Fertility in horses encompasses the physiological processes and factors influencing reproductive success in equine species. It involves the study of reproductive anatomy, endocrinology, and behavior, as well as the management practices that affect breeding outcomes. Key aspects include the estrous cycle, conception rates, and factors impacting stallion and mare fertility. Reproductive technologies such as artificial insemination, embryo transfer, and hormonal therapies are also explored to enhance breeding efficiency. This page compiles peer-reviewed research studies and scholarly articles that examine the biological mechanisms, management strategies, and technological advancements related to equine fertility.
Younglai EV.The research studied the effect of follicular fluid and plasma on the steroid-producing activity of granulosa cells isolated from the ovaries of horses in heat. The results could potentially provide […]
Channing CP.Granulosa cells were harvested from follicles of mares at various stages of the oestrous cycle and maintained in a tissue culture medium containing 15% horse serum, 30% medium '199' and 55% Hanks's solution. Between days 4 and 10 of culture the granulosa cells harvested from small follicles (1–2 cm. diam.) of mares in the midluteal phase of the cycle secreted an average of 0·36 pg. progesterone/cell/day. Cells harvested from large follicles of mares in the late and/or early oestrous stage of the cycle secreted an average of 29·5 pg. progesterone cell/day; the cells harvested from the large...
Bugno-Poniewierska M, Bielecka M, Pietras N, Kij-Mitka B, Podstawski Z, Długosz B.The Hucul horse is a Polish primitive breed with a small population size, which highlights the importance of preserving the genetic resources. The cryopreservation of semen is essential for creating gene banks, but its effect on the acrosome reaction in Hucul stallions has not yet been investigated. The acrosome reaction is one of the most important physiological events associated with the fertilization process. Therefore, our goal was to determine the level of acrosome reaction in chilled and frozen/thawed Hucul stallion semen using the FluoAcro test and the SCA semen analysis system. We foun...
Wen X, Bou G, He Q, Liu Q, Yi M, Ren H.The reproductive ability of equine species is a critical component of equine breeding programs, with sperm quality serving as a primary determinant of reproductive success. In this study, we perform an integrative analysis of proteomics and metabolomics in seminal plasma to identify proteins and metabolites associated with sperm quality and reproductive ability in equine species. Methods: We utilized the CEROS instrument to assess the morphology and motility of sperm samples from three horses and three donkeys. Additionally, we statistically analyzed the mating frequency and pregnancy rates in...
Ramírez-Agámez L, Crowley JB, Love CC, Hernández-Avilés C.Currently, Intracytoplasmic Sperm Injection (ICSI) on in vitro-matured equine oocytes obtained by transvaginal oocyte aspiration (TVA) is the method of choice for in vitro production of equine blastocysts in a clinical setting. A protocol for conventional in vitro fertilization (cIVF) using either fresh or frozen/thawed stallion sperm incubated under capacitating conditions (Tyrode's Albumin Lactate Pyruvate medium + penicillamine, hypotaurine, epinephrine; FERT-PHE) has been recently reported. Several factors that may impact the clinical applicability of this cIVF protocol have yet to be st...
Segabinazzi L, Lisboa FP, Zutter B.Limited response to conventional therapies and rising antibiotic resistance emphasize the need for alternative treatments for infectious endometritis. A recent in vitro study showed promising antimicrobial activity of a commercial uterine cleaning sanitizer (UCS) against endometritis pathogens. However, its safety and efficacy in mares remain untested. Objective: This study aimed to assess the clinical safety of intrauterine infusion of UCS in reproductively sound mares. Methods: Exp. 1. Six healthy mares with endometrial biopsies classified as I or IIA had two intrauterine infusions of UCS pe...
