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Topic:Reproductive Technology
Reproductive technology in horses encompasses a range of scientific techniques and procedures aimed at assisting and enhancing equine reproduction. These technologies include artificial insemination, embryo transfer, and cryopreservation of gametes and embryos. They are employed to improve breeding efficiency, manage genetic diversity, and preserve valuable genetic material. Artificial insemination involves the collection and introduction of semen into the mare's reproductive tract, while embryo transfer allows for the harvesting and implantation of embryos from donor to recipient mares. Cryopreservation involves freezing and storing sperm, oocytes, or embryos for future use. This page compiles peer-reviewed research studies and scholarly articles that investigate the methodologies, applications, and outcomes of reproductive technologies in equine breeding and management.
Transcriptome Sequencing and Differential Expression Analysis of Ovaries from Kazakh Mares During Seasonal Quiescence and Estrus Activation. Kazakh horses are typical seasonal breeders, and ovarian activity is markedly reduced during the non-breeding period. Hormonal stimulation can induce ovarian functional responses during seasonal anestrus; however, the early ovarian transcriptional changes associated with this response remain incompletely understood. In this study, ovarian transcriptome sequencing was performed in 12 Kazakh mares examined during the seasonal anestrous period. The mares were classified into a non-hormonally stimulated seasonal quiescent group (DB, = 6) and a hormone-induced ovarian activation group (DY, = 6) f...
Histomorphometric and Histochemical Changes in the Mare Tuba Uterina During the Oestrous Cycle and Follicular Cyst Condition. This study evaluated histomorphometric and histochemical changes in the mare tuba uterina during different reproductive stages and under follicular cyst conditions. Forty nonpregnant mares were classified into follicular, luteal, post-ovulation and follicular cyst groups (n = 10/group). Histological evaluation of the isthmus, ampulla and infundibulum was performed using haematoxylin and eosin staining, while periodic acid-Schiff (PAS) staining was used to assess epithelial secretory activity. Morphometric parameters included number of primary mucosal folds, fold length, epithelial height a...
Effects of the Freezing Diluent Tonicity and Prefreezing Cooling Rates on Post-Thaw Sperm Quality Markers in the Pure-Bred Arabian Stallion. Stallion semen cryopreservation remains limited by inconsistent post-thaw sperm quality and fertility. This study evaluated the effects of freezing extender effective tonicity and prefreezing cooling rate on post-thaw sperm characteristics in pure-bred Arabian stallions. In a two-phase design, ejaculates ( = 40) from 10 stallions were processed using extenders with different osmotic conditions (330, 390, and 450 mOsm/kg) and subjected to cooling durations of 45 min, 1.5 h, or 3 h. Sperm quality was assessed using CASA, functional assays, flow cytometry, transcriptomic analysis, and...
Extreme male reproductive skew limits effective population size in American Standardbred horses. Standardbred horses are widely used for harness racing in North America, Europe, Australia, and New Zealand. In the U.S., two gaits (Pacers and Trotters) are genetically differentiated at a level typical for different horse breeds. We used the complete pedigree for all registered American Standardbred foals born 1970-2014 (>200 K Trotters and > 500 K Pacers) to calculate annual and lifetime reproductive skew and its consequences for the effective number of breeders per year (Nb) and effective size per generation (Ne). With rare exceptions, females can only produce 0 or 1 foal per year, w...
The effects of clomiphene citrate on reproductive parameters in the mare. Clomiphene citrate (CC) is a longstanding human fertility drug that has yet to be investigated in horses. The objective was to evaluate effects of CC on mare reproduction. After follicle ablation on Day 0, treatment mares (n=5) received 2 grams of CC intravenously on Days 1-5 while control mares (n=4) received no treatment. Transrectal ultrasonography was performed on Days 1-5 and 8, and transvaginal oocyte aspiration occurred on Day 8. Hormones were analyzed on Days 0-5, 8, 11, and 15. Mares receiving CC exhibited higher uterine edema grades compared to control mares (P=0.009). Antral follicl...
Implications of dominance deviations for reproductive and morphological traits in the genetic management of the Pura Raza Española horse. Dominance is a non-additive genetic effect involving allele interaction at the same locus. In animal breeding, it has often been ignored due to its complexity and the low accuracy of pedigree-based estimates. This study analysed dominance variance components for reproductive traits [age at first foaling (AFF), reproductive efficiency (RE), interval between first and second foaling (I12)] and morphological traits [scapulo-ischial length (SIL), dorsal sternal diameter (DSD), knee circumference (KC)] in Pura Raza Española (PRE) mares. The aim was to assess the magnitude of dominance effects acro...
