Gestation in horses refers to the period during which a mare carries a developing fetus, typically lasting around 11 months, or approximately 340 days. This process involves a series of physiological and hormonal changes that support fetal development and prepare the mare for parturition. Key stages of equine gestation include fertilization, embryonic development, and fetal growth, each characterized by specific developmental milestones. Monitoring the health and progress of gestation is essential for ensuring the well-being of both the mare and the foal. This page compiles peer-reviewed research studies and scholarly articles that explore the various aspects of equine gestation, including hormonal regulation, fetal development, and factors influencing gestational length and outcomes.
Palmieri V, Catone G, Conte A, Di Palma T, Liguori P, Izzo I, Vullo C.Uterine rupture is an uncommon but life-threatening complication of equine reproduction, typically associated with dystocia, uterine torsion, fetal manipulation, or hydrops. Tears may occur in either the uterine horns or body, although involvement of the ventral uterine body is rare. This case report describes an 11-year-old Arabian mare at 350 days of gestation that developed abdominal pregnancy secondary to uterine torsion and full-thickness ventral uterine rupture, resulting in fetal death and the free presence of the fetus within the peritoneal cavity. Surgical removal of the fetus and pri...
Liu Y, Wang X, Wang G, Wu Z, He Q, Zhao B, Du M, Zhao Y, Bou G, Bai D, Dugarjaviin M, Zhang X.Horse breeding and management have a globally extensive history, with horses serving vital roles in transportation, warfare, agriculture, and cultural activities. In China, particularly in Inner Mongolia, the horse industry faces challenges such as harsh winters and limited nutritional research for local breeds, especially during late gestation. This critical period is essential for fetal development and maternal health, and inadequate nutrition can lead to complications like nutritional abortions and poor foal growth. Similar issues exist worldwide in cold climates or regions with seasonal pa...
Boubakeur E, Belmdjahed M.Gestation length is a key parameter in equine reproductive management, yet its variability remains poorly documented in Barb and Arabian mares under Algerian conditions. Objective: This study aims to determine gestation length in mares and to assess the influence of various factors, including breed, year of mating, mating month, mare age, parity, reproductive status, stallion and the foal's sex on gestation duration. Methods: A total of 133 mares from the National Stud Farm of Tiaret (Algeria) were monitored over the period 2021-2024. Results: The mean gestation length was 332.5 days (range: 3...
Liu P, Yang F, Li J, Li C, Guo X, Li X.This study aimed to investigate the impact of dietary L-citrulline supplementation on the health of mares during late gestation. Thirty-two healthy mares in late pregnancy were randomly assigned to four groups: a control group (CON, 0 g/d) and three treatment groups receiving 15, 30, and 45 g/d/head of L-citrulline, respectively. The trial spanned 72 days, including a 12-day adaptation phase and a 60-day formal feeding period. A fixed daily feeding amount of 11.2 kg/head was provided, ensuring complete consumption and consistent dry matter intake across all groups. Results demonstrated that su...
Hernashki H, Samimi AS, Imani M, Oloumi MM.Prepubic tendon rupture (PPTR) is a rare but life-threatening complication in late-term pregnant mares. It results in abdominal wall failure, ventral oedema and a poor prognosis for both the mare and foetus. A 14-year-old multiparous Kurdish mare at approximately 310 days of gestation presented with acute ventral distension, reluctance to walk and cranial displacement of the udder. Clinical evaluation revealed tachycardia, pallor and Grade 3/4 ventral oedema. Haematology indicated leucocytosis and haemoconcentration. Transabdominal ultrasonography showed a viable foetus and severe thinning of ...
Çortu A, Çınar H.Rectal examination is routine in equine reproduction but may trigger acute stress affecting welfare and safety. Intraocular pressure (IOP) responds rapidly to autonomic changes and may capture short-lived stress responses. Objective: To evaluate whether rectal examination acutely affects IOP and behavioral responses in mares, and whether reactions differ by reproductive status. Methods: Twenty Rahvan mares (10 pregnant, 30-40 days' gestation; 10 non-pregnant; 4-7 years) underwent transrectal examination without sedation. IOP was measured bilaterally at six time points: 2 min pre-exam (T1), dur...
