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This experiment was designed to investigate the effects of cold season supplementation with different nutrient level diets on the production performance and apparent digestibility of nutrients and economic benefits of Tianzhu white yaks. Ten Tianzhu white yak bulls of 0.5, 2.5 and 4.5 years of age in good condition were selected and randomly divided into high nutritional level group (group H) and low nutritional level group (group L) for feeding, with 5 bulls in each group. The integrated net energy of feed (NEmf) of group H and group L were 97.84 MJ/kg and 81.54 MJ/kg, respectively, with a pre-feeding period of 15 d, and a positive test period of 90 d. The results showed that: daily weight gain, carcass weight, and slaughter rate of yaks at the three age between the two groups showed no significant differences (P>0.05), and the feed-to-weight ratio of the three age groups of group H was lower than that of group L yak. The apparent digestibility of dry matter and acid detergent fiber of group H at 0.5 years of age was extremely or significantly lower than that of group L (P<0.01 or P<0.05), and that the digestibility of dry matter and acid detergent fiber nutrients of group H at 2.5 years of age was significantly lower than that of group L (P<0.05), and the apparent digestibility of crude protein in group H at 4.5 years of age was highly significantly higher than that of group L, while the apparent digestibility of neutral detergent fiber was lower than that of group L (P<0.01). The apparent digestibility of dry matter, crude protein and neutral detergent fiber of yaks in groups H and L at different ages increased significantly with age (P<0.01 or P<0.05). The profit of group L was higher than that of group H in all three age groups when yaks were fed with equal amounts of diets. The results showed that 35∶65 of ratio of dietary concentrate to crude in the cold season could significantly improve the production performance and economic benefits of Tianzhu white yaks. [ABSTRACT FROM AUTHOR]

The experiment explored the effects of supplementing different energy levels of concentrate feed on the serum biochemical indicators, growth performance, and ruminal fermentation parameters of Tianzhu white yak. The experiment was divided into two periods: The first period involved concentrate supplementation during the winter and spring grazing period, and the second period was the lush grass grazing period without supplementation. A total of 30 healthy male Tianzhu white yak calves, aged six months and weighing (46.62±4.37) kg, were selected and randomly divided into three groups with five replicates in each group and two yaks in each replicate according to a randomized block design. The control group was normally grazed without concentrate supplementation, while the experimental group I and group II were supplemented with concentrate feeds with metabolizable energy of 10.83 and 11.76 MJ/kg after grazing, respectively. The initial feeding amount of concentrate was 0.70 kg per head, with an increase of 0.05 kg every 15 days, and the final supplementation amount was 1.20 kg per head. The experimental period was 365 days, with a supplementation period of 150 days during the winter and spring, and a normal grazing period of 215 days. The results showed that cold-season supplementation increased the weight and weight gain of yaks at 11, 12, and 18 months of age, and during the periods of 6~11 months and 12~18 months of age (P<0.05), with group II having higher weight and weight gain at all ages compared to group I (P<0.05). The Gompertz model fit better than the Bertalantty model for all groups, with the experimental groups having higher breakpoint weights and breakpoint months than the control group, and group II having the highest breakpoint weight and month. The ruminal fluid acetic acid content, acetic acid/propionic acid ratio, and pH value in groups I and II were lower than in the control group (P<0.05), while the concentrations of propionic acid, isobutyric acid, butyric acid, isovaleric acid, valeric acid, and ammonia nitrogen were higher than in the control group (P<0.05), and the ammonia nitrogen concentration in the group II was higher than that in the experimental group I (P<0.05). The serum glucose, total cholesterol, triglycerides, and total protein concentration in groups I and II were higher than in the control group (P<0.05). The study indicates that cold-season supplementation with different energy levels of concentrate feed promoted the growth and development of yak calves, altered the ruminal fermentation patterns, and serum biochemical indicators, with the supplementation of concentrate feed with a metabolizable energy of 11.76 MJ/kg showing better results. [ABSTRACT FROM AUTHOR]

