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Topic:Fertility
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.
Advanced mare age impairs the ability of in vitro-matured oocytes to correctly align chromosomes on the metaphase plate. Advanced mare age is associated with declining fertility and an increased risk of early pregnancy loss. Compromised oocyte quality is probably the primary reason for reduced fertility, but the defects predisposing to embryonic death are unknown. In women, advanced age predisposes to chromosome segregation errors during meiosis, which lead to embryonic aneuploidy and a heightened risk of miscarriage. Objective: To evaluate the effect of advanced mare age on chromosome alignment and meiotic spindle morphology in in vitro-matured (IVM) oocytes. Methods: Morphometric and morphological analysis. M...
Freezing of Stallion Semen: In Vitro Evaluation of Motility and Acrosin Activity in Sperm Cells Cryopreserved Using Different Semen Extenders. The work described here aimed to verify the efficiency of different extenders for cryopreservation of equine semen using sperm motility and acrosin activity as spermatic parameters. The semen was fractioned into two equal parts and resuspended in an 11% lactose solution in a 1:1 proportion, where it remained for 20 minutes at room temperature. The semen was centrifuged at 600 g for 10 minutes, and after the second centrifugation, each pellet received the freezing extender (Merck or Zorlesco) and was loaded into 4 mL straws. Each straw was placed in liquid nitrogen vapor steam for 15 minutes ...
Horse Y chromosome assembly displays unique evolutionary features and putative stallion fertility genes. Dynamic evolutionary processes and complex structure make the Y chromosome among the most diverse and least understood regions in mammalian genomes. Here, we present an annotated assembly of the male specific region of the horse Y chromosome (eMSY), representing the first comprehensive Y assembly in odd-toed ungulates. The eMSY comprises single-copy, equine specific multi-copy, PAR transposed, and novel ampliconic sequence classes. The eMSY gene density approaches that of autosomes with the highest number of retained X-Y gametologs recorded in eutherians, in addition to novel Y-born and transp...
Influence of cycle stage, age and endometrial biopsy score on oxytocin receptor distribution and gene expression in the cervix and uterus of non-pregnant mares. Persistent breeding-induced endometritis (PBIE) or delayed uterine clearance (DUC) are major causes of mare subfertility. Oxytocin and its receptor are thought to play significant roles in the pathogenesis of DUC but the specific roles of oxytocin receptor (OR) distribution and gene expression remain undefined. In this study both OR distribution and gene expression in the endometrium, myometrium and cervix during both luteal and non-luteal phases in non-pregnant mares (n = 27) of differing age (young: 2-9 years, n = 17; old: > 10 years, n = 10) and endometrial biopsy score were ...
Intracellular calcium chelating agent (BAPTA-AM) aids stallion semen cooling and freezing-thawing. This study aimed to investigate the effects of different concentrations of 1,2-bis-(o-aminophenoxy)-ethane-N,N,N0 N0-tetraacetic acid, tetra-acetoxymethyl ester (BAPTA-AM), an intracellular calcium chelating agent, on stallion semen cooling and freezing-thawing. After collection, semen was extended (1:1 v/v) on a skim milk-based extender, centrifuged and resuspended at 400 million/ml into cooling or freezing extenders containing 0, 5, 25, 50, 100 and 200 μΜ BAPTA-AM. Motility parameters were assessed after cooling in Equitainer at 5°C for 12, 24, 48, 72 and 120 hr and after freezing-tha...
Association of equine sperm population parameters with outcome of intracytoplasmic sperm injections. Limited clinical information is available regarding sperm population parameters that are important for use with equine intracytoplasmic sperm injection (ICSI). Therefore, the appropriateness of a sample of sperm is typically not known before ICSI. The aim of our study was to determine which sperm population characteristics were predictive of ICSI outcome. Frozen-thawed sperm samples (n = 114) from 37 stallions in a clinical program were analyzed after ICSI for percentages of normal morphology (MORPH+), live as assessed by eosin/nigrosin stain (LIVE+), membrane intact as assessed by hypoosmot...
Concentrations of non-permeable cryoprotectants and equilibration temperatures are key factors for stallion sperm vitrification success. Vitrification is based on rapid freezing by direct exposure of sperm to liquid nitrogen (LN). This study evaluated the effect of non-permeable CPAs and equilibration temperature on stallion sperm quality after vitrification. In Experiment 1, different concentrations of sucrose (20, 50, 100 mM; mmol/L) and bovine serum albumin (BSA 1%, 5%, 10%) were compared including different temperatures for the equilibration (≈22 °C or 5 °C). Vitrification was performed dropping 30 μl sperm suspension directly into LN In Experiment 2, conventional sperm freezing using 2.2% of glycerol in 0.5 ...
