Whole-genome scanning for the litter size trait associated genes and SNPs under selection in dairy goat (Capra hircus)

Analysis of genetic diversity and selection signatures on the Zhashi Brown goat through whole genome sequencing data

The Zhashi Brown goat is native to Hengyang Municipality in Hunan Province in southern China and boasts a rich history. The goats exhibit exceptional traits, including heat and insect resistance, strong reproductive capabilities and superior meat production. Despite these merits, the currently limited population requires immediate conservation endeavors. In this study, we conducted whole-genome resequencing on 21 Zhashi Brown goats. Additionally, we performed a joint analysis using published whole-genome data from 119 goats, including Chengdu Brown goat, Matou goat, Wuxue goat, Xiangdong Black goat, Qaidam Cashmere goat, Ujumqin Cashmere goat and Shanbei Cashmere goat. The results revealed that the Zhashi Brown goat is genetically more pure than other Southern Chinese goat breeds. Furthermore, the genetic diversity (nucleotide diversity, linkage disequilibrium, runs of homozygosity and inbreeding coefficient) of the Zhashi Brown goat's genome is at a low level among the eight breeds, indicating the need for further conservation. Employing analytical methodologies such as composite likelihood ratio, nucleotide diversity, integrated haplotype score, the fixation index and cross-population extended haplotype homozygosity, we systematically scanned selective signals within the genomic landscape of Zhashi Brown goat. The outcomes underscore strong selection signals associated with genes implicated in immune response, heat tolerance, reproductive performance and meat quality. These findings make a significant contribution to our understanding of the genetics framework associated with adaptive traits in Zhashi Brown goat. Furthermore, this study explores the genetic diversity of the Zhashi Brown goat, which may contribute to the theoretical framework for conserving its genetic resources, while the identified trait-associated variations could inform future strategies to optimize selective breeding programs.

Design and verification of a 25 K multiple-SNP liquid-capture chip by target sequencing for dairy goat

BACKGROUND

In the genetic breeding research of dairy goats, traditional genotyping methods have limitations, and existing goat chips have shortcomings in functional loci and other aspects, which cannot meet the precise genetic analysis needs of dairy goats. Genotyping by Target Sequencing (GBTS) in the new generation of sequencing technology provides the possibility to solve these problems.

RESULTS

A large number of candidate SNP sites related to important economic traits in dairy goats were identified through various analysis and screening methods. The chip ultimately retained 27,396 SNP sites for probe design, which can detect 46,459 SNPs. The site distribution is uniform, and the sequencing data efficiency, base quality, alignment rate, and other indicators are good. The chip SNP detection rate is high and the heterozygosity of gene typing is reasonable. GWAS was performed on 200 dairy goats for litter size and birth weight traits, and multiple genome-wide significantly related SNPs and related genes (litter size trait: SCAP, PTPN23, KIF9, ANTXRL, and GRID1. birth weight trait: NALCN, LRRN2, TMEM132D, COL5A2, and HS3ST1) were detected.

CONCLUSION

The 25 K multiplex SNP liquid phase capture chip designed in this study has excellent performance and is of great value for genetic research and breeding of dairy goats, providing strong support for the development of the dairy goat industry.

Potential Candidate Genes Associated with Litter Size in Goats: A Review

This review examines genetic markers associated with litter size in goats, a key reproductive trait impacting productivity in small ruminant farming. Goats play a vital socioeconomic role in both low- and high-income regions; however, their productivity remains limited due to low reproductive efficiency. Litter size, influenced by multiple genes and environmental factors, directly affects farm profitability and sustainability by increasing the output per breeding cycle. Recent advancements in genetic research have identified key genes and pathways associated with reproductive traits, including gonadotropin-releasing hormone (GnRH), inhibin (INHAA), Kit ligand (KITLG), protein phosphatase 3 catalytic subunit alpha (PPP3CA), prolactin receptor (PRLR), POU domain class 1 transcription factor 1 (POU1F1), anti-Müllerian hormone (AMH), bone morphogenetic proteins (BMP), growth differentiation factor 9 (GDF9), and KISS1 and suppressor of mothers against decapentaplegic (SMAD) family genes, among others. These genes regulate crucial physiological processes such as folliculogenesis, hormone synthesis, and ovulation. Genome-wide association studies (GWASs) and transcriptomic analyses have pinpointed specific genes linked to increased litter size, highlighting their potential in selective breeding programs. By incorporating genomic data, breeding strategies can achieve higher selection accuracy, accelerate genetic gains, and improve reproductive efficiency. This review emphasizes the importance of genetic markers in optimizing litter size and promoting sustainable productivity in goat farming.

The Evolution and Role of Molecular Tools in Measuring Diversity and Genomic Selection in Livestock Populations (Traditional and Up-to-Date Insights): A Comprehensive Exploration

Distinctive molecular approaches and tools, particularly high-throughput SNP genotyping, have been applied to determine and discover SNPs, potential genes of interest, indicators of evolutionary selection, genetic abnormalities, molecular indicators, and loci associated with quantitative traits (QTLs) in various livestock species. These methods have also been used to obtain whole-genome sequencing (WGS) data, enabling the implementation of genomic selection. Genomic selection allows for selection decisions based on genomic-estimated breeding values (GEBV). The estimation of GEBV relies on the calculation of SNP effects using prediction equations derived from a subset of individuals in the reference population who possess both SNP genotypes and phenotypes for target traits. Compared to traditional methods, modern genomic selection methods offer advantages for sex-limited traits, low heritability traits, late-measured traits, and the potential to increase genetic gain by reducing generation intervals. The current availability of high-density genotyping and next-generation sequencing data allow for genome-wide scans for selection. This investigation provides an overview of the essential role of advanced molecular tools in studying genetic diversity and implementing genomic selection. It also highlights the significance of adaptive selection in light of new high-throughput genomic technologies and the establishment of selective comparisons between different genomes. Moreover, this investigation presents candidate genes and QTLs associated with various traits in different livestock species, such as body conformation, meat production and quality, carcass characteristics and composition, milk yield and composition, fertility, fiber production and characteristics, and disease resistance.

Genomic Signatures of Domestication in European Seabass (Dicentrarchus labrax L.) Reveal a Potential Role for Epigenetic Regulation in Adaptation to Captivity

Genome scans provide a comprehensive method to explore genome-wide variation associated with traits under study. However, linking individual genes to broader functional groupings and pathways is often challenging, yet crucial for understanding the evolutionary mechanisms underlying these traits. This task is particularly relevant for multi-trait processes such as domestication, which are influenced by complex interactions between numerous genetic and non-genetic factors, including epigenetic regulation. As various traits within the broader spectrum of domestication are selected in concert over time, this process offers an opportunity to identify broader functional overlaps and understand the integrated genetic architecture underlying these traits. In this study, we analyzed approximately 600,000 SNPs from a Pool-Seq experiment comparing eight natural-origin and 12 farmed populations of European seabass in the Mediterranean Sea region. We implemented two genome scan approaches and focused on genomic regions supported by both methods, resulting in the identification of 96 candidate genes, including nine CpG islands, which highligt potential epigenetic influences. Many of these genes and CpG islands are in linkage groups previously associated with domestication-related traits. The most significantly overrepresented molecular function was "oxidoreductase activity". Furthermore, a dense network of interactions was identified, connecting 22 of the candidate genes. Within this network, the most significantly enriched pathways and central genes were involved in "chromatin organization", highlighting another potential epigenetic mechanism. Altogether, our findings underscore the utility of interactome-assisted pathway analysis in elucidating the genomic architecture of polygenic traits and suggest that epigenetic regulation may play a crucial role in the domestication of European seabass.

Genetic insights into litter size in goats: A meta-analysis of KISS1 and BMP15 SNP variants

Litter size is a key trait in livestock breeding. The BMP15 and KISS1 genes have been studied in goats, but results on their association with litter size are inconsistent. The objective of this study was to employ a meta-analysis approach to investigate the genetic relationship between the BMP15 (g.735 G>A) and KISS1 (g.2540 C>T and g.2510 G>A) genes and litter size in goats. A total of five studies (including 12 breeds) were included for the g.735 G>A mutation, three studies (including nine breeds) for g.2540 C>T, and two studies (including six breeds) for g.2510 G>A in this meta-analysis. The meta-analysis was conducted under four different genetic models: recessive (GG + AG vs. AA), dominant (GG vs. AG + AA), additive (GG vs. AA) and codominant (GG + AA vs. AG) models of inheritance. Data were analyzed under either random or fixed effects models based on the estimates of I2 estimates. A sensitivity analysis was performed by removing one study at a time to determine the stability of the overall results. Funnel plots and the Egger regression tests were also used to assess the publication bias among studies. Significant associations (P< 0.05) were observed between the g.2540 C>T and g.2510 G>A loci and litter size in goats under the additive (SMD = -0.469, 95 % CI = -0.908 to -0.030, P-value = 0.036) and codominant (SMD = 0.147, 95 % CI = 0.003-0.291, P = 0.046) genetic models, respectively. Our results did not identify any significant association between g.735 G>A of BMP15 and litter size under the investigated genetic models.

