White Yak Research Articles

Ultrasound-assisted thawing of frozen white yak meat: Effects on thawing rate, meat quality, nutrients, and microstructure

The objective of this study was to assess the effects of ultrasound-assisted thawing (UAT) on the quality of longissimus dorsi muscles from white yak meat (WYM). Ultrasonic power levels of 0, 200, 400, and 600 W (frequency of 20 kHz) were used to assist thawing. The thawing rate, meat quality, nutrient substances, volatile compounds, and microstructure of the WYM were determined. The results showed that ultrasonic thawing treatment reduced thawing times by 30.95–64.28% compared to control. The meat quality results revealed that the thawing loss, cooking loss, L* and b* values, and pH values decreased significantly while the a* value and cutting force increased significantly (P < 0.05) at the lower 400 W power level compared with the control. In addition, the free amino acid (FAA), mineral, and vitamin (especially water-soluble vitamins) contents were significantly (P < 0.05) increased with the ultrasound treatment. UAT significantly (P < 0.05) increased the content of volatile compounds, an effect that was highest in the UAT-400 W group. Partial least squares discrimination analysis (PLS-DA) showed that 2,4-heptadienal was critical in distinguishing the UAT groups from the control. When the ultrasonic power was lower than 400 W, the muscle cell area was significantly (P < 0.05) increased but decreased when higher power was used. Therefore, UAT improves the thawing efficiency and quality of frozen WYM, particularly at a power level of 400 W, and these findings have potential applications in the meat industry.

Variation in the yak lipin-1 gene and its association with milk traits.

The aim of this research was to identify variation in the yak lipin-1 gene (LPIN1) and determine whether this variation affects milk traits. PCR-single stranded conformational polymorphism (PCR-SSCP) analysis was used to detect variation in the 5' untranslated region of LPIN1 in 500 yaks from four populations: Tianzhu white yaks, Qinghai yaks, wild × domestic-cross yaks and Gannan yaks. Four unique PCR-SSCP patterns, representing four different DNA sequence variants (named A, B, C and D), were observed. These contained six single nucleotide polymorphisms. Female Gannan yaks with BC genotype produced milk with a higher fat content (P < 0.001) and total milk solids (P < 0.001), than those with the AA, AB and BB genotypes. These results would suggest that LPIN1 is having an effect on yak milk fat synthesis.

Mitochondrial genome evidence suggests Cooperia sp. from China may represent a distinct species from Cooperia oncophora from Australia

Cooperia spp. are parasitic nematodes parasitizing in small intestine of ruminants with a worldwide distribution. Infection of ruminants with Cooperia species can cause severe enteritis, causing significant socio-economic losses to the livestock industry. However, it is yet to know whether there is genetic diversity in mitochondrial (mt) DNA sequences of Cooperia nematodes from different geographic regions. The objective of the present study was to examine sequence difference in mt genomes between Cooperia sp. from China and other Cooperia species. We determined the sequences of the internal transcribed spacer (ITS-1 and ITS-2) of nuclear ribosomal DNA (rDNA) of 11 Cooperia specimens collected from the small intestine of a Tianzhu White yak in Gansu Province, northwestern China, which had 99% similarity with that of C. oncophora from Brazil (GenBank accession Number: AJ544290) in ITS-1, and 99% similarity with those from Denmark (AB245040), Scotland and Australia (AJ000032) in ITS-2, indicating that specimens used in the present study should at least represent parasites in Cooperia. We then determined the complete mt genome sequences of one representative specimen of Cooperia sp. from China (CspC), compared the mt DNA sequences with that of C. oncophora from Australia (COA, GQ888713), and conducted phylogenetic analysis with selected nematodes using both maximum likelihood (ML) and Bayesian inference (BI) methods based on both concatenated 12 PCGs, rrnL and rrnS sequences and partial cox2 sequences. The complete mt genome sequence of CspC (KY769271) is 13, 583 bp in length, which is 91 bp shorter than that from COA. The sequence difference over the entire mt genome between CspC and COA was 12.2% in nucleotide and 6.3% in inferred amino acids, with nad4L and nad1 being the most variable and the most conserved PCGs, respectively. Phylogenetic analysis indicated that CspC and COA were closely-related but distinct taxa. The determination of mt genome sequences for Cooperia sp. from China also provides novel resources for further studies of taxonomy, systematics and population genetics of Cooperia from different geographical locations.

Screening for signatures of selection of Tianzhu white yak using genome-wide re-sequencing.

