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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.
Fetal Membrane Removal in the Mare: Proactive Versus Reactive Approaches. Retained fetal membranes are the most common postpartum condition in mares. Although the incidence of retained fetal membranes is low, the consequences for the health of the mare can be severe (metritis, endotoxemia, laminitis, death). Oxytocin administration is often the first line of therapy for management of retained fetal membranes. Removal of fetal membranes using umbilical vessel infusion and manual membrane removal are effective tools for reducing risks associated with abnormally heavy membranes, retained membranes, or for mares that are geographically limited for veterinary care.
In Vitro and In Vivo Efficiency of Extenders Added to Thawed Stallion Semen. Addition of extenders to thawed semen could improve fertility. Objective: To determine the efficiency of extenders to increase viability of thawed semen, measured by sperm parameters in vitro and pregnancy rates after artificial insemination (AI). Methods: Sperm motility and acrosin activity were measured during a thermoresistance test (TRT). Results: Progressive motility decreased (P<0.05) after 30 min in thawing semen treated with saline solution (SS) and only after 60 min with Tyrode's solution (TS) or freezing diluent (FD). The total motility decreased (P<0.05) after 60 min in thawed semen...
Single-stage reconstruction of third-degree perineal lacerations in horses under general anesthesia: Utrecht repair method. To describe perioperative management, surgical procedure, and outcome in mares with third-degree perineal lacerations (TDPL) treated with a single-stage repair, the Utrecht repair method (URM). Methods: Retrospective study. Methods: Twenty mares with TDPL. Methods: Medical records of mares with TDPL reconstructed with a URM were reviewed for perioperative management; surgical outcome; and postoperative fertility, athletic performance, and complications. Results: Mares ranged in age from 3.5 to 11 years. Long-term follow-up was available for 13 mares. Mean duration of follow-up was 9 years ...
Rosiglitazone in the thawing medium improves mitochondrial function in stallion spermatozoa through regulating Akt phosphorylation and reduction of caspase 3. The population of stallion spermatozoa that survive thawing experience compromised mitochondrial functionality and accelerated senescence, among other changes. It is known that stallion spermatozoa show very active oxidative phosphorylation that may accelerate sperm senescence through increased production of reactive oxygen species. Rosiglitazone has been proven to enhance the glycolytic capability of stallion spermatozoa maintained at ambient temperature. Thus, we hypothesized that thawed sperm may also benefit from rosiglitazone supplementation. Thawed sperm were washed and resuspended in Ty...
Supplemental Antibiotics in a Commercial Extender for Stallion Semen. Commonly marketed semen extenders contain various antibiotic types and concentrations to control bacterial growth from stallion's external genitalia. An experiment was conducted to test the effects of supplemental amikacin disulfate (1,000 μg/mL) + potassium penicillin G (1,000 IU/ML: INRA-AP), or ticarcillin-clavulanate (1,000 μg/mL: INRA-TIM) in the INRA 96 extender, on sperm function and antimicrobial activity, compared with extender without supplemental antibiotics (INRA-C). In freshly extended semen (Time 30m), no differences were observed among the three treatment groups for sperm m...
Endometrial histopathology, bacteriology and cytology outcomes in mares with early embryonic death (EED): a field study. Early embryonic death (EED) is one of the causes of infertility in the mare. We compared endometrial environment in 9 mares with EED and 13 mares in diestrus phase. Cotton swab (CS), cytobrush (CB) and uterine biopsy (B) samples were obtained for the cytological, bacteriological and histopathological examinations. In the first step we compared CS and CB methods to biopsy as a reference method, as B revealed the highest number of positive results in cytological and bacteriological examinations in both groups. In turn, we also compared cytological, bacteriological and histopathological findings ...
Identification of proteoforms of albumin and kallikrein in stallion seminal plasma and their correlations with sperm motility. The aim of this study was to identify the proteoforms of albumin and kallikrein in stallion seminal plasma (SP), and to determine their correlations with sperm motility parameters. The experimental material consisted of ejaculates from 8 stallions, which were collected during the breeding and non-breeding seasons (BS and NBS, respectively). SP proteins were identified by 2-D PAGE and mass spectrometry (MALDI TOT/TOF MS). Sperm motility parameters were analyzed using the CASA system. Protein expression (integrated optical density-IOD) of albumin proteoforms 1 (ALB 1) and 2 (ALB 2) and kallikrei...
