Interspecies Chimerism with Mammalian Pluripotent Stem Cells.

Interspecies blastocyst complementation enables organ-specific enrichment of xenogenic pluripotent stem cell (PSC) derivatives. Here, we establish a versatile blastocyst complementation platform based on CRISPR-Cas9-mediated zygote genome editing and show enrichment of rat PSC-derivatives in several tissues of gene-edited organogenesis-disabled mice. Besides gaining insights into species evolution, embryogenesis, and human disease, interspecies blastocyst complementation might allow human organ generation in animals whose organ size, anatomy, and physiology are closer to humans. To date, however, whether human PSCs (hPSCs) can contribute to chimera formation in non-rodent species remains unknown. We systematically evaluate the chimeric competency of several types of hPSCs using a more diversified clade of mammals, the ungulates. We find that naïve hPSCs robustly engraft in both pig and cattle pre-implantation blastocysts but show limited contribution to post-implantation pig embryos. Instead, an intermediate hPSC type exhibits higher degree of chimerism and is able to generate differentiated progenies in post-implantation pig embryos.

Single-nuclei RNA sequencing (snRNA-seq) uncovers trophoblast cell types and lineages in the mature bovine placenta.

Ruminants have a semi-invasive placenta, which possess highly vascularized placentomes formed by maternal endometrial caruncles and fetal placental cotyledons and required for fetal development to term. The synepitheliochorial placenta of cattle contains at least two trophoblast cell populations, including uninucleate (UNC) and binucleate (BNC) cells that are most abundant in the cotyledonary chorion of the placentomes. The interplacentomal placenta is more epitheliochorial in nature with the chorion developing specialized areolae over the openings of uterine glands. Of note, the cell types in the placenta and cellular and molecular mechanisms governing trophoblast differentiation and function are little understood in ruminants. To fill this knowledge gap, the cotyledonary and intercotyledonary areas of the mature day 195 bovine placenta were analyzed by single nuclei analysis. Single-nuclei RNA-seq analysis found substantial differences in cell type composition and transcriptional profiles between the two distinct regions of the placenta. Based on clustering and cell marker gene expression, five different trophoblast cell types were identified in the chorion, including proliferating and differentiating UNC and two different types of BNC in the cotyledon. Cell trajectory analyses provided a framework for understanding the differentiation of trophoblast UNC into BNC. The upstream transcription factor binding analysis of differentially expressed genes identified a candidate set of regulator factors and genes regulating trophoblast differentiation. This foundational information is useful to discover essential biological pathways underpinning the development and function of the bovine placenta.

Energy metabolism disorders during in vitro maturation of bovine cumulus-oocyte complexes interfere with blastocyst quality and metabolism.

Glucose and fatty acids (FA) metabolism disturbances during oocyte in vitro maturation (IVM) affect their metabolism and surrounding cumulus cells, but only inhibition of glucose metabolism decreases embryo culture efficiency. Therefore, the present experiment aimed to reveal if glucose or FA metabolism inhibition leads to the disruption of embryo developmental potential, and to characterize the metabolic landscape of embryos reaching the blastocyst stage. Inhibitors of glucose (IO + DHEA) or FA (ETOMOXIR) metabolism were applied during IVM, and the control group was matured under standard conditions. Blastocysts obtained from experimental and control groups were analyzed with regard to lipidome and metabolome (mass spectrometry), transcriptome (RNA-Seq) and fluorescence lipid droplets staining (BODIPY). We showed that inhibition of glucose and fatty acid metabolism leads to cellular stress response compromising the quality of preimplantation embryos. The inhibition of energy metabolism affects membrane fluidity as well as downregulates fatty acids biosynthesis and gene expression of trophectoderm cell line markers. Therefore, we conclude that oocyte maturation environment exerts a substantial effect on preimplantation development programming at cellular and molecular levels.

A High-Coverage Mesolithic Aurochs Genome and Effective Leveraging of Ancient Cattle Genomes Using Whole Genome Imputation.