Laparoscopic transection of restrictive bands of the mesosalpinx as adjunct to the use of prostaglandin E2 for mares with suspected uterine tubal blockage. To describe the laparoscopic transection of restrictive bands of the mesosalpinx as a useful adjunct to the topical application of prostaglandin E to treat mares with suspected uterine tubal blockage. Methods: A standard left flank laparoscopic approach was made to the abdomen using three laparoscopic portals. If restrictive bands of the mesosalpinx were observed traversing the uterine tube perpendicularly, they were carefully transected and 1 mg of prostaglandin E was then applied to the external surface of the uterine tube. Skin incisions were closed with surgical staples and the procedure...
Carnosine as malondialdehyde scavenger in stallion seminal plasma and its role in sperm function and oxidative status. Semen biotechniques may impair sperm quality due to excessive production of reactive oxygen species (ROS). Additionally, products of the oxidative reaction, especially involving lipids (e.g., malondialdehyde - MDA), may be even more harmful to sperm. Carnosine, previously reported to be present in seminal plasma of several species, may be a key factor on sperm tolerance to biotechniques by counterattacking the deleterious influence of MDA. Therefore, the aim of this study was to measure the levels of carnosine present in equine seminal plasma and relate these findings with sperm function and o...
Impact of Equine and Bovine Oocyte Maturation in Follicular Fluid From Young and Old Mares on Embryo Production in Vitro. Equine follicular fluid (FF) provides autocrine and paracrine factors from theca, granulosa, and cumulus cells, both reflecting and impacting oocyte and follicle maturation. We hypothesized that maturation of oocytes in FF from old versus young mares has a deleterious effect on oocyte maturation and their subsequent developmental potential. Follicular fluid was collected from the large, dominant follicle from young mares (4-13 years) or old mares (21-26 years) and classified as: (1) Noninduced follicular fluid (NFF), FF from noninduced follicle 33 ± 3 mm, or (2) Induced follicular fluid (I...
Effects of mares’ age and day of gestation on efficacy of transvaginal ultrasound-guided twin reduction. Transvaginal ultrasound-guided aspiration (TUA) is a procedure which can be used for the reduction of twins post-fixation in the mare. The aim of this study was to evaluate the effect of the age of mares and the day of gestation on the outcome of TUA treatment. Methods: In 88 mares, diagnosed pregnant with twins, TUA of the yolk sac or allantoic fluid was performed between day 30 and 62 of gestation. Mares were aged 3-22 years. Ultrasonographic examination for a viable singleton pregnancy was performed by referring veterinarians 5-7 days and 4 weeks after TUA. Based on reported findings, effec...
Effect of feeding pomegranate seed oil as a source of conjugated linolenic acid on Arabian stallion semen quality in cooled and postthawed condition. The objective was to assess the influence of pomegranate seed oil supplementation on the quality of fresh, cooled and frozen-thawed Arabian breed stallion semen. Eight stallions (n = 4 per group) received their normal diet (control group) or normal diet top dressed with 200 ml of pomegranate seed oil (PSO group). Semen was collected every fifteen days for 90 days. Stallions were reversed across the treatments after a sixty-day interval. In cooled and stored condition (2, 12 and 24 hr), spermatozoa motion characteristics, membrane integrity, viability, morphology and lipid peroxidation wer...
Equine sperm-bound antisperm antibodies are associated with poor semen quality. Antisperm antibodies (ASAs) have been associated with infertility in stallions. The objectives of this study were to investigate the frequency of ASA-positive semen samples in satisfactory and non-satisfactory breeder stallions, the association between ASA binding and semen quality, and factors that may affect the diagnosis. Breeding soundness examinations were performed in 21 stallions and the percentage of IgG- and IgA-bound spermatozoa was evaluated using flow cytometry. Median IgG and IgA binding did not differ between the first and second ejaculates. The percentage of IgA-bound spermatozo...
Effects of implants containing the GnRH agonist deslorelin on testosterone release and semen characteristics in Shetland stallions. The hypothesis in this study was continuous treatment of stallions with the GnRH agonist deslorelin inhibits reproductive functions. A 2-week pre-experimental period was followed by an 11-week deslorelin implant treatment. Stallions received 4.7 (D1, n = 7), or 18.8 mg deslorelin (D2, n = 5) or remained untreated (C, n = 5). Libido, sperm motility, membrane integrity, DNA fragmentation, estrogen receptors, basal plasma testosterone and Anti Muellerian hormone (AMH) concentrations were evaluated once weekly during the treatment period. The testosterone response to the GnRH agonist buserelin a...