The Tianzhu white yak, a domestic yak indigenous to the Qilian Mountains, migrated inland from the Qinghai-Tibet Plateau. Specific ecological and long-term artificial selection influenced the evolution of its pure white coat and physiological characteristics. Therefore, it is not only a natural population that represents a genomic selective region of environmental adaptability but is also an animal model for studying the pigmentation of the yak coat. A total of 24261829 variants, including 22445252 SNPs, were obtained from 29 yaks by genome-wide re-sequencing. According to the results of a selective sweep analysis of Tianzhu white yak in comparison to Tibetan yaks, nine candidate genes under selection in Tianzhu white yak were identified by combining π, Tajima's D, πA/πB and FST statistics, with threshold standards of 5%. These genes include PDCD1, NUP210, ABCG8, NEU4, LOC102287650, D2HGDH, COL4A1, RTP5 and HDAC11. Five of the nine genes were classified into 12 molecular signaling pathways, and most of these signaling pathways are involved in environmental information processing, organismal systems and metabolism. A majority of these genes has not been implicated in previous studies of yak coat color and high-altitude animals. Our findings are helpful not only for explaining the molecular mechanism of yak coat pigmentation but also for exploring the genetic changes in Tianzhu white yak due to environmental adaptation.

Experimental investigations on microstructures and mechanical properties of white yak horns sheath

Abstract The horns of male bovines often show excellent mechanical properties due to the hierarchical microstructures. In this paper, the mechanical properties of white yak horn sheaths were studied by tensile and compressive tests, the moisture effect on the fracture toughness of the yak horn sheaths was explored through the three-point bending test. Meanwhile, in order to reveal the relation between the microstructure damages and the macroscopic mechanical properties of yak horn sheaths, the fracture surface of the tensile specimens was observed by scanning electron microscope (SEM). From the experimental results, it follows that the yak horn sheath was found to have a multiscale damage mode, including delamination of lamellae (macroscale), shear deformation of the scales and distortion of the hollow cavities (mesoscale), and matrix cracking and fiber filaments pull-out (microcosmic). Besides, the horn sheath was observed to have a typical laminated structure with interlaminar cavities extending along the growth direction of the horn. The laminated structures and cavities have the potential of energy absorption and can lead to higher energy dissipation, which helps toughen the horn sheath.

Proteomic analysis of Tianzhu White Yak (Bos grunniens) testis at different sexual developmental stages.

To explore the protein expression profiles of white yak (Bos grunniens) testis at different sexual developmental stages. The protein profiles of yak testis were determined using two-dimensional electrophoresis and the expression levels of 298 protein spots were analyzed. Mass spectrometry was performed to identify those significantly differential expressed proteins; Western blotting was used to confirm the results. During the developmental stages, 29 protein spots showed more than twofold differences (p<0.05) at ≥1 time point and were successfully identified. Two proteins were upregulated with age (category 1), five proteins (17.2%) were downregulated with age (category 2), four proteins were upregulated before 4years of age and downregulated thereafter (category 3), fifteen proteins were upregulated before 2years of age and downregulated thereafter (category 4), and three proteins fluctuated with age (category 5). The expression patterns of regucalcin and heat shock 60kDa protein in category 2 were confirmed. The 29 differentially expressed proteins from yak testes (some had more than one function) were categorized into binding (n=15), catalytic activity (n=13), molecular function regulator (n=4), antioxidant (n=4), molecular transducer (n=2), transporter (n=1), and structural molecule (n=1). The identification and analysis of these testis proteins may assist in understanding the developmental biology of reproduction system in male yak.

Hoof pressure and trampling intensity of yaks are higher than those of Tibetan sheep in a Tianzhu alpine meadow