Telomere-to-telomere genome assembly of a male goat reveals variants associated with cashmere traits

A complete goat (Capra hircus) reference genome enhances analyses of genetic variation, thus providing insights into domestication and selection in goats and related species. Here, we assemble a telomere-to-telomere (T2T) gap-free genome (2.86 Gb) from a cashmere goat (T2T-goat1.0), including a Y chromosome of 20.96 Mb. With a base accuracy of >99.999%, T2T-goat1.0 corrects numerous genome-wide structural and base errors in previous assemblies and adds 288.5 Mb of previously unresolved regions and 446 newly assembled genes to the reference genome. We sequence the genomes of five representative goat breeds for PacBio reads, and use T2T-goat1.0 as a reference to identify a total of 63,417 structural variations (SVs) with up to 4711 (7.42%) in the previously unresolved regions. T2T-goat1.0 was applied in population analyses of global wild and domestic goats, which revealed 32,419 SVs and 25,397,794 SNPs, including 870 SVs and 545,026 SNPs in the previously unresolved regions. Also, our analyses reveal a set of selective variants and genes associated with domestication (e.g., NKG2D and ABCC4) and cashmere traits (e.g., ABCC4 and ASIP).

Genetic characterization and selection of litter size traits of Guizhou Black goat and Meigu goat

The aim of this study is to explore the genetic characteristics of Guizhou Black goats and Meigu goats and their relationship to reproductive performance through population structure analysis, genetic diversity assessment, and selection signal analysis. Blood samples of 19 Guizhou Black goats and 11 Meigu goats were collected for whole-genome high-throughput sequencing. Using PCA and ADMIXTURE analyses, their population structure and genetic relationships were revealed. Further genetic diversity analysis showed that although there is significant population differentiation, the levels of genetic diversity are similar. Subsequently, these goats were categorized into high-yield and low-yield groups based on their litter sizes, with 15 goats in each group. Then, a selection signal analysis was performed using FST and π ratios for 33,563 SNP loci. The results identified six candidate genes, including KCNIP4, GFRA2, and DGKH, which are significantly associated with high litter performance. These findings enhanced our understanding of the genetic characteristics and population structure of Guizhou Black goats and Meigu goats. Moreover, they provide an important theoretical foundation and scientific basis for further breeding improvements.

Population Structure and Selection Signatures in Chinese Indigenous Zhaotong Pigs Revealed by Whole-Genome Resequencing

Zhaotong pig (ZTP) is a Chinese indigenous pig breed in Yunnan Province, known for its unique body shape and appearance, good meat quality, strong foraging ability, and adaptability. However, there is still a lack of research on its genome. In order to investigate the genetic diversity, population structure, and selection signatures of the breed, we conducted a comprehensive analysis by resequencing on 30 ZTPs and comparing them with genomic data from 10 Asian wild boars (AWBs). A total of 45,514,452 autosomal SNPs were detected in the 40 pigs, and 23,649,650 SNPs were retained for further analysis after filtering. The HE, HO, PN, MAF, π, and Fis values were calculated to evaluate the genetic diversity, and the results showed that ZTPs had higher genetic diversity and lower inbreeding coefficient compared with AWBs. Population structure was analyzed using NJ tree, PCA, ADMIXTURE, and LD methods. It was found that ZTPs were population independent of AWBs and had a lower LD decay compared to AWBs. Moreover, the results of the IBS genetic distance and G matrix showed that most of the individuals had large genetic distances and distant genetic relationships in ZTPs. Selection signatures were detected between ZTPs and AWBs by using two methods, FST and π ratio. Totals of 1104 selected regions and 275 candidate genes were identified. Finally, functional enrichment analysis identified some annotated genes that might affect fat deposition (NPY1R, NPY5R, and NMU), reproduction (COL3A1, COL5A2, GLRB, TAC3, and MAP3K12), growth (STAT6 and SQOR), tooth development (AMBN, ENAM, and ODAM), and immune response (MBL2, IL1A, and DNAJA3). Our results will provide a valuable basis for the future effective protection, breeding, and utilization of ZTPs.

Evaluating genomic inbreeding of two Chinese yak (Bos grunniens) populations

BACKGROUND

Yaks are a vital livestock in the Qinghai-Tibetan Plateau area for providing food products, maintaining sustainable ecosystems, and promoting cultural heritage. Because of uncontrolled mating, it is impossible to estimate inbreeding level of yak populations using the pedigree-based approaches. With the aims to accurately evaluate inbreeding level of two Chinese yak populations (Maiwa and Jiulong), we obtained genome-wide single nucleotide polymorphisms (SNPs) by DNA sequencing and calculated five SNP-by-SNP estimators ([Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]), as well as two segment-based estimators of runs of homozygosity (ROH, [Formula: see text]) and homozygous-by-descent (HBD, [Formula: see text]). Functional implications were analyzed for the positional candidate genes located within the related genomic regions.

RESULTS

A total of 151,675 and 190,955 high-quality SNPs were obtained from 71 Maiwa and 30 Jiulong yaks, respectively. Jiulong had greater genetic diversity than Maiwa in terms of allele frequency and nucleotide diversity. The two populations could be genetically distinguished by principal component analysis, with the mean differentiation index (Fst) of 0.0054. The greater genomic inbreeding levels of Maiwa yaks were consistently supported by all five SNP-by-SNP estimators. Based on simple proportion of homozygous SNPs ([Formula: see text]), a lower inbreeding level was indicated by three successfully sequenced old leather samples that may represent historical Maiwa yaks about five generations ago. There were 3304 ROH detected among all samples, with mean and median length of 1.97 Mb and 1.0 Mb, respectively. A total of 94 HBD segments were found among all samples, whereas 92 of them belonged to the shortest class with the mean length of 10.9 Kb. Based on the estimates of [Formula: see text] and [Formula: see text], however, there was no difference in inbreeding level between Maiwa and Jiulong yaks. Within the genomic regions with the significant Fst or enriched by ROH, we found several candidate genes and pathways that have been reported to be related to diverse production traits in farm animals.

CONCLUSIONS

We successfully evaluated the genomic inbreeding level of two Chinese yak populations. Although different estimators resulted in inconsistent conclusions on their genomic inbreeding levels, our results may be helpful to implement the genetic conservation and utilization programs for the two yak populations.

Illuminating Genetic Diversity and Selection Signatures in Matou Goats through Whole-Genome Sequencing Analysis

(1) Background: Matou goats, native to Hunan and Hubei provinces in China, are renowned for their exceptional meat and skin quality. However, a comprehensive whole-genome-based exploration of the genetic architecture of this breed is scant in the literature. (2) Methods: To address this substantial gap, we used whole-genome sequences of 20 Matou goats and compared them with published genomic data of 133 goats of different breeds across China. This comprehensive investigation sought to assess genetic diversity, population structure, and the presence of genomic selection signals. (3) Results: The whole genome of Matou goat populations yielded a substantial catalog of over 19 million single nucleotide polymorphisms (SNPs), primarily distributed within intergenic and intron regions. The phylogenetic tree analysis revealed distinct clades corresponding to each goat population within the dataset. Notably, this analysis positioned Matou goats in a closer genetic affinity with Guizhou White goats, compared to other recognized goat breeds. This observation was corroborated by principal component analysis (PCA) and admixture analysis. Remarkably, Matou goats exhibited diminished genetic diversity and a notable degree of inbreeding, signifying a reduced effective population size. Moreover, the study employed five selective sweep detection methods (including PI, CLR, PI-Ratio, Fst, and XP-EHH) to screen top signal genes associated with critical biological functions, encompassing cardiomyocytes, immunity, coat color, and meat quality. (4) Conclusions: In conclusion, this study significantly advances our understanding of the current genetic landscape and evolutionary dynamics of Matou goats. These findings underscore the importance of concerted efforts in resource conservation and genetic enhancement for this invaluable breed.

Genetic diversity and selection signatures in Hainan black goats revealed by whole-genome sequencing data

Understanding the genetic characteristics of indigenous goat breeds is crucial for their conservation and breeding efforts. Hainan black goats, as a native breed of south China's tropical island province of Hainan, possess distinctive traits such as black hair, a moderate growth rate, good meat quality, and small body size. However, they exhibit exceptional resilience to rough feeding conditions, possess high-quality meat, and show remarkable resistance to stress and heat. In this study, we resequenced the whole genome of Hainan black goats to study the economic traits and genetic basis of these goats, we leveraged whole-genome sequencing data from 33 Hainan black goats to analyze single nucleotide polymorphism (SNP) density, Runs of homozygosity (ROH), Integrated Haplotype Score (iHS), effective population size (Ne), Nucleotide diversity Analysis (Pi) and selection characteristics. Our findings revealed that Hainan black goats harbor a substantial degree of genetic variation, with a total of 23 608 983 SNPs identified. Analysis of ROHs identified 53 710 segments, predominantly composed of short fragments, with inbreeding events mainly occurring in ancient ancestors, the estimates of inbreeding based on ROH in Hainan black goats typically exhibit moderate values ranging from 0.107 to 0.186. This is primarily attributed to significant declines in the effective population size over recent generations. Moreover, we identified 921 candidate genes within the intersection candidate region of ROH and iHS. Several of these genes are associated with crucial traits such as immunity (PTPRC, HYAL1, HYAL2, HYAL3, CENPE and PKN1), heat tolerance (GNG2, MAPK8, CAPN2, SLC1A1 and LEPR), meat quality (ACOX1, SSTR1, CAMK2B, PPP2CA and PGM1), cashmere production (AKT4, CHRM2, OXTR, AKT3, HMCN1 and CDK19), and stress resistance (TLR2, IFI44, ENPP1, STK3 and NFATC1). The presence of these genes may be attributed to the genetic adaptation of Hainan black goats to local climate conditions. The insights gained from this study provide valuable references and a solid foundation for the preservation, breeding, and utilization of Hainan black goats and their valuable genetic resources.

