Topic:Pregnancy
Pregnancy in horses, or equine gestation, is a physiological process that involves the development of a foal within the mare over approximately 11 months. This period is characterized by distinct stages, including fertilization, embryonic development, and fetal growth. Throughout gestation, mares undergo various physiological and hormonal changes to support the developing fetus. Monitoring pregnancy in horses involves assessing fetal health and mare well-being through veterinary examinations and diagnostic tools such as ultrasound. This page compiles peer-reviewed research studies and scholarly articles that explore the physiological processes, management practices, and health considerations associated with equine pregnancy.
In Vitro and In Vivo Development of Horse Cloned Embryos Generated with iPSCs, Mesenchymal Stromal Cells and Fetal or Adult Fibroblasts as Nuclear Donors. The demand for equine cloning as a tool to preserve high genetic value is growing worldwide; however, nuclear transfer efficiency is still very low. To address this issue, we first evaluated the effects of time from cell fusion to activation (<1h, n = 1261; 1-2h, n = 1773; 2-3h, n = 1647) on in vitro and in vivo development of equine embryos generated by cloning. Then, we evaluated the effects of using different nuclear donor cell types in two successive experiments: I) induced pluripotent stem cells (iPSCs) vs. adult fibroblasts (AF) fused to ooplasts injected with the pluripotency-inducin...
Identification of the most abundant proteins in equine amniotic fluid by a proteomic approach. Characterisation of the physiologic equine amniotic fluid (AF) proteome is a prerequisite to study its changes during diseases and discover new biomarkers. The aim of this study was to identify by a proteomic approach the most abundant proteins of equine AF. AF samples were collected at parturition from 24 healthy mares that delivered healthy foals. All samples were subjected to sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) on 4-12% gels. A pool of the 24 samples, after SDS-PAGE, was cut in 25 slices, trypsin-digested and analysed by mass spectrometry (MS) for protein i...
Breakthroughs in Equine Embryo Cryopreservation. Most equine embryos are collected from the donor mare and transferred immediately as fresh embryos or shipped cooled to a recipient station for transfer within 24 hours. Very few equine embryos are frozen despite the numerous advantages of embryo cryopreservation. There are 2 major hurdles: Only the small embryos (<300 μm) provide good pregnancy rates after freezing/thawing and transfer. Also there is no good procedure for superovulating mares; thus, extra embryos for freezing are not readily available. Using either a slow cool or a vitrification method, pregnancy rates of small equine e...
Why doesn’t conventional IVF work in the horse? The equine oviduct as a microenvironment for capacitation/fertilization. In contrast to man and many other mammalian species, conventional in vitro fertilization (IVF) with horse gametes is not reliably successful. The apparent inability of stallion spermatozoa to penetrate the zona pellucida in vitro is most likely due to incomplete activation of spermatozoa (capacitation) because of inadequate capacitating or fertilizing media. In vivo, the oviduct and its secretions provide a microenvironment that does reliably support and regulate interaction between the gametes. This review focuses on equine sperm-oviduct interaction. Equine sperm-oviduct binding appears to be...
The Calcium-Sensing Receptor and the Reproductive System. Active placental transport of maternal serum calcium (Ca(2+)) to the offspring is pivotal for proper development of the fetal skeleton as well as various organ systems. Moreover, extracellular Ca(2+) levels impact on distinct processes in mammalian reproduction. The calcium-sensing receptor (CaSR) translates changes in extracellular Ca(2+)-concentrations into cellular reactions. This review summarizes current knowledge on the expression of CaSR and its putative functions in reproductive organs. CaSR was detected in placental cells mediating materno-fetal Ca(2+)-transport such as the murine int...
Progestin withdrawal at parturition in the mare. Mammalian pregnancies need progestogenic support and birth requires progestin withdrawal. The absence of progesterone in pregnant mares, and the progestogenic bioactivity of 5α-dihydroprogesterone (DHP), led us to reexamine progestin withdrawal at foaling. Systemic pregnane concentrations (DHP, allopregnanolone, pregnenolone, 5α-pregnane-3β, 20α-diol (3β,20αDHP), 20α-hydroxy-5α-dihydroprogesterone (20αDHP)) and progesterone) were monitored in mares for 10days before foaling (n=7) by liquid chromatography-mass spectrometry. The biopotency of dominant metabolites was assessed using luci...
