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.
HENNING MW.1. Two outbreaks of infectious equine abortions are reported; both
with a very high abortion incidence.
2. In the majority of the abortions studied the foetal organs were found
to be extensively invaded by S. abortus-equi but in others this organism
could not be recovered from the foetus or after-birth.
3. Both donkey and horse mares were found to be susceptible, donkeys
being on the whole more resistant than horses.
4. Abortion was successfully produced in both horse and donkey mares
by means of (a) the oral administration of minced abortus-equi infected
foetal organs (4 cas...
Vitoria A, Barrachina L, Romero A, Fuente S, de Blas I, Gil L, Vázquez FJ.A new surgical technique using a polyether ether ketone (PEEK) anchoring device for testicle-sparing laparoscopic inguinal hernioplasty in stallions was described in 2023 and is known as the PEEK harpoon technique (PHT). In breeding stallions, it is essential that the surgery is effective in preventing inguinal hernia but also that it does not impair the testicular function. This study aims to evaluate whether the PHT may affect testicular function. To achieve that, changes in the testicular blood flow, sperm production and motility characteristics were assessed 28 days after use of the PHT. S...
Alim S, Cheppali SK, Pawar SS, Swamy MJ.Fibronectin type-II (FnII) proteins are major constituents in the seminal plasma of many mammals and play a crucial role in sperm capacitation. Additionally, the seminal FnII proteins from bull and horse exhibit chaperone-like activity (CLA), by acting as small heat shock proteins (shsps). The present work demonstrates that the major FnII protein of donkey seminal plasma, DSP-1 exhibits CLA with broad specificity and protects various client proteins such as alcohol dehydrogenase, lactate dehydrogenase and enolase against thermal and oxidative stress. Binding of phosphorylcholine (PrC) - the he...
Stricklin OE, McKenzie EC, Sriboonyapirat P, Russell DS, White CN.To determine whether Miniature Horse mares are predisposed to hemoperitoneum from nonneoplastic ovarian hemorrhage and report the clinical characteristics of this disorder. Methods: 51 equines with hemoperitoneum, including 22 nonminiature mares and 9 Miniature Horse mares, identified by searching medical records of a tertiary large animal hospital for confirmed hemoperitoneum cases between 2012 and 2023. Methods: Signs of hemoperitoneum in miniature mares included lethargy, inappetence, colic, tachycardia, and moderate to severe anemia (PCV ranging from 11% to 19%). Five miniature mares did n...
Risvanli A, Hatipoglu F, Salykov R, Timurkaan N, Kadiralieva N, Kasymalieva KK, Seker I, Ekinci E.In the current study, we aimed to determine the distribution of telocytes in the ovary, oviduct and uterus of Kyrgyz mares depending on whether they were pregnant. We also studied the progression during the first 6 months of pregnancy. To this end, ovary, oviduct and uterus tissues from 53 Kyrgyz mares were obtained post-mortem. The mare tissue samples were divided into two groups: pregnant (n = 43) and non-pregnant (n = 10). Telocyte levels in the tissues were determined using light microscopic and immunohistochemical methods. Subsequently, the data acquired were evaluated based on ...
Ulaangerel T, Mu S, Sodyelalt J, Yi M, Zhao B, Hao A, Wen X, Han B, Bou G.The success or failure of embryo fixation is crucial for embryo attachment and later development. As an epithelial chorioallantoic placenta-type animal, the horse has a special process of embryo implantation, and the mechanism of embryo fixation in horses is still unclear. Methods: In this study, the structural and transcriptomic characteristics of endometrial tissue from the fixed and nonfixed sides of 20-day gestation embryos in Mongolian horses were investigated to search for important genes and potential molecular markers associated with the fixation phase of equine embryos. Results: A com...