Ancient genomic analyses are often restricted to utilizing pseudohaploid data due to low genome coverage. Leveraging low-coverage data by imputation to calculate phased diploid genotypes that enables haplotype-based interrogation and single nucleotide polymorphism (SNP) calling at unsequenced positions is highly desirable. This has not been investigated for ancient cattle genomes despite these being compelling subjects for archeological, evolutionary, and economic reasons. Here, we test this approach by sequencing a Mesolithic European aurochs (18.49×; 9,852 to 9,376 calBCE) and an Early Medieval European cow (18.69×; 427 to 580 calCE) and combine these with published individuals: two ancient and three modern. We downsample these genomes (0.25×, 0.5×, 1.0×, and 2.0×) and impute diploid genotypes, utilizing a reference panel of 171 published modern cattle genomes that we curated for 21.7 million (Mn) phased SNPs. We recover high densities of correct calls with an accuracy of >99.1% at variant sites for the lowest downsample depth of 0.25×, increasing to >99.5% for 2.0× (transversions only, minor allele frequency [MAF] ≥ 2.5%). The recovery of SNPs correlates with coverage; on average, 58% of sites are recovered for 0.25× increasing to 87% for 2.0×, utilizing an average of 3.5 million (Mn) transversions (MAF ≥2.5%), even in the aurochs, despite the highest temporal distance from the modern reference panel. Our imputed genomes behave similarly to directly called data in allele frequency-based analyses, for example consistently identifying runs of homozygosity >2 Mb, including a long homozygous region in the Mesolithic European aurochs.

Genomic Reconstruction of the Successful Establishment of a Feralized Bovine Population on the Subantarctic Island of Amsterdam.

The feral cattle of the subantarctic island of Amsterdam provide an outstanding case study of a large mammalian population that was established by a handful of founders and thrived within a few generations in a seemingly inhospitable environment. Here, we investigated the genetic history and composition of this population using genotyping and sequencing data. Our inference showed an intense but brief founding bottleneck around the late 19th century and revealed contributions from European taurine and Indian Ocean Zebu in the founder ancestry. Comparative analysis of whole-genome sequences further revealed a moderate reduction in genetic diversity despite high levels of inbreeding. The brief and intense bottleneck was associated with high levels of drift, a flattening of the site frequency spectrum and a slight relaxation of purifying selection on mildly deleterious variants. Unlike some populations that have experienced prolonged reductions in effective population size, we did not observe any significant purging of highly deleterious variants. Interestingly, the population's success in the harsh environment can be attributed to preadaptation from their European taurine ancestry, suggesting no strong bioclimatic challenge, and also contradicting evidence for insular dwarfism. Genome scan for footprints of selection uncovered a majority of candidate genes related to nervous system function, likely reflecting rapid feralization driven by behavioral changes and complex social restructuring. The Amsterdam Island cattle offers valuable insights into rapid population establishment, feralization, and genetic adaptation in challenging environments. It also sheds light on the unique genetic legacies of feral populations, raising ethical questions according to conservation efforts.

Characterization of highly pathogenic avian influenza virus in retail dairy products in the US.

In March 2024, clade 2.3.4.4b H5N1 highly pathogenic avian influenza virus (HPAIV) was detected in dairy cattle in the US, and it was discovered that the virus could be detected in raw milk. Although affected cow's milk is diverted from human consumption and current pasteurization requirements are expected to reduce or eliminate infectious HPAIV from the milk supply, a study was conducted to characterize whether the virus could be detected by quantitative real-time RT-PCR (qrRT-PCR) in pasteurized retail dairy products and, if detected, to determine whether the virus was viable. From 18 April to 22 April 2024, a total of 297 samples of Grade A pasteurized retail milk products (23 product types) were collected from 17 US states that represented products from 132 processors in 38 states. Viral RNA was detected in 60 samples (20.2%), with qrRT-PCR-based quantity estimates (non-infectious) of up to 5.4log1050% egg infectious doses per mL, with a mean and median of 3.0log10/mL and 2.9log10/mL, respectively. Samples that were positive for type A influenza by qrRT-PCR were confirmed to be clade 2.3.4.4 H5 HPAIV by qrRT-PCR. No infectious virus was detected in any of the qrRT-PCR-positive samples in embryonating chicken eggs. Further studies are needed to monitor the milk supply, but these results provide evidence that the infectious virus did not enter the US pasteurized milk supply before control measures for HPAIV were implemented in dairy cattle.IMPORTANCEHighly pathogenic avian influenza virus (HPAIV) infections in US dairy cattle were first confirmed in March 2024. Because the virus could be detected in raw milk, a study was conducted to determine whether it had entered the retail food supply. Pasteurized dairy products were collected from 17 states in April 2024. Viral RNA was detected in one in five samples, but infectious virus was not detected. This provides a snapshot of HPAIV in milk products early in the event and reinforces that with current safety measures, infectious viruses in milk are unlikely to enter the food supply.