Verstraete MH, Norris JK, Loux SC, De Spiegelaere W, Carossino M, Daels P, Dini P.The placenta mediates critical interactions between mother and offspring that guide development and impact long-term health. Despite its importance, the cellular organization of the equine (Equus caballus) placenta remains poorly defined. The equine epitheliochorial placenta, characterized by the absence of trophoblast invasion and prominent endocrine activity, provides a unique comparative model for studying placental cellular composition and development. Methods: We applied single-cell RNA sequencing to chorioallantois tissue collected from first-trimester (n = 1) and term (n = 2) equine...
Ledeck J, Dubrowski T, Schoumacher M, Peeters S, Le Goff C, Egyptien S, Deleuze S, Cavalier E, Ponthier J.Refined profiling of conjugated estrogens and androgens during equine pregnancy using liquid chromatography-tandem mass spectrometry (LC-MS/MS) could provide accurate fetal-sex determination. Current methods for fetal-sex prediction remain limited by timing, accuracy, and operator expertise. This study investigated sex-specific differences in maternal conjugated steroid profiles to develop a reliable, non-invasive predictive method. Samples were collected from 141 mares of various breeds starting at sixteen weeks of pregnancy. The samples were pooled according to gestational stage, divided int...
Risvanli A, Salykov R, Timurkaan N, Seker I, Ekinci E.This study was conducted to examine glandular histological changes in the uterus of Kyrgyz breed mares during the first 6 months of pregnancy. The study used 53 Kyrgyz breed mares; 43 of these were at different stages of pregnancy, while 10 were non-pregnant mares. Uterine samples obtained at the slaughterhouse were evaluated histomorphometrically; endometrial thickness, gland density, gland epithelial height and gland diameter were measured. In conclusion, it was concluded that in Kyrgyz mares, endometrial thickness, glandular epithelial height and diameter increased as pregnancy progressed...
Dantas FTDR, Canisso IF, Feijó LS, de Vasconcelos PMF, Campos ML, Ulanov AV, Li Z, Pizzi GLBL, Nogueira CEW, Curcio BR.Doxycycline is widely used in equine medicine, yet data on its pharmacokinetics and safety during late gestation are scarce. We investigated the pharmacokinetics, fetoplacental diffusion, and safety of compounded oral doxycycline in late-term pregnant mares. In the first experiment, six mares at 300 days of gestation received a single oral dose (10 mg/kg), and plasma concentrations were measured using LC-MS/MS. Pharmacokinetic analysis using non-compartmental and compartmental models showed rapid absorption, with a mean Cmax of about 6000 ng/mL reached within 0.8 h and a terminal half-life ...
Satué K, Fauci D, Fazio E, Velasco-Martínez MG, Bruschetta G, Medica P.This study investigates sequential changes in serum protein fractions during gestation in 31 pregnant Spanish Purebred mares compared to 15 non-pregnant control. Total serum proteins (TSP) were measured using the Biuret method, while albumin (ALB), total globulins (tGLOB), and their subfractions (α₁, α₂, β₁, β₂, γ-GLOB) were analyzed by agarose gel electrophoresis. Pregnant mares showed significant changes in serum protein profiles throughout gestation. TSP and tGLOB concentrations increased from mid to late pregnancy (months 6-11), while ALB concentrations declined between months...
Lawson JM, Verheyen KL, Laroucau K, Bryan JS, Smith KC, Foote AK, de Mestre AM.Umbilical cord torsion (UCT) is the most frequent pathology of the equine umbilical cord (UC) and a prominent cause of abortion, yet objective data on its features remain limited. This study compared UCT with clinically normal pregnancies (CNP) to (i) identify gross and histological features of the UC and fetal membranes, (ii) determine whether UCT is associated with fetal growth restriction, and (iii) rule out infectious aetiologies. Gross and histological features of the UC, chorioallantois and amnion were compared between groups. Fetal weight and crown-rump length were analysed relative to ...