Isolation of high-quality stallion spermatozoa: a comparison of methods and their effects on sperm quality and yield, DNA damage, and functional competence by ICSI. Intracytoplasmic sperm injection (ICSI) is the primary method for equine in vitro embryo production, yet outcomes may be influenced by sperm selection techniques. Objective: This study compared four isolation methods: EquiPure™, Vetmotl™, Felix™, and Samson™, to assess effects on sperm quality and embryo development. Methods: Semen was collected from four fertile stallions, processed and evaluated for sperm motility, viability, DNA integrity, and yield of high-quality cells relative to input. Isolated samples were compared to non-isolated (centrifuged) samples. Spermatozoa were used fo...
Sperm Energy-restriction and Recovery (SER) enhances equine sperm function and embryo development after ICSI. Assisted reproductive technologies (ART) are extensively used in domestic animal reproduction; however, improving their efficiency and consistency remains a major challenge for achieving reliable reproductive outcomes. The equine industry faces unique challenges related to sperm capacitation, which limited the success of conventional in vitro fertilization (IVF) for many years. Consequently, intracytoplasmic sperm injection (ICSI) became the most widely used technique for commercial in vitro embryo production. Even though a successful IVF protocol was recently developed, substantial opportunit...
Genome-Wide Characterization of the TGF-β Gene Family in Donkey (Equus asinus) Reveals Lineage-Specific Gene Duplications and Deleterious Mutations. The transforming growth factor-beta (TGF-β) superfamily regulates diverse biological processes, including proliferation, differentiation, apoptosis, tissue remodeling, and reproductive signaling across metazoans. Here, we performed a genome-wide characterization of the TGF-β gene family in donkey (, ASM1607732v2) using comparative genomics and bioinformatics analyses, with horse (, EquCab3.0) as a reference to investigate evolutionary conservation and functional divergence. Genome assemblies and proteomes were retrieved from NCBI, and TGF-β genes were identified using BLASTp and HMMER searc...
Advanced paternal age is associated with reduced reproductive success and offspring racing performance in Australian Thoroughbred racehorses. Reproductive ageing influences fertility and offspring fitness across mammals. In humans and model organisms, paternal age has been associated with changes in sperm quality and genomic integrity, including oxidative stress, DNA damage, and epigenetic alterations; however, these mechanisms have not been directly examined in large equine populations. Thoroughbred racehorses provide a system to investigate paternal age effects at scale using detailed breeding records. In this retrospective observational study, with data from 35 retired stallions and 33,546 progeny, we assessed associations betwee...
Achieving Success in Conventional Equine Embryo Transfer: A Practical Review. Equine embryo transfer is a well-established procedure in horse breeding programs and it's used to increase the number of offspring from valuable mares, obtain embryos from mares in competition and produce foals from mares unable to carry a pregnancy to term. The success of embryo recovery depends mainly on the day of flushing, management of insemination, and the fertility of donor mare and stallion. Other relevant factors include donor age and reproductive status, number of ovulations, operator experience, and flushing technique. Pregnancy rates after transfer are influenced by donor-recipien...
Chromosomal chaos: understanding aneuploidy associated with assisted reproductive technologies. Pregnancy loss remains a significant challenge for the equine breeding industry, with substantial economic and management consequences. Chromosomal abnormalities have emerged as a central driver of pregnancy loss, particularly during early gestation, highlighting the need to better understand the etiology of this inherent genetic instability. Concurrently, the rapid expansion of assisted reproductive technologies (ART) offers promise for improving equine reproductive efficiency alongside the traditional practice of natural cover. However, the increasing use of in vitro embryo production (IVP) ...
Follicular growth and atresia at the time of oocyte aspiration differentially affect in vitro embryo production in mares. Ovum pick-up (OPU) followed by intracytoplasmic sperm injection (ICSI) is increasingly used in horses, yet embryo production rates remain variable, potentially reflecting differences in oocyte developmental competence at the time of aspiration. We investigated whether the stage of the follicular wave, growth phase (GP) versus atresia phase (AP), and associated endocrine profiles in mares, influence oocyte developmental competence. Mares underwent follicular ablation to synchronize follicular waves, and oocytes were aspirated during GP or AP for in vitro production of embryos. Serum concentrati...
