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Topic:Reproduction
Reproduction in horses encompasses the biological processes and mechanisms involved in the breeding and development of equine offspring. This includes the study of reproductive anatomy, physiology, and endocrinology in both mares and stallions. Key areas of interest include the estrous cycle, ovulation, conception, gestation, and parturition. Researchers also examine factors influencing fertility, reproductive technologies such as artificial insemination and embryo transfer, and management practices that impact reproductive success. This page compiles peer-reviewed research studies and scholarly articles that explore the physiological, genetic, and environmental aspects of equine reproduction.
Insights from healthy mares reveal that mammalian uteri harbor a diverse virome. The Earth's estimated 10 virions, primarily phages, significantly impact microbial ecosystems. Despite their abundance, viromes remain relatively understudied-particularly in domestic animals. While recent studies have described a dynamic commensal microbiome in mammalian uteri, no research has yet characterized the commensal virome in a mammalian uterus. In this study, we report for the first time the presence of a sparse, but diverse native virome in the equine uterus. The resulting virome database consists of 513 non-redundant viral genomes (> 2 kb). Taxonomic annotations revealed the...
Molecular detection of pathogenic Leptospira spp. in mares with reproductive disorders enrolled in embryo transfer programs. Equine genital leptospirosis (EGL) is associated with reproductive disorders in mares. However, its occurrence in embryo transfer (ET) programs remains poorly characterized. Objective: Given the scarcity of data on the circulation of Leptospira spp. in mares enrolled in ET programs, this study aimed to investigate the serological and molecular occurrence of Leptospira spp. in mares with a history of reproductive disorders from 13 stud farms dedicated to embryo transfer in Brazil. Methods: Serum and endometrial cytobrush samples (ECS) were collected from 70 unvaccinated mares. Serological analy...
FGF2, LIF, and IGF1 supplementation during in vitro maturation or culture improves equine ICSI embryo development in an age-dependent manner. Ovum pickup (OPU) combined with intracytoplasmic sperm injection (ICSI) has reshaped equine assisted reproduction, enabling embryo production from mares and stallions with constrained breeding opportunities; however, limited efficiency of in vitro maturation (IVM) and in vitro culture (IVC) continues to hinder embryo production. Growth factor supplementation with fibroblast growth factor 2 (FGF2), leukemia inhibitory factor (LIF), and insulin-like growth factor 1 (IGF1) in combination (FLI) has been shown to enhance oocyte and embryo developmental competence in several species. Objective: This...
Factors influencing gestation length in Mares in the Tiaret region, Algeria. Gestation length is a key parameter in equine reproductive management, yet its variability remains poorly documented in Barb and Arabian mares under Algerian conditions. Objective: This study aims to determine gestation length in mares and to assess the influence of various factors, including breed, year of mating, mating month, mare age, parity, reproductive status, stallion and the foal's sex on gestation duration. Methods: A total of 133 mares from the National Stud Farm of Tiaret (Algeria) were monitored over the period 2021-2024. Results: The mean gestation length was 332.5 days (range: 3...
The Equine Reproductive Microbiota: Composition, Dynamics, Dysbiosis, and Implications for Fertility in Mares and Stallions. The equine reproductive microbiota has emerged as an important factor influencing reproductive health and fertility in both mares and stallions. Traditionally, the equine uterus was considered sterile, and microbial presence was interpreted primarily in the context of infection. However, sequencing-based studies have demonstrated that the reproductive tract, including the uterus and semen, contains detectable microbial communities or microbial DNA signatures, challenging this traditional paradigm. In mares, the vaginal microbiota is consistently dominated by , , , and , whereas the uterine env...
Nano-Encapsulated Vitamin E Enhances Cryo-Resistance of Stallion Spermatozoa: A Comprehensive Evaluation of Sperm Quality, Kinematic Parameters, Antioxidant Capacity, Microbiota and Ultrastructure. This experiment explores the comparative ability of vitamin E (VE) and its nano-emulsion (VEN) in enhancing cryo-resistance of stallion spermatozoa by examining semen quality, kinematic variables, acrosome integrity, apoptosis, antioxidant capacity, ultra-structural alterations and microbiota of cryopreserved stallion sperm. Semen from five stallions (8-10 years) was cryopreserved with 0.1 or 1 mM of VE or VEN; and a non-additive group served as the control. The VEN particles ranged in size from 72 to 172 nm, with a mean diameter of 287 nm. Supplementation with VE (1 mM) or VEN (0.1 ...
miRNA Sequencing and Differential Analysis of Testis in 1-Year-Old and 2-Year-Old Kazakh Horses. The represents a significant genetic resource within China's population, characterized by notable resilience and an ability to thrive on coarse forage. Nevertheless, a decline in its numbers has been observed recently, making the improvement of its reproductive performance crucial for the preservation of this breed and the advancement of the related industry. In this study, testicular tissues from 1-year-old (pre-pubertal) and 2-year-old (post-pubertal) were analyzed. miRNA sequencing was conducted on tissues from these age groups, followed by bioinformatics analyses to elucidate the functi...