Complexity and modification of the bull sperm glycocalyx during epididymal maturation.

Mammalian spermatozoa have a surface covered with glycocalyx, consisting of heterogeneous glycoproteins and glycolipids. This complexity arises from diverse monosaccharides, distinct linkages, various isomeric glycans, branching levels, and saccharide sequences. The glycocalyx is synthesized by spermatozoa developing in the testis, and its subsequent alterations during their transit through the epididymis are a critical process for the sperm acquisition of fertilizing ability. In this study, we performed detailed analysis of the glycocalyx on the sperm surface of bull spermatozoa in relation to individual parts of the epididymis using a wide range (24) of lectins with specific carbohydrate binding preferences. Fluorescence analysis of intact sperm isolated from the bull epididymides was complemented by Western blot detection of protein extracts from the sperm plasma membrane fractions. Our experimental results revealed predominant sequential modification of bull sperm glycans with N-acetyllactosamine (LacNAc), followed by subsequent sialylation and fucosylation in a highly specific manner. Additionally, variations in the lectin detection on the sperm surface may indicate the acquisition or release of glycans or glycoproteins. Our study is the first to provide a complex analysis of the bull sperm glycocalyx modification during epididymal maturation.

Single-cell RNA-Seq reveals the earliest lineage specification and X chromosome dosage compensation in bovine preimplantation embryos.

Lineage specification and X chromosome dosage compensation are two crucial biological processes that occur during preimplantation embryonic development. Although extensively studied in mice, the timing and regulation of these processes remain elusive in other species, including humans. Previous studies have suggested conserved principles of human and bovine early development. This study aims to provide fundamental insights into these programs and the regulation using a bovine embryo model by employing single-cell transcriptomics and genome editing approaches. The study analyzes the transcriptomes of 286 individual cells and reveals that bovine trophectoderm/inner cell mass transcriptomes diverge at the early blastocyst stage, after cavitation but before blastocyst expansion. The study also identifies transcriptomic markers and provides the timing of lineage specification events in the bovine embryo. Importantly, we find that SOX2 is required for the first cell decision program in bovine embryos. Moreover, the study shows the occurrence of X chromosome dosage compensation from morula to late blastocyst and reveals that this compensation results from downregulation of X-linked genes in female embryonic cells. The transcriptional atlas generated by this study is expected to be widely useful in improving our understanding of mammalian early embryo development.

Histone remodeling reflects conserved mechanisms of bovine and human preimplantation development.

How histone modifications regulate changes in gene expression during preimplantation development in any species remains poorly understood. Using CUT&Tag to overcome limiting amounts of biological material, we profiled two activating (H3K4me3 and H3K27ac) and two repressive (H3K9me3 and H3K27me3) marks in bovine oocytes, 2-, 4-, and 8-cell embryos, morula, blastocysts, inner cell mass, and trophectoderm. In oocytes, broad bivalent domains mark developmental genes, and prior to embryonic genome activation (EGA), H3K9me3 and H3K27me3 co-occupy gene bodies, suggesting a global mechanism for transcription repression. During EGA, chromatin accessibility is established before canonical H3K4me3 and H3K27ac signatures. Embryonic transcription is required for this remodeling, indicating that maternally provided products alone are insufficient for reprogramming. Last, H3K27me3 plays a major role in restriction of cellular potency, as blastocyst lineages are defined by differential polycomb repression and transcription factor activity. Notably, inferred regulators of EGA and blastocyst formation strongly resemble those described in humans, as opposed to mice. These similarities suggest that cattle are a better model than rodents to investigate the molecular basis of human preimplantation development.

Extension services can promote pasture restoration: Evidence from Brazil's low carbon agriculture plan.

