestic yak and its hybrid had made it possible for nomads of Inner Asia — Mongols and Buryats — to significantly extend economic boundaries of their ethnic territories and inhabit montane grasslands and shrublands.

Dynamics of livestock population in Himachal Pradesh

An attempt has been made to analyse the trends in livestock population in Himachal Pradesh in last two decades. Minor livestock species like Yak, Pig, Horse, Mule, Donkey and Camel population was excluded from the study as their all combined population accounted for only 1% of the total livestock population in the state in the 20th livestock census. The percent growth rates were calculated for all inter census period from 1997 to 2019. The study concluded that total livestock population in Himachal Pradesh has shown negative trend over the years 1997-2019. Except for the 190.2 % growth of crossbred/ exotic cattle population in the state, all other including Indigenous cattle, Buffalo, sheep and goat population has shown negative growth in the mentioned period i.e. 1997-2019. The recent census has recorded negative growth rate for all livestock species excluding crossbred cattle.

Sympatric Yaks and Plateau Pikas Promote Microbial Diversity and Similarity by the Mutual Utilization of Gut Microbiota.

Interactions between species provide the basis for understanding coexisting mechanisms. The plateau pika (Ochotona curzoniae) and the yak (Bos grunniens) are considered competitors because they have shared habitats and consumed similar food on the Qinghai–Tibetan Plateau for more than 1 million years. Interestingly, the population density of plateau pikas increases with yak population expansion and subsequent overgrazing. To reveal the underlying mechanism, we sequenced the fecal microbial 16S rDNA from both sympatric and allopatric pikas and yaks. Our results indicated that sympatry increased both gut microbial diversity and similarity between pikas and yaks. The abundance of Firmicutes, Proteobacteria, Cyanobacteria, and Tenericutes decreased, while that of Verrucomicrobia increased in sympatric pikas. As for sympatric yaks, Firmicutes, Bacteroidetes, and Spirochaetes significantly increased, while Cyanobacteria, Euryarchaeota, and Verrucomicrobia significantly decreased. In sympatry, plateau pikas acquired 2692 OTUs from yaks, and yaks obtained 453 OTUs from pikas. The predominant horizontally transmitted bacteria were Firmicutes, Bacteroidetes, Verrucomicrobia, and Proteobacteria. These bacteria enhanced the enrichment of pathways related to prebiotics and immunity for pikas, such as heparin sulfate, heparin, chitin disaccharide, chondroitin-sulfate-ABC, and chondroitin-AC degradation pathways. In yaks, the horizontally transmitted bacteria enhanced pathways related to hepatoprotection, xenobiotic biodegradation, and detoxification. Our results suggest that horizontal transmission is a process of selection, and pikas and yaks tend to develop reciprocity through the horizontal transmission of gut microbiota.

Geographical Detector-based influence factors analysis for Echinococcosis prevalence in Tibet, China.

Echinococcosis, caused by genus Echinococcus, is the most pathogenic zoonotic parasitic disease in the world. In Tibet of the People’s Republic of China, echinococcosis refers principally to two types of severe zoonosis, cystic echinococcosis (CE) and alveolar echinococcosis (AE), which place a serious burden on public health and economy in the local community. However, research on the spatial epidemiology of echinococcosis remains inadequate in Tibet, China. Based on the recorded human echinococcosis data, maps of the spatial distribution of human CE and AE prevalence in Tibet were produced at city level and county level respectively, which show that the prevalence of echinococcosis in northern and western Tibet was much higher than that in other regions. We employ a geographical detector to explore the influencing factors for causing CE and AE while sorting information on the maps of disease prevalence and environment factors (e.g. terrain, population, and yak population). The results of our analysis showed that biological factors have the most impact on the prevalence of echinococcosis, of which the yak population contributes the most for CE, while the dog population contributes the most for AE. In addition, the interaction between various factors, as we found out, might further explain the disease prevalence, which indicated that the echinococcosis prevalence is not simply affected by one single factor, but by multiple factors that are correlated with each other complicatedly. Our results will provide an important reference for the evaluation of the echinococcosis risk, control projects, and prevention programs in Tibet.