Vallejo-Soto P, Dorado J, Herrera-García R, Álvarez-Delgado C, Gómez-Laguna J, Santiago Á, Manrique M, González Ariza A, León Jurado JM....Assisted reproductive techniques are often extrapolated from horses to donkeys, despite poorer fertility outcomes in jennies. This issue has been attributed to unknown uterine species-specific differences. This study compared, through histomorphometry, the endometrium of jennies and mares. Endometrial biopsies (N = 12) were taken from reproductively sound jennies (n = 6) and mares (n = 6) in estrus. Histomorphometric analysis evaluated luminal (LE, µm) and glandular epithelium height (GE, µm), glandular lumen diameter (LD, µm), glandular area (GA, µm), the number of glands (#G), and glandu...
Cui B, Liu Y, Wu X, Li X.The objective of this study was to evaluate the effects of exogenous GnRH administration at the beginning of estrus synchronisation in mares during the spring transitional period. Estrus was synchronised using a progesterone releasing intravaginal device (PRID). The PRID was left in the vagina for 10 days, followed by an injection of 0.4 mg of cloprostenol at PRID removal. The GnRH group (n = 32) was subjected to intramuscular administration of 100 μg of the GnRH agonist triptorelin at PRID insertion, while the control group (n = 32) received 1 mL of sterile physiological sali...
Equine chronic degenerative endometritis (CDE) is a progressive process characterized by endometrial fibrosis that could be responsible for alterations of uterine environment and foetal-maternal communication. Objective: The aim of this study was to try to restore this communication by intrauterine administrations of amniotic cell-derived extracellular vesicles (AMC-EVs) in a case series. Methods: Twelve mares were selected on the basis of their reproductive history of early embryonic loss or abortion and clinical suspicion of CDE subsequently verified with histopathological examination of end...
Motta D, Aymée L, Roussouliéres I, Di Azevedo MIN, Jacob JCF, Lilenbaum W.Leptospirosis is a zoonotic disease caused by spirochetes of the genus Leptospira. Equine genital leptospirosis (EGL) has been described as a chronic and silent syndrome, presenting reproductive alterations such as abortion, stillbirth, placentitis, embryonic loss, repeat breeding syndrome, and subfertility. This study aimed to investigate the genital Leptospira infection in naturally infected mares with poor reproductive performance, as well as to genetically characterize the agents. A total of 41 mares with a history of poor reproductive performance were selected. Sera were collected for ser...
Cortez JV, Cervi D, Ruiz AJ, Grupen CG.Nicotinic acid (NA) treatment during in vitro maturation (IVM) has been shown to elevate nicotinamide adenine dinucleotide (NAD) levels and improve oocyte developmental competence. Suboptimal equine oocyte IVM systems currently limit the efficiency of viable embryo in vitro production. This study evaluated NA supplementation during IVM for cloned equine embryo production, using oocytes from abattoir-sourced ovaries and live mares via ovum pick-up (OPU). Abattoir-derived oocytes (n = 694) were treated without or with 50 or 200 μM NA during the 18 h holding period (Pre-IVM). Next, OPU-deriv...
Tsopp E, Kilk K, Gambini A, Tvrdà E, Viljaste-Seera A, Tuppits U, Jaakma Ü.Equine in vitro embryo production (IVP) via ovum pick-up (OPU) and intracytoplasmic sperm injection (ICSI) has gained prominence in sport-horse breeding due to high success rates, efficient semen utilization, and year-round embryo production, including from mares with fertility challenges or postmortem. However, assessing viability of early-stage ICSI-produced equine embryos remains challenging due to subjective morphological evaluations and limited visibility of developmental features. Non-invasive metabolomic analysis of culture media offers a promising alternative to enhance embryo selectio...
Armangau M, Lurier T, Josson A.Offspring Sex Ratio (OSR) at birth in mammals is generally assumed to follow a 1:1 male-to-female distribution, yet deviations in OSR have been observed and may be influenced by maternal and paternal factors. In this study we have focused on the effect of paternal factors (stallion age and breed) and breeding methods on the OSR. Using a retrospective dataset of 251,783 foal births recorded in France between 2015 and 2024, we applied generalized linear mixed models to evaluate the effects of these variables on the likelihood of producing a female foal. Stallion identity was included as a random...