Innovation and improved practices in the livestock sector represent key opportunities tomeet global climate goals. This paper provides evidence that extension services can pro-mote pasture restoration in cattle ranching in Brazil. We use a randomized controlledtrial implemented in the context of the ABC Cerrado (a large-scale program launched in2014 aimed at fostering technology adoption through a combination of training andtechnical assistance) to examine the effects of different types of extension on agriculturalpractices, input use, and productivity. Providing technical assistance to previously trainedproducers promoted pasture restoration, induced farmers to use inputs more intensively,helped them to improve their management and soil conservation practices, and substan-tially increased revenues. A cost­benefit calculation indicates that US$1 invested in theABC Cerrado program increased profits by US$1.08 to $1.45. Incorporating carbonsavings amplifies this return considerably.

Comprehensive analysis of differentially expressed mRNAs, circRNAs, and miRNAs and their ceRNA network in the testis of cattle-yak, yak, and cattle.

Cattle-yak is a hybrid offspring resulting from the crossbreeding of yak and cattle, and it exhibits substantial heterosis in production performance. However, male sterility in cattle-yak remains a concern. Reports suggest that noncoding RNAs are involved in the regulation of spermatogenesis. Therefore, in this study, we comprehensively compared testicular transcription profiles among cattle, yak, and cattle-yak. Numerous differentially expressed genes (DEGs), differentially expressed circRNAs (DECs), and differentially expressed miRNAs (DEMs) were identified in the intersection of two comparison groups, namely cattle versus cattle-yak and yak versus cattle-yak, with the number of DEGs, DECs, and DEMs being 4968, 360, and 59, respectively. The DEGs in cattle-yaks, cattle, and yaks were mainly associated with spermatogenesis, male gamete generation, and sexual reproduction. Concurrently, GO and KEGG analyses indicated that DEC host genes and DEM source genes were involved in the regulation of spermatogenesis. The construction of a potential competing endogenous RNA network revealed that some differentially expressed noncoding RNAs may be involved in regulating the expression of genes related to testicular spermatogenesis, including miR-423-5p, miR-449b, miR-34b/c, and miR-15b, as well as previously unreported miR-6123 and miR-1306, along with various miRNA-circRNA interaction pairs. This study serves as a valuable reference for further investigations into the mechanisms underlying male sterility in cattle-yaks.

Characterization of Mycobacterium orygis, Mycobacterium bovis, and Mycobacterium caprae Infections in Humans in Western Canada.

Epidemiologic research on zoonotic tuberculosis historically used Mycobacterium bovis as a surrogate measure, however, increased reports of human tuberculosis caused by other animal-associated Mycobacterium tuberculosis complex members like Mycobacterium orygis necessitates their inclusion. We performed a retrospective cohort study including persons infected with any animal-lineage M. tuberculosis complex species in Alberta, Canada, from January 1995 to July 2021, identifying 42 patients (20 M. bovis, 21 M. orygis, one M. caprae). Demographic, epidemiologic and clinical characteristics were compared against persons with culture-confirmed M. tuberculosis infection. The proportion of culture-positive infections caused by M. orygis increased continuously from 2016-2020. Significantly more females at a higher median age were impacted by M. orygis, with all patients originating from South Asia. M. bovis caused significantly more extra-pulmonary disease, and disproportionately impacted young females, particularly those pregnant or post-partum. All infections were acquired abroad. These findings can aid in developing targeted public health interventions.

VPBrowse: Genome-based representation of MS/MS spectra to quantify 10,000 bovine proteins.

SWATH is a data acquisition strategy acclaimed for generating quantitatively accurate and consistent measurements of proteins across multiple samples. Its utility for proteomics studies in nonlaboratory animals, however, is currently compromised by the lack of sufficiently comprehensive and reliable public libraries, either experimental or predicted, and relevant platforms that support their sharing and utilization in an intuitive manner. Here we describe the development of the Veterinary Proteome Browser, VPBrowse (http://browser.proteo.cloud/), an on-line platform for genome-based representation of the Bos taurus proteome, which is equipped with an interactive database and tools for searching, visualization, and building quantitative mass spectrometry assays. In its current version (VPBrowse 1.0), it contains high-quality fragmentation spectra acquired on QToF instrument for over 36,000 proteotypic peptides, the experimental evidence for over 10,000 proteins. Data can be downloaded in different formats to enable analysis using popular software packages for SWATH data processing whilst normalization to iRT scale ensures compatibility with diverse chromatography systems. When applied to published blood plasma dataset from the biomarker discovery study, the resource supported label-free quantification of additional proteins not reported by the authors previously including PSMA4, a tissue leakage protein and a promising candidate biomarker of animal's response to dehorning-related injury.