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

Simple Summary: Skeletal muscle growth and development are closely related to the growth performance of livestock and poultry, and miRNAs are involved in skeletal muscle growth and development by negatively regulating target genes. In this study, the Gannan yak and the Tianzhu white yak which have large differences in production performance were used as research subjects. The difference of muscle fibers was analyzed by fiber staining. A total of 254 differentially expressed (DE) miRNAs were screened by transcriptome sequencing. Functional enrichment analysis revealed that the target genes were significantly enriched in muscle growth-related terms and pathways. By constructing a DE miRNA- DE mRNA interaction network, 18 key miRNAs related to muscle growth and development such as miR-3968-z, miR-2478-z, novel-m0143-3p, novel-m0024-3p, novel-m0128-5p, and novel-m0026-3p were screened. These results help us to explore the key influencing factors of skeletal muscle development in different breeds of yaks, and lay a foundation for further research on the molecular regulatory mechanisms of muscle growth and development. The Gannan yak, a superior livestock breed found on the Tibetan Plateau, exhibits significantly enhanced body size, weight, and growth performance in comparison to the Tianzhu white yak. MiRNAs play a pivotal role in regulating muscle growth by negatively modulating target genes. In this study, we found the average diameter, area, and length of myofibers in Gannan yaks were significantly higher than those of Tianzhu white yaks. Further, we focused on analyzing the longissimus dorsi muscle from both Gannan yaks and Tianzhu white yaks through transcriptome sequencing to identify differentially expressed (DE)miRNAs that influence skeletal muscle development. A total of 254 DE miRNAs were identified, of which 126 miRNAs were up-regulated and 128 miRNAs were down-regulated. GO and KEGG enrichment analysis showed that the target genes of these DE miRNAs were significantly enriched in signaling pathways associated with muscle growth and development. By constructing a DE miRNA- DE mRNA interaction network, we screened 18 key miRNAs, and notably, four of the candidates (novel-m0143-3p, novel-m0024-3p, novel-m0128-5p, and novel-m0026-3p) targeted six genes associated with muscle growth and development (DDIT4, ADAMTS1, CRY2, AKIRIN2, SIX1, and FOXO1). These findings may provide theoretical references for further studies on the role of miRNAs in muscle growth and development in Gannan yaks. [ABSTRACT FROM AUTHOR]

Abstract Background The 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). Results The hair length measurement result showed a significant difference between LHY and NHY on the forehead and the shoulder (P-value

Background: The 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). Results: The 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. Conclusions: The 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. [ABSTRACT FROM AUTHOR]

The Gannan yak, a superior livestock breed found on the Tibetan Plateau, exhibits significantly enhanced body size, weight, and growth performance in comparison to the Tianzhu white yak. MiRNAs play a pivotal role in regulating muscle growth by negatively modulating target genes. In this study, we found the average diameter, area, and length of myofibers in Gannan yaks were significantly higher than those of Tianzhu white yaks. Further, we focused on analyzing the longissimus dorsi muscle from both Gannan yaks and Tianzhu white yaks through transcriptome sequencing to identify differentially expressed (DE)miRNAs that influence skeletal muscle development. A total of 254 DE miRNAs were identified, of which 126 miRNAs were up-regulated and 128 miRNAs were down-regulated. GO and KEGG enrichment analysis showed that the target genes of these DE miRNAs were significantly enriched in signaling pathways associated with muscle growth and development. By constructing a DE miRNA- DE mRNA interaction network, we screened 18 key miRNAs, and notably, four of the candidates (novel-m0143-3p, novel-m0024-3p, novel-m0128-5p, and novel-m0026-3p) targeted six genes associated with muscle growth and development (DDIT4, ADAMTS1, CRY2, AKIRIN2, SIX1, and FOXO1). These findings may provide theoretical references for further studies on the role of miRNAs in muscle growth and development in Gannan yaks.

Abstract Background The hair coat is available for the yak to live in the harsh environment of the plateau. Besides, improving the hair production of yak is necessary for its textile industry development. Hair grows from hair follicles (HFs). The HFs undergo periodic growth after birth and are regulated by the complex gene regulatory network. However, the molecular mechanism of HFs regeneration in the Tianzhu white yak remains unclear. RNA editing is a post-transcriptional mechanism that regulates gene expression and produces new transcripts. Hence, we investigated the influence of the A-to-I RNA editing events on the HFs cycle of the Tianzhu white yak. Results We finally identified 54,707 adenosine-to-inosine (A-to-I) RNA editing sites (RESs) from RNA sequencing data of the HFs cycle in the Tianzhu white yak. Annotation results showed RESs caused missense amino acid changes in 7 known genes. And 202 A-to-I editing sites altered 23 target genes of 140 microRNAs. A total of 1,722 differential RESs were identified during the HFs cycle of Tianzhu white yak. GO and KEGG enrichment analysis revealed several signaling pathways and GO terms involved skin development, hair growth, and HFs cycle. Such as genes with differential RNA editing levels were significantly enriched in the peroxisome, metabolic pathways, Notch signaling pathway, and PPAR signaling pathway. Besides, the editing sites in HFs development-related genes FAS, APCDD1, WWOX, MPZL3, RUNX1, KANK2, DCN, DSC2, LEPR, HEPHL1, and PTK2B were suggested as the potential RESs involving HFs development. Conclusion This study investigated the global A-to-I RNA editing events during the HFs cycle of yak skin tissue and expanded the knowledge of A-to-I RNA editing on the HFs cycle. Furthermore, this study revealed that RNA editing-influenced genes may regulate the HFs cycle by participating in the HFs development-related pathways. The findings might provide new insight into the regulation of RNA editing in hair growth.