Whole-genome resequencing reveals genomic variation and dynamics in Ethiopian indigenous goats

Ethiopia has about 52 million indigenous goats with marked phenotypic variability, which is the outcome of natural and artificial selection. Here, we obtained whole-genome sequence data of three Ethiopian indigenous goat populations (Arab, Fellata, and Oromo) from northwestern Ethiopia and analyzed their genome-wide genetic diversity, population structure, and signatures of selection. We included genotype data from four other Ethiopian goat populations (Abergelle, Keffa, Gumuz, and Woyto-Guji) and goats from Asia; Europe; and eastern, southern, western, and northern Africa to investigate the genetic predisposition of the three Ethiopian populations and performed comparative genomic analysis. Genetic diversity analysis showed that Fellata goats exhibited the lowest heterozygosity values (Ho = 0.288 ± 0.005 and He = 0.334 ± 0.0001). The highest values were observed in Arab goats (Ho = 0.310 ± 0.010 and He = 0.347 ± 4.35e-05). A higher inbreeding coefficient (FROH = 0.137 ± 0.016) was recorded for Fellata goats than the 0.105 ± 0.030 recorded for Arab and the 0.112 ± 0.034 recorded for Oromo goats. This indicates that the Fellata goat population should be prioritized in future conservation activities. The three goat populations showed the majority (∼63%) of runs of homozygosity in the shorter (100-150 Kb) length category, illustrating ancient inbreeding and/or small founder effects. Population relationship and structure analysis separated the Ethiopian indigenous goats into two distinct genetic clusters lacking phylogeographic structure. Arab, Fellata, Oromo, Abergelle, and Keffa represented one genetic cluster. Gumuz and Woyto-Guji formed a separate cluster and shared a common genetic background with the Kenyan Boran goat. Genome-wide selection signature analysis identified nine strongest regions spanning 163 genes influencing adaptation to arid and semi-arid environments (HOXC12, HOXC13, HOXC4, HOXC6, and HOXC9, MAPK8IP2), immune response (IL18, TYK2, ICAM3, ADGRG1, and ADGRG3), and production and reproduction (RARG and DNMT1). Our results provide insights into a thorough understanding of genetic architecture underlying selection signatures in Ethiopian indigenous goats in a semi-arid tropical environment and deliver valuable information for goat genetic improvement, conservation strategy, genome-wide association study, and marker-assisted breeding.

Genetic characterization of the Latvian local goat breed and genetic traits associated with somatic cell count

The Latvian local goat (LVK) breed represents the only native domestic goat breed in Latvia, but its limited population places it within the endangered category. However, the LVK breed has not yet undergone a comprehensive genetic characterization. Therefore, we completed whole genome sequencing to reveal the genetic foundation of the LVK breed while identifying genetic traits linked to the somatic cell count (SCC) levels. The study included 40 genomes of LVK goats sequenced to acquire at least 35x or 10x coverage. A Principal component analysis, a genetic distance tree, and an admixture analysis showed LVK's similarity to some European breeds, such as Finnish Landrace, Alpine, and Saanen, which aligns with the breed's history. An analysis of genome-wide heterozygosity, nucleotide diversity, and LD analysis indicated that the LVK population exhibits substantial levels of genetic diversity. LVK genome was dominated by short runs of homozygosity (ROHs, ≤ 500 kb) with a median length of 25 kb. With FROH 2.49%, average inbreeding levels were low; however, FROH ranged broadly from 0.13 to 12.2%. With the exception of one pure-blood breeding buck exhibiting FROH of 9.3% and FSNP of 8.5%, animals with at least 66% LVK ancestry showed moderate or no inbreeding. Overall, this study demonstrated that the LVK goats can be differentiated from imported breeds, although the population has a complex genetic structure. We were able to identify potential genetic traits associated with SCC levels, although the kinship of the animals and the heterogenic substructure of the population might have largely influenced the association analysis. We identified 26 genetic variants associated with SCC levels, which included the potentially relevant SNP rs662053371 in the OSBPL8 gene, indicating a potential signal linked to lipid metabolism in goats. To conclude, these findings present valuable insight into the genetic structure of the LVK breed for the conservation of local genetic resources.

Genetic Diversity, Population Structure and Selection Signature in Begait Goats Revealed by Whole-Genome Sequencing

Goats belong to a group of animals called small ruminants and are critical sources of livelihood for rural people. Genomic sequencing can provide information ranging from basic knowledge about goat diversity and evolutionary processes that shape genomes to functional information about genes/genomic regions. In this study, we exploited a whole-genome sequencing data set to analyze the genetic diversity, population structure and selection signatures of 44 individuals belonging to 5 Ethiopian goat populations: 12 Aberegalle (AB), 5 Afar (AF), 11 Begait (BG), 12 Central highlands (CH) and 5 Meafure (MR) goats. Our results revealed the highest genetic diversity in the BG goat population compared to the other goat populations. The pairwise genetic differentiation (FST) among the populations varied and ranged from 0.011 to 0.182, with the closest pairwise value (0.003) observed between the AB and CH goats and a distant correlation (FST = 0.182) between the BG and AB goats, indicating low to moderate genetic differentiation. Phylogenetic tree, ADMIXTURE and principal component analyses revealed a classification of the five Ethiopian goat breeds in accordance with their geographic distribution. We also found three top genomic regions that were detected under selection on chromosomes 2, 5 and 13. Moreover, this study identified different candidate genes related to milk characteristics (GLYCAM1 and SRC), carcass (ZNF385B, BMP-7, PDE1B, PPP1R1A, FTO and MYOT) and adaptive and immune response genes (MAPK13, MAPK14, SCN7A, IL12A, EST1 DEFB116 and DEFB119). In conclusion, this information could be helpful for understanding the genetic diversity and population structure and selection scanning of these important indigenous goats for future genetic improvement and/or as an intervention mechanism.

Genetic Architecture of Abdominal Fat Deposition Revealed by a Genome-Wide Association Study in the Laying Chicken

Fat has a high energy density, and excessive fatness has been recognized as a problem for egg production and the welfare of chickens. The identification of a genetic polymorphism controlling fat deposition would be helpful to select against excessive fatness in the laying hen. This study aimed to estimate genomic heritability and identify the genetic architecture of abdominal fat deposition in a population of chickens from a Dongxiang blue-shelled local breed crossbred with the White Leghorn. A genome-wide association study was conducted on abdominal fat percentage, egg production and body weights using a sample of 1534 hens genotyped with a 600 K Chicken Genotyping Array. The analysis yielded a heritability estimate of 0.19 ± 0.04 for abdominal fat percentage; 0.56 ± 0.04 for body weight at 72 weeks; 0.11 ± 0.03 for egg production; and 0.24 ± 0.04 for body weight gain. The genetic correlation of abdominal fat percentage with egg production between 60 and 72 weeks of age was -0.35 ± 0.18. This implies a potential trade-off between these two traits related to the allocation of resources. Strong positive genetic correlations were found between fat deposition and weight traits. A promising locus close to COL12A1 on chromosome 3, associated with abdominal fat percent, was found in the present study. Another region located around HTR2A on chromosome 1, where allele substitution was predicted to be associated with body weight gain, accounted for 2.9% of phenotypic variance. Another region located on chromosome 1, but close to SOX5, was associated with egg production. These results may be used to influence the balanced genetic selection for laying hens.

Landscape genomics reveals adaptive divergence of indigenous sheep in different ecological environments of Xinjiang, China

Sheep are important livestock animals that have evolved under various ecological pressures. Xinjiang is a region with diverse and harsh environments that have shaped many local sheep breeds with unique characteristics and environmental adaptability. However, these breeds are losing ecological flexibility due to the promotion of intensive farming practices. Here we sequenced 14 local sheep breeds from Xinjiang and analyzed their genetic structure and gene flow with other sheep breeds from neighboring regions. The Tibetan Plateau was the geographic origin of Xinjiang native sheep evolution. We performed genome-environment association analysis and identified Bio9: Mean Temperature of Driest Quarter and Bio15: Precipitation Seasonality as the key environmental factors affecting Xinjiang local sheep and the key genes involved in their survival and adaptation. We classified Xinjiang native sheep breeds into six groups based on their differential genes by pairwise selective sweep analysis and Community Network Analysis. We analyzed transcriptome expression data of 832 sheep tissues and detected tissue-specific enrichment of six group-specific genes in different biological systems. Our results revealed the genetic basis of year-round estrus, drought tolerance, hypoxia resistance, and cold tolerance traits of Xinjiang sheep breeds. Moreover, we proposed conservation strategies for Xinjiang local sheep breeds and provided theoretical guidance for breeding new sheep breeds under global extreme environments.