Ali A, Derar DR, Alaeyeari AA, Alharbi YM.This study aimed to monitor intrauterine fetal growth, establish predictive equations for gestational age estimation, and determine the optimal period for fetal sexing in Arabian horses using ultrasonography. Unassigned: Seven Arabian mares were monitored from insemination to parturition using transrectal ultrasonography. The following fetal and embryonic parameters were measured: embryonic vesicle (EV), crown-rump length (CRL), biparietal diameter (BIP), stomach diameter (STD), chest depth (CHD), abdominal diameter (ABD), kidney length (KDL), eyeball diameter (EBD), and eye lens length (ELL)....
Roxon CA, Deacon LJ, Abraham M, Stefanovski D, Sertich PL.Gestation length is not a reliable indicator of fetal maturity due to the variability of normal gestation length in the mare. A standard method to accurately predict equine fetal maturity is not being used clinically. The presence of continuous gastrointestinal peristalsis, as detected ultrasonographically, is an indicator that both human and canine fetuses are mature (can survive after elective cesarean section). To determine if continuous gastrointestinal peristalsis, which we termed Phase 5, was a valid indicator of fetal maturity in the horse, and whether this indicator varied in late-gest...
Mouncey R, de Mestre AM, Arango-Sabogal JC, Verheyen KL.Gestational and early-life exposures may modulate development during growth and influence future athletic performance. Objective: To investigate associations between gestational and early-life exposures in Thoroughbreds and (i) likelihood of racing, (ii) total number of runs and (iii) total prizemoney by the end of the 3-year-old year. Methods: Prospective cohort. Methods: Daily records were kept on the location and duration of turnout, management and veterinary-attended episodes of disease or injury from birth until leaving the farm or study exit for 129 Thoroughbred foals on six stud farms. ...
Satué K, Medica P, Fauci D, Gímenez ED, Fazio E.Catecholamines (CATs) are essential neuroendocrine regulators with plasma concentrations that naturally fluctuate during pregnancy. Age-related changes in CATs, observed in humans and animals, suggest that gestation and aging together influence catecholaminergic activity. Blood samples were collected from Spanish Purebred mares categorized into three age cohorts (4-7 years, n = 18; 8-10 years, n = 18; 11-15 years, n = 18) across four defined gestational stages: first trimester (T1), second trimester (T2), third trimester (T3), and the final bimester (B4). Plasma concentrations of a...
Scoggin KE, Adlan F, Fedorka CE, Rakha SI, Stout TAE, Troedsson MHT, Ali HE.The insulin-like growth factor (IGF) system regulates implantation, placental development, and angiogenesis in eutherian mammals. However, little is known about the changes in this system in equine placenta (chorioallantois; CA) and the endometrium (EN) during pregnancy, or the relationship to vascular endothelial growth factor () expression. The current study investigated the expression of the IGF system components, namely the ligands ( and ), their receptors (, , and ), and their binding proteins ( and s) in equine CA at 45 days, 4, 6, 10, and 11 months of gestational age (GA) and immediatel...
Wilson CS, Carrick J, Begg A, Shearer P, Stewart M, Brookes VJ.Despite emerging disease syndromes in Australian Thoroughbred horses in recent years, there is no formal surveillance for fetal loss in the industry. This study aimed to characterise the distribution of equine pregnancy loss > 45 days of gestation in a major Thoroughbred breeding region to provide insights into causes, prevention, and surveillance feasibility. Methods: Data were collected from 574 fetal loss submissions to veterinary pathology services between February 2015 and November 2021. Variables included date of fetal loss, gestational age, diagnosis, foal weight, and mare age. Dia...
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...
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 ...
Nabenishi H, Tsuda T, Omoya Y, Ishii T.This study aimed to detect characteristic changes in the behavior and body surface temperature (BST) of pregnant mares before parturition using camera image analysis. A total of 53 pregnant Thoroughbred mares, which were individually stabled in box stalls, were included in this study. The mares were continuously monitored using a digital camera system comprising a thermal imaging camera and a visible camera. For the automatic determination of the x and y coordinates of each mare, the centroid of the mares was calculated using image processing software. Subsequently, trajectory analysis was per...
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...