White coat pigmentation is a striking phenotype of many domesticated species and has various genetic controls. The Tianzhu White yak, an indigenous breed with a complete white coat, has fascinated Tibetans for centuries. However, the genetic basis of this trait remains unknown. Here, we conducted population genomics analysis and genome‐wide association study based on the whole‐genome sequencing data of 38 white and 59 non‐white‐coated yak. The results revealed the presence of KIT‐linked Cs alleles characterized by the translocations between chromosomes 6 and 29 in all‐white yak. Furthermore, structural variations showed additional duplications of the Cs alleles in white yak compared with colour‐sidedness cattle. Interestingly, the Cs alleles associated with the white coat phenotype in yak were found to have introgressed from taurine cattle. Our findings unveil the shared genetic control of the white coat phenotype and its evolution in closely related bovine species. [ABSTRACT FROM AUTHOR]

Background: The hair coat is available for the yak to live in the harsh environment of the plateau. Besides, improving the hair production of yak is necessary for its textile industry development. Hair grows from hair follicles (HFs). The HFs undergo periodic growth after birth and are regulated by the complex gene regulatory network. However, the molecular mechanism of HFs regeneration in the Tianzhu white yak remains unclear. RNA editing is a post-transcriptional mechanism that regulates gene expression and produces new transcripts. Hence, we investigated the influence of the A-to-I RNA editing events on the HFs cycle of the Tianzhu white yak. Results: We finally identified 54,707 adenosine-to-inosine (A-to-I) RNA editing sites (RESs) from RNA sequencing data of the HFs cycle in the Tianzhu white yak. Annotation results showed RESs caused missense amino acid changes in 7 known genes. And 202 A-to-I editing sites altered 23 target genes of 140 microRNAs. A total of 1,722 differential RESs were identified during the HFs cycle of Tianzhu white yak. GO and KEGG enrichment analysis revealed several signaling pathways and GO terms involved skin development, hair growth, and HFs cycle. Such as genes with differential RNA editing levels were significantly enriched in the peroxisome, metabolic pathways, Notch signaling pathway, and PPAR signaling pathway. Besides, the editing sites in HFs development-related genes FAS, APCDD1, WWOX, MPZL3, RUNX1, KANK2, DCN, DSC2, LEPR, HEPHL1, and PTK2B were suggested as the potential RESs involving HFs development. Conclusion: This study investigated the global A-to-I RNA editing events during the HFs cycle of yak skin tissue and expanded the knowledge of A-to-I RNA editing on the HFs cycle. Furthermore, this study revealed that RNA editing-influenced genes may regulate the HFs cycle by participating in the HFs development-related pathways. The findings might provide new insight into the regulation of RNA editing in hair growth. [ABSTRACT FROM AUTHOR]

The main cell types in the hair follicle development process of Tianzhu white yak during the catagen were analyzed at the single cell level，aiming to perform functional prediction and bioinformatics analysis on the characteristic genes of the main cell groups， and to explore the hair follicle development mechanism during catagen. Single cell RNA sequencing was used to analyze the heterogeneity of degenerative hair follicles during catagen，and known marker molecules were used to screen and identify cell groups. GO and KEGG analysis were performed on the main identified cell groups，and immune tissue analysis was performed on the key molecules involved in hair follicle morphogenesis. The results showed that catagen of Tianzhu white yak was involved in IFE-DC cells，epidermal cell lines，melanocytes， INFU and other cell groups. Its characteristic genes were mainly involved in biological processes such as epidermis development，epithelial cell differentiation，super fiber tissue development，tissue morphogenesis and cell morphology. KEGG enrichment analysis discovered that the characteristic genes were mainly enriched in adhesion connection，cell cycle，RNA transport and other pathways related to hair follicle development. The different involved cell types contained 28 common genes such as GJA1，FKBP4，KRT1，KRT80 and FGFR2. This study successfully identified the main cell groups of Tianzhu white yak during catagen，obtained the enrichment pathways of characteristic genes， and revealed the hair follicle development mechanism during catagen. [ABSTRACT FROM AUTHOR]

