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Topic:Mares
Mares and horses are integral components of equine studies, focusing on the reproductive and behavioral aspects of equine biology. Mares, or adult female horses, play a significant role in breeding programs and are often studied for their reproductive physiology, gestation, and maternal behaviors. Horses, as a broader category, encompass both sexes and all age groups, providing a comprehensive view of equine anatomy, physiology, and behavior. Research in this area often investigates the differences and similarities between mares and other horses in terms of hormonal cycles, reproductive health, and social interactions. This page compiles peer-reviewed studies and scholarly articles that explore the biological and behavioral characteristics of mares and horses, offering insights into their roles in equine science and management.
Veterinarian and breeder perspectives surrounding ovum pick-up and intracytoplasmic sperm injection in mares: A survey study. There is an ethical debate about the application of ovum pick-up (OPU) and intracytoplasmic sperm injection (ICSI) in mares. Objective: To survey the opinions of equine veterinarians and breeders of sport horses on the ethics of using OPU-ICSI in mares. Methods: Cross-sectional descriptive study. Methods: Three surveys were distributed. The first targeted breeders ('Breeder Survey') who were actively involved in sport horse breeding. The second targeted veterinarians performing OPU ('OPU-Reprovets Survey'). The third targeted general equine practitioners ('Practitioner Survey'). There were six...
Endocrine and uterine hemodynamic differences between intra- and interspecific equine pregnancies during early gestation. Interspecific equine pregnancies (mare x donkey) are associated with altered endocrine patterns and increased pregnancy loss; however, the relationship between hormonal dynamics, luteal activity, and uterine hemodynamics in relation to conceptus origin remains incompletely understood. This study aimed to evaluate the influence of conceptus origin on endocrine profiles, supplementary corpora lutea (SCL) formation, and uterine hemodynamics, and to investigate the relationships among these variables. Twenty mares were initially included; however, six were excluded due to pregnancy loss or incompl...
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...
Differential Serum Cytokine Profiles in Aborting and Subclinically Infected Pregnant Mares with Equine Herpesvirus Type 1. Equine herpesvirus type 1 (EHV-1) is a major cause of reproductive loss in mares. This cross-sectional field study evaluated serum concentrations of interleukin-2 (IL-2), interleukin-10 (IL-10), interferon-alpha (IFN-α), and interferon-gamma (IFN-γ), together with the IL-10/IL-2 and IFN-γ/IL-10 ratios, in 26 vaccinated pregnant Thoroughbred mares. The analytical cohort comprised healthy, EHV-1 PCR-negative mares (HM, n = 10), EHV-1 PCR-positive mares sampled within 4 h after fetal expulsion at approximately the sixth month of gestation (AM, n = 9), and EHV-1 PCR-positive pregnant mares with...
Short-term effects of pulsed electromagnetic field therapy on subjective flexion-associated lameness responses and circulating cytokines in horses with distal tarsal osteoarthritis. Pulsed electromagnetic field (PEMF) therapy is commonly used in equine sports medicine for its proposed anti-inflammatory effects; however, limited controlled studies have evaluated its physiologic effects in horses. Objective: The objective of this study was to investigate the effects of PEMF therapy on flexion-induced lameness and circulating cytokines in horses with radiographic evidence of distal tarsal osteoarthritis. Methods: Six mares were enrolled in a repeated-measures crossover design in which each horse served as its own control. Horses were evaluated at baseline (sham PEMF) and at ...
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...
Russell’s viper envenomation in a 9-month pregnant mare saved with high-dose antivenom: a first-in-world case report. Snakebite during pregnancy is an uncommon but potentially catastrophic event, with maternal and foetal outcomes closely related to the severity of envenomation. While snakebite in pregnant women has been sporadically reported and is known to be associated with significant obstetrical complications, envenomation in animals, particularly in pregnant horses, is exceedingly rare. Only a few isolated cases of snakebite in horses have been documented, and to the best of our knowledge, snakebite in a pregnant mare has not been previously reported in the medical or veterinary literature. Russell's vip...