Comparative analysis of mRNA and circRNA expression profiles and interaction networks in testicular tissues of Mongolian horses before and after sexual maturity. Mongolian horses, celebrated for their resilience and adaptability, undergo marked physiological transformations during sexual maturation. This study employed whole-transcriptome sequencing to conduct a comparative analysis of mRNA and circular RNA (circRNA) expression profiles, along with their interactive regulatory networks, in testicular tissues of Mongolian horses pre- and post-sexual maturity. Histological examinations using hematoxylin-eosin (H.E.) and 4’,6-diamidino-2-phenylindole (DAPI) staining revealed distinct morphological differences between sexually immature and mature testicu...
Hyperactivation and Tyrosine Phosphorylation of Cryopreserved Stallion Spermatozoa in Relation to Conventional In Vitro Fertilization Blastocyst Production. Challenges in establishing clinical conventional in vitro fertilization (IVF) in horses include variation in sperm and oocyte quality, which can be affected by mare age. Extended preincubation of stallion spermatozoa has resulted in successful IVF. However, there is limited research on the impact of preincubation on sperm characteristics and IVF success. Objective: Responses of frozen-thawed stallion spermatozoa over time under IVF preincubation conditions were evaluated, and samples based on specific responses were tested for their ability to fertilize oocytes, including those from older mare...
Membrane and mitochondrial antioxidants improve post-thaw functional quality of stallion spermatozoa. Cryopreservation of stallion semen induces oxidative stress that compromises sperm motility, membrane integrity, and mitochondrial function. Given the high mitochondrial reliance of equine spermatozoa and their susceptibility to oxidative damage, compartment-specific antioxidant strategies may improve post-thaw functional resilience. This study evaluated the effects of astaxanthin, a membrane-active carotenoid, and MitoTEMPO, a mitochondria-targeted superoxide scavenger, on the functional and oxidative status of frozen-thawed stallion spermatozoa. Ejaculates from nine stallions were cryopreser...
Age, embryo donor status, and insemination with chilled semen all predispose to persistent breeding-induced endometritis in warmblood mares. Persistent breeding-induced endometritis (PBIE) is a common reason for mares failing to establish pregnancy. Objective: To examine the hypothesis that advancing mare age and embryo donor status predispose to PBIE and compromise fertility. Methods: Retrospective analysis of the impact of mare age, breeding system (embryo donor versus broodmare), and semen type (chilled versus frozen-thawed) on the likelihood of PBIE and subsequent pregnancy/embryo recovery. Methods: Warmblood mares (n = 769) inseminated during 1745 oestrous cycles were divided into three age categories (≤6, 7-13 and ≥14...
ProAKAP4 as a predictor of semen freezability in Asturcon ponies. Cryopreservation is a valuable tool in equine reproduction, although its success remains highly variable among stallions. The proAKAP4 protein has been proposed as a molecular marker of sperm quality and cryotolerance. Objective: This study aimed to evaluate the relationship between proAKAP4 concentration and sperm cryotolerance in ejaculates from Asturcon ponies, and to assess whether proAKAP4 levels in fresh semen can predict post-thaw sperm quality parameters before and after cryopreservation. Methods: Twenty-four ejaculates from eight different stallions were used (three ejaculates per ani...
Equine Oocyte and Embryo Metabolism in the ART Setting: Current Knowledge and Clinical Significance. Equine in vitro embryo production has become very efficient and is used extensively worldwide for the clinical production of foals. What we know so far about offspring health and performance is promising; however, elements of the in vitro process remain unphysiological when compared to in vivo conditions. Studying the metabolism of oocytes and embryos can help inform the optimisation of culture systems and identify aberrations if they occur. Given the growing body of knowledge on the downstream effects of an inadequate peri-conception environment, both in vivo and in vitro, it is imperative th...
Holding immature equine oocytes for up to 3 nights prior to ICSI under practical shipping conditions (10-22 °C) is compatible with blastocyst development. In vitro embryo production via intracytoplasmic sperm injection (ICSI) is widely used in equine reproductive management. Shipping of immature oocytes allows oocyte recovery for ICSI to be performed by referring veterinarians. However, delays in oocyte shipment are common, and their effect on outcomes is unclear. Shipping is typically done at about 22 °C, but previous studies have shown that holding at 15 °C maintains equine oocyte developmental competence. We hypothesized that lower temperatures may better support oocyte viability if the case that delays occur. Oocytes (n = 664) were rec...