Genetic analysis of Taishu horses on and off Tsushima Island: Implications for conservation. Taishu horses are a native Japanese breed, of which only 41 individuals remained on Tsushima Island in 2018. Their genetic diversity is considered lower than that of other Japanese native horse breeds; thus, it needs to be investigated for sustainable conservation of this breed. Historical records revealed that several Taishu individuals were released areas off-Tsushima Island in mid-1980s. At present, Taishu horses living outside of Tsushima Island, hereafter referred to as Non-Tsushima Taishus (NTTs), are tagged. However, the genetic structure of the NTT individuals remains unclear, and such...
Hematochemical Patterns in Follicular Fluid and Blood Stream in Cycling Mares: A Comparative Note. The aim of this study was to verify the existence of possible cross-talk between biochemical contents of follicular fluid (FF) and systemic concentrations according to the follicular development of the metabolites: glucose (GLU), lactate (LACT), cholesterol (CHOL), triglycerides (TG), total bilirubin (T BIL), blood urea nitrogen (BUN), and creatinine (CREAT); enzymatic activities: gamma-glutamyl transferase (GGT), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), and aspartate aminotransferase (AST); electrolytes: calcium (Ca), phosphorus (P), sodium (Na), chloride (Cl), potassium (K), ...
Landscape of Overlapping Gene Expression in the Equine Placenta. Increasing evidence suggests that overlapping genes are much more common in eukaryotic genomes than previously thought. These different-strand overlapping genes are potential sense-antisense (SAS) pairs, which might have regulatory effects on each other. In the present study, we identified the SAS loci in the equine genome using previously generated stranded, paired-end RNA sequencing data from the equine chorioallantois. We identified a total of 1261 overlapping loci. The ratio of the number of overlapping regions to chromosomal length was numerically higher on chromosome 11 followed by chrom...
Steroids in the establishment and maintenance of pregnancy and at parturition in the mare. Historically, studies on the endocrinology of pregnancy and parturition in horses have made major contributions of relevance to mammals in general. Recent use of liquid chromatography mass spectrometry, measuring multiple steroid hormones simultaneously in blood, foetal and placental tissues throughout normal gestation, and in mares with experimentally induced placentitis, has advanced our current understanding of many of the unusual strategies seen during gestation and at foaling. This includes the stimulation of luteal steroidogeneisis by equine chorionic gonadotropin (eCG) from the endometr...
Periovulatory administration of firocoxib did not alter ovulation rates and mitigated post-breeding inflammatory response in mares. Non-steroidal anti-inflammatory drugs (NSAIDs) are a therapeutic option for the treatment of inflammation. However, negative effects of non-selective NSAIDs for treatment of mares with endometritis have been described, including delayed uterine clearance and impairment of ovulations. Firocoxib is a specific cyclooxygenase-2 (COX-2) inhibitor and has the ability to act in the uterus of mares. We investigated the effects of firocoxib on ovulation rate, numbers of polymorphonuclear neutrophils (PMNs), and COX-2 protein levels in the endometrial tissue of susceptible mares after insemination. Two ...
Effect of proinflammatory cytokines on endometrial collagen and metallopeptidase expression during the course of equine endometrosis. Equine endometrosis (endometrial fibrosis) is a degenerative chronic process that occurs in the uterus of the mare and disturbs proper endometrial function. Fibrosis is attributed to excessive deposition of extracellular matrix (ECM) components. The turnover of ECM is mediated by matrix metallopeptidases (MMP). Previously, it was shown that cytokines modulate MMP expression in other tissues and may regulate fibrosis indirectly by attracting inflammatory cells to the site of inflammation and directly on various tissues. However, the regulation of MMP expression in equine endometrosis is still r...
Validation of a portable device (iSperm® ) for the assessment of stallion sperm motility and concentration. The objective of this study was to evaluate the accuracy of a novel, portable device (iSperm Equine for assessing concentration and motility of stallion semen). In the first experiment, semen concentration was determined by the iSperm Equine (Aidmics Biotechnology), Androvision (Minitube) and NucleoCounter SP-100™ (ChemoMetec). The total motility and progressive motility were determined by the iSperm Equine and the Androvision using the manufacturer's guidelines. Frozen/thawed semen samples (n = 33) at various dilutions were analysed for concentration and motility with the above-mentioned ...