The ability of spermatozoa to withstand cryopreservation differs between stallions. While the underlying mechanisms of these differences are not fully understood, seminal plasma (SP) may play a crucial role in modulating sperm cryotolerance. Seminal plasma contains a heterogeneous population of extracellular vesicles (sEVs), nanometer-sized membrane particles that can transfer biomolecules to sperm modulating their function. This study aimed to isolate and characterize two sized-sEV subsets-small (S-) and large (L-)-from stallion SP, and to evaluate their involvement in sperm freezability. Sem...
Medica AJ, Gibb Z, Ortiz-Rodriguez JM, Swegen A.Heavy use of antioxidants in equine in vitro fertilisation (IVF) media may suppress the reactive oxygen species (ROS) signals stallion sperm need for capacitation, which depends on high mitochondrial activity and a well-maintained endogenous redox homeostasis. A species-specific approach balancing oxidative protection with controlled ROS signalling could improve fertilisation efficiency and reduce prolonged incubation times.
González N, Varela A, de Blas N, Gil L.At present, oviductal pathologies and their influence on mare fertility have not been clearly determined. Checking changes throughout the year in the oviductal structure may be relevant to understand the influence on the appearance of problems in oviductal functionality and, thus, the impact on fertility, which is the objective of this work. The oviducts of 56 mares were examined. Their anatomy, permeability, oviductal cellularity and the presence of pathologies were assessed to establish the correlations between the time of the year and each of these parameters. We cannot conclude whether the...
Nunes MM, Gurgel JRC, Munhoz ML, de Giuli V, Carneiro GF, Miragaya MH, Gallelli MF, Guimaraes JD.The aim of this study was to assess the effect of lyophilized freezing extenders, which can be stored at room temperature, on stallion post-thaw sperm total motility (TM). Ejaculates of 28 stallions were frozen with four different extenders: two commercial freezing extenders offered worldwide and two novel lyophilized extenders (STAR and MX3), and two different cryopreservation protocols (CP1 with an equilibration period of 20 min. and CP2 with an equilibration period of 60 min.). The TM was assessed after thaw. Mean TM did not show significant differences between cryopreservation protocols wi...
Pasch L, Stefanovski D, Dobbie T, Lewis G, Turner RM.Historically, 8 × 0.5 ml straws, containing approximately 800 million sperm and 250 million progressively motile sperm were provided as a single 'breeding dose' of cryopreserved stallion semen. With the use of deep horn artificial insemination, there is a trend to reduce the number of 0.5 ml straws sold as a breeding dose, sometimes down to as little as one straw. Our aims were to determine if the number of straws provided as a breeding dose, as well as other mare, stallion and management factors, have an impact on pregnancy outcome in mares inseminated with cryopreserved semen. Unexpectedly,...
Caldevilla M, Ferrante A, Neild DM.The addition of antioxidants to cryopreservation media reportedly improves sperm post-thaw quality and reproductive performance after artificial insemination. Therefore, the objectives of this study were to evaluate if the addition of L-carnitine and pyruvate to freezing media, or their addition to samples after thawing, improves the post-thaw quality of equine spermatozoa. Thus, in Experiment 1, stallion semen samples were cryopreserved in: (1) EDTA-glucose-based extender with 20% egg yolk and 5% dimethylformamide (EDTA control); (2) skim milk-based extender with 20% egg yolk and 5% dimethylf...
Gaber JTH, Cuervo-Arango J, Plaza-Dávila M, Martínez-Boví R.This experiment was performed to evaluate whether intrafollicular treatment of PGE2 or PGF2α administered in early estrus would induce normal ovulation, progesterone production (Experiment 1) and pregnancy (Experiment 2). In Experiment 1, mares in estrus after 2 days of endometrial edema were injected in all largest dominant follicles (28-35 mm in diameter) with 0.5 mL of sterile water containing 500 μg PGE2 (n = 6), 125 μg PGF2α (n = 6) or placebo (n = 7) (Hour 0). Ultrasound examinations were performed daily, until ovulation or anovulation was detected, and daily blood samples ...