Transcriptome Sequencing and Differential Analysis of Testes in One- and Two-Year-Old Kazakh Horses. This study systematically elucidated the developmental characteristics and molecular regulatory mechanisms of the testis during the critical period of sexual maturation in Kazakh horses by combining histological observation of one- and two-year-old testicular tissues with transcriptomic sequencing. In the testes of one-year-old horses, no obvious lumen was observed, and the interior is mainly comprising supporting cells and spermatogonia on the basement membrane; in contrast, in the testes of two-year-old horses, the tubular lumen was complete with spermatogonia, spermatocytes, and spermatozoa...
Relationship between the estrus duration in cyclic mares and the endometrial gene expression on day 7 post-ovulation. This study investigated the effect of estrus duration on endometrial gene expression in cyclic mares on Day 7 post-ovulation, focusing on transcripts relevant to early pregnancy: uterocalin (P19), insulin-like growth factor 1 (IGF1), fibroblast growth factor 2 (FGF2), progesterone receptor (PGR), and estrogen receptor alpha (ESR1). Twelve mares were classified according to the estrus duration in long estrus (LE, ≥ 3 days of endometrial edema; n = 7) or short estrus (SE, 0.1). ESR1 expression was undetectable in all samples. These findings suggest that prolonged estrus enhances P19 e...
Comparative analysis of the transcriptome and methylome in distinct trophoblast populations at the time of embryo implantation in mares. BACKGROUND: During equine implantation, two distinct trophoblast subpopulations are identified: the invasive chorionic girdle (CG) and the non-invasive allantochorion. The invasive CG trophoblast is believed to modulate the maternal immune response and facilitates embryo attachment to the endometrium, while the allantochorion contributes to placental development without breaching the endometrium. However, the mechanisms underlying differential adhesion and immune modulation by these two lineages remain poorly understood. This study aimed to investigate the regulation of biological processes un...
Fungal endometritis in broodmares: clinical presentation, prevalence in Ireland and diagnostic performance of cytology. Fungal endometritis is an uncommon uterine condition associated with poor fertility. Objective: This study aimed to 1) provide a descriptive summary of 11 cases of fungal endometritis, 2) assess prevalence trends of fungal endometritis over time, 3) assess fungal species distribution in diagnostic samples, and 4) evaluate the diagnostic accuracy of cytology. Methods: Study 1 reviewed records of 11 mares diagnosed with fungal endometritis for history, presentation, treatment, and outcome. Study 2 analysed 6,727 uterine samples (swabs and lavages; 2019-2024) for factors influencing fungal cultur...
Periovulatory administration of therapeutic and supratherapeutic doses of firocoxib does not impair induced ovulation or follicular dynamics in mares treated with a GnRH analogue. To evaluate the effects of therapeutic and supratherapeutic periovulatory doses of firocoxib on ovulation and follicular dynamics in mares. Methods: Seventy cycling mares were randomly assigned to receive firocoxib at 0.1 mg/kg (n = 27), firocoxib at 0.3 mg/kg (n = 22), or no treatment (control; n = 21). Treatments were initiated on Day 0, defined as the day of ovulation induction with a GnRH analogue administered intramuscularly, with firocoxib administered intravenously on Day 0 and Day 1 (24 h apart). Follicular diameter and ovulation timing were assessed by transrectal ultrasonography. Res...
Multi-omics profiling of the testes in Kazakh horses across sexual maturation. Equus caballus is a species of considerable economic and cultural significance. However, the regulatory networks involved in equine sexual maturation remain unclear and eventually limit its reproduction and utilization. In this study, testicular tissues from eight Kazakh horses at two developmental stages (2 years, representing pre-maturation, and 3 years, representing post-maturation) were analyzed using whole transcriptome sequencing, data-independent acquisition (DIA) proteomics, and untargeted metabolomics. An integrated regulatory network was constructed encompassing ceRNA, mRNA, prot...
miRNA Sequencing and Differential Analysis of Testes from 1-Year-Old and 3-Year-Old Kazakh Horses. This study aims to elucidate the miRNA regulatory mechanisms during the developmental process of Kazakh horse testes at 1 and 3 years of age. Through miRNA sequencing and bioinformatics analysis of testicular tissues from 1-year-old and 3-year-old horses, a developmentally stage-specific miRNA expression profile was constructed. A total of 1640 miRNAs were identified, among which 437 (380 up-regulated and 57 down-regulated) exhibited significant differential expression between the two age groups, including eca-miR-16, eca-miR-17, eca-miR-103, and eca-miR-199a-5p. Functional enrichment analysis...
Saliva and plasma metabolome analysis during the five days before foaling in the mare. Saliva is a relevant biofluid for real-time welfare-friendly monitoring of systemic events in animals, because some bioanalytes have a systemic origin and its collection is painless, stress-free and non-invasive. Our aim was to analyze the metabolome of equine saliva during the five days before foaling, with a focus on identifying metabolites whose level significantly changed before parturition, that could be potential salivary biomarkers of the onset of parturition. We compared the saliva and plasma metabolomes to investigate their relationship. Saliva and blood samples were collected from tw...