Use of a cervical stent for long-term treatment of pyometra in the mare: A report of three cases. An effective long-term treatment is necessary for mares with pyometra, because the condition tends to recur. In many affected animals, several conformational or anatomical anomalies contribute to impaired uterine clearance. Ovariohysterectomy is the surgical procedure of choice. Conservative therapy consists of draining and flushing the uterus, and systemic anti-inflammatory and antimicrobial treatment. Uterine secretions tend to accumulate again after local treatment, especially in mares with poor vaginal conformation or cervical adhesions. Herein, we describe three cases in which a cervical ...
Transcriptome analysis reveals that fertilization with cryopreserved sperm downregulates genes relevant for early embryo development in the horse. Artificial insemination with cryopreserved spermatozoa is a major assisted reproductive technology in many species. In horses, as in humans, insemination with cryopreserved sperm is associated with lower pregnancy rates than those for fresh sperm, however, direct effects of sperm cryopreservation on the development of resulting embryos are largely unexplored. The aim of this study was to investigate differences in gene expression between embryos resulting from fertilization with fresh or cryopreserved sperm. Embryos were obtained at 8, 10 or 12 days after ovulation from mares inseminated post-...
In Vitro Culture of Embryos from Horses. Establishment of optimal methods for equine embryo culture has been slow when compared to some domestic species. In part, this delay was caused by the failure of standard in vitro fertilization techniques in horses. However, the development of intracytoplasmic sperm injection (ICSI) for the assisted fertilization of equine oocytes has resulted in a renewed interest in establishing optimal methods for embryo culture. Currently, ICSI-produced equine embryos are cultured using media designed for other species or other cell cultures and, typically, with the addition of serum. Although systems spec...
Tamoxifen in horses: pharmacokinetics and safety study. Tamoxifen (TAM), a selective modulator of estrogen receptors (SERMs) has been recently explored as a therapeutic option for the oral treatment of airway inflammation in the horse. The objective of this work was to establish pharmacokinetic parameters of TAM and its main metabolites in equines, as well as to determine its clinical safety in short-term treatments. Results: We determined TAM and its three main metabolites (4-OH tamoxifen, endoxifen, and N-desmethyl tamoxifen) in plasma after single administration of 0.25 mg/kg in healthy adult horses ( = 12). A maximum concentration of TAM w...
Genetic characteristics and phylogenetic relationship of Parascaris spp. from Equus zebra, E. caballus, and E. asinus. The equine Parascaris spp. is large, parasitic nematodes, and predominantly focuses on the intestine of foals and young weanlings. There are two roundworms, Parascaris equorum and Parascaris univalens, recognized among equine hosts. In this study, all fifty-nine Parascaris worms were harvested from three different equine hosts (twenty specimens from Equus zebra, twenty specimens from E. caballus, and nineteen specimens from E. asinus). The ribosomal gene (ITS) and mitochondrial genes (cox1 and nadh1) were amplified to identify and genetically characterize these worms. Analysis of ITS sequences...
The Effect of Routine Postpartum Uterine Lavage on Endometrial Cytology, Culture, and Pregnancy Rates in Thoroughbred Broodmares. Minimizing the interval between parturition and successful rebreeding of thoroughbred broodmares is important in maintaining annual foal production and broodmare profitability. Routine postpartum uterine lavage may help achieve this by aiding uterine clearance and involution in the early postpartum period and increasing pregnancy rates. This retrospective study investigates the effect of postpartum uterine lavage in 32 thoroughbred mares housed on a single farm in Australia in 2014 and 2015. In the control year (2014), postpartum uterine lavage was not performed. In the treatment year (2015), ...
Effect of cumulus cell removal and sperm pre-incubation with progesterone on in vitro fertilization of equine gametes in the presence of oviductal fluid or cells. In spite of many attempts to establish an in vitro fertilization (IVF) technique in the equine, no efficient conventional IVF technique is available. The presence of oviductal fluid or oviductal cells during IVF helps to improve embryo production in vitro but is not sufficient to reach high fertilization rates. Thus, our aim was to perform equine IVF either after sperm pre-incubation with oviductal fluid or in the presence of oviductal cells, and to evaluate the effect of cumulus removal from the oocyte or sperm pre-incubation with progesterone. In experiments 1 and 2, IVF was performed in the...
The recipient’s Day after ovulation and the number of corpora lutea influence the likelihood of pregnancy in mares following transfer of ICSI frozen embryos. Asynchronous embryo transfer is an excellent tool to investigate how subtle differences in the uterine environment affect embryo development and survival. Progesterone secreted from the corpus luteum following ovulation is one of the main factors responsible for establishing endometrial receptivity for the pre-implantation embryo via complex alterations in the expression of genes involved in the secretion of the histotroph. The objective of this retrospective study was to determine whether the recipient's Day after ovulation and the number of CL at ET influence the pregnancy rates of IVP horse...