Byambaragchaa M, Park SH, Park MH, Kang MH, Min KS.Equine chorionic gonadotropin (eCG) hormone, comprising highly glycosylated α- and β-subunits, elicits responses similar to follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in non-equid species. This study aimed to establish a mass production of recombinant eCG (rec-eCG) using CHO DG44 cells. Single-chain rec-eCG β/α was expressed in CHO DG44 cells. FSH- and LH-like activities were evaluated in CHO-K1 and HEK 293 cells expressing the equine LH/CG receptor (eLH/CGR), rat LH/CGR (rLH/CGR), and rFSHR. pERK1/2 activation and β-arrestin 2 recruitment were assessed in PathHunter ...
Lösle M, Lin CW, Beil-Wagner J, Aebi M, Buch T.Equine chorionic gonadotropin (eCG) is a widely used hormone that synchronizes the female cycle and induces estrus in livestock. eCG is a heterodimeric glycoprotein composed of non-covalently linked α- and β-chains whose glycosylation profiles determine the in vivo activity of the hormone. The commercially available eCG products are crudely purified from the serum of pregnant mares, hence called pregnant mare serum gonadotropin (PMSG). Appropriate glycosylation of the protein is crucial for the correct binding to the receptor, receptor activation, and its half-life. The exact protein composi...
Hardefeldt LY, Thomas K, Begg L.Antimicrobial resistance (AMR) is a problem for equine practitioners in Australia, but antimicrobial use in practice has been largely understudied. We aimed to evaluate equine veterinarians' intentions of prescribing antimicrobials in areas where we perceived there to be wide ranges of practice - dentistry, reproduction and for nonbactericidal effects. Methods: An online cross-sectional survey of veterinarians working in equine practice was conducted over 4 months in 2023 and 2024. Antimicrobial use, including compounding practices, for reproductive and dental disorders, and nonbactericidal...
Cuervo-Arango J, Necchi D, Clutton-Brock A, Profaska M, Crabtree J, Claes A.This retrospective clinical study describes different techniques for transvaginal follicle aspiration in mares and compares results from 5 different commercial ovum pick-up (OPU) clinics in which the same operator aspirated mares using different systems and equipment: Clinic 1 (n = 42 mares, two-operator OPU technique, double-lumen-echogenic-tip needle, and manual syringe-assisted flushing of follicles), Clinic 2 (n = 28 mares, single-operator-OPU-technique, double-lumen-echogenic-tip needle, infusion pump controlled by foot-pedal for follicle flushing), Clinic 3 (n = 18 mares, sin...
Talib MT, Nasir A, Kashif M, Rahman A, Rehman AU, Akbar H, Nadeem A, Howe DK, Azam MN.The aim of this study was to determine the prevalence of anti-Neospora (N.) caninum and anti-N. hughesi antibodies in horses and to appraise the associated risk factors in the two central districts (Jhang and Toba Tek Singh) of Punjab Province, Pakistan. A total of 300 horse sera were analyzed for the presence of antibodies to Neospora spp. using a competitive ELISA. The overall prevalence of antibodies against Neospora species in horses was 25 % (75/300; 95 % CI 20.1-29.9). The prevalence of antibodies to N. caninum and N. hughesi species was 12.3 % (37/300; 95 % CI 8.6-16) and 19.3 % (5...
Brito LFC.Semen analysis is an important laboratory diagnostic test for stallions. Evaluation of sperm motility is integral to basic semen analysis and results are important for breeding management and clinical practice. Computer-assisted sperm analysis (CASA) allows objective sperm motility evaluation and increases analytical precision. The objective of the present study was to validate a portable CASA system (AndroScope). Fresh/cooled semen samples (33 ejaculates, 18 stallions) and frozen semen (40 ejaculates and one epididymal flush, 27 stallions) were evaluated using the AndroScope and the IVOS II C...