Endometrial Evaluation Using Video-Assisted Hysteroscopy After Uterine Prolapse Management in a Mare. This case report describes the successful application of video-assisted hysteroscopy to evaluate endometrial recovery in a 6-year-old mare following treatment for complete uterine prolapse secondary to dystocia. Upon presentation, the uterus was manually reduced and supported with a Buhner's suture. A multimodal medical protocol, including broad-spectrum antibiotics, anti-inflammatory drugs and uterine lavage, was initiated. Five days after reduction, an endoscopic evaluation was performed using a dedicated videovaginoscope without uterine insufflation. The procedure provided high-resolution i...
Comparative analysis of uterine inflammation in jennies and mares after insemination with cryopreserved donkey semen. The limited fertility of jennies inseminated with frozen donkey semen remains a major challenge for donkey reproduction and conservation, contrasting with the more favorable outcomes observed in mares. Species-specific differences in post-breeding uterine inflammation have been proposed as a key factor underlying this disparity. This study compared the uterine inflammatory response and pregnancy outcomes of jennies and mares inseminated with frozen donkey semen. Twelve jennies and eleven mares were monitored over 48 and 44 estrous cycles, respectively. Artificial insemination (AI) was performe...
Generation of equine-specific local antibiograms: reproductive tract of mares and fillies in Western Australia. Antimicrobial resistance (AMR) may lead to increasing inefficacy and treatment failure of bacterial infections in the future. Antimicrobial stewardship (AMS) programmes are critical to ensuring the continued efficacy of available antimicrobials. There is a lack of published evidence-based data on the susceptibility of isolates from common reproductive infections encountered in mares. This study aims to provide equine veterinarians in Western Australia (WA) with the most appropriate first-line empirical antimicrobials for infections of the mare reproductive tract. Methods: A retrospective study...
Sex determination and genetic screening of equine embryos with whole genome amplification and real-time PCR. Reliable pre-implantation sex determination and genetic screening enables informed embryo transfer decisions in equine breeding while avoiding later interventions. We developed a streamlined workflow that couples rapid whole genome amplification (WGA) with a multiplex real-time PCR targeting ETSTY5 as a Y-specific marker and UBC as an autosomal control. On purified equine DNA, sex was correctly assigned down to 10 pg gDNA and to a single fibroblast cell. Direct testing of embryo biopsies without WGA yielded inconsistent results, whereas introducing a short WGA step produced tight allelic-discr...
Conditional Antioxidant Protection of Stallion Spermatozoa by Butylated Hydroxytoluene Under Induced Oxidative Stress. Despite advances in the method, equine semen cryopreservation still leads to a marked decline in sperm quality, partly attributed to oxidative stress, which motivates the search for lipophilic antioxidants capable of stabilizing the plasma membrane during cooling and freezing. This study performed three experiments to evaluate butylated hydroxytoluene (BHT) as an additive to commercial skim milk-based (Botu-Sêmen) and egg yolk-based (Botu-Crio) extenders. In Experiment 1, a dose-response curve (0.5, 1.0, and 1.5 mM) was performed using stallion semen to assess toxicity and establish a safe ...
Embryonic vesicle diameter at first pregnancy diagnosis in in vivo- and in vitro-derived pregnancies and its relationship with pregnancy loss in the mare. This retrospective study compared the relationship between embryonic vesicle diameter at first pregnancy diagnosis and early embryonic loss (EEL) across three pregnancy types: artificially inseminated broodmares (AI; n = 263), recipients carrying in vivo-derived flushed embryos (IVD-F; n = 312), and recipients carrying in vitro-produced embryos by intracytoplasmic sperm injection (IVP-ICSI; n = 161). Vesicle diameter was recorded at Day 12 post-ovulation in AI, Day 4 post-embryo transfer (ET) for IVD-F, and Day 7 post-ET for IVP-ICSI pregnancies. Mean (±SD) vesicle diameters and E...
Novel application of a PMSG assay for measurement of circulating LH levels in horses. Luteinizing hormone (LH) plays a pivotal role in equine reproductive physiology, yet its measurement has traditionally relied on radioimmunoassays (RIA), which present safety, accessibility, and regulatory challenges. This study evaluates the use of a commercially available pregnant mare serum gonadotropin (PMSG) enzyme-linked immunosorbent assay (ELISA) as an alternative for quantifying circulating LH in horses. Given the 100% peptide identity between equine LH and PMSG, we hypothesized that the PMSG ELISA would detect LH with high specificity and sensitivity. Blood samples from healthy, cycl...