Investigation on mRNA expression and genetic variation within goat SMAD2 gene and its association with litter size

The SMAD family member 2 (SMAD2), a member of the TGF-beta superfamily, executes a significant part in the oogenesis and ovulation process. A genome-wide selective sweep analysis also found SMAD2 was different in the fertility groups of Laoshan dairy goats; whether this gene was linked to litter size was unknown. Therefore, SMAD2 was chosen to study its effects on Shaanbei white cashmere goat reproduction and mRNA expression profile. Herein, the mRNA expression level of SMAD2 was firstly determined in female goat tissues, revealing significant differences in mRNA levels of different tissues (p < 0.05), including ovary tissue, indicating a potential role for SMAD2 in goat prolificacy. Then, using six pairs of primers, only one indel locus (P3-Del-12-bp) was found to be polymorphic in goat SMAD2 (n = 501). ANOVA also revealed that a P3-Del-12-bp deletion was significantly related to first-born litter size (p = 0.037). The Chi-square (χ2) test revealed that the ID genotype was significantly more prevalent in mothers with multiple lambs (p = 0.01), indicating that heterozygous individuals (ID) are more likely to produce multiple lambs. Our findings suggest that the SMAD2 gene's P3-Del-12-bp deletion could be used to improve goat breeds by assisting with litter size selection.

Investigation of the association between goat DNMT3B gene polymorphism and growth traits

The DNA methyltransferase 3 beta (DNMT3B) gene is key for DNA methylation and has been well recognized in regulating growth and development. A previous observation indicated that an 11-bp indel of DNMT3B affected the reproductive traits in goats, yet the effect of this polymorphism on body measurement traits in goats has not been reported. This study aims to investigate the associations between DNMT3B gene polymorphism and goat growth traits. We investigated this 11-bp indel in 2184 goats and three genotypes have been found in Shaanbei white cashmere goat (SBWC): insertion/insertion (II), deletion/deletion (DD) and insertion/deletion (ID). Only ID and DD genotypes were detected in Nubian goats and Guizhou heima goat (GZHM). The allele frequencies analyzed revealed that the 'D' allele frequencies were higher in all three goat breeds. Further association analysis demonstrated that this indel is markedly associated with the cannon circumference (CC) and cannon circumference index (CCI) of SBWC and cannon circumference (CC) of Nubian goats (p < .05). The CC and CCI are essential indicators to measure the growth status of goats. In summary, our study sheds some light on the potential impact of the 11-bp indel polymorphism of the DNMT3B gene on improving the growth traits in goats.

Genome-Wide Association Study of the Reproductive Traits of the Dazu Black Goat (Capra hircus) Using Whole-Genome Resequencing

Reproductive traits are the basic economic traits of goats and important indicators in goat breeding. In this study, Dazu black goats (DBGs; n = 150), an important Chinese local goat breed with excellent reproductive performance, were used to screen for important variation loci and genes of reproductive traits. Through genome-wide association studies (GWAS), 18 SNPs were found to be associated with kidding traits (average litter size, average litter size in the first three parity, and average litter size in the first six parity), and 10 SNPs were associated with udder traits (udder depth, teat diameter, teat length, and supernumerary teat). After gene annotation of the associated SNPs and in combination with relevant references, the candidate genes, namely ATP1A1, LRRC4C, SPCS2, XRRA1, CELF4, NTM, TMEM45B, ATE1, and FGFR2, were associated with udder traits, while the ENSCHIG00000017110, SLC9A8, GLRB, GRIA2, GASK1B, and ENSCHIG00000026285 genes were associated with litter size. These SNPs and candidate genes can provide useful biological information for improvement of the reproductive traits of goats.

Construction of a circRNA- lincRNA-lncRNA-miRNA-mRNA ceRNA regulatory network identifies genes and pathways linked to goat fertility

Background: There is growing interest in the genetic improvement of fertility traits in female goats. With high-throughput genotyping, single-cell RNA sequencing (scRNA-seq) is a powerful tool for measuring gene expression profiles. The primary objective was to investigate comparative transcriptome profiling of granulosa cells (GCs) of high- and low-fertility goats, using scRNA-seq. Methods: Thirty samples from Ji'ning Gray goats (n = 15 for high fertility and n = 15 for low fertility) were retrieved from publicly available scRNA-seq data. Functional enrichment analysis and a literature mining approach were applied to explore modules and hub genes related to fertility. Then, interactions between types of RNAs identified were predicted, and the ceRNA regulatory network was constructed by integrating these interactions with other gene regulatory networks (GRNs). Results and discussion: Comparative transcriptomics-related analyses identified 150 differentially expressed genes (DEGs) between high- and low-fertility groups, based on the fold change (≥5 and ≤-5) and false discovery rate (FDR <0.05). Among these genes, 80 were upregulated and 70 were downregulated. In addition, 81 mRNAs, 58 circRNAs, 8 lincRNAs, 19 lncRNAs, and 55 miRNAs were identified by literature mining. Furthermore, we identified 18 hub genes (SMAD1, SMAD2, SMAD3, SMAD4, TIMP1, ERBB2, BMP15, TGFB1, MAPK3, CTNNB1, BMPR2, AMHR2, TGFBR2, BMP4, ESR1, BMPR1B, AR, and TGFB2) involved in goat fertility. Identified biological networks and modules were mainly associated with ovary signature pathways. In addition, KEGG enrichment analysis identified regulating pluripotency of stem cells, cytokine-cytokine receptor interactions, ovarian steroidogenesis, oocyte meiosis, progesterone-mediated oocyte maturation, parathyroid and growth hormone synthesis, cortisol synthesis and secretion, and signaling pathways for prolactin, TGF-beta, Hippo, MAPK, PI3K-Akt, and FoxO. Functional annotation of identified DEGs implicated important biological pathways. These findings provided insights into the genetic basis of fertility in female goats and are an impetus to elucidate molecular ceRNA regulatory networks and functions of DEGs underlying ovarian follicular development.

Identifying Candidate Genes for Litter Size and Three Morphological Traits in Youzhou Dark Goats Based on Genome-Wide SNP Markers

This study aimed to reveal the potential genetic basis for litter size, coat colour, black middorsal stripe and skin colour by combining genome-wide association analysis (GWAS) and selection signature analysis and ROH detection within the Youzhou dark (YZD) goat population (n = 206) using the Illumina GoatSNP54 BeadChip. In the GWAS, we identified one SNP (snp54094-scaffold824-899720) on chromosome 11 for litter size, two SNPs on chromosome 26 (snp11508-scaffold142-1990450, SORCS3) and chromosome 12 (snp55048-scaffold842-324525, LOC102187779) for coat colour and one SNP on chromosome 18 (snp56013-scaffold873-22716, TCF25) for the black middorsal stripe. In contrast, no SNPs were identified for skin colour. In selection signature analysis, 295 significant iHS genomic regions with a mean |iHS| score > 2.66, containing selection signatures encompassing 232 candidate genes were detected. In particular, 43 GO terms and one KEGG pathway were significantly enriched in the selected genes, which may contribute to the excellent environmental adaptability and characteristic trait formation during the domestication of YZD goats. In ROH detection, we identified 4446 ROH segments and 282 consensus ROH regions, among which nine common genes overlapped with those detected using the iHS method. Some known candidate genes for economic traits such as reproduction (TSHR, ANGPT4, CENPF, PIBF1, DACH1, DIS3, CHST1, COL4A1, PRKD1 and DNMT3B) and development and growth (TNPO2, IFT80, UCP2, UCP3, GHRHR, SIM1, CCM2L, CTNNA3 and CTNNA1) were revealed by iHS and ROH detection. Overall, this study is limited by the small population size, which affects the results of GWAS to a certain extent. Nevertheless, our findings could provide the first overview of the genetic mechanism underlying these important traits and provide novel insights into the future conservation and utilisation of Chinese goat germplasm resources.

New insight into copy number variations of goat SMAD2 gene and their associations with litter size and semen quality

Copy number variations (CNV) contribute significantly to genetic variations. Numerous studies have shown that CNV affects phenotypic traits in livestock. The SMAD family member 2 (SMAD2) is a leading candidate gene in reproduction and has a crucial effect on litter size. Additionally, SMAD2 is also required for male reproduction and influences male germ cell development. However, there are no reports on investigating the effect of CNVs in the SMAD2 gene on reproductive traits in goat. Therefore, the goal of this study was to explore associations between CNV of the SMAD2 gene and litter size and semen quality in Shaanbei white cashmere (SBWC) goats. In this study, two CNVs within the SMAD2 were identified in 352 SBWC goats (50 males and 302 females). The association analysis revealed that only CNV2 was significantly associated with female goat first-born litter size (P = 3.59 × 10^-4), male semen concentration (P < 0.01), ejaculation volume, live sperm count, and sperm deformity rate (P < 0.05). In terms of phenotypic performance, the individuals with loss genotypes outperformed those with other genotypes. CNV1 and CNV2 genotype combinations containing their dominant genotypes were also associated with goat litter size (P = 1.7 × 10^-5), but no differences in semen quality were found. In summary, CNV2 of the SMAD2 gene is useful for molecular marker-assisted selection breeding, as it is associated with essential goat reproductive traits.