Intrauterine ozone therapy reduces bacterial load in mares with mixed bacterial endometritis: a longitudinal study. Mixed bacterial endometritis poses a therapeutic challenge in mares due to the coexistence of multiple pathogens with divergent antimicrobial susceptibility profiles. This study evaluated the effects of intrauterine ozone insufflation on uterine bacterial load and endometrial inflammatory response in mares with naturally acquired mixed bacterial endometritis. Fifteen mares with mixed bacterial infection were allocated to two treatment groups: a pathological control group receiving pure medical oxygen insufflation (PC; n = 6) and an ozone-treated group receiving 42 µg/mL ozone for three c...
Seasonal modulation of platelet indices in mares. Platelet indices provide valuable information on platelet activation, heterogeneity, and production kinetics, yet their physiological variability remains poorly characterized in horses. Although seasonal changes in platelet count have been described, the seasonal modulation of derived platelet indices in mares remains poorly understood. The aim of this study was to evaluate the seasonal variation of platelet count and derived platelet indices in clinically healthy mares from the Valencia region (Spain), and to assess their interrelationships. Forty clinically healthy Spanish Purebred mares (6-...
Species-Specific Mechanisms of Sperm Transport: Predominant Roles of Motility in Ewes and Uterine Contractility in Mares. The factors controlling sperm transport within the female genital tract vary among species. The aim of this study was to quantify the respective roles of sperm motility and uterine contractions in passage of sperm within the reproductive tract of the mare and ewe. Sperm imaging was performed in vivo within the female genital tract of mares and ewes using probe-based confocal laser endomicroscopy (pCLE) after intrauterine insemination during two stages of the cycle characterized by high (oestrus) or low (luteal phase) uterine contractility. Fluorescent microbeads (2 µm in diameter) were insemi...
Efficiency of transvaginal oocyte aspiration (TVA), post-mortem ovary harvest (OH), and Intracytoplasmic Sperm Injection (ICSI) in a Quarter Horse mare population in North America. In a clinical setting, Intracytoplasmic Sperm Injection (ICSI)-derived equine blastocysts can be obtained either by transvaginal oocyte aspiration (TVA) or post-mortem ovary harvest (OH). Most peer-reviewed retrospective reports have described the suitability of these techniques for obtaining blastocysts, pregnancies, and live foals, particularly in Warmblood horse populations in Europe. In this study, retrospective data from Quarter Horse client-owned mares subjected to TVA-ICSI (n = 105; 151 cycles) or OH-ICSI (n = 42) at an academic institution in North America between 2023 and 2025...
Growth Performance, Milk Productivity, Productive Longevity, and Milk Composition of Mugalzhar Horses. The Mugalzhar horse is an important native breed of Kazakhstan, valued for its adaptability, milk production, and meat productivity under extensive pasture-based management. This study evaluated the relationships among first-lactation milk yield, productive longevity, lifetime milk production, growth, morphometric traits, and milk composition in the Mugalzhar horse breed using data from 100 mares with complete lifetime production records, 108 adult mares and 12 stallions for morphometric evaluation, and 68 foals (35 colts and 33 fillies) for growth analysis. The study was conducted on Mugalzha...
The Effects of Cysteamine Zinc Supplementation on Blood Hormones, Intestinal Flora, and Metabolites in Lactating Mares. This study aimed to investigate the effects of cysteamine zinc (CS-Zn) supplementation on blood biochemical indices, blood hormones, fecal fermentation, fecal microbial diversity, and blood metabolites in lactating mares. Blood samples were collected via jugular venipuncture, and fecal samples were collected via rectal sampling before morning tethering on days 30, 60, and 90 of the trial. Fecal samples were analyzed for volatile fatty acids (VFAs) and microbial diversity, while changes in blood biochemical indices, blood hormones, and blood non-targeted metabolomics were also analyzed. The res...