Gonzalez SW, Espy BMK, Stefanovski D, Turner RM.Monitoring gestation and predicting parturition in mares with unknown breeding dates is challenging, especially in pasture bred herds of bucking horses. Transrectal ultrasonographic measurement of fetal vitreous body length is a validated predictor of foaling dates, but previous research suggested a need for breed-specific parameters to develop accurate indices for respective breeds. This study aimed to develop a scale associating fetal vitreous body length with days before parturition (DBP) in bucking horses. Biannual data collection over 2 years identified 199 pregnancies out of 240 reproduc...
Debes L, Venner M, Koether K, Vervuert I, Blanco M, Sieme H, Sielhorst J.Little is known about the health status of foals born alive from mares treated for placental disease. The aims of the present study were (1) to compare the neonatal health status and health development during the rearing period of foals born from mares treated for ultrasonographically assessed placental abnormalities (UPA) to age-matched healthy foals from the same warmblood stud and (2) analyze the influence of mare's placental health on colostrum quality. Foals (n = 127) born from mares with UPA (UPA group; P) in 2017-2019 were compared to 127 foals born from healthy mares (control group; ...
Silva GC, Nogueira CEW, Scalco R, Pizzi GLBL, Leite TA, Bastos R, Curcio BR.Gestation length (GL) in horses varies widely, influenced by multiple variables, including maternal, fetal, and environmental factors. This study aimed to investigate and quantify the relative contributions of climatic (photoperiod and temperature-humidity index - [THI]), maternal (age and parity), fetal (sex) and environmental (year and month of foaling) variables influencing gestation length in Thoroughbred mares. Retrospective data encompassing 704 pregnancies across nine breeding seasons in tropical and subtropical Brazilian climates were analyzed. Stepwise regression analysis identified f...
Peere S, Van den Branden E, Broothaers K, Polfliet E, Smits K, Govaere J.Transfer of in vitro-produced (IVP) equine embryos is associated with a higher incidence of monozygotic multiple pregnancies, but this remains a rarity. The outcome of monozygotic twin gestation is poor, and good management techniques are lacking. In addition, hydrops conditions are exceptional in horses, with hydroallantois occurring more frequently than hydramnion. Most hydrops conditions will lead to compromise or death of the foal and mare. A 6-year-old multiparous standardbred recipient mare, 332 days pregnant, diagnosed with a monozygotic twin and hydrops with a dead co-twin, gave birth ...
Kehlbeck A, Blanco M, Venner M, Freise F, Gunreben B, Sieme H.Fragile foal syndrome (FFS) or warmblood FFS Type 1 (WFFS) is a recessive, autosomal, hereditary, genetic defect causing late abortions, stillbirths and non-viable foals. Whether early pregnancy losses occur is unknown. Objective: To investigate how WFFS affects pregnancies and whether early pregnancy losses occur in WFFS matings and if there is a difference in pregnancy success between matings where both parents were allele carriers and those where only mare or stallion were WFFS carriers. Methods: Retrospective cohort study. Methods: Breeding records from a Warmblood stud farm were evaluated...
Arroyo E, Whitelock LM, Stanton ME, Stevenson V, de Aguiar LH, Kelleman A.Hydropsical conditions in domestic animals are characterized by abnormal fluid accumulation. While their complete pathophysiology remains unclear, factors such as changes in chorioallantoic membranes, placentitis, or fetal abnormalities may contribute. Hydrops present as a medical emergency that can cause complications for the mare. Early diagnosis and treatment are crucial for the mare's prognosis, as fetal survival is often poor. This report describes a case of hydroallantois in a 9-year-old pregnant Quarter mare at 271 days of gestation, leading to dystocia of a non-viable foal with multipl...
Perera TRW, Bromfield EG, Gibb Z, Nixon B, Sheridan AR, Rupasinghe T, Skerrett-Byrne DA, Swegen A.Understanding the systemic biochemistry of early pregnancy in the mare is essential for developing new diagnostics and identifying causes for pregnancy loss. This study aimed to elucidate the dynamic lipidomic changes occurring during the initial stages of equine pregnancy, with a specific focus on days 7 and 14 post-ovulation. By analysing and comparing the plasma lipid profiles of pregnant and non-pregnant mares, the objective of this study was to identify potential biomarkers for pregnancy and gain insights into the biochemical adaptations essential for supporting maternal recognition of pr...