Uterus proliferative period ceRNA network of Yunshang black goat reveals candidate genes on different kidding number trait

Pregnancy loss that occurs in the uterus is an important and widespread problem in humans and farm animals and is also a key factor affecting the fecundity of livestock. Understanding the differences in the fecundity of goats may be helpful in guiding the breeding of goats with high fecundity. In this study, we performed RNA sequencing and bioinformatics analysis to study the uterus of Yunshang black goats with high and low fecundity in the proliferative period. We identified mRNAs, long non-coding RNAs (lncRNAs), and microRNAs (miRNAs) by analyzing the uterine transcriptomes. The target genes of the identified miRNAs and lncRNAs were predicted, and miRNA-mRNA interaction and competitive endogenous RNA (ceRNA) networks were constructed. By comparisons between low- and high-fecundity groups, we identified 1,674 differentially expressed mRNAs (914 were upregulated, and 760 were downregulated), 288 differentially expressed lncRNAs (149 were upregulated, and 139 were downregulated), and 17 differentially expressed miRNAs (4 were upregulated, and 13 were downregulated). In addition, 49 miRNA-mRNA pairs and 45 miRNA-lncRNA pairs were predicted in the interaction networks. We successfully constructed a ceRNA interaction network with 108 edges that contained 19 miRNAs, 11 mRNAs, and 73 lncRNAs. Five candidate genes (PLEKHA7, FAT2, FN1, SYK, and ITPR2) that were annotated as cell adhesion or calcium membrane channel protein were identified. Our results provide the overall expression profiles of mRNAs, lncRNAs, and miRNAs in the goat uterus during the proliferative period and are a valuable reference for studies into the mechanisms associated with the high fecundity, which may be helpful to guide goat to reduce pregnancy loss.

Genetic diversity and signatures of selection in BoHuai goat revealed by whole-genome sequencing

BACKGROUND

Cross breeding is an important way to improve livestock performance. As an important livestock and poultry resource in Henan Province of China, Bohuai goat was formed by crossing Boer goat and Huai goat. After more than 20 years of breeding, BoHuai goats showed many advantages, such as fast growth, good reproductive performance, and high meat yield. In order to better develop and protect Bohuai goats, we sequenced the whole genomes of 30 BoHuai goats and 5 Huai goats to analyze the genetic diversity, population structure and genomic regions under selection of BoHuai goat. Furthermore, we used 126 published genomes of world-wide goat to characterize the genomic variation of BoHuai goat.

RESULTS

The results showed that the nucleotide diversity of BoHuai goats was lower and the degree of linkage imbalance was higher than that of other breeds. The analysis of population structure showed that BoHuai goats have obvious differences from other goat breeds. In addition, the BoHuai goat is more closely related to the Boer goat than the Huai goat and is highly similar to the Boer goat. Group by selection signal in the BoHuai goat study, we found that one region on chromosome 7 shows a very strong selection signal, which suggests that it could well be the segment region under the intense artificial selection results. Through selective sweeps, we detected some genes related to important traits such as lipid metabolism (LDLR, STAR, ANGPTL8), fertility (STAR), and disease resistance (CD274, DHPS, PDCD1LG2).

CONCLUSION

In this paper, we elucidated the genomic variation, ancestry composition, and selective signals related to important economic traits in BoHuai goats. Our studies on the genome of BoHuai goats will not only help to understand the characteristics of the crossbred but also provide a basis for the improvement of cross-breeding programs.

Screening Indels from the whole genome to identify the candidates and their association with economic traits in several goat breeds

In the present study, the re-sequencing of our previous whole-genome sequencing (WGS) for selected individuals of Dazu-black goat (DBG) and Inner-Mongolia Cashmere goat (IMCG) breeds was used to detect and compare the differentiation in Indels depending on the reference genome of goat. Then, three selected candidate Indels rs668795676, rs657996810, and rs669452874 of the three genes SUFU, SYCP2L and GLIPR1L1, respectively, have been chosen, based on the results of prior GWAS across the genome, and examined for their association with body weight and dimensions (body height, body length, heart girth, chest width, cannon circumference, and chest depth) by kompetitive allele specific PCR assay for 342 goats from the three studied goat breeds (DBG, n = 203; ♂99, ♀104), IMCG (n = 65; 15♂, 50♀), and Hechuan white goat (HWG, n = 74; 34♂, 40♀) breeds. The analysis of 192.747 Gb WGS revealed an average 334,151 Indels in the whole genome of DBG and IMCG breeds. Chromosome 1 had a maximum number of mutations (Indels) of 58,497 and 55,527 for IMCG and DBG, respectively, while chromosome 25 had the least number of mutations of 15,680 and 16,103 for IMCG and DBG, respectively. The majority of Indels were either Ins or Del of short fragments of 1-5 bp, which covered 79.06 and 71.78% of the total number of Indels mutations in IMCG and DBG, respectively. Comparing the differences of Indels between the studied goat breeds revealed 100 and 110 unique Indels for IMCG and DBG, respectively. The Indels loci in the intron region were unique for both studied goat breeds which were related to 30 and 38 candidate genes in IMCG and DBG, respectively, including SUFU, SYCP2L, and GLIPR1L1 genes. Concerning rs669452874 locus, body height and body length of Del/Del genotype in DBG were significantly higher (P < 0.05) than that of Ins/Del genotype, while body height and body length of Del/Del genotype in IMCG were significantly higher (P < 0.01) than those of Ins/Ins genotype, whereas body height and body length and heart girth of Del/Del genotype in HWG were significantly higher (P < 0.01) than those of the Ins/Del and Ins/Ins genotypes. Thus, Del/Del genotype of rs669452874 locus can be used as a candidate molecular marker related to the body dimensions in the studied goat breeds.

Litter size influences rumen microbiota and fermentation efficiency, thus determining host early growth in goats

Introduction

Multiple litters are accompanied by low birth weight, low survival rates, and growth rates in goats during early life. Regulating rumen microbiota structure can indirectly or directly affect host metabolism and animal growth. However, the relationship between high litter size and rumen microbiome, rumen fermentation, and growth performance in goat kids is unclear.

Methods

In the present study, thirty 6-month-old, female goats were investigated, of which 10 goats were randomly chosen from single, twin and triplet goats respectively, and their birth weight was recorded. From birth, all goats were subjected to the same feed and management practices. Individual weaning and youth body weight were measured, and the rumen fluid samples were collected to characterize the bacterial communities and to determine the ruminal volatile fatty acids (VFA), free amino acids (AA), and free fatty acids (FA) concentration of those young goats.

Results and Discussion

Compared with the single and twin goats, triplet goats have lower weaning and youth body weight and average daily gain (ADG). Ruminal propionate, butyrate, and total VFA were decreased in triplet goats. Meanwhile, ruminal AA, such as branched chain amino acids (BCAA), essential amino acids (EAA), unsaturated fatty acids (UFA), and monounsaturated fatty acids (MUFA) were decreased, while saturated fatty acids (SFA) and odd and branched chain fatty acids (OBCFA) were increased in triplet goats. Our results also revealed that litter size significantly affected the rumen bacterial communities, and triplet goats had a lower the Firmicutes: Bacteroidota ratio, the abundance of Firmicutes phylum, Rikenellaceae family, and Rikenellaceae RC9 gut group, and had a higher proportion of Prevotellaceae family, and several genera of Prevotellaceae, such as Prevotella, and unclassified f Prevotellaceae. Furthermore, Spearman's correlation network analysis showed that the changes in the rumen bacteria were associated with changes in rumen metabolites. In conclusion, this study revealed that high litter size could bring disturbances to the microbial communities and decrease the rumen fermentation efficiency and growth performance, which can be utilized to better understand variation in microbial ecology that will improve growth performance in triplet goats.

Genomic Regions Associated with Wool, Growth and Reproduction Traits in Uruguayan Merino Sheep

The aim of this study was to identify genomic regions and genes associated with the fiber diameter (FD), clean fleece weight (CFW), live weight (LW), body condition score (BCS), pregnancy rate (PR) and lambing potential (LP) of Uruguayan Merino sheep. Phenotypic records of approximately 2000 mixed-age ewes were obtained from a Merino nucleus flock. Genome-wide association studies were performed utilizing single-step Bayesian analysis. For wool traits, a total of 35 genomic windows surpassed the significance threshold (PVE ≥ 0.25%). The proportion of the total additive genetic variance explained by those windows was 4.85 and 9.06% for FD and CFW, respectively. There were 42 windows significantly associated with LWM, which collectively explained 43.2% of the additive genetic variance. For BCS, 22 relevant windows accounted for more than 40% of the additive genetic variance, whereas for the reproduction traits, 53 genomic windows (24 and 29 for PR and LP, respectively) reached the suggestive threshold of 0.25% of the PVE. Within the top 10 windows for each trait, we identified several genes showing potential associations with the wool (e.g., IGF-1, TGFB2R, PRKCA), live weight (e.g., CAST, LAP3, MED28, HERC6), body condition score (e.g., CDH10, TMC2, SIRPA, CPXM1) or reproduction traits (e.g., ADCY1, LEPR, GHR, LPAR2) of the mixed-age ewes.