Molecular characterization and analysis of the association of growth hormone 1 gene with growth traits in Chinese indigenous yak (Bos grunniens)

This study aimed to investigate the effects of polymorphisms in growth hormone 1 (GH1) gene on the growth traits in Chinese indigenous yak. Using the polymerase chain reaction-restriction fragment length polymorphism (PCR-PFLP) approach, one novel single-nucleotide polymorphism (SNP), termed as g.1721G>A, was identified in the exon 4 of GH1 gene in 423 individuals of yak population. Based on the chi-square (χ2) test, the frequencies of g.1721G>A alleles agreed with Hardy-Weinberg equilibrium (HWE) (P < 0.05). A significant association was observed between this SNP and several growth traits (P < 0.01 or P < 0.05), in which the genotype GG exhibited the best values. The present study suggested that the identified SNP was a useful genetic marker for the improvement of growth traits in Chinese indigenous yak.

Accuracies of Genomic Prediction for Growth Traits at Weaning and Yearling Ages in Yak.

Simple SummaryGenomic selection is a new technology in animal breeding after the selection according to the best linear unbiased prediction (BLUP) value and marker assisted selection. Genomic selection has gradually been used in practical applications over recent years following the advent of high-density single nucleotide polymorphism (SNP) chips for livestock and poultry. Yak are a critical species on the Qinghai–Tibet Plateau, which is of great significance to herders. The early selection of yak could save feeding costs and shorten the generation interval. In the present study, we estimated the accuracy of genomic prediction compared with different classical models for yak early growth traits. The results of cross-validation indicated that the average predictive accuracy ranged from 0.147 to 0.391. The average correlation coefficient between prediction and true phenotype was 0.4.Genomic selection is a promising breeding strategy that has been used in considerable numbers of breeding projects due to its highly accurate results. Yak are rare mammals that are remarkable because of their ability to survive in the extreme and harsh conditions predominantly at the so-called “roof of the world”—the Qinghai–Tibetan Plateau. In the current study, we conducted an exploration of the feasibility of genomic evaluation and compared the predictive accuracy of early growth traits with five different approaches. In total, four growth traits were measured in 354 yaks, including body weight, withers height, body length, and chest girth in two early stages of development (weaning and yearling). Genotyping was implemented using the Illumina BovineHD BeadChip. The predictive accuracy was calculated through five-fold cross-validation in five classical statistical methods including genomic best linear unbiased prediction (GBLUP) and four Bayesian methods. Body weights at 30 months in the same yak population were also measured to evaluate the prediction at 6 months. The results indicated that the predictive accuracy for the early growth traits of yak ranged from 0.147 to 0.391. Similar performance was found for the GBLUP and Bayesian methods for most growth traits. Among the Bayesian methods, Bayes B outperformed Bayes A in the majority of traits. The average correlation coefficient between the prediction at 6 months using different methods and observations at 30 months was 0.4. These results indicate that genomic prediction is feasible for early growth traits in yak. Considering that genomic selection is necessary in yak breeding projects, the present study provides promising reference for future applications.

Yak genetic resources of India: distribution, types and characteristics

In India, the yaks are reared by the people residing between 3,000 and 5,000 meters above mean sea level in the states of Jammu-Kashmir, Himachal Pradesh, Uttrakhand, Sikkim, Arunachal Pradesh and West Bengal. Yaks thrive well in these extremely cold regions with hypoxic conditions providing milk, meat, hide, fibre, manure and draught power to the local population. They are able to withstand the fodder scarcity endemic to these regions in the winter months. The total yak population in our country is 0.76 lakhs. Jammu and Kashmir has the maximum population of yak (0.54 lakh), possessing about 71% of the total yak population of the country, followed by Arunachal Pradesh (18.34%) and Sikkim (5.26%). The milk yield per lactation in indigenous yaks is 250–500 kg in a lactation period of 260–300 days. The birth weight of indigenous yaks in males and females is 14.20±0.33 and 13.20±0.34 kg, which increases to 201.23±4.79 and 178.13±3.26 kg, respectively, at 2 years of age. Mainly, four types of Indian yaks have been described namely Arunachali, Ladakhi, Sikkimi and Himachali. Out of these, Arunachali yaks are the first and only recognized breed of Indian yaks. This review summarizes the population trends, attributes of indigenous yaks in general as well of specific types of indigenous yaks available in India.