Effect of embryo transfer technique on the likelihood of pregnancy in the mare: a comparison of conventional and Wilsher’s forceps-assisted transfer. The aim of this study was to compare the success of embryo transfer (ET) performed by veterinarians with different degrees of experience using one of two ET techniques. Over three years, 179 embryos were transferred by three operators with moderate to high experience using a 'conventional' manual technique, and 170 embryos were transferred by four operators with little or no previous ET experience using a 'Wilsher' technique (Polansky speculum and Wilsher's cervical forceps). The pregnancy status of recipient mares at the first pregnancy diagnosis and the embryo loss by the last examination we...
Sperm nuclear protamines: A checkpoint to control sperm chromatin quality. Protamines are nuclear proteins which are specifically expressed in haploid male germ cells. Their replacement of histones and binding to DNA is followed by chromatin hypercondensation that protects DNA from negative influences by environmental factors. Mammalian sperm contain two types of protamines: PRM1 and PRM2. While the proportion of the two protamines is highly variable between different species, abnormal ratios within a species are known to be associated with male subfertility. Therefore, it is more than likely that correct protamine expression represents a kind of chromatin checkpoint...
Nitric oxide in frozen-thawed equine sperm: Effects on motility, membrane integrity and sperm capacitation. Nitric oxide (NO) is a reactive nitrogen species (RSN) that, over the years, has been shown to be integrated with biological and physiological events, including reproductive processes. NO can affect the functionality of spermatozoa through free radical scavenging, deactivating and inhibiting the production of superoxide anions (O). However, the role of NO in mammalian spermatozoa physiology seems paradoxical. The aim of this study was to investigate the effects of NO on motility, hyperactivation, membrane integrity, peroxidation, and capacitation in cryopreserved equine sperm. Ejaculates were ...
Effect of urine contamination on stallion semen freezing ability. Urospermia is a common ejaculatory dysfunction of stallions. Current practice suggests that urine contaminated semen should not be used for cryopreservation. The aim of this study was to determine effects of urine contamination on semen freezing. Sixty-five ejaculates from eight stallions were divided into no urine (CONT), low (20% urine, LOW), and high (50% urine, HIGH) samples. Semen was extended with a commercial cooling extender, cushion-centrifuged, resuspended to 200 million/mL in a commercial egg-yolk based extender, and cryopreserved in liquid nitrogen. A subset of ejaculates (n = ...
Anti-Müllerian hormone profiling in prepubertal horses and its relationship with gonadal function. Anti-Müllerian hormone (AMH) has gained increasing interest as a biomarker for assessment of gonadal activity. The ability to predict the ovarian follicular reserve of prepubertal female horses (fillies) or to identify stallions with testicular pathologies already during their prepubertal life has not been analyzed so far. Both would help to select fertile horses and reduce costs associated with keeping animals. The objectives of the present study were to (1) assess AMH, LH, FSH, progesterone (females) and testosterone (males) dynamics in prepubertal horses from birth onwards and (2) determin...
Variable Inter-assay Estimation of Sperm DNA Fragmentation In Stallions Classified as Good and Bad Semen Freezers. Semen cryopreservation causes DNA damage, thus requiring continuous monitoring. Objective: To compare two assays for sperm DNA fragmentation (SDF) from stallions with contrasting semen freezability. Methods: Thirteen stallions were classified as good semen freezers (GSF) or bad semen freezers (BSF). Ejaculates were cryopreserved with three diluents. Semen was subject to SDF evaluation using the sperm chromatin structure assay (SCSA) and Halomax after thawing (0 h) and after a 4 h thermoresistance test. Results: On semen of BSF, analysis by SCSA was similar between evaluations, but Halomax show...
Horse embryo diameter is influenced by the embryonic age but not by the type of semen used to inseminate donor mares. The diameter of embryos recovered from mares on Day 8 after ovulation varies greatly, from as little as 130 μm to as much as 2500 μm. Several factors have been proposed to affect embryo size at recovery, one of which is the type of semen (frozen vs fresh or cooled-transported) used to inseminate the mare. In addition, it has been shown that smaller embryos (<300 μm) recovered on Day 8 are less likely than larger embryos to result in successful pregnancy after transfer. However, whether the actual age of the embryo (interval from fertilization to flushing) in relation to its size also ...
Seminal plasma influences the fertilizing potential of cryopreserved stallion sperm. Seminal plasma (SP) contains proteins that may influence cryosurvival and prevent capacitation-like changes due to freezing and thawing. The objective of this study was to investigate the effect of adding pooled SP from "good" (GF) or "bad" (BF) freezer stallions on sperm cells' fertilizing ability. "Good freezers" refers to stallions that usually produce ejaculates which can withstand cryopreservation, whilst "bad freezer" stallions produce ejaculates which cannot tolerate the freezing process. A heterologous zona binding assay with in vitro matured bovine oocytes was used to assess the bind...