Trampling by grazing animals exerts a comprehensive and serious effect on grassland vegetation and soil. In order to compare the trampling of yaks and Tibetan sheep under different grazing intensities, we examined the hoof pressure and trampling intensity (based on trampling area and hoof-print count) of white yaks (Poephagus grunniens) and Tibetan sheep (Ovis ammon) in an alpine meadow of Tianzhu County, Gansu Province, China, under conditions where either grazing area or livestock number were controlled. The average areas trampled by yaks and Tibetan sheep were 39.2 and 21.6 cm2 respectively. The average hoof pressure of yaks and Tibetan sheep were 6.89 and 3.13 kg cm–2 respectively. The yak-to-sheep ratio of the average area trampled was 1.81:1, whereas the yak-to-sheep ratio of average hoof pressure was 2.20:1. Average ingestion and walking trampling intensities of yaks were 384.8 × 103 and 247.1 × 103 kg cm–2, respectively, in controlled grazing areas, and 439.1 × 103 and 756.3 × 103 kg cm–2, respectively, in areas of controlled livestock numbers. These values for Tibetan sheep were 15.3 × 103 and 120.3 × 103 kg cm–2 in controlled grazing areas, and 42.6 × 103 and 128.2 × 103 kg cm–2 in areas of controlled livestock numbers. In controlled grazing areas, the ingestion and walking trampling intensities of yaks were 25.2 and 5.4 times higher, respectively, than those of sheep. Under areas of controlled livestock numbers, these values were 10.3 and 5.9 times higher, respectively, than those of sheep. The average trampling intensity of yaks was 7.3 times higher than that of the sheep. Therefore, under conditions of similar grazing intensity, yaks cause more damage than Tibetan sheep in alpine meadows.

Population genetic variations of the MMP3 gene revealed hypoxia adaptation in domesticated yaks (Bos grunniens).

ObjectiveAs an iconic symbol of Qinghai-Tibetan Plateau and of high altitude, yak are subjected to hypoxic conditions that challenge aerobic metabolism. Matrix metalloproteinases-3 (MMP3) is assumed to be a key target gene of hypoxia-inducible factor-1α that function as a master regulator of the cellular response to hypoxia. Therefore, the aim of this investigation was to identify the DNA polymorphism of MMP3 gene in domestic yak and to explore its possible association with high-altitude adaptation.MethodsThe single-nucleotide polymorphisms (SNPs) genotyping and mutations scanning at the MMP3 locus were conducted in total of 344 individuals from four domestic Chinese yak breeds resident at different altitudes on the Qinghai-Tibetan Plateau, using high-resolution melting analysis and DNA sequencing techniques.ResultsThe novel of SNPs rs2381 A→G and rs4331 C→G were identified in intron V and intron VII of MMP3, respectively. Frequencies of the GG genotype and the G allele of SNP rs2381 A→G observed in high-altitude Pali yak were significantly higher than that of the other yak breeds resident at middle or low altitude (p<0.01). No significant difference was mapped for SNP rs4331 C→G in the yak population (p>0.05). Haplotype GC was the dominant among the 4 yak breeds, and Pearson correlation analysis showed that the frequencies of GC was significantly lower in Ganan (GN), Datong (DT), and Tianzhu white yaks (TZ) compared with Pali (PL) yak. The two SNPs were in moderate linkage disequilibrium in high-altitude yaks (PL) but not in middle-altitude (GN, DT) and low-altitude (TZ) yaks.ConclusionThese results indicate that MMP3 may have been subjected to positive selection in yak, especially that the SNP rs2381 A→G mutation and GC haplotypes might contribute to adaptation for yak in high-altitude environments.

Comprehensive Analysis of MicroRNA⁻Messenger RNA from White Yak Testis Reveals the Differentially Expressed Molecules Involved in Development and Reproduction.

Testis development is a vital and tightly regulated process in mammals. Understanding the biological mechanisms underlying testis development will benefit the animal reproduction industry. Expression changes in microRNA and messenger RNA in response to dynamic regulation effects have been associated with this process. However, very little is known about the roles of these molecules in yak development. Using whole-genome small RNA and messenger RNA sequencing, we performed a comprehensive analysis of the microRNA–messenger RNA interaction network expression in the testicles of Tianzhu white yaks during three developmental stages. Using Short Time-series Expression Miner analysis we identified 589 differentially expressed microRNAs (DERs) and 3383 differentially expressed messenger RNAs (DEGs) in the three age groups. A total of 93 unique DEGs are primarily involved in reproduction and testis development. Subsequently, four integration networks were constructed according to the DEGs and DERs in three biological processes. Nineteen DEGs were potentially regulated by 60 DERs, of which miR-574 and target gene AURKA played a crucial role in yak testis development and reproduction. The results of this study provide a basis for further exploration of the microRNA–messenger RNA interactions in testis development and reproduction and aid in uncovering the molecular mechanisms of spermatogenesis in male mammals.

Molecular epidemiology and characterization of bovine leukemia virus in domestic yaks (Bos grunniens) on the Qinghai-Tibet Plateau, China.