Declining testicular function in the aging stallion: Management options and future therapies. Declining fertility in association with declining testicular function is commonly seen as stallions age and can be the cause of significant economic losses in the equine breeding industry. This manuscript describes how to clinically recognize the signs of age-related declining testicular function (testicular degeneration) and also provides mare and stallion management strategies for improving reproductive outcomes. Finally, the current understanding of the pathophysiology of the disease is presented, including the results of recent studies that are beginning to uncover the underlying causes fo...
Researching immunocontraceptive vaccines with mares (Equus caballus) as both a target and model for African elephant (Loxodonta africana) cows: A review. A sequence of studies is reviewed that reported the domestic horse (Equus caballus) mare as an appropriate and accessible research platform for recording clinical and laboratory data post-immunisation with anti- GnRH and -zona pellucida (ZP) immunocontraceptive vaccines. Experience with a native porcine ZP (pZP) vaccine in African elephant (Loxodonta africana) cows highlighted needs for improving vaccine formulations and more clearly defining associated ovarian effects and safety profiles. Initially, the efficacy, reversibility and safety of the GnRH vaccine Improvac® in mares was demonstrate...
Alteration of the mare’s immune system by the synthetic progestin, altrenogest. Progestins are immunomodulatory in a variety of species. In the horse, the most commonly administered synthetic progestin is altrenogest (ALT), but its effect on the immune system of the non-pregnant mare is unknown. Peripheral blood mononuclear cells (PBMCs) from diestrous mares were incubated with varying concentrations of progesterone (P4) or ALT to assess intracellular production of IFNγ and the expression of select cytokines. Additionally, ten mares received either ALT or VEH daily utilizing a switchback design beginning on the day of ovulation and continuing for 7 days. Circulating PBM...
Failure to detect equid herpesvirus types 1 and 4 DNA in placentae and healthy new-born Thoroughbred foals. Equid herpesvirus type 1 is primarily a respiratory tract virus associated with poor athletic performance that can also cause late gestation abortion, neonatal foal death and encephalomyelopathy. Horizontal transmission is well described, whereas evidence of vertical transmission of equid herpesvirus type 1 associated with the birth of a healthy foal has not been demonstrated. This study sampled a population of Thoroughbred mares (n = 71), and their healthy neonatal foals and foetal membranes, to test for the presence of both equid herpesvirus types 1 and 4 using a quantitative polymerase chai...
Bacteria detected in the genital tract, semen or pre-ejaculatory fluid of Swedish stallions from 2007 to 2017. Although artificial insemination (AI) was developed as a means of controlling disease transmission, pathogens can still be transmitted to females in semen used for AI. In addition, bacteria can cause deterioration in sperm quality during storage. Semen becomes contaminated by the male's normal bacterial flora as it passes out of the reproductive tract but potential pathogens may also contaminate the semen. Therefore, semen samples from stallions to be used for AI are tested before the breeding season to minimize transmission of pathogens to inseminated mares. In Sweden, semen samples are teste...
Intrahost Selection Pressure Drives Equine Arteritis Virus Evolution during Persistent Infection in the Stallion Reproductive Tract. Equine arteritis virus (EAV) is the causative agent of equine viral arteritis (EVA), a reproductive and respiratory disease of horses. Following natural infection, 10 to 70% of infected stallions can become carriers of EAV and continue to shed virus in the semen. In this study, sequential viruses isolated from nasal secretions, buffy coat cells, and semen of seven experimentally infected and two naturally infected EAV carrier stallions were deep sequenced to elucidate the intrahost microevolutionary process after a single transmission event. Analysis of variants from nasal secretions and buffy...
Histopathological lesions in reproductive organs, distal spinal cord and peripheral nerves of horses naturally infected with Trypanosoma equiperdum. Dourine, a venereal transmitted trypanosomosis caused by Trypanosoma equiperdum, has different clinical signs related to the reproductive and nervous system. Pathologic tissue changes associated with the disease are poorly described. The present study describes the histopathological lesions in naturally T. equiperdum-infected horses in the chronical stage of dourine. Results: Four chronically dourine diseased horses underwent a post-mortem examination. They were Woo test negative, but CATT/T. evansi positive, had a low packed cell volume (PCV) and exhibited obvious clinical signs of dourine. P...