Whole-genome resequencing reveals genetic diversity and selection characteristics of dairy goat

The dairy goat is one of the earliest dairy livestock species, which plays an important role in the economic development, especially for developing countries. With the development of agricultural civilization, dairy goats have been widely distributed across the world. However, few studies have been conducted on the specific characteristics of dairy goat. In this study, we collected the whole-genome data of 89 goat individuals by sequencing 48 goats and employing 41 publicly available goats, including five dairy goat breeds (Saanen, Nubian, Alpine, Toggenburg, and Guanzhong dairy goat; n = 24, 15, 11, 6, 6), and three goat breeds (Guishan goat, Longlin goat, Yunshang Black goat; n = 6, 15, 6). Through compared the genomes of dairy goat and non-dairy goat to analyze genetic diversity and selection characteristics of dairy goat. The results show that the eight goats could be divided into three subgroups of European, African, and Chinese indigenous goat populations, and we also found that Australian Nubian, Toggenburg, and Australian Alpine had the highest linkage disequilibrium, the lowest level of nucleotide diversity, and a higher inbreeding coefficient, indicating that they were strongly artificially selected. In addition, we identified several candidate genes related to the specificity of dairy goat, particularly genes associated with milk production traits (GHR, DGAT2, ELF5, GLYCAM1, ACSBG2, ACSS2), reproduction traits (TSHR, TSHB, PTGS2, ESR2), immunity traits (JAK1, POU2F2, LRRC66). Our results provide not only insights into the evolutionary history and breed characteristics of dairy goat, but also valuable information for the implementation and improvement of dairy goat cross breeding program.

Genome-wide analysis for the melatonin trait associated genes and SNPs in dairy goat (Capra hircus) as the molecular breeding markers

Previous studies have reported that the endogenous melatonin level is positively associated with the quality and yield of milk of cows. In the current study, a total of 34,921 SNPs involving 1,177 genes were identified in dairy goats by using the whole genome resequencing bulked segregant analysis (BSA) analysis. These SNPs have been used to match the melatonin levels of the dairy goats. Among them, 3 SNPs has been identified to significantly correlate with melatonin levels. These 3 SNPs include CC genotype 147316, GG genotype 147379 and CC genotype 1389193 which all locate in the exon regions of ASMT and MT2 genes. Dairy goats with these SNPs have approximately 5-fold-higher melatonin levels in milk and serum than the average melatonin level detected in the current goat population. If the melatonin level impacts the milk production in goats as in cows, the results strongly suggest that these 3 SNPs can serve as the molecular markers to select the goats having the improved milk quality and yield. This is a goal of our future study.

Identification of Candidate Genes for Twinning Births in Dezhou Donkeys by Detecting Signatures of Selection in Genomic Data

Twinning trait in donkeys is an important manifestation of high fecundity, but few reports are available elucidating its genetic mechanism. To explore the genetic mechanism underlying the twin colt trait in Dezhou donkeys, DNA from 21 female Dezhou donkeys that had birthed single or twin colts were collected for whole-genome resequencing. FST, θπ and Tajima’s D were used to detect the selective sweeps between single and twin colt fecundity in the Dezhou donkey groups. Another set of 20 female Dezhou donkeys with single or multiple follicles during estrus were selected to compare concentrations of reproductive hormone including follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2) and progesterone (P4). Four candidate genes including ENO2, PTPN11, SOD2 and CD44 were identified in the present study. The CD44 gene had the highest FST value, and ENO2, PTPN11 and SOD2 were screened by two joint analyses (FST and θπ, θπ and Tajima’s D). There was no significant difference in the LH, FSH and P4 levels between the two groups (p > 0.05); however, the serum E2 content in the multi-follicle group was significantly higher than that in the single-follicle group (p < 0.05). The identified candidate genes may provide new insights into the genetic mechanism of donkey prolificacy and may be useful targets for further research on high reproductive efficiency.

Whole genome re-sequencing reveals artificial and natural selection for milk traits in East Friesian sheep

The East Friesian sheep is one of the important high-yielding dairy sheep breeds, but still little is known about their genetic and genomic variation during domestication. Therefore, we analyzed the genomic data of 46 sheep with the aim of identifying candidate genes that are closely related to milk production traits. Our genomic data consisted of 20 East Friesian sheep and 26 Asian Mouflon wild sheep. Finally, a total of 32590241 SNPs were identified, of which 0.61% (198277) SNPs were located in exonic regions. After further screening, 122 shared genomic regions in the top 1% of F ST and top 1% of Nucleotide diversity ratio were obtained. After genome annotation, these 122 candidate genomic regions were found to contain a total of 184 candidate genes. Finally, the results of KEGG enrichment analysis showed four significantly enriched pathways (P < 0.05): beta-Alanine metabolism (SMOX, HIBCH), Pathways in cancer (GLI2, AR, TXNRD3, TRAF3, FGF16), Non-homologous end-joining (MRE11), Epstein-Barr virus infection (TRAF3, PSMD13, SIN3A). Finally, we identified four important KEGG enrichment pathways and 10 candidate genes that are closely related to milk production in East Friesian sheep. These results provide valuable candidate genes for the study of milk production traits in East Friesian sheep and lay an important foundation for the study of milk production traits.

Genetic architecture and selection of Anhui autochthonous pig population revealed by whole genome resequencing

The genetic resources among pigs in Anhui Province are diverse, but their value and potential have yet to be discovered. To illustrate the genetic diversity and population structure of the Anhui pigs population, we resequenced the genome of 150 pigs from six representative Anhui pigs populations and analyzed this data together with the sequencing data from 40 Asian wild boars and commercial pigs. Our results showed that Anhui pigs were divided into two distinct types based on ancestral descent: Wannan Spotted pig (WSP) and Wannan Black pig (WBP) origins from the same ancestor and the other four populations origins from another ancestor. We also identified several potential selective sweep regions associated with domestication characteristics among Anhui pigs, including reproduction-associated genes (CABS1, INSL6, MAP3K12, IGF1R, INSR, LIMK2, PATZ1, MAPK1), lipid- and meat-related genes (SNX19, MSTN, MC5R, PRKG1, CREBBP, ADCY9), and ear size genes (MSRB3 and SOX5). Therefore, these findings expand the catalogue and how these genetic differences among pigs and this newly generated data will be a valuable resource for future genetic studies and for improving genome-assisted breeding of pigs and other domesticated animals.

Meta-analysis of association between c.963A>G single-nucleotide polymorphism on BMP15 gene and litter size in goats

Litter size is an important economic trait in the goat industry. Previous studies on the bone morphogenetic protein 15 (BMP15) gene detected some single-nucleotide polymorphisms (SNPs) such as c.963A > G that were associated with an increase in ovulation rate and litter size. The aim of this study was to conduct a meta-analysis on the effect of this polymorphism on litter size. We gathered and pooled data from five eligible published studies. To investigate the effect of c.963A > G on litter size, we utilized four different genetic models assuming dominant (GG  +  GA vs. AA), recessive (GG vs. GA  +  AA), additive (GG vs. AA) and co-dominant (GG  +  AA vs. GA) model of inheritance. Data were analyzed under random-effects models based on the I 2 value. Furthermore, sensitivity analysis was carried out to validate the stability of results. The results showed that the c.963A > G polymorphism is associated with litter size when applying a dominant model (standardized mean difference (SMD) is 0.815, 95 % CI [0.170, 1.461], P  value  =  0.013) and also with an additive model (SMD  =  0.755, 95 % CI [0.111, 1.400], P  value  =  0.022). However, the effect of c.963A > G polymorphism was not significant under recessive (SMD  =  0.186, 95 % CI [ - 0.195, 4.259], P  value  =  0.339) and co-dominant (SMD  =   - 0.119, 95 % CI [ - 0.525, 0.288], P  value  =  0.568) models. Sensitivity analysis demonstrated that dropping studies with wide confidence intervals affects overall results under the assumption of an additive model. The meta-analysis results revealed that the AA genotype could be positively connected with litter size in goats.

Retrotransposon Insertion Polymorphisms (RIPs) in Pig Reproductive Candidate Genes

Retrotransposons account for more than one-third of the pig reference genome. On account of the genome variability in different breeds, structural variation (SV) caused by retrotranspos-on-generated deletion or insertion (indel) may have a function in the genome. Litter size is one of the most important reproductive traits and significantly impacts profitability in terms of pig production. We used the method of bioinformatics, genetics, and molecular biology to make an analysis among different pig genomes. Predicted 100 SVs were annotated as retrotransposon indel in 20 genes related to reproductive performance. The PCR detection based on these predicted SVs revealed 20 RIPs in 20 genes, that most RIPs (12) were generated by SINE indel, and eight RIPs were generated by the ERV indel. We selected 12 RIPs to make the second round PCR detection in 24 individuals among nine pig breeds. The PCR detection results revealed that the RIP-A1CF-4 insertion in the breed of Bama, Large White, and Meishan only had the homozygous genotype but low to moderately polymorphisms were present in other breeds. We found that RIP-CWH43-9, RIP-IDO2-9, RIP-PRLR-6, RIP-VMP1-12, and RIP-OPN-1 had a rich polymorphism in the breed of Large White pigs. The statistical analysis revealed that RIP-CWH43-9 had a SINE insertion profitable to the reproductive traits of TNB and NBA but was significantly affected (p < 0.01) and (p < 0.05) in the reproductive traits of litter birthweight (LW) in Large White. On the other hand, the SINE insertion in IDO2-9 may be a disadvantage to the reproductive traits of LW, which was significantly affected (p < 0.05) in Large White. These two RIPs are significant in pig genome research and could be useful molecular markers in the breeding system.