Bukhari SSUH, Urooj S.In winter anestrous, prolonged melatonin secretion inhibits gonadotropin-releasing hormone (GnRH). However, synthetic GnRH analogues such as buserelin can stimulate follicular development. We aimed to investigate clinical relationship between retinol, cholecalciferol, and buserelin for inducing estrous in anestrous mares (Equus caballus). We used a total of twenty-one anestrous mares, randomly divided into three groups of seven animals. Group A received retinol, cholecalciferol, and buserelin; group B received buserelin; and group C was control. Groups A, B, and C had 71.42% (n = 5; 95% CI...
Gugole PM, Zannoni A, Forni M, Iacono E, Zambelli F, Merlo B.This study investigates the effects of overnight holding and naloxone (Nx) supplementation on the vitrification outcomes of equine immature oocytes. Oocytes were divided into six experimental groups based on treatment combinations: fresh (F) and held (H) control oocytes, oocytes vitrified with or without Nx (10 M) (VIT and VIT-Nx), oocytes vitrified after overnight holding with or without Nx (10 M) (H-VIT and H-VIT-Nx). They were assessed for survival, meiotic competence, intracellular oxidative stress, mitochondrial activity and distribution, apoptosis, and apoptotic gene expression. At sur...
Abah KO, Ligocka-Kowalczyk Z, Itodo JI, Ameh G, Partyka A, Nizanski W.Accurately predicting male fertility is crucial for the animal breeding industry due to its significant economic implications. Existing literature suggests that mammalian fertility is partially dependent on sperm DNA integrity. However, routine semen analysis often fails to detect DNA damage and does not consistently correlate with field fertility outcomes. While assessing sperm DNA integrity provides valuable biological insights, its role in diagnosing animal infertility remains uncertain. Results: This meta-analysis evaluated the association between sperm DNA fragmentation (SDF) and fertilit...
Cuervo-Arango J, Sala-Ayala L, Márquez-Moya A, Martínez-Boví R.The objective of this study was to determine the effect of two aspiration pressures (75 vs. 150 mmHg), the follicle flushing method (injection pump controlled by a foot pedal vs. a plastic syringe) and the twisting of the OPU needle on oocyte recovery and in vitro embryo production. OPU data from a total of 104 warmblood sport mares belonging to a commercial OPU-ICSI program were collected as part of a prospective study split into three experiments. Each mare was used only once for OPU. In Experiment 1, the mares' follicles were aspirated using either a high aspiration pressure (flow rate of 1...
Khan IU, Khairullah AR, Khan AY, Rehman AU, Mustofa I.This review explores advanced strategies for enhancing fertility and optimizing reproductive outcomes in equine breeding programs. Horses, being seasonal breeders, present unique reproductive challenges influenced by environmental and physiological factors such as photoperiods, hormone cycles, and aging. Key approaches discussed include hormonal therapies, artificial light manipulation, and nutritional supplementation to improve ovulation and conception rates during the breeding season. Specific hormones such as gonadotropin-releasing hormone analogs, equine follicle-stimulating hormone, and p...
Filho RRR, França DS, Alonso MA, Riccio AV, Affonso FJ, Brito MM, Francischini MCP, Nichi M, Boakari Y, Fernandes CB.During gestation, there is a higher energy demand which increases oxygen requirements. As a result, there is an elevated production of reactive oxygen species. Notably, unlike in horses, the effects of maternal age and parity on women's oxidative profiles are well-documented. Thus, this study aimed to investigate oxidative changes in mares during the last third of gestation and the postpartum period, considering age and parity. Seventeen mares were categorized by age (3-7, 8-11, ≥12 years) and parity (nulliparous, 1-3, 4-6 parities). Oxidative processes were assessed using Thiobarbituric Aci...