Medica AJ, Gibb Z, Aitken RJ.In vitro semen purification techniques have been developed that seek to mimic the in vivo selection process in order to generate the highest possible chance of oocyte fertilization following artificial insemination. Numerous methods have been developed to isolate functional spermatozoa for artificial insemination, yet only one method, single-layer centrifugation using commercial preparations like EquiPure, has been widely employed. In this study, we have introduced a novel approach for isolating spermatozoa and compared their quality to those isolated using EquiPure. The AI port system (Mempha...
Hernández-Avilés C, Ramírez-Agámez L, Varner DD, Raudsepp T, Love CC.Cases of stallion subfertility due to acrosome dysfunction have been recognized since the 1990s. While some of these were observed in stallions with reduced sperm motility and morphology, a more severe form has been reported in stallions with normal-to-excellent sperm quality parameters, which is also uniquely observed in individuals of the Thoroughbred registry. These stallions carry a susceptibility genotype (A/A-A A in the gene FKBP6, exon 5) for Impaired Acrosomal Exocytosis (IAE). Current clinical observations from our group have identified a few highly subfertile stallions from other bre...
Teixeira-Soares CM, Viana AG, Carvalho RPR, Barros E, Ramirez-Lopez C, Moura AA, Machado-Neves M.Endometritis is the leading cause of subfertility in mares and a significant challenge to equine reproduction. Unraveling uterine fluid proteome may promote advancements in the knowledge of endometritis etiopathogeneses and its diagnosis and therapeutic practices. Therefore, we aimed to characterize and compare the protein profile of the uterine fluid from healthy mares and animals diagnosed with endometritis. Mangalarga Marchador breed mares from Muriaé - Brazil were divided into control, infectious endometritis, and post-breeding endometritis groups (n = 8/ group). Uterine fluid was collect...
Arnold LC, Stout TAE, Beitsma MM, Deelen CC, Rizzo M, Leemans B, Galli C, Colleoni S, Lazzari G, Barandalla M, Claes ANJ.It is not known whether the likelihood of pregnancy after transfer of cryopreserved equine in vitro produced (IVP) blastocysts is related to post-thaw morphological characteristics, or could be impacted by other factors such as embryo biopsy prior to cryopreservation. This study examined associations between post-thaw morphological appearance of equine IVP embryos, and biopsy prior to slow-freezing, on the likelihood of pregnancy. Biopsy of IVP blastocysts was performed by harvesting cells herniated through the intra-cytoplasmic sperm injection (ICSI)-derived hole in the zona pellucida (ZP). M...
Cuervo-Arango J.The objective of this study was to compare the fertility of diestrous mares with a follicle ≥ 30 mm in diameter treated with prostaglandin F2α (PGF) (PGF group) or left untreated for 7 days (SP group). Standardbred mares (n = 46) were assigned randomly to the SP (n = 23) and PGF groups (n = 23) when they were identified with a corpus luteum (CL) of unknown age and a follicle ≥ 30 mm in diameter (Day 0). The most frequent outcome in the PGF group was estrus and ovulation of the dominant follicle (74 %), while the outcomes of the SP mares 7 days after Day 0 were more variable: estrus and fo...
Angyal E, Vincze B, Somoskői B, Sós-Koroknai V, Balogh P, Dankó GN, Cseh S, Kútvölgyi G.The anti-Müllerian hormone (AMH) is a granulosa cell-derived hormone that has been associated with female fertility and reflects the population of growing follicles. This study aimed to evaluate the average concentration of AMH in Lipizzaner mares, as well as to determine the relationship between AMH concentration and follicle number and size. We also investigated the relationship between the age of mares and their AMH levels. The possible effect of seasonality of AMH levels was also assessed. Twenty-three mares between 6 and 24 years of age were included in the experiment. Mares were divided...