Cracks in the ice: biological challenges and incremental progress in equine oocyte vitrification. Equine oocyte vitrification could enhance the flexibility of in vitro embryo production, yet developmental competence remains reduced. Only vitrification of oocytes matured in vivo yields foaling rates comparable to fresh oocytes. Recent advances in vitrification at the germinal vesicle (GV) stage, supported by systematic comparisons of cryoprotective agents and exposure times, has enabled consistent blastocyst production and birth of several foals. Comparative studies of GV and metaphase II (MII) stages suggest biological advantages of vitrification after in vitro maturation (IVM), warranting...
Cytogenetic, genomic, and reproductive characterization of four pura Raza Española mares carrying a 64, X, del(X),t(X; Y) complex karyotype. Chromosomal abnormalities involving the sex chromosomes constitute critical genetic factors influencing fertility in horses. Nevertheless, a substantial proportion of individuals carrying sex chromosomal abnormalities exhibit normal reproductive phenotypes, which complicates their identification until adulthood. Here, we present four mares carrying a complex deletion/translocation rearrangement with the karyotype formula 64, X, del(X)(p∼25),t(X; Y)(p∼25; q∼15). The cases analyzed belong to three unrelated families of Pura Raza Española (PRE), all presenting the same chromosomal abnormal...
Novel technique for correcting urovagina via urethral transposition in the horse. Vesicovaginal reflux is a common cause of infertility in mares. Surgical correction is commonly recommended and involves caudal relocation of the urethral orifice which forces the urine to be expelled caudally. There have been several previously described techniques. Complications associated with caudal urethral extension occur in 11-33.3% of cases. Objective: To identify a novel technique for performing caudal urethral translocation that effectively corrects vesicovaginal reflux with minimal associated complications. Methods: In vivo experiment and clinical case series. Methods: The experimen...
Embryo developmental kinetics and vitrification in relation to pregnancy outcome, foaling percentage and foal sex. While fast in vitro embryo development has been associated with improved outcomes, the relationships of slow in vitro embryo development and vitrified versus fresh in vitro produced (IVP) embryo transfer to foaling percentage and foal sex are less explored. Objective: To determine the relationships of (1) day of blastocyst formation (D7-11 after intracytoplasmic sperm injection (ICSI)) and (2) vitrification and warming method (one- and three-step) versus fresh transfer with pregnancy, early pregnancy loss (EPL), foaling percentage and foal sex. Methods: Retrospective clinical study. Methods: B...
Retained fetal membranes in light breed mares hospitalized for attended parturition. Retention of fetal membranes (RFM) is well described in draft breeds, whereas data on light breed mares remains limited and inconsistent. Objective: This retrospective study aimed to describe the frequency, associated factors, treatments, and consequences of RFM in light breed mares hospitalized for attended parturition. Methods: Medical records of 321 light breed mares hospitalized for attended parturition at the Veterinary Teaching Hospital, University of Bologna, were retrospectively reviewed. Data collected included: breed, previous history of RFM, age, parity, assisted reproductive techni...
Ovarian follicle dynamics in the plains zebra (Equus quagga). Understanding follicular dynamics during the estrous cycle is essential for developing breeding programs and assisted reproductive technologies (ARTs) in any species. In this context, knowledge of follicular dynamics and related uterine changes in the plains zebra (Equus quagga) is essential to increase the declining population of this vital African species and to provide comparative insights into more endangered zebra species. Likely due to the difficulty of handling these wild species, no detailed reproductive study using ultrasonography has been performed in any zebra. Therefore, the presen...
Conventional IVF in the horse past, present, and future: physiological and technical insights. For decades, conventional in vitro fertilization (IVF) in the horse was ineffective, leading to reliance on intracytoplasmic sperm injection (ICSI) for both research and clinical in vitro embryo production. However, the ability to achieve IVF is essential to the study of key reproductive processes, including sperm capacitation, fertilization, and early embryonic development. Recently we have established a repeatable and efficient IVF system for horses, using long-term (9-22 h) sperm pre-incubation. For clinical use, IVF has many features that may support higher embryo quality than does ICSI, a...
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...
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...
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...
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...
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...
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...
Impact of donor mare and stallion identity on the likelihood of pregnancy after transfer of in vitro produced embryos. The success of in vitro embryo production (IVEP) is influenced by donor mare and stallion. Objective: To determine whether donor mare and stallion influence the pregnancy rate after transfer of in vitro produced (IVP) blastocysts and to identify factors influencing the likelihood of obtaining one or more pregnancies from a single IVEP session. Methods: Retrospective clinical study. Methods: The influence of the following variables on pregnancy outcome was assessed in 2292 transfers of IVP blastocysts: speed of in vitro embryo development, embryo grade after thawing, age of the donor mare, blas...