Bovine leukemia virus (BLV) is a member of the genus Deltaretrovirus of the family Retroviridae and cause a chronic lymphosarcoma, which is extensive in cattle. In yaks (Bos grunniens), the distribution, strains and genetic characteristics of BLV have rarely been studied. The aim of our study was to investigate BLV infections in domestic yaks and determine the genetic variability of BLV circulating in a region of the Qinghai Tibet Plateau, China. Blood samples were collected from 798 yaks, which were from different farms from Gansu, Qinghai and Sichuan provinces surrounding the Qinghai-Tibet Plateau. Nested PCR targeting BLV long terminal repeats was used to detect the BLV provirus. The highest prevalence of BLV infection was in Gansu province, where it was 18.93% (39/206) in white yaks from Tianzhu City and 19.14% (31/162) in black yaks from Gannan City. In Qinghai and Sichuan provinces, the prevalence of BLV in black yaks was 14.83% (35/236) and 14.94% (29/194), respectively. The prevalence of BLV was not significantly different in yaks up to one year old than in older animals. Phylogenetic analysis was performed using 16 different env-gp51 (497-bp) gene sequences from the three provinces and 71 known BLV strains, which revealed that in both Gansu and Qinghai provinces, genotypes 6 and 10 of the BLV strains were at high levels, whereas only genotype 10 was prevalent in Sichuan Province. Phylogenetic analysis and sequence comparisons revealed 95.7-99.8% sequence identity among the full-length env genes of 16 strains, nearly full-length genome sequences of six BLV strains, and those of the known genotypes 6 and 10 of BLV. This study provides comprehensive information is regarding the widespread infection of domestic yaks with BLV on the Qinghai-Tibet Plateau of China, and shows that at least two BLV genotypes (genotypes 6 and 10) are circulating in this population.

Seroprevalence of and risk factors for Neospora caninum infection in yaks (Bos grunniens) in China

The aim of the present study was to detect the seroprevalence of Neospora caninum infection in yaks in Gansu province, China. Serum samples from 974 white yaks and 610 black yaks were tested by a commercial competitive-inhibition ELISA for the detection of specific anti-N. caninum antibodies.; N. caninum antibodies were detected in 10.4% of yaks with higher prevalence in black (11.5% of 610) than white yak (8.6% of 974). Age, regions and sampling times were considered as risk factors associated with N. caninum infection. These results revealed the seroprevalence of N. caninum in white yaks for the first time in China.

Molecular investigation of piroplasma infection in white yaks (Bos grunniens) in Gansu province, China

Piroplasmosis, including theileriosis and babesiosis, is a tick-borne haemoprotozoan disease responsible for huge economic losses to livestock industry. In China, the biology of piroplasms infective to cattle was well understood on the basis of pathogen isolations and molecular epidemiological surveys in the past few decades. But very limited information about the infection status of piroplasms in white yak (Bos grunniens), a semi-wild and endemic breed, has been recorded, so far. A total of 350 blood samples was collected from white yaks in 11 towns of Tianzhu Tibetan Autonomous County of Gansu province, China, during April to July 2015. The samples were tested using species-specific polymerase chain reaction (PCR) for Babesia bovis, B. bigemina, Theileria annulata, T. orientalis and T. sinensis. Positive samples were further sequenced and confirmed via sequence alignment. The results showed a high prevalence of piroplasms in the white yaks, 38.3%(134/350). Four Babesia/Theileria species were detected. The prevalences were 8.3% (B. bigemina), 7.7% (T. annulata), 9.7% (T. orientalis) and 26.0% (T. sinensis).No B. bovis-positive samples were detected. The single infections of B. bigemina, T. annulata, T. orientalis and T. sinensis were 2.3%, 2.6%, 5.1% and 16.9%, respectively. 11.4%(40/350) of these animals presented co-infections with 2 or 3 parasite species, in which 80.0% of co-infection had T. sinensis infection and no co-infections with 4 parasite species was detected. This is the first report to investigate the Babesia/Theileria infection in white yaks using molecular diagnostic method, for detection of B. bigemina, T. annulata, T. sergenti and T. sinensis. The findings also offer novel insights into the role of white yaks in Babesia/Theileria epidemiology and valuable information for the control and management of piroplasmosis in white yaks.

A Molecular Survey of Babesia Species and Detection of a New Babesia Species by DNA Related to B. venatorum from White Yaks in Tianzhu, China.