Asif S, Gulzar MW.Endometritis is a significant cause of infertility in mare. Some infectious agents disrupt the endometrium's innate immune system, resulting in a prolonged systemic inflammatory response that circulates via the blood or cellular degeneration, which ultimately leads to endometritis from bacterial endotoxins. Numerous biological processes use various small, non-coding RNA molecules called MicroRNAs. MicroRNAs (miRNAs) regulate gene expression after transcription by blocking transcription and translation. This manuscript examines patho-morphological discoveries in equine endometritis, the express...
Dubeibe-Marin DF, Borraez DF, Gomez-López DL, Velasco-Acosta DA.This study evaluated the effect of the presence and location of the corpus luteum (CL) on quantity and competence of equine cumulus-oocyte complexes (COCs). Pairs of ovaries were collected at the slaughterhouse and classified into three groups: ovaries with CL (CL+); ovaries with CL in the contralateral ovary (CL-) and ovaries without a CL (NCL). Were evaluated COC quantity, morphology, nuclear maturation rate, and intrafollicular progesterone concentration and gene expression (BAX, BMP-15, ODC1, GDF9, AURKA) in both cumulus cells and oocytes after in vitro maturation. Results showed a lower r...
Spacek SG, Hernández-Avilés C, Ramírez-Agámez L, Pearson M, Love CC.Cryopreservation of stallion epididymal sperm has become a common clinical procedure after routine castration, euthanasia, or acute death. Unique features of epididymal sperm compared to ejaculated sperm include the requirement to remove sperm from the cauda epididymis, lack of exposure to seminal plasma, and potential recovery of large sperm numbers. In this study, the effect of the flushing technique (Extender (INRA) vs. AIR), freezing extender (LE, CMLE, MFR5, CFR5, or BOTU), and the concentration at which sperm are cryopreserved (200, 400, or 800 × 10 sperm/mL) on post-thaw epididymal s...
Jones CJP, Wilsher S, Aplin JD.We report a lectin histochemical study of oviductal ampulla and isthmus of thirteen mares euthanised at anestrus (1), estrus (5), 1-day post-ovulation (5) or diestrus (2). Staining with a panel of 5 lectins recognizing N-Acetylgalactosamine (GalNAc) residues revealed mosaicism in glycan expression in some specimens of ampulla and isthmus, peaking at estrus and 1-day post-ovulation (ov+1). In the ampulla, this presented as positively stained areas of both ciliated and non-ciliated cells in otherwise negatively-stained ampullae, ranging from small foci (diestrus) to areas up to 200 microns in le...
Maria Feitosa Ribeiro L, Bersot Gomes JV, Hernando Ortiz Vega W, da Silva Alves A, Netto Machado M, Junio Wutke L, Raquel Quirino C....Stallion breeding is mostly based on desirable phenotypic traits, with little consideration for semen quality. Objective: To identify relationships among semen parameters in stallions using a non-invasive, integrative approach across summer and winter seasons. Methods: Twenty-four stallions were evaluated, in which semen collections, testicular thermography, and Doppler velocimetry of the testicular artery by Doppler ultrasonography were performed, in addition to the measurement of physiological, environmental, and heat stress parameters, both in winter (coat weather) and summer (T-shirt weath...
Huggins L, Dini P, Santos E, Dujovne G.A Gypsy Vanner stallion presented with a history of subfertility and abnormal dense, grey ejaculate. Reproductive examination including ultrasound, cytology, and bacteriology confirmed the diagnosis of seminal vesiculitis. After evaluation of several ejaculates, bilateral blocked ampullae were confirmed by azoospermia and a low level of alkaline phosphatase (30 IU/L) in the filtered fraction. Continuous semen collections, along with oral antibiotics treatment, were performed at the owner's facility for five weeks. After readmission, a successful collection was obtained with a high concentratio...