Whole-genome sequence analysis reveals selection signatures for important economic traits in Xiang pigs

Xiang pig (XP) is one of the best-known indigenous pig breeds in China, which is characterized by its small body size, strong disease resistance, high adaptability, favorite meat quality, small litter sizes, and early sexual maturity. However, the genomic evidence that links these unique traits of XP is still poorly understood. To identify the genomic signatures of selection in XP, we performed whole-genome resequencing on 25 unrelated individual XPs. We obtained 876.70 Gb of raw data from the genomic libraries. The LD analysis showed that the lowest level of linkage disequilibrium was observed in Xiang pig. Comparative genomic analysis between XPs and other breeds including Tibetan, Meishan, Duroc and Landrace revealed 3062, 1228, 907 and 1519 selected regions, respectively. The genes identified in selected regions of XPs were associated with growth and development processes (IGF1R, PROP1, TBX19, STAC3, RLF, SELENOM, MSTN), immunity and disease resistance (ZCCHC2, SERPINB2, ADGRE5, CYP7B1, STAT6, IL2, CD80, RHBDD3, PIK3IP1), environmental adaptation (NR2E1, SERPINB8, SERPINB10, SLC26A7, MYO1A, SDR9C7, UVSSA, EXPH5, VEGFC, PDE1A), reproduction (CCNB2, TRPM6, EYA3, CYP7B1, LIMK2, RSPO1, ADAM32, SPAG16), meat quality traits (DECR1, EWSR1), and early sexual maturity (TAC3). Through the absolute allele frequency difference (ΔAF) analysis, we explored two population-specific missense mutations occurred in NR6A1 and LTBP2 genes, which well explained that the vertebrae numbers of Xiang pigs were less than that of the European pig breeds. Our results indicated that Xiang pigs were less affected by artificial selection than the European and Meishan pig breeds. The selected candidate genes were mainly involved in growth and development, disease resistance, reproduction, meat quality, and early sexual maturity. This study provided a list of functional candidate genes, as well as a number of genetic variants, which would provide insight into the molecular basis for the unique traits of Xiang pig.

Single nucleotide polymorphisms in the 3′ UTR of follistatin-like 4 and scavenger receptor class B member 1 are associated with Dazu black goat litter size

The untranslated regions (UTR) of genes play crucial roles in regulating gene expression at the post-transcriptional level such as affecting mRNA stabilization. In this study, 26 single nucleotide polymorphisms (SNPs) and one deletion located in UTR were genotyped from 186 Dazu black goats via SNaPshot, and the correlation between genotype and litter size was analyzed. Results indicated that two SNP loci, SNP_chr17-20182525 and SNP_chr7-65652612, which are located at the 3′UTR of scavenger receptor class B member 1 and follistatin-like 4, are significantly (p<0.05) correlated with the litter size of first parity goats. SNP_chr7-65652612 is also significantly associated with the total litter size of first and second parity offspring (p<0.05). In conclusion, SNP_chr7-65652612 and SNP_chr17-20182525 have correlation with the litter size of Dazu black goat and they are potential genetic markers for litter size breeding.

Differentially Expressed Circular RNA Profile Signatures Identified in Prolificacy Trait of Yunshang Black Goat Ovary at Estrus Cycle

CircRNAs acting as miRNA sponges play important roles in the growth process of animal individuals. The prolificacy trait of goats is involved in many pathways, however, the variation of circRNA expression profiles in the different phases of the estrus cycle at high and low fecundity groups is still unknown. Here, we analyzed the circRNA profiles of ovarian tissues among high and low fecundity groups in the follicular phase (HF vs LF), high and low fecundity groups in the luteal phase (HL vs LL), and high and low fecundity in the whole estrus cycle (HF vs HL and LF vs LL) using RNA-seq. A total of 283 (114 upregulated and 169 downregulated), 559 (299 upregulated and 260 downregulated), 449 (254 upregulated and 195 downregulated), and 314 (210 upregulated and 104 downregulated) differentially expressed (DE) circRNAs were screened in HF vs LF, HF vs HL, HL vs LL, and LF vs LL groups, respectively. Enrichment analysis suggested that the targeting of DE circRNAs was mainly enriched in oocyte meiosis, the GnRH signaling pathway, and estrogen signaling pathway. After integrating our previous study of miRNA-seq, there were 56 miRNAs that could target to 192 DE circRNAs, including the miR-133 family (including miR-133a-3p and miR-133b), miR-129-3p, and miR-21, which also had important influence on the prolificacy trait of goats. Then, 18 circRNAs with coding potential were obtained by four software predictions, and 9 circRNAs were validated by RT-qPCR. Together, circRNAs play a key role in the prolificacy trait and the transformation of the follicular phase to the luteal phase in the estrus cycle of goats.

Genomic characterization of the world's longest selection experiment in mouse reveals the complexity of polygenic traits

BACKGROUND

Long-term selection experiments are a powerful tool to understand the genetic background of complex traits. The longest of such experiments has been conducted in the Research Institute for Farm Animal Biology (FBN), generating extreme mouse lines with increased fertility, body mass, protein mass and endurance. For >140 generations, these lines have been maintained alongside an unselected control line, representing a valuable resource for understanding the genetic basis of polygenic traits. However, their history and genomes have not been reported in a comprehensive manner yet. Therefore, the aim of this study is to provide a summary of the breeding history and phenotypic traits of these lines along with their genomic characteristics. We further attempt to decipher the effects of the observed line-specific patterns of genetic variation on each of the selected traits.

RESULTS

Over the course of >140 generations, selection on the control line has given rise to two extremely fertile lines (>20 pups per litter each), two giant growth lines (one lean, one obese) and one long-distance running line. Whole genome sequencing analysis on 25 animals per line revealed line-specific patterns of genetic variation among lines, as well as high levels of homozygosity within lines. This high degree of distinctiveness results from the combined effects of long-term continuous selection, genetic drift, population bottleneck and isolation. Detection of line-specific patterns of genetic differentiation and structural variation revealed multiple candidate genes behind the improvement of the selected traits.

CONCLUSIONS

The genomes of the Dummerstorf trait-selected mouse lines display distinct patterns of genomic variation harbouring multiple trait-relevant genes. Low levels of within-line genetic diversity indicate that many of the beneficial alleles have arrived to fixation alongside with neutral alleles. This study represents the first step in deciphering the influence of selection and neutral evolutionary forces on the genomes of these extreme mouse lines and depicts the genetic complexity underlying polygenic traits.

The statistical power of genome-wide association studies for threshold traits with different frequencies of causal variants

This study aimed to investigate the effects of incidence rate, heritability, and polygenic variance on the statistical power of genome-wide association studies (GWAS) for threshold traits. Different incidence rates of threshold trait (1, 3, 5, 10, 25, 40, 50, 60, 75 and 90%), heritability (10 and 25%), and polygenic variance ratio (0 and 25%) were simulated separately for common (MAF ≥ 0.05), low-frequency (0.05 > MAF ≥ 0.01), and rare (MAF < 0.01) variants. Association studies were performed by logistic and linear mixed models. The highest statistical powers were observed in common and low-frequency variants with an incidence of 25-50% and 10-40%, respectively, but for rare variants, the highest statistical power was observed at low incidence. For all causal variant frequencies, the estimated heritability decline with an increase in incidence rate. We found high statistical power for traits with high heritability. In contrast, those with a high polygenic variance ratio have lower statistical power to detect common causal variants using a linear mixed model. These results demonstrate that the incidence rate of threshold traits, heritability, and polygenic variance may affect the statistical power of GWAS. Therefore, it is recommended that the effect of incidence rate, heritability, and polygenic variance be considered in designing GWAS for threshold traits.

Population validation of reproductive gene mutation loci and association with the litter size in Nubian goat

Litter size is an important component trait of doe reproduction. By improving it, production efficiency and economic benefits can be significantly provided. Genetic marker-assisted selection (MAS) based on proven molecular indicators could enhance the efficacy of goat selection, as well as litter size trait. Many molecular markers have been identified that they can be used to improve litter size in different goat breeds. However, the presence and value of these markers vary among goat breeds. In the present study, we used the reported loci on other breeds of goat as candidate loci to detect whether these loci appear in this Nubian goat population; then we proceed to genotype and detect surrounding loci (50 bp) by multiplex PCR and sequencing technology. As a result, 69 mutations (59 SNPs and 10 indels) were screened out from 23 candidate genes in Nubian goat population, 12 loci were significantly associated with the litter size of first-parity individuals; 5 loci were significantly associated with the litter size of second-parity individuals; 3 loci were significantly associated with the litter size of third-parity individuals. In addition, five loci were significantly associated with the average litter size. The additive effect value of KITLG: g.18047318 G>A in first parity, KITLG: g.18152042G>A in third parity, KISS-1: g.1341674 C>G in first parity, and GHR: g.32134187G>A in second parity exceed more than 0.40, and the preponderant alleles are G, C, A and G, respectively. Further, linkage disequilibrium analysis of 21 mutation loci shows that 3 haplotype blocks are formed, and the litter size of combination type AACC in KISS-1 gene and AAGG in KITLG gene are significantly lower than that of other combinations genotype in first parity (P<0.05). These findings can provide effective candidate DNA markers for selecting superior individuals in Nubian goat breeding.