Sperm quality assays: How good are they? The horse perspective. Sperm quality assays have increased in number in the last 10 years. Most of these assays are flow cytometry based in application and are modified from assays that have been developed to measure somatic cell function. The goal of any sperm quality assay should be to advance the clinicians/researchers understanding of sperm cell function and the relationship to fertility. While these assays appear to measure somatic cell-like functions in sperm there tends to be little understanding how the results of these assays relate to fertility.
Grass greenness flush can influence breeding phenology and fertility in equatorial thoroughbred mares in the absence of photoperiod variation. Reproductive phenology is an important trait subjected to natural selection. Current horses in America belong to the Palearctic original populations after being introduced by European colonizers. Photoperiod variation is the main environmental factor for the adjustment of reproductive timing in horses, but is absent in equatorial areas. Here we hypothesize that seasonality of green-grass availability may influence breeding phenology in equatorial regions. We used data of 929 services to mares from 2006 to 2011 in a thoroughbred equine exploitation in Ecuador that experienced strong grass seaso...
Identification of serotoninergic system components in stallion sperm. Assisted reproductive techniques have been used on several domestic animals to preserve desirable traits in strains of high genetic and commercial value; however in equines its efficiency rate is relatively low. To increase the conception ratio in stallions, some research groups have used pharmacological treatments which promote sperm hyperactivation in order to increase male's fertility rates. In this way, our previous work suggests that serotonin (5-HT) could be a good pharmacological candidate that facilitates conception rate in domestic horses. 5-HT is a neurohormone involved in several re...
Lower blastocyst quality after conventional vs. Piezo ICSI in the horse reflects delayed sperm component remodeling and oocyte activation. The aim of this study was to evaluate the differential effects of conventional and Piezo-driven ICSI on blastocyst development, and on sperm component remodeling and oocyte activation, in an equine model. Methods: In vitro-matured equine oocytes underwent conventional (Conv) or Piezo ICSI, the latter utilizing fluorocarbon ballast. Blastocyst development was compared between treatments to validate the model. Then, oocytes were fixed at 0, 6, or 18 h after injection, and stained for the sperm tail, acrosome, oocyte cortical granules, and chromatin. These parameters were compared between inject...
Simultaneous evaluation of superoxide content and mitochondrial membrane potential in stallion semen samples provides additional information about sperm quality. An improved fertility prediction for stallions is of importance for equine breeding. Here, we investigate the potential of a combined staining of stallion spermatozoa for superoxide and mitochondrial membrane potential (MMP) for this purpose. Semen samples were analysed immediately after arrival at the laboratory, as well as after 24 h. Superoxide was measured by MitoSOXRed, while MMP was measured with JC-1. Menadione was used to stimulate superoxide production. In addition, other parameters of sperm quality, namely motility, membrane integrity, chromatin integrity, sperm kinematics and Hoec...
Implication of transcriptome profiling of spermatozoa for stallion fertility. Poor fertility of breeding stallions is a recognised problem in the equine industry. The aim of the present study was to detect molecular pathways using two groups of stallions that differed in pregnancy rates as well as in the proportion of normal and motile spermatozoa. RNA was isolated from spermatozoa of each stallion and microarray data were analysed to obtain a list of genes for which transcript abundance differed between the groups (P ≤0.05, fold change ≥1.2). In all, there were 437 differentially expressed (DE) genes between the two groups (P ≤ 0.05, fold change ≥1.2). Next, th...
Effects of immunization against bone morphogenetic protein-15 and growth differentiation factor-9 on ovarian function in mares. Currently there is no contraceptive vaccine that can cause permanent sterility in mares. This study investigates the effect of vaccination against oocyte-specific growth factors, Bone Morphogenetic Protein 15 (BMP-15) and Growth Differentiation Factor 9 (GDF-9), on ovarian function of mares. It was hypothesized that immunization against these growth factors would prevent ovulation and/or accelerate depletion of the oocyte reserve. For this study, 30 mares were randomly assigned to three groups (n = 10/group) and vaccinated with BMP-15 or GDF-9 peptides conjugated to KLH and adjuvant, or a ...
Blastocyst production after intracytoplasmic sperm injection with semen from a stallion with testicular degeneration. In horse breeding, intracytoplasmic sperm injection (ICSI) has gained interest to obtain offspring from subfertile individuals. This paper presents a case report of a stallion with severe testicular degeneration. Semen analysis showed very low motility and 83.5% of detached heads. Histology of a testicular biopsy showed severely decreased spermatogenesis, while transmission electron microscopy of the sperm cells revealed no significant abnormalities. A total of 39 oocytes were fertilized by ICSI with frozen-thawed spermatozoa of this stallion: 25 oocytes with intact spermatozoa and 24 with det...