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 4 years of age and downregulated thereafter (category 3), fifteen proteins were upregulated before 2 years of age and downregulated thereafter (category 4), and three proteins fluctuated with age (category 5). The expression patterns of regucalcin and heat shock 60 kDa 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. [ABSTRACT FROM AUTHOR]

The aim of this study was to identify differentially expressed proteins in the follicular fluid of Tianzhu white yak during diestrus. Follicles obtained from female yak were divided into four groups according to their diameter: 0–2, 2–4, 4–6 mm, and greater than 6 mm. The follicular fluid was directly aspirated from the follicles and mixed according to follicular size, and two-dimensional gel electrophoresis was carried out on the crude follicular fluid samples. Thirty-four differentially expressed spots were generated from these four sizes of follicles. Fourteen of these spots were analyzed by MALDI-TOF/TOF-MS and identified as: AS3MT, VDP, ANKRD6, C10orf107 protein, MRP4, MAPKAP1, AGO3, profilin-β-actin, SPT2 homolog, AGP, AR, RNF20, obscurin-like-1, and one unnamed protein. These proteins were first reported in follicular fluid, in addition to VDP and AGP. Based on existing knowledge of their function and patterns of expression, we hypothesize that most of these differentially expressed proteins play a role in ovarian follicular growth and development, dominant follicle selection, or follicular atresia and development of oocytes; however, the function of the other differentially expressed proteins in reproduction remains ambiguous.

The IGF family is essential for normal embryonic and postnatal development and plays important roles in the immune system, myogenesis, bone metabolism and other physiological functions, which makes the study of its structure and biological characteristics important. Tianzhu white yak (Bos grunniens) domesticated under alpine hypoxia environments, is well adapted to survive and grow against severe hypoxia and cold temperatures for extended periods. In this study, a full coding sequence of the IGF2 gene of Tianzhu white yak was amplified by reverse transcription PCR and rapid-amplification of cDNA ends (RACE) for the first time. The cDNA sequence revealed an open reading frame of 450 nucleotides, encoding a protein with 179 amino acids. Its expression in different tissues was also studied by Real time PCR. Phylogenetic tree analysis indicated that yak IGF2 was similar to Bos taurus, and 3D structure showed high similarity with the human IGF2. The putative full CDS of yak IGF2 was amplified by PCR in five tissues, and cDNA sequence analysis showed high homology to bovine IGF2. Moreover the super secondary structure prediction showed a similar 3D structure with human IGF2. Its conservation in sequence and structure has facilitated research on IGF2 and its physiological function in yak.

Estrus refers to the phase when the female is sexually receptive and ovarian follicles are maturing under regulation by gonadotropic hormones. Pregnancy is the process of fertilization and development of offspring. To study the ovarian proteome changes of Tianzhu white yak between estrus and pregnancy, 12 ovaries from 6 pregnant and 12 ovaries from 6 estrous yak cows were used and ovarian proteins were separated by 2-DE and analyzed by PDQuest 8.0 software. 20 differentially expressed spots were identified with MALDI-TOF-TOF/MS. Totally 15 different proteins were detected. COMMD1, PMK, TM, CG, VIM, ALDH1A1, SNX7, MRPs, MDH were related to steroid hormone synthesis and regulation, energy metabolism, pregnancy maintenance and early embryo development. These differentially expressed proteins might be useful to detect protein candidates of ovarian function, clarify the mechanisms of ovarian development and understand the reproductive physiological mechanism of the Tianzhu white yak.

To estimate the phylotaxonomic position of Tianzhu white yak (Poephagus grunniens), multiple subunit genes of cytochromecoxidase (cox) were sequenced: 1545 bp ofcox1(JF946751), 684 bp ofcox2(JN008944) and 781 bp ofcox3(JF946752). Sequence divergences ofcoxgenes between yaks and cattle/zebus (5.7% incox1, 7.7% incox2and 6.45% incox3) were higher than those between yaks and American bisons (2.4% incox1, 3.0% incox2and 2.1% incox3). Molecular phylogenetic analysis with these genes also found that yaks and American bisons firstly clustered in one clade, indicating there was higher genetic comparability than that of cattle/zebus. The findings sustained the idea that in the choice of nomenclature yaks belong to the subgenus ofPoephagus.According to the nucleotide substitution rate ofcoxgenes among species of Bovinae, the speculated divergence time of yaks from cattle/zebus, American bisons, European bisons, Asian buffaloes/African buffaloes was 1.05–1.50 million years ago (MYA), 2.85–3.89 MYA, 2.90–3.70 MYA, 6.85–7.50 MYA, respectively. The sequential evolution of Bovinae members could be predicted that buffaloes were first to be domesticated during the end of Miocene and the early of Pliocene. In the end of Pliocene, the Bovinae genera were evolved toBos, BisonandPoephagus. Poephaguswas the latest evolved genera among the species of Bovinae. [ABSTRACT FROM AUTHOR]