Bovine babesiosis is a tick-transmitted disease caused by different species of Babesia. The white yak is a unique yak breed that lives only in Tianzhu in the Tibetan Autonomous County, Gansu Province, in northwestern China. Previous research using the ELISA method has confirmed that the white yak could become infected with B. bigemina. The objective of this study was the molecular detection and identification of Babesia species in white yaks. A total of 409 white yak blood samples were collected from 11 areas of the Tianzhu Tibetan Autonomous County in Northwest China from April to August, 2015. The V4 hypervariable region of Babesia 18S rRNA was amplified from extracted genomic DNA using nested PCR and sequenced. The nearly full-length sequence of 18S rRNA including the V4 region from the newly discovered Babesia was amplified and sequenced with Sanger method. PCR detection and sequencing indicated that 4/409 samples were positive for B. bigemina, 3/409 samples were positive for B. bovis, and 5/409 samples were positive for B. ovata. Additionally, a new Babesia species was found in 4/409 white yaks. A unique sequence of 1,627 bp was obtained from two of the four samples. The sequence was similar to Babesia species Akita (98.5%) found in Ixodes ovatus and B. venatorum (98%) and shared a 98% identity with B. divergens and a 98.1% identity with B. odocoilei. This study provides new data about Babesia infections in white yaks in northwestern China, and a new Babesia species similar to B. venatorum was identified in white yaks for the first time.

Seroprevalence and Risk Factors of Fascioliasis in Yaks, Bos grunniens, from Three Counties of Gansu Province, China

The aim of this study was to determine the seroprevalence and risk factors of fascioliasis in yaks, Bos grunniens, from 3 counties of Gansu Province in China. A total of 1,584 serum samples, including 974 samples from white yaks from Tianzhu, 464 from black yaks from Maqu, and 146 from black yaks from Luqu County, were collected and analyzed using ELISA to detect IgG antibodies against Fasciola hepatica. The overall F. hepatica seroprevalence was 28.7% (454/1,584), with 29.2% in white yaks (284/974) and 27.9% in black yaks (170/610). The seroprevalence of F. hepatica in yaks from Tianzhu, Luqu, and Maqu was 29.2%, 22.6%, and 29.5%, respectively. Female yaks (30.9%) had higher F. hepatica seroprevalence than male yaks (23.4%). Also, F. hepatica seroprevalence varied by different age group from 24.1% to 33.8%. Further, the seroprevalence ranged from 21.8% to 39.1% over different seasons. Interestingly, the season and age of yaks were associated with F. hepatica infection in yaks in the investigated areas. These findings provided a basis for further studies on this disease in yaks from 3 counties of Gansu Province in northwestern China, which may ultimately support the development of effective control strategies of fascioliasis in these areas.

Detection of Enterocytozoon bieneusi in White Yaks in Gansu Province, China.

Enterocytozoon bieneusi, the most common zoonotic pathogen of microsporidiosis, has been found in various animals and humans, but no information is available concerning the prevalence and genotypes of E. bieneusi in white yaks (Bos grunniens). In the present study, 353 faecal samples from white yaks in Tianzhu Tibetan Autonomous County, Gansu Province, Northwestern China, were collected and examined by PCR amplification of the internal transcribed spacer gene to estimate E. bieneusi prevalence and identify their genotypes. Of the 353 faecal samples, 4 (1.13%) were tested E. bieneusi-positive. Sequences analysis revealed that two known genotypes, namely, I (n = 1) and BEB4 (n = 2), and a novel genotype, namely, WCY1 (n = 1), were found in this study. Among them, genotype WCY1 was clustered into Group 1, and genotypes I and BEB4 belonged to Group 2. The present study firstly indicates the existence of E. bieneusi in yaks in Gansu Province, Northwestern China. This is also the first record of E. bieneusi in white yaks. Effective measures should be taken to control E. bieneusi infection in white yaks, other animals, and humans.

Seroprevalence and risk factors of bovine viral diarrhoea virus (BVDV) infection in yaks (Bos grunniens) in northwest China.

Bovine viral diarrhoea virus (BVDV), a member of the Pestivirus genus, is an important pathogen of cattle worldwide, causing reproductive disorders in adult cattle and mucosal disease in calves. However, limited information about BVDV infection in yaks (Bos grunniens) in China is available, especially in white yaks which is a unique yak breed that only lives in Tianzhu Tibetan Autonomous County (TTAC), Gansu Province, northwest China. Therefore, we conducted a cross-sectional study to estimate the seroprevalence and risk factors associated with BVDV infection in 1584 yaks in Gansu province, northwest China, between April 2013 and March 2014 using an indirect ELISA test. The overall seroprevalence of BVDV in yaks was 37.56% (595/1584), with 45.08% (275/610) in black yaks and 32.85% (320/974) in white yaks. Moreover, positive yaks were found in all four regions, varied from 33.22 to 40.31%. Male yaks had a similar seroprevalence (37.84%) with that of the female yaks (37.11%). Season, species and geographical origins of yaks were considered as risk factors analyzed by logistic regression model. To our knowledge, this is the first report of seroprevalence and risk factors associated with BVDV infection in white yaks in China.