Weems CW, Weems YS, Randel RD.Prostaglandins impact on ovarian, uterine, placental, and pituitary function to regulate reproduction in female livestock. They play important roles in ovulation, luteal function, maternal recognition of pregnancy, implantation, maintenance of gestation, microbial-induced abortion, parturition, postpartum uterine and ovarian infections, and resumption of postpartum ovarian cyclicity. Prostaglandins have both positive and negative effects on reproduction; they are used to synchronize oestrus, terminate pseudopregnancy in mares, induce parturition, and treat retained placenta, luteinized cysts, ...
Murphy BD, Martinuk SD.Cells from the chorionic girdle of the equine trophoblast invade the maternal endometrium at day 36 of gestation and become established as secretory elements known as the endometrial cups. These structures, which persist for 40-60 days, produce a gonadotropin which can be found in circulation until about day 130 of gestation. This glycoprotein has been identified in the horse and the donkey, with the former having received much better characterization. It consists of 2 noncovalently linked peptide chains; an alpha-subunit of 96 amino acids, which is common to that found in other horse glycopro...
Allen WR, Wilsher S, Turnbull C, Stewart F, Ousey J, Rossdale PD, Fowden AL.The interacting influences of maternal size and fetal genotype on placental and fetal development in the mare were assessed by comparing conventional within-breed Thoroughbred (Tb-in-Tb, n = 7) and Pony (P-in-P, n = 7) control pregnancies established by artificial insemination (AI) with between-breed (Tb-in-P, n = 8; deprived in utero condition and P-in-Tb, n = 7; luxurious in utero condition) experimental pregnancies established by embryo transfer. All foals were born spontaneously and the mean (+/- SEM) duration of gestation in the two groups of control mares was significantly different (P <...
Porter JK, Thompson FN.Fescue toxicosis in livestock is due to ingestion of endophyte (Acremonium coenophialum) -infected tall fescue. Understanding mechanisms responsible for decreased calving and growth rates, delayed onset of puberty, and impaired function of corpora lutea in heifers at puberty consuming endophyte-infected fescue is an emerging field in reproductive toxicology. The condition decreases overall productivity through a reduction in reproductive efficiency, reduced weight gains, and lowered milk production. Reproduction in cattle may be further compromised by winter coat retention, increased susceptib...
Allen WR, Stewart F.A tough, elastic glycoprotein capsule envelops the equine blastocyst between Days 6 and 23 after ovulation. It maintains the spherical configuration of, and provides physical support for, the embryo as it traverses the entire uterine lumen during Days 6-17, propelled by myometrial contractions that are stimulated by pulsatile release of prostaglandin F2alpha and prostaglandin E2. The capsule also accumulates constituents of the exocrine secretions of the endometrial glands ('uterine milk') as nutrients for the mobile embryo as it releases its antiluteolytic maternal recognition-of-pregnancy si...
Smits K, Willems S, Van Steendam K, Van De Velde M, De Lange V, Ververs C, Roels K, Govaere J, Van Nieuwerburgh F, Peelman L, Deforce D, Van Soom A.During maternal recognition of pregnancy (MRP), a conceptus-derived signal leads to the persistence of the corpus luteum and the maintenance of gestation. In the horse, the nature of this signal remains to be elucidated. Several studies have focused on the changes in gene expression during MRP, but little information exists at the protein level. The aim of this study was to identify the proteins at the embryo-maternal interface around signalling of MRP in the horse (day 13) by means of mass spectrometry. A distinct influence of pregnancy was established, with 119 proteins differentially expres...
Klohonatz KM, Cameron AD, Hergenreder JR, da Silveira JC, Belk AD, Veeramachaneni DN, Bouma GJ, Bruemmer JE.During early pregnancy, the conceptus and mare communicate to establish pregnancy. Cell-secreted vesicles (e.g., exosomes) have been reported in serum. Exosomes contain bioactive materials, such as miRNA, that can mediate cell responses. We hypothesized that a) exosomes are present in mare circulation and quantity varies with pregnancy status, b) exosomes contain miRNAs unique to pregnancy status, and c) miRNAs target pathways in endometrium based upon pregnancy status of the mare. First, serum samples were obtained from mares in a crossover design, with each mare providing samples from a preg...