Preliminary Metabolomic Analysis: Serum Metabolomic Dynamics During Estrus Synchronization in Kazakh Mares. This study aimed to analyze the differences in serum metabolomes at different stages of estrus synchronization in Kazakh horses, to characterize dynamic changes in serum metabolites during estrus synchronization, and to screen potential metabolic markers and key regulatory pathways. Four sampling stages (M1: intravaginal device insertion; M3: device removal, labeled consistently with the pre-experiment timeline; P: 24 h post-PG injection; L: tertiary follicle emergence) were selected. The research results showed that 37 significantly different metabolites (DAMs) were identified in the M1-vs.-M...
Mares with severe equine asthma exhibit a narrower trachea than geldings in a retrospective radiographic study of 189 horses. To evaluate potential relationships between sex, asthma severity, and tracheal diameter in adult horses through the use of thoracic radiography. Unassigned: This was a retrospective case-control study of horses that underwent thoracic radiography at the Université de Montréal from 2018 through 2024. Horses were classified as control, mild/moderate asthma, or severe asthma (SEA) according to the latest consensus statement on equine asthma. To account for radiographic magnification and body size, standardized ratios of tracheal diameter relative to the fifth thoracic vertebral body length and ...
Sequencing and Differential Analysis of miRNA in the Ovaries of Kazakh Horses During Estrus and Anestrus States. To reveal the regulatory role of miRNA in the estrous cycle transition of Kazakh horse ovaries and improve their reproductive efficiency, this study took the ovaries of Kazakh horses in the estrus period (DY group) and the quiescent period (DB group) as research objects. Small RNA sequencing and bioinformatics analysis were used to systematically analyze the expression characteristics and functional pathways of miRNA under the two physiological states. A total of 161 million high-quality miRNA tags were obtained through sequencing. Principal component analysis showed that the intra-group repea...
Platelet indices’ dynamic in broodmares: Effects of parity and lactation. Lactation and parity are physiological factors influencing platelet (PLT) indices, yet their combined effects in mares remain poorly characterized. As a dynamic process, lactation involves metabolic and endocrine changes that may influence thrombopoiesis; therefore, reproductive history and lactation stage may modulate PLT indices. Objective: To characterize longitudinal platelet (PLT) indices during early lactation in mares and evaluate the influence of parity on thrombopoietic responses. Methods: Fifty-five clinically healthy Spanish Purebred mares were included (20 primiparous and 25 multip...
Factors Influencing Equine Embryo Outcomes in OPU‑ICSI Systems: Insights from a Large‑Scale Program in Brazil. Equine OPU‑ICSI supports commercial IVEP, yet substantial variability persists. We retrospectively analyzed a large dataset generated in Brazil spanning Quarter Horses, Warmbloods, and Mangalarga to evaluate whether predictors previously identified in the literature show comparable patterns under distinct ecological and breeding conditions. Overall oocyte and embryo outcomes were aligned with broadly reported trends from previous studies. Oocytes retrieved from estrous mares bearing a dominant follicle exhibited higher maturation and blastocyst rates. Stallion effects segregated into distinc...
Antibiofilm action of ozonated sunflower oil against bacteria isolated from the uterus of mares susceptible to endometritis. This study aimed to characterize the antibiofilm action of ozone-enriched sunflower oil (O) against pathogens associated with endometritis in mares. Initially, samples from 41 mares with a history of subfertility were stored in BHI broth and 0.9% NaCl solution. The samples underwent microbial culture, identification, and sensitivity testing at LABRAPE-UFRPE, Brazil. Biofilm production was evaluated by the crystal violet method. Subsequently, biofilm-forming bacteria were subjected to the action of different concentrations of ozonated sunflower oil. Of the 21 isolates tested for biofilm produc...
Mammary neuroendocrine tumor in a mare. A 10-y-old American Paint Horse mare was presented to the Equine Field Services at Virginia-Maryland College of Veterinary Medicine (Blacksburg, VA, USA) for evaluation of mastitis and a possible abscess in the right mamma. Histologic evaluation of a mammary biopsy revealed a densely cellular, infiltrative neoplasm with cells arranged in packets supported by thin stroma. In a neuroendocrine immunohistochemistry panel, the neoplastic cells did not immunolabel for neuron-specific enolase or synaptophysin, positively immunolabeled for chromogranin A, and had moderate scattered immunolabeling for ...