Differences in gene expression and variable splicing events of ovaries between large and small litter size in Chinese Xiang pigs

BACKGROUND

Although lots of quantitative trait loci (QTLs) and genes present roles in litter size of some breeds, the information might not make it clear for the huge diversity of reproductive capability in pig breeds. To elucidate the inherent mechanisms of heterogeneity of reproductive capability in litter size of Xiang pig, we performed transcriptome analysis for the expression profile in ovaries using RNA-seq method.

RESULTS

We identified 1,419 up-regulated and 1,376 down-regulated genes in Xiang pigs with large litter size. Among them, 1,010 differentially expressed genes (DEGs) were differently spliced between two groups with large or small litter sizes. Based on GO and KEGG analysis, numerous members of genes were gathered in ovarian steroidogenesis, steroid biosynthesis, oocyte maturation and reproduction processes.

CONCLUSIONS

Combined with gene biological function, twelve genes were found out that might be related with the reproductive capability of Xiang pig, of which, eleven genes were recognized as hub genes. These genes may play a role in promoting litter size by elevating steroid and peptide hormones supply through the ovary and facilitating the processes of ovulation and in vivo fertilization.

A Review on the General Cheese Processing Technology, Flavor Biochemical Pathways and the Influence of Yeasts in Cheese

Cheese has a long history and this naturally fermented dairy product contains a range of distinctive flavors. Microorganisms in variety cheeses are an essential component and play important roles during both cheese production and ripening. However, cheeses from different countries are still handmade, the processing technology is diverse, the microbial community structure is complex and the cheese flavor fluctuates greatly. Therefore, studying the general processing technology and relationship between microbial structure and flavor formation in cheese is the key to solving the unstable quality and standardized production of cheese flavor on basis of maintaining the flavor of cheese. This paper reviews the research progress on the general processing technology and key control points of natural cheese, the biochemical pathways for production of flavor compounds in cheeses, the diversity and the role of yeasts in cheese. Combined with the development of modern detection technology, the evolution of microbial structure, population evolution and flavor correlation in cheese from different countries was analyzed, which is of great significance for the search for core functional yeast microorganisms and the industrialization prospect of traditional fermented cheese.

Whole-genome resequencing reveals genetic characteristics of different duck breeds from the Guangxi region in China

Distinctive indigenous duck (Anas platyrhynchos) populations of Guangxi, China, evolved due to the geographical, cultural, and environmental variability of this region. To investigate the genetic diversity and population structure of the indigenous ducks of Guangxi, 78 individuals from eight populations were collected and sequenced by whole-genome resequencing with an average depth of ∼9.40×. The eight indigenous duck populations included four breeds and four resource populations. Moreover, the genome data of 47 individuals from two typical meat-type breeds and two native egg-type breeds were obtained from a public database. Calculation of heterozygosity, nucleotide diversity (π), Tajima’s D, and F_ST indicated that the Guangxi populations were characterized by higher genetic diversity and lower differentiation than meat-type breeds. The highest diversity was observed in the Xilin-Ma ducks. Principal component, structure, and phylogenetic tree analyses revealed the relationship between the indigenous duck populations of Guangxi. A mild degree of differentiation was observed among the Guangxi populations, although three populations were closer to the meat or egg breeds. Indigenous populations are famous for their special flavor, small body size, and slow growth rates. Selective sweep analysis revealed the candidate genes and pathways associated with these growth traits. Our findings provide a valuable source of information regarding genetic diversity, population conservation, and genome-associated breeding of ducks.

Detecting the footprint of selection on the genomes of Murciano-Granadina goats

Artificial selection is one of the major forces modifying the genetic composition of livestock populations. Identifying genes under selection could be useful to elucidate their impact on phenotypic variation. We aimed to identify genomic regions targeted by selection for dairy and pigmentation traits in Murciano-Granadina goats. Performance of a selection scan based on the integrated haplotype score test in a population of 1183 Murciano-Granadina goats resulted in the identification of 77 candidate genomic regions/SNPs. The most significant selective sweeps mapped to chromosomes 1 (69.86 Mb), 4 (41.80-49.95 Mb), 11 (65.74 Mb), 12 (31.24 and 52.51 Mb), 17 (34.76-37.67 Mb), 22 (31.75 Mb), and 26 (26.69-31.05 Mb). By using previously generated RNA-Seq data, we built a catalogue of 6414 genes that are differentially expressed across goat lactation (i.e. 78 days post-partum, early lactation; 216 days post-partum, late lactation; 285 days post-partum, dry period). Interestingly, 183 of these genes mapped to selective sweeps and several of them display functions related with lipid, protein, and carbohydrate metabolism, insulin signaling, cell proliferation, as well as mammary development and involution. Of particular interest are the CSN3 and CSN1S2 genes, which encode two major milk proteins. Additionally, we found three pigmentation genes (GLI3, MC1R, and MITF) co-localizing with selective sweeps. Performance of a genome-wide association study and Sanger sequencing and TaqMan genotyping experiments revealed that the c.801C>G (p.Cys267Trp) polymorphism in the melanocortin 1 receptor (MC1R) gene is the main determinant of the black (GG or GC genotypes) and brown (CC genotypes) colorations of Murciano-Granadina goats.

Genome-Wide Analyses Reveal Genetic Convergence of Prolificacy between Goats and Sheep

The litter size of domestic goats and sheep is an economically important trait that shows variation within breeds. Strenuous efforts have been made to understand the genetic mechanisms underlying prolificacy in goats and sheep. However, there has been a paucity of research on the genetic convergence of prolificacy between goats and sheep, which likely arose because of similar natural and artificial selection forces. Here, we performed comparative genomic and transcriptomic analyses to identify the genetic convergence of prolificacy between goats and sheep. By combining genomic and transcriptomic data for the first time, we identified this genetic convergence in (1) positively selected genes (CHST11 and SDCCAG8), (2) differentially expressed genes (SERPINA14, RSAD2, and PPIG at follicular phase, and IGF1, GPRIN3, LIPG, SLC7A11, and CHST15 at luteal phase), and (3) biological pathways (genomic level: osteoclast differentiation, ErbB signaling pathway, and relaxin signaling pathway; transcriptomic level: the regulation of viral genome replication at follicular phase, and protein kinase B signaling and antigen processing and presentation at luteal phase). These results indicated the potential physiological convergence and enhanced our understanding of the overlapping genetic makeup underlying litter size in goats and sheep.

Shared Ancestry and Signatures of Recent Selection in Gotland Sheep

Gotland sheep, a breed native to Gotland, Sweden (an island in the Baltic Sea), split from the Gute sheep breed approximately 100 years ago, and since, has probably been crossed with other breeds. This breed has recently gained popularity, due to its pelt quality. This study estimates the shared ancestors and identifies recent selection signatures in Gotland sheep using 600 K single nucleotide polymorphism (SNP) genotype data. Admixture analysis shows that the Gotland sheep is a distinct breed, but also has shared ancestral genomic components with Gute (~50%), Karakul (~30%), Romanov (~20%), and Fjällnäs (~10%) sheep breeds. Two complementary methods were applied to detect selection signatures: A Bayesian population differentiation F_ST and an integrated haplotype homozygosity score (iHS). Our results find that seven significant SNPs (q-value < 0.05) using the F_ST analysis and 55 significant SNPs (p-value < 0.0001) using the iHS analysis. Of the candidate genes that contain significant markers, or are in proximity to them, we identify several belongings to the keratin genes, RXFP2, ADCY1, ENOX1, USF2, COX7A1, ARHGAP28, CRYBB2, CAPNS1, FMO3, and GREB1. These genes are involved in wool quality, polled and horned phenotypes, fertility, twining rate, meat quality, and growth traits. In summary, our results provide shared founders of Gotland sheep and insight into genomic regions maintained under selection after the breed was formed. These results contribute to the detection of candidate genes and QTLs underlying economic traits in sheep.

Detection of selection signatures for response to Aleutian mink disease virus infection in American mink

Aleutian disease (AD) is the most significant health issue for farmed American mink. The objective of this study was to identify the genomic regions subjected to selection for response to infection with Aleutian mink disease virus (AMDV) in American mink using genotyping by sequencing (GBS) data. A total of 225 black mink were inoculated with AMDV and genotyped using a GBS assay based on the sequencing of ApeKI-digested libraries. Five AD-characterized phenotypes were used to assign animals to pairwise groups. Signatures of selection were detected using integrated measurement of fixation index (F_ST) and nucleotide diversity (θπ), that were validated by haplotype-based (hap-FLK) test. The total of 99 putatively selected regions harbouring 63 genes were detected in different groups. The gene ontology revealed numerous genes related to immune response (e.g. TRAF3IP2, WDR7, SWAP70, CBFB, and GPR65), liver development (e.g. SULF2, SRSF5) and reproduction process (e.g. FBXO5, CatSperβ, CATSPER4, and IGF2R). The hapFLK test supported two strongly selected regions that contained five candidate genes related to immune response, virus–host interaction, reproduction and liver regeneration. This study provided the first map of putative selection signals of response to AMDV infection in American mink, bringing new insights into genomic regions controlling the AD phenotypes.