Allen WR.The equine embryo takes 6 days to traverse the oviduct and, when it finally enters the uterus, it remains spherical in shape and moves continually throughout the uterine lumen until day 17 after ovulation to deliver its maternal recognition of pregnancy signal to the entire endometrium. Between day 25 and day 35 after ovulation, the trophoblast cells of a discrete annulate portion of the chorion multiply rapidly and acquire an invasive phenotype and, between day 36 and day 38, migrate deeply into the maternal endometrium to form the equine-unique endometrial protuberances known as endometrial ...
Carter AM, Enders AC.Epitheliochorial placentation is a derived condition and has evolved separately in strepsirrhine primates and laurasiatherians (pangolins, whales, and hoofed mammals). Usually it is associated with a long gestation period, small litters, and precocial young. Oxygen transfer is facilitated by indenting of the uterine and trophoblast epithelia by maternal and fetal capillaries, respectively. Histotrophic nutrition is important, and adaptations include areolas and hemophagous regions. In pigs and horses, for example, iron is transported as uteroferrin secreted from the uterine glands and taken up...
Allen WR, Wilsher S.Constant, self induced mobility throughout the uterine lumen between days 6 and 17 after ovulation, complete envelopment by a self-secreted glycoprotein capsule between days 7 and 30 and 'injection' of specialised, gonadotrophin-secreting trophoblast cells into the maternal endometrium at days 35-37 are three unusual aspects of equine embryogenesis. The outer trophoblast layer of the allantochorion finally establishes a stable, microvillous contact with the lumenal epithelium of the endometrium around days 40-42 and placentation commences thereafter. The allantochorion elongates steadily until...
Stout TA, Allen WR.Between at least day 9 and day 16 after ovulation the spherical equine conceptus migrates continuously throughout the uterine lumen, propelled by peristaltic myometrial contractions. This unusually long period of intrauterine movement ensures that the conceptus delivers its anti-luteolytic signal to the entire endometrium to achieve luteostasis. The present experiment tested the hypothesis that prostaglandins stimulate the myometrial contractions that result in the migration of the conceptus. Serial ultrasonographic examinations of the uteri of eight mares performed during 2 h periods between ...
Bucca S, Fogarty U, Collins A, Small V.Ultrasound assessment of feto-placental well-being has found its application in the equine field, as a valid diagnostic tool. Most reports on equine fetal parameters focus on advanced to late gestation. The aim of the present study was to further validate the technique of ultrasound evaluation of the equine fetal environment, by extending its application to earlier stages of pregnancy. Fetal parameters were collected (on 150 pregnancies) over a 3-year period. Data included in the study were selected according to the clinical behaviour of the mare, the neonate/fetus and fetal membranes at the t...
Qi M, Zhou H, Wang H, Wang R, Xiao L, Arrowood MJ, Li J, Zhang L.A total of 262 fecal specimens collected from grazing horses at five locations in Xinjiang, China were examined by PCR for Cryptosporidium spp. and Giardia duodenalis. The Cryptosporidium and G. duodenalis infection rates were 2.7% and 1.5%, respectively. Seven Cryptosporidium-positive specimens were found in foals (16.3%), and four G. duodenalis-positive specimens were found in mares (2.5%). Sequence analyses of 18S rRNA and gp60 genes revealed that seven animals were positive for the subtype VIaA15G4 of Cryptosporidium horse genotype. G. duodenalis assemblages A and B were identified by mole...
Swegen A, Grupen CG, Gibb Z, Baker MA, de Ruijter-Villani M, Smith ND, Stout TAE, Aitken RJ.Early pregnancy in the mare is a poorly understood, high risk period during which the embryo communicates its presence to the maternal endometrium. Remarkably, the maternal recognition of pregnancy signal is unknown in the horse. This study aimed to profile the proteins secreted by equine blastocysts into their immediate environment, along with proteins contained in the blastocoel and within the acellular embryo capsule. Embryos were recovered on day 8 after ovulation and cultured for 48 hours. Secretomes of day 9 and day 10 embryos were analyzed by LC-MS/MS and supported by analysis of blast...