Hannan MA, Watanabe H, Takeyama A, Yoshida S, Wudamu D, Lkhagvasuren N, Claes A, Stout TAE, Cheong SH, Haneda S, Nambo Y.This study evaluated the viability of in vitro embryo production using ovum pick-up (OPU) and intracytoplasmic sperm injection (ICSI) as breeding techniques for pure and crossbred Hokkaido native ponies (n = 9). Oocytes were collected using transvaginal ultrasound-guided follicle aspiration. ICSI was performed on in vitro matured oocytes using frozen semen. Embryonic cultures were monitored using time-lapse cinematography. Blastocysts were cryopreserved and, after thawing, were transferred non-surgically into recipient mares. Over nine OPU sessions, the mean number of aspirated follicles was 2...
da Silva-Álvarez E, Gómez-Arrones V, Correa-Fiz F, Martín-Cano FE, Gaitskell-Phillips G, Carrasco JJ, Rey J, Aparicio IM, Peña FJ, Alonso JM....This study aims to unveil potential differences in the vaginal and uterine microbiomes in mares and jennies, and to identify possible mechanisms involved in uterine immune homeostasis. The microbiota was characterized using 16S rRNA sequencing, and the uterine proteome was analyzed using UHPLC/MS/MS in 18 samples from healthy mares and 14 from jennies. While taxonomic analysis revealed high interspecies similarities, β-diversity analysis showed distinct clustering, with only two vaginal taxa and five uterine taxa differing between species. Despite compositional differences, PICRUSt analysis s...
Renaudin CD, Picandet V, Kass PH.Using the equation of Hartwig et al. and the table established for light breed horses, day of gestation was predicted in 108 Warmblood (WB) and 59 racehorses (Thoroughbred [TB] and Standardbred [STB]) pregnant mares. In WB, gestational ages were predicted within 2 weeks from 100 to 200 days of gestation using biparietal diameter (BPD), aortic diameter (AortD) or femur length (FL); within 2 weeks from 100 to 250 days using BPD or AortD; within 2 weeks from 100 to 300 days using BPD alone; and within 3 weeks from 100 to 350 days using eye approximated volume (EyV) alone. In the ...
Baatar T, Song D, Weng Y, Wang G, Jin L, Guo R, Li B, Dugarjaviin M.The epigenetic regulation of gene expression through the covalent modification of histones is crucial for developing germline cells. To study the regulatory role of alternative splicing (AS) of euchromatic histone lysine methyltransferase 2 (EHMT2/G9A) in spermatogenesis in Mongolian horses, this study first examines the localization of the EHMT2 gene in testicular support cells and then predicts the higher-order structures of sequences with and without AS. Two types of lentiviral vectors for overexpression were subsequently constructed for the EHMT2 gene, one with AS and one without, to infec...
Samie KA, Kowalewski MP, Schuler G, Gastal GDA, Bollwein H, Scarlet D.In horses, the mechanisms behind ovarian follicle growth and oocyte maturation remain largely unknown. In other species, oocyte-secreted factors growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) have been related to the acquisition of developmental competence and to interaction with granulosa cells for the regulation of follicle development. This study assessed the expression and localization of GDF9 in the equine ovary, and its possible relationship with granulosa cell function. Results: Using custom-made antibodies, GDF9 protein was localized in oocytes from th...
Warren AS, Werner LA, Thombs LA, Rodgerson DH, Spirito MA, Sandow CB, McCracken MJ.To report the impact of ventral midline colopexy on colic, recurrence of large colon volvulus (LCV) and time to next live foal. Methods: Retrospective case control study. Methods: A total of 188 Thoroughbred broodmares surgically treated for LCV (2016-2020). Methods: Horses treated for LCV were grouped based on whether they received a colopexy (CP) or did not (NCP). All broodmares that underwent a second LCV surgery were subsequently categorized into two groups: those that received a colopexy (RCP) and those that did not (NRCP). Differences in the number of horses with large colon compromise, ...