Interleukin 12 on extracellular matrix-related factors and functional characteristics of equine endometrial fibroblasts. Tissue fibrosis is described as the excessive accumulation of extracellular matrix (ECM) components. This process is associated with inflammation, and the interaction between fibroblasts and immune cells plays a key role, driving the progression of fibrosis. Results of recent study suggest that interleukin (IL)-12 may play a role in the processes associated with the development of fibrosis. This proinflammatory cytokine is synthesized and released by macrophages, dendritic cells, and B cells. Objective: The objective of this study was to determine: (i) the expression of IL-12 and its receptor ...
Genetic Diversity in Domestic Horses: Temporal Patterns, the Influence of Assisted Reproductive Technologies, and Implications for the American Quarter Horse. Genetic diversity is the heritable variation within and among populations and is essential for the long-term health and selection potential of domestic horses. Previous studies show diversity across breeds is shaped by effective population size, founder events, artificial selection, and levels of inbreeding. While some closed-studbook breeds retain moderate genetic diversity, others have experienced rapid losses due to popular-sire effects and recent and extensive inbreeding. Even so, mare lines continue to help maintain genetic diversity within these populations. Assisted Reproductive Technol...
Risk factors for post-partum colic in a population of UK and Irish Thoroughbred broodmares. Broodmares are at increased risk of gastrointestinal colic. However, colic risk factors specific to this population have not been investigated. Objective: To investigate horse- and management-level risk factors for post-partum colic in a cohort of Thoroughbred broodmares in the United Kingdom and Ireland. Methods: Prospective, nested case-control study. Methods: Twenty-nine Thoroughbred stud farms in the United Kingdom and Ireland were recruited, and 1044 mares were followed over the 2021 and/or 2022 foaling seasons. Data were collected on signalment, medical and management history for post-pa...
Blood ammonia levels: A potential indicator of high-risk pregnancy in Thoroughbred broodmares. Exposure to high blood ammonia (hyperammonemia) interferes with gestation due to its detrimental effect on hormone levels, fetal development, the immune system, placental integrity, and fertility of broodmares. Increases in ammonia levels are dangerous and elusive, as damage may occur from earlier peaks, resulting in the trapping of ammonia in the amniotic fluid and then disappearing from the blood circulation before clinical symptoms are observed. Thus, it should be recognized early and treated immediately before complications arise. This study aimed to investigate if blood ammonia levels in ...
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...
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...
Maternal age-related changes in renin-angiotensin-aldosterone system and electrolyte homeostasis during equine pregnancy. The renin-angiotensin-aldosterone system (RAAS) plays a key role in fluid and electrolyte homeostasis during pregnancy. In humans and laboratory animals, maternal age has been shown to modulate RAAS activity, potentially altering the secretion of renin (REN), angiotensin II (ANG-II), and aldosterone (ALD), thereby influencing sodium (Na⁺) and potassium (K⁺) regulation. Objective: To evaluate whether maternal age influences RAAS activity in pregnant mares. Methods: Forty-five Spanish Purebred mares were monitored monthly over 11 months of pregnancy and categorized into three age groups: You...
Metabolomic Analysis of the Effects of Cysteamine Zinc on the Composition and Amino Acid Profile of Mare’s Milk. This study aims to investigate the effects of cysteamine zinc supplementation on milk production, composition, amino acid profile, and metabolites in mares. Building on prior experimental findings, a dose of 7 mg/kg body weight of CS-Zn was selected for the experimental group, which was compared with a control group. Milk samples were collected at various time points, and milk yield was recorded each time. Routine analysis of milk components, as well as the determination of milk metabolites and amino acids, were performed. The results indicated that, compared to the control group, the experime...
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...