In order to provide a scientific basis to develop and utilize the tail hair and dress hair of the Tianzhu white yak, the hair fiber structure and the similarities and differences of Tianzhu white yak was compared with human hair. Using optical microscopy, scanning electron microscopy, and ultrastructure of the performance of the amino acid analyzer, spectrum analyzer, the Tianzhu White yak dress hair, tail hair and human hair were observed. The results showed that the range of the tail hair, dress hair and human hair fiber fineness are from 52. 5 μm to 109. 8 μm, the content of the marrow wool is 1. 8% to 17%; the breaking force and elongation of the single fiber is greater than or equal to 60cN and 50%, respectively, three fibers are composed of 18 kinds of amino acids. The scales were arranged like clutter and the cross-section is oval or nearly circular. The performance and structure of the dress hair and tail hair of the Tianzhu white yak is similar to the human hair, the dress hair is more similar to the human hair, the is an ideal raw material, which to produce the ideal of high-end wig and suit lining raw materials. [ABSTRACT FROM AUTHOR]

The present study was carried out to investigate the efficiency of superovulation, oestrus synchronization, and embryo recovery in Tianzhu white yaks and also to confirm the pregnancy rate of black yaks, to which embryos collected from white yaks were transplanted. Forty-seven yaks were selected from different experiment groups, including 10 Tianzhu white female yaks (donor, group A) and 37 black female yaks (recipient, groups B and C). Superovulation of the donor was induced by the application procedure of CIDR-B + FSH + PG. Oestrus synchronization of recipients was induced using two methods: group B was given the same treatment as group A, except that the follicle-stimulating hormone (FSH) injection was not administered, whereas group C was injected with cloprostenol only once when corpus luteum (corpora lutea) was (were) palpated. The results showed that the oestrous rates in group A were higher (80%) than those in group B (60%) and group C (44.5%). As for the efficiency of superovulation, it was indicated that the mean numbers (±SD) of total corpora lutea, follicles, viable (transferable), and degenerated embryos were 4.75 ± 2.19, 1.13 ± 0.83, 2.50 ± 1.31, and 1.38 ± 0.92, respectively. The mean embryo recovery rates were 55.6%. All together, 18 viable embryos of Tianzhu white yak were obtained and 12 of them were transplanted to 10 recipients. The pregnancy rate was 50% and the delivery rate was 40%. [ABSTRACT FROM AUTHOR]

The regulatory mechanisms controlling post-natal muscle development in the yak (Bos grunniens) are still largely unknown, yet the growth and development of muscle is a complex process that plays a crucial role in determining the yield and quality of an animal's meat. In this study, we performed a transcriptome analysis based on the RNA sequencing (RNA-Seq) of yak longissimus dorsi muscle tissue obtained from calves (6 months of age; 6 M), young adults (30 months of age; 30 M) and adult (54 months of age; 54 M) to identify which genes are differentially expressed and to investigate their temporal expression profiles. In total, 1788 differentially expressed genes (DEGs) (|log2FC| ≥ 1, P-adjusted < 0.05) were detected by pairwise comparisons between the different age groups. The expression levels of 10 of the DEGs were confirmed using reverse transcription-quantitative PCR (RT-qPCR), and the results were consistent with the transcriptome profile. A time-series expression profile analysis clustered the DEGs into four groups that could be divided into two classes (P < 0.05): class 1 profiles, which had up-regulated patterns of gene expression and class 2 profiles, which featured down-regulated patterns. Based on that cluster analysis, GO enrichment analysis revealed 1073, 127, and 184 terms as significantly enriched in biological process (BP), cellular component (CC), and molecular function (MF) categories in the class 1 profiles, while 714, 66, and 206 terms were significantly enriched in BP, CC, and MF in the class 2 profiles. A KEGG pathway analysis revealed that DEGs from the class 1 profiles were enriched in 62 pathways, with the most enriched being the phosphoinositide 3-kinase (PI3K) - protein kinase B (Akt)-signaling pathway. The DEGs from the class 2 profiles were enriched in 16 pathways, of which forkhead box protein O (FoxO) - signaling was the most enriched. Taken together, these results provide insight into the mechanisms of skeletal muscle development, as well suggesting some potential genes of importance for yak meat production., (Copyright © 2022 Elsevier B.V. All rights reserved.)