Stout TA, Allen WR.A growing equine conceptus must suppress the cyclical release of PGF(2 alpha) from the endometrium to effect maternal recognition of its presence in the uterus. Paradoxically, the conceptus itself secretes PGF(2 alpha), together with other prostaglandins. In this study, the PGF(2 alpha) and PGE(2) content of, and production in vitro by, day 10-32 equine conceptuses were measured and the influence of pregnancy on the concentrations of these prostaglandins in the uterine lumen was examined. In vitro, the release of both prostaglandins per mg conceptus tissue was very high on day 10 after ovulati...
Manteca Vilanova X, De Briyne N, Beaver B, Turner PV.Collection of blood from pregnant mares for extraction of equine chorionic gonadotropin (eCG) is a critical but relatively unknown and poorly regulated practice in the countries in which it occurs. Equine chorionic gonadotropin is a hormone that is widely used to enhance reproductive performance and management of dairy and beef cattle, sheep, goats, and pigs kept under intensive housing systems. eCG is extracted from the blood of brood mares between days 40-120 of gestation. Although alternatives have been sought, there is currently no efficacious replacement, natural or synthetic, for eCG. Re...
Bowers S, Gandy S, Anderson B, Ryan P, Willard S.The objective of this study was to investigate use of digital infrared thermal imaging (DITI) to determine whether surface temperature gradient differences exist between pregnant and nonpregnant mares as a noncontact method to determine pregnancy status. On the day measurements were collected, each pregnant mare (n=10; beginning at 292.4+/-1.4 d of gestation) was paired with a nonpregnant mare (n=17). Ambient temperature, DITI measurements (left and right flank, wither temperatures [i.e., animal surface control] and background temperature), and rectal temperatures were obtained every 7 d for 5...
Wang T, Hu L, Wang Y, Liu W, Liu G, Zhu M, Zhang W, Wang C, Ren H, Li L.Equine herpesvirus-8 (EHV-8) is one of the most economically significant viruses that infect mammals of the genus Equus worldwide, which cause severe respiratory diseases and abortion in horses. However, there is no report of abortion caused by EHV-8 in donkeys. The present case report is about a 4-year-old donkey having an abortion and showing a serious respiratory issue on the 296th day of pregnancy. Bacteriological and molecular tests were used to screen possible bacterial/viral pathogens to detect the etiological agent. Salmonella abortus equi, EHV-1, EHV-4, and EAV were all negative in th...
Smith KC, Mumford JA, Lakhani K.Four Welsh Mountain pony mares at 3 months of gestation and one mare at 5 months were inoculated intranasally with equid herpesvirus-1 (EHV-1: Ab4 isolate) at doses of 10(5) to 10(6.6) TCID50. All five mares became infected, but no cases of paresis or abortion occurred. On days 8, 9, 11, 12 (3-month-pregnant mares) and 13 (5-month-pregnant mare) after infection, a detailed examination of the pregnant uterus was made. Small numbers of vascular lesions with EHV-1 antigen expression in endothelial cells were present in the uteri of the early gestational mares; thrombi were rare and foci of thromb...
McCue PM, Ferris RA.An understanding of the normal events of foaling, causes of dystocia and clinical outcomes is important for equine practitioners. Objective: The goals of the present study were to: 1) evaluate factors that influence gestation length; 2) report duration of Stage II labour; 3) determine the frequency of dystocia and premature placental separation; and 4) determine the relationship between problems at foaling and foal survival. Methods: Foaling records of 1047 mare births were evaluated. Results: The average gestation length was 342.7 days [corrected] +/- 0.4 days, with no effect of mare age or b...
Bigler NA, Bruckmaier RM, Gross JJ.Maternal care is essential to optimally support survival of the offspring. During evolution of mammalian species, different phenotypes have evolved in relation to gestation length, number, size, and maturation stage of the offspring at parturition, as well as colostrum and milk composition. The aim of the present review is to describe relationships between placental function and colostrum and milk composition in different mammalian species. Species covered in this article include humans, rabbits, rodents (rat and mouse), carnivores (cats and dogs), and a variety of ungulate species (cattle, sh...