Ziadi C, Valera M, Laseca N, Perdomo-González D, Demyda-Peyrás S, de Los Terreros AR, Molina A. By simultaneously integrating both genotyped and non-genotyped animals into genetic evaluation, the single-step genomic BLUP method enhanced the accuracy of genetic assessments. This study aimed to compare the increase in prediction reliability (R) between restricted maximum likelihood (REML) and single-step genomic REML (ssGREML) in the Pura Raza Española (PRE) horse breed. The dataset comprised reproductive records for seven fertility traits from 47,502 females, with a total of 57,316 animals represented in the pedigree. A total of 4009 animals were genotyped using the EQUIGENE 90K SNP ar...
Medica A, Aitken RJ, Swegen A, Gibb Z.Context Equine reproductive technologies are crucial for overcoming challenges in natural fertilisation, particularly in sub-fertile stallions and breeding programs focused on genetic conservation and performance enhancement. Assisted reproductive technologies (ARTs), such as artificial insemination (AI), intracytoplasmic sperm injection (ICSI), and in vitro fertilisation (IVF), improve fertility outcomes and enable breeding across geographical distances. Aims This review examines sperm isolation techniques used in ART, evaluating their efficacy, limitations, and potential to enhance reproduct...
Wen X, Ren H, He Q, Yi M, Ulaangerel T, Bou G.Horses and donkeys, as integral members of the equine family, exhibit distinct reproductive capabilities and characteristics. Seminal plasma, the fluid component of semen, contains a variety of proteins that play critical roles in sperm function and fertility. This study aimed to systematically compare the protein profiles in the seminal plasma of horses and donkeys, thereby elucidating the molecular differences between these two species. The study utilized 4D-DIA proteomics technology to analyze seminal plasma from horses and donkeys and further validated key proteins through Western blot. Ou...
Barandalla M, Colleoni S, Perota A, Galli C, Lazzari G.The introduction of ovum pick-up, Intracytoplasmic Sperm Injection (ICSI) and in vitro embryo production in equine reproduction offers significant advantages, including overcoming infertility, high blastocyst yields, embryo cryopreservation, and preimplantation genetic testing (PGT) by collecting few cells extruded spontaneously during embryo growth using a mouth pipette. PGT enables embryo selection before transfer and is particularly useful in breeds with a preference for specific offspring genders, coat color, and detecting genetic diseases. Here, we present the first large-scale validation...
Herkenhoff ME.MicroRNAs (miRNAs) are molecules that regulate gene expression by targeting the 3' untranslated region (UTR) of mRNAs. They are essential in numerous biological processes like growth, metabolism, and muscle development. miRNA research has become crucial in livestock breeding, offering solutions for improving animal health and productivity. This review focuses on miRNAs' roles in equine performance, reproduction, and disease, highlighting key findings and future applications in these areas. It discusses the use of circulating miRNAs (ci-miRNA) as biomarkers for athletic performance, particularl...
Scarlet D, Schuler G, Malama E, Bollwein H, Bocci C, Colleoni S, Lazzari G, Galli C, Kowalewski MP.Despite recent improvements in equine ovum pick-up (OPU) combined with intracytoplasmic sperm injection (ICSI), there is still significant inter-individual variability. In this study, serum concentrations of the oocyte-secreted factors growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15), as well as the GDF9/BMP15 complex, anti-Müllerian hormone (AMH), progesterone (P4), and free and conjugated estradiol-17β (E2), were determined in 59 mares (3-24 years) at the time of OPU. Mares were classified retrospectively, based on the number of embryos obtained, into low or...
Medica AJ, Swegen A, Seifi-Jamadi A, McIntosh K, Gibb Z.Oxidative stress plays a critical role in regulating sperm function, yet species-specific antioxidant mechanisms remain poorly understood. This study compared hydrogen peroxide (H2O2) tolerance in horse and human sperm and investigated the roles of catalase and glutathione peroxidase (GPx) in horses. A H2O2 dose-response assay (0-2000 µM) showed that horse sperm were significantly more resistant to oxidative damage, with an IC50 for progressive motility over 14-fold higher than that of human sperm (391.6 µM vs. 27.3 µM). Horse sperm also accumulated more intracellular H2O2 without loss of m...