Proinflammatory CD14highCD16low monocytes/macrophages prevail in Treponema phagedenis-associated bovine digital dermatitis.

Digital dermatitis (DD) is a skin disease in cattle characterized by painful inflammatory ulcerative lesions in the feet, mostly associated with local colonization by Treponema spp., including Treponema phagedenis. The reason why most DD lesions remain actively inflamed and progress to chronic conditions despite antibiotic treatment remains unknown. Herein, we show an abundant infiltration of proinflammatory (CD14highCD16low) monocytes/macrophages in active DD lesions, a skin response that was not mitigated by topical treatment with oxytetracycline. The associated bacterium, T. phagedenis, isolated from DD lesions in cattle, when injected subcutaneously into mice, induced abscesses with a local recruitment of Ly6G+ neutrophils and proinflammatory (Ly6ChighCCR2+) monocytes/macrophages, which appeared at infection onset (4 days post challenge) and persisted for at least 7 days post challenge. When exploring the ability of macrophages to regulate inflammation, we showed that bovine blood-derived macrophages challenged with live T. phagedenis or its structural components secreted IL-1ß via a mechanism dependent on the NLRP3 inflammasome. This study shows that proinflammatory characteristics of monocytes/macrophages and neutrophils dominate active non-healing ulcerative lesions in active DD, thus likely impeding wound healing after antibiotic treatment.

Single-cell profiling reveals transcriptome dynamics during bovine oocyte growth.

BACKGROUND: Mammalian follicle development is characterized by extensive changes in morphology, endocrine responsiveness, and function, providing the optimum environment for oocyte growth, development, and resumption of meiosis. In cattle, the first signs of transcription activation in the oocyte are observed in the secondary follicle, later than during mouse and human oogenesis. While many studies have generated extensive datasets characterizing gene expression in bovine oocytes, they are mostly limited to the analysis of fully grown and matured oocytes. The aim of the present study was to apply single-cell RNA sequencing to interrogate the transcriptome of the growing bovine oocyte from the secondary follicle stage through to the mid-antral follicle stage. RESULTS: Single-cell RNA-seq libraries were generated from oocytes of known diameters (< 60 to > 120 µm), and datasets were binned into non-overlapping size groups for downstream analysis. Combining the results of weighted gene co-expression network and Trendy analyses, and differently expressed genes (DEGs) between size groups, we identified a decrease in oxidative phosphorylation and an increase in maternal -genes and transcription regulators across the bovine oocyte growth phase. In addition, around 5,000 genes did not change in expression, revealing a cohort of stable genes. An interesting switch in gene expression profile was noted in oocytes greater than 100 µm in diameter, when the expression of genes related to cytoplasmic activities was replaced by genes related to nuclear activities (e.g., chromosome segregation). The highest number of DEGs were detected in the comparison of oocytes 100-109 versus 110-119 µm in diameter, revealing a profound change in the molecular profile of oocytes at the end of their growth phase. CONCLUSIONS: The current study provides a unique dataset of the key genes and pathways characteristic of each stage of oocyte development, contributing an important resource for a greater understanding of bovine oogenesis.

Genetic diversity and recent ancestry based on whole-genome sequencing of endangered Swedish cattle breeds.

Several indigenous cattle breeds in Sweden are endangered. Conservation of their genetic diversity and genomic characterization is a priority.Whole-genome sequences (WGS) with a mean coverage of 25X, ranging from 14 to 41X were obtained for 30 individuals of the breeds Fjällko, Fjällnära, Bohuskulla, Rödkulla, Ringamåla, and Väneko. WGS-based genotyping revealed 22,548,028 variants in total, comprising 18,876,115 single nucleotide polymorphisms (SNPs) and 3,671,913 indels. Out of these, 1,154,779 SNPs and 304,467 indels were novel. Population stratification based on roughly 19 million SNPs showed two major groups of the breeds that correspond to northern and southern breeds. Overall, a higher genetic diversity was observed in the southern breeds compared to the northern breeds. While the population stratification was consistent with previous genome-wide SNP array-based analyses, the genealogy of the individuals inferred from WGS based estimates turned out to be more complex than expected from previous SNP-array based estimates. Polymorphisms and their predicted phenotypic consequences were associated with differences in the coat color phenotypes between the northern and southern breeds. Notably, these high-consequence polymorphisms were not represented in SNP arrays, which are used routinely for genotyping of cattle breeds.This study is the first WGS-based population genetic analysis of Swedish native cattle breeds. The genetic diversity of native breeds was found to be high. High-consequence polymorphisms were linked with desirable phenotypes using whole-genome genotyping, which highlights the pressing need for intensifying WGS-based characterization of the native breeds.