Troedsson MH, Woodward EM.Equine endometritis is characterized by the expression of pro- and anti- inflammatory cytokines and an influx of polymorphonuclear neutrophils (PMNs) into the uterus. Mares resistant to persistent endometritis clear the inflammation within 24-36 h after exposure to microorganisms or semen. These mares have a rapid increase of pro-inflammatory cytokines and an upregulation of inflammatory modulating cytokines within 6h after exposure to inflammatory challenge. In conjunction with effective uterine contractions, these events are believed to be responsible for the transient nature of the inflamma...
Klohonatz KM, Hess AM, Hansen TR, Squires EL, Bouma GJ, Bruemmer JE.The mechanism for maternal recognition of pregnancy (MRP) in horses is unknown. To maintain a pregnancy, a mobile conceptus must be recognized by the uterus before d 14 postovulation (PO). This recognition prevents endometrial secretion of PGF2α on d14 through 16, which would otherwise initiate luteolysis. The objective of this study was to evaluate gene expression in the endometrium of pregnant and nonpregnant mares during and after MRP to identify possible genes involved during this time. Twelve normally cycling mares were used in a crossover design and randomly assigned to a specific colle...
Renaudin CD, Troedsson MH, Gillis CL, King VL, Bodena A.The objective of this study was to determine normal variations in the utero placental thickness during mid- and late gestation in the mare. Normal, healthy pregnant mares (n = 9) were examined monthly from 4 mo of gestation until parturition by transrectal and transabdominal ultrasonography. At each examination, the combined thickness of the uterus and the placenta (CTUP) was measured at the placento-cervical junction (transrectally) and at the uterine body or the uterine horns (transabdominally). In addition, the echogenicity of the amniotic and allantoic fluids was evaluated by transrectal u...
Caillaud M, Duchamp G, Gérard N.A growing body of evidence suggests that the interleukin-1 system is involved in periovulatory events. Previous work from our lab demonstrated that in the mare, interleukin-1beta (IL-1beta) increases the ovulatory rate of metaphase II oocytes. The present study was conducted to analyze in vivo the effect of IL-1 on oocyte cytoplasmic maturation, ovulation and pregnancy rate. In the present work, IL-1beta (experiment 1, n = 13; experiment 2, n = 25) and interleukin-1RA (IL-1RA; experiment 1, n = 25) were injected intrafollicularly by using the transvaginal ultrasound-guided injection method. In...
Claes A, Stout TAE.In vitro embryo production (IVEP) via Ovum Pick-Up (OPU) and Intracytoplasmic Sperm Injection (ICSI) has become a popular breeding technique in Warmblood mares because of the high success rate and several practical advantages. IVEP offers a solution for a variety of reproductive issues including, but not limited to, sub-fertility in stallions or mares, poor quality or scarce frozen semen, difficulty in synchronizing donor and recipient mares, and inefficient use of recipient mares. In 515 OPU-ICSI sessions performed in our facility in 2021, a mean of 25.9 antral follicles were aspirated yield...
Aurich C, Budik S.Early equine pregnancy shares many features with that of more intensively assessed domestic animals species, but there are also characteristic differences. Some of those are poorly understood. Descent of the equine conceptus into the uterine lumen occurs at day 5 to 6 after ovulation but is only possible when the embryo secretes prostaglandin E2. Although maintenance of equine pregnancy probably involves secretion of a conceptus derived anti-luteolytic factor, this agent has not been identified. Rapid growth, conceptus mobility and presence of an acellular capsule at the time of maternal recog...
Antczak DF, de Mestre AM, Wilsher S, Allen WR.A remarkable feature of equine pregnancy is the development of the invasive trophoblast of the chorionic girdle and its formation of the gonadotrophin-secreting endometrial cup cells in early gestation. The details of this process have been revealed only slowly over the past century, since the first description of the endometrial cups in 1912. This centennial presents an opportunity to review the characteristics of the cells and molecules involved in this early, critical phase of placentation in the mare. The invasiveness of the chorionic girdle trophoblast appears to represent an atavistic at...