Comprehensive investigation of nucleotide diverdity in yaks.

To understand the maternal genetic diversity of Tianzhu white yak better, we analyzed mtDNA D-loop sequences of 209 Tianzhu white yaks, which are from the central region of Tianzhu white yak habitat. Accordingly, a total of 45 haplotypes were identified in Tianzhu white yaks in this study, and 18 of them were unique. The nucleotide diversity and haplotype diversity of population studied were 0.024±0.003 and 0.946±0.007 respectively, revealing that Tianzhu white yak possess a relatively high genetic diversity. The phylogenetic analysis, combining D-loop sequences in this study with 533 previous published D-loop sequences of 13 yak breeds, indicated that Tianzhu white yaks fell mainly into haplogroup A and that a small portion belonged to haplogroups B, C, D and E. Moreover, six haplotypes of 20 individuals identified in Tianzhu white yak were in the taurine haplogroup, indicating hybridization between Bos taurus and Tianzhu white yaks. In summary, this study supplies a comprehensive maternal genetic pattern for Tianzhu white yak and provides a basic reference for future breeding programs to conserve the purebred Tianzhu white yak.

First molecular survey and identification of Anaplasma spp. in white yaks (Bos grunniens) in China.

Anaplasmosis is caused by a group of obligate intracellular bacteria in the genus Anaplasma, which are transmitted by ticks and infect humans, domestic animals and wildlife. This study was conducted to determine the prevalence and molecular characterization of Anaplasma spp. in semi-wild white yaks sampled in Tianzhu Tibetan Autonomous County, northwest China. Out of 332 samples tested, 35 (10·9%) were positive for Anaplasma spp. The positive rates were 6·2% (20/322) and 5·3% (17/322) for Anaplasma bovis and Anaplasma phagocytophilum in white yaks, respectively. None of the sample was positive for Anaplasma marginale. Two (0·6%) samples were simultaneously positive to A. bovis and A. phagocytophilum. Sequence analysis of the 16S rRNA gene revealed two genotypes (ApG1 and ApG2) of A. phagocytophilum and two sequence types (ST1 and ST2) of A. bovis in white yaks. This study is the first to document the presence of Anaplasma in white yaks. Our findings extend the host range for Anaplasma species and provide more valuable information for the control and management of anaplasmosis in white yaks.

First Report of Bovine Leukemia Virus Infection in Yaks (Bos mutus) in China.

Enzootic bovine leukosis (EBL) is a chronic lymphosarcoma disease of cattle caused by bovine leukemia virus (BLV). No information is available concerning the epidemiology of BLV infection in yaks (Bos mutus). One thousand five hundred and eighty-four serum samples from 610 black yaks and 974 white yaks from Gansu province, northwest China, were collected between April 2013 and March 2014 and tested for BLV antibodies using a commercially available ELISA kit. The overall BLV seroprevalence in yaks was 21.09% (334/1584), with 24.26% (148/610) black yaks and 19.10% (186/974) white yaks yielding positive results. Risk factor analysis indicated that with the exception of breed (OR = 1.36, 95% CI = 1.06–1.73, P < 0.05), the age, region, gender, farm, and the numbers of pregnancies were not considered as risk factors for the presence of BLV in yaks included in this study. This is the first report of BLV infection in yaks in China, which provides information for controlling BLV infection in yaks.

Molecular characterization of Giardia duodenalis from white yaks in China.

Giardia duodenalis is one of the most common enteric parasites of humans and animals, including companion animals, livestock and wildlife. To date, the information about the prevalence and molecular characterization of G. duodenalis infection in white yaks was limited. In the present study, a total of 208 white yak fecal samples were collected from Tianzhu Tibetan Autonomous County (TTAC) between September 2013 and March 2014. Of the 208 white yak fecal samples, four samples (1.92%, all collected in March 2014) tested G. duodenalis-positive by PCR amplification of triosephosphate isomerase (tpi) gene. Sequence analysis confirmed the presence of G. duodenalis assemblage E. The present study revealed the presence and genotype of G. duodenalis in white yaks for the first time, and extended the host range of G. duodenalis. These results provided useful information for further genotyping or subtyping studies of G. duodenalis in white yaks.