Genome-wide analysis reveals genomic diversity and signatures of selection in Qinchuan beef cattle.

BACKGROUND: Indigenous Chinese cattle have abundant genetic diversity and a long history of artificial selection, giving local breeds advantages in adaptability, forage tolerance and resistance. The detection of selective sweeps and comparative genome analysis of selected breeds and ancestral populations provide a basis for understanding differences among breeds and for the identification and utilization of candidate genes. We investigated genetic diversity, population structure, and signatures of selection using genome-wide sequencing data for a new breed of Qinchuan cattle (QNC, n = 21), ancestral Qinchuan cattle (QCC, n = 20), and Zaosheng cattle (ZSC, n = 19). RESULTS: A population structure analysis showed that the ancestry components of QNC and ZSC were similar. In addition, the QNC and ZSC groups showed higher proportions of European taurine ancestry than that of QCC, and this may explain the larger body size of QNC, approaching that of European cattle under long-term domestication and selection. A neighbor-joining tree revealed that QCC individuals were closely related, whereas QNC formed a distinct group. To search for signatures of selection in the QNC genome, we evaluated nucleotide diversity (θπ), the fixation index (FST) and Tajima's D. Overlapping selective sweeps were enriched for one KEGG pathway, the apelin signaling pathway, and included five candidate genes (MEF2A, SMAD2, CAMK4, RPS6, and PIK3CG). We performed a comprehensive review of genomic variants in QNC, QCC, and ZSC using whole-genome sequencing data. QCC was rich in novel genetic diversity, while diversity in QNC and ZSC cattle was reduced due to strong artificial selection, with divergence from the original cattle. CONCLUSIONS: We identified candidate genes associated with production traits. These results support the success of selective breeding and can guide further breeding and resource conservation of Qinchuan cattle.

Whole-genome sequencing reveals genomic diversity and selection signatures in Xia'nan cattle.

BACKGROUND: The crossbreeding of specialized beef cattle breeds with Chinese indigenous cattle is a common method of genetic improvement. Xia'nan cattle, a crossbreed of Charolais and Nanyang cattle, is China's first specialized beef cattle breed with independent intellectual property rights. After more than two decades of selective breeding, Xia'nan cattle exhibit a robust physique, good environmental adaptability, good tolerance to coarse feed, and high meat production rates. This study analyzed the population genetic structure, genetic diversity, and genomic variations of Xia'nan cattle using whole-genome sequencing data from 30 Xia'nan cattle and 178 published cattle genomic data. RESULT: The ancestry estimating composition analysis showed that the ancestry proportions for Xia'nan cattle were mainly Charolais with a small amount of Nanyang cattle. Through the genetic diversity studies (nucleotide diversity and linkage disequilibrium decay), we found that the genomic diversity of Xia'nan cattle is higher than that of specialized beef cattle breeds in Europe but lower than that of Chinese native cattle. Then, we used four methods to detect genome candidate regions influencing the excellent traits of Xia'nan cattle. Among the detected results, 42 genes (θπ and CLR) and 131 genes (FST and XP-EHH) were detected by two different detection strategies. In addition, we found a region in BTA8 with strong selection signals. Finally, we conducted functional annotation on the detected genes and found that these genes may influence body development (NR6A1), meat quality traits (MCCC1), growth traits (WSCD1, TMEM68, MFN1, NCKAP5), and immunity (IL11RA, CNTFR, CCL27, SLAMF1, SLAMF7, NAA35, and GOLM1). CONCLUSION: We elucidated the genomic features and population structure of Xia'nan cattle and detected some selection signals in genomic regions potentially associated with crucial economic traits in Xia'nan cattle. This research provided a basis for further breeding improvements in Xia'nan cattle and served as a reference for genetic enhancements in other crossbreed cattle.

An across breed, diet and tissue analysis reveals the transcription factor NR1H3 as a key mediator of residual feed intake in beef cattle.

BACKGROUND: Provision of feed is a major determinant of overall profitability in beef production systems, accounting for up to 75% of the variable costs. Thus, improving cattle feed efficiency, by way of determining the underlying genomic control and subsequently selecting for feed efficient cattle, provides a method through which feed input costs may be reduced. The objective of this study was to undertake gene co-expression network analysis using RNA-Sequence data generated from Longissimus dorsi and liver tissue samples collected from steers of two contrasting breeds (Charolais and Holstein-Friesian) divergent for residual feed intake (RFI), across two consecutive distinct dietary phases (zero-grazed grass and high-concentrate). Categories including differentially expressed genes (DEGs) based on the contrasts of RFI phenotype, breed and dietary source, as well as key transcription factors and proteins secreted in plasma were utilised as nodes of the gene co-expression network. RESULTS: Of the 2,929 DEGs within the network analysis, 1,604 were reported to have statistically significant correlations (≥ 0.80), resulting in a total of 43,876 significant connections between genes. Pathway analysis of clusters of co-expressed genes revealed enrichment of processes related to lipid metabolism (fatty acid biosynthesis, fatty acid ß-oxidation, cholesterol biosynthesis), immune function, (complement cascade, coagulation system, acute phase response signalling), and energy production (oxidative phosphorylation, mitochondrial L-carnitine shuttle pathway) based on genes related to RFI, breed and dietary source contrasts. CONCLUSIONS: Although similar biological processes were evident across the three factors examined, no one gene node was evident across RFI, breed and diet contrasts in both liver and muscle tissues. However within the liver tissue, the IRX4, NR1H3, HOXA13 and ZNF648 gene nodes, which all encode transcription factors displayed significant connections across the RFI, diet and breed comparisons, indicating a role for these transcription factors towards the RFI phenotype irrespective of diet and breed. Moreover, the NR1H3 gene encodes a protein secreted into plasma from the hepatocytes of the liver, highlighting the potential for this gene to be explored as a robust biomarker for the RFI trait in beef cattle.

Genomic dissection of the correlation between milk yield and various health traits using functional and evolutionary information about imputed sequence variants of 34,497 German Holstein cows.

BACKGROUND: Over the last decades, it was subject of many studies to investigate the genomic connection of milk production and health traits in dairy cattle. Thereby, incorporating functional information in genomic analyses has been shown to improve the understanding of biological and molecular mechanisms shaping complex traits and the accuracies of genomic prediction, especially in small populations and across-breed settings. Still, little is known about the contribution of different functional and evolutionary genome partitioning subsets to milk production and dairy health. Thus, we performed a uni- and a bivariate analysis of milk yield (MY) and eight health traits using a set of ~34,497 German Holstein cows with 50K chip genotypes and ~17 million imputed sequence variants divided into 27 subsets depending on their functional and evolutionary annotation. In the bivariate analysis, eight trait-combinations were observed that contrasted MY with each health trait. Two genomic relationship matrices (GRM) were included, one consisting of the 50K chip variants and one consisting of each set of subset variants, to obtain subset heritabilities and genetic correlations. In addition, 50K chip heritabilities and genetic correlations were estimated applying merely the 50K GRM. RESULTS: In general, 50K chip heritabilities were larger than the subset heritabilities. The largest heritabilities were found for MY, which was 0.4358 for the 50K and 0.2757 for the subset heritabilities. Whereas all 50K genetic correlations were negative, subset genetic correlations were both, positive and negative (ranging from -0.9324 between MY and mastitis to 0.6662 between MY and digital dermatitis). The subsets containing variants which were annotated as noncoding related, splice sites, untranslated regions, metabolic quantitative trait loci, and young variants ranked highest in terms of their contribution to the traits` genetic variance. We were able to show that linkage disequilibrium between subset variants and adjacent variants did not cause these subsets` high effect. CONCLUSION: Our results confirm the connection of milk production and health traits in dairy cattle via the animals` metabolic state. In addition, they highlight the potential of including functional information in genomic analyses, which helps to dissect the extent and direction of the observed traits` connection in more detail.