[A case of 63,X/64,XX mosaicism in a subfertile pony mare]. The present case report describes a 6-year old subfertile pony mare, which became pregnant after the eleventh artificial insemination. The examination of the ovaries and the uterus did not reveal any abnormal clinical findings and the mare showed a regular oestrous cycle. Based on cytogenetic and molecular genetic analyses it became possible to elucidate the observed subfertility. The mosaic karyotype of the mare consisted of 63,X (20%) and 64,XX (80%) cells. A PCR analysis failed to amplify sequences from the equine SRY gene. The observed classic 63,X/64,XX mosaicism is a plausible explanatio...
Central Nervous System and Vertebrae Development in Horses: a Chronological Study with Differential Temporal Expression of Nestin and GFAP. The neural system is one of the earliest systems to develop and the last to be fully developed after birth. This study presents a detailed description of organogenesis of the central nervous system (CNS) at equine embryonic/fetal development between 19 and 115Â days of pregnancy. The expression of two important biomarkers in the main structure of the nervous system responsible for neurogenesis in the adult individual, and in the choroid plexus, was demonstrated by Nestin and glial fibrillary acid protein (GFAP) co-labeling. In the 29th day of pregnancy in the undifferentiated lateral ventricle...
Vitrification of in vitro-produced and in vivo-recovered equine blastocysts in a clinical program. There is a clinical demand for cryopreservation of both in vivo-recovered and in vitro-produced (IVP) equine embryos. We previously reported successful vitrification of expanded equine blastocysts in fine-diameter microloader pipette tips (MPTs) after blastocoel collapse, in a research setting. Here, we report the results of clinical application of the MPT vitrification technique for both in vivo-recovered and IVP blastocysts. In vivo-recovered blastocysts were obtained by referring veterinarians on Days 6 to 8 after ovulation, and shipped 1 to 10 hours to the laboratory before vitrificat...
Equine 5α-reductase activity and expression in epididymis. The 5α-reductase enzymes play an important role during male sexual differentiation, and in pregnant females, especially equine species where maintenance relies on 5α-reduced progesterone, 5α-dihydroprogesterone (DHP). Epididymis expresses 5α-reductases but was not studied elaborately in horses. Epididymis from younger and older postpubertal stallions was divided into caput, corpus and cauda and examined for 5α-reductase activity and expression of type 1 and 2 isoforms by quantitative real-time polymerase chain reaction (qPCR). Metabolism of progesterone and testosterone to DHP and dihydro...
Prospective study investigating transplacental transmission of equine piroplasmosis in thoroughbred foals in Trinidad. Equine piroplasmosis caused by Theileria equi and Babesia caballi is endemic in Trinidad and Tobago. Transmission occurs by ticks of the family Ixodidae. T. equi can also be transmitted transplacentally; however transplacental transmission of B. caballi is unknown. This study aims to investigate transplacental transmission of equine piroplasmosis from thoroughbred mares naturally infected via the tick vector. Whole blood and serum samples were collected from 117 mares in the fifth month of pregnancy. Blood samples were also collected from each of their foals (89 in total) within the first 36h ...
Convergent evolution of pregnancy-specific glycoproteins in human and horse. Pregnancy-specific glycoproteins (PSGs) are members of the carcinoembryonic antigen cell adhesion molecule (CEACAM) family that are secreted by trophoblast cells. PSGs may modulate immune, angiogenic and platelet responses during pregnancy. Until now, PSGs are only found in species that have a highly invasive (hemochorial) placentation including humans, mice and rats. Surprisingly, analyzing the CEACAM gene family of the horse, which has a non-invasive epitheliochorial placenta, with the exception of the transient endometrial cups, we identified equine CEACAM family members that seem to be rel...
Placental abnormalities in equine pregnancies generated by SCNT from one donor horse. Placental changes associated with SCNT have been described in several species, but little information is available in this area in the horse. We evaluated the ultrasonographic, gross, and histopathological characteristics of placentas from three successful and five unsuccessful equine SCNT pregnancies, established using cells from a single donor horse. Starting at approximately 6-month gestation, the pregnancies were monitored periodically using transrectal (TR) and transabdominal (TA) ultrasonography (US) to examine the placentas, fetal fluids, and fetuses. Of the five mares that aborted, one...
Field fertility of liquid stored and cryopreserved flow cytometrically sex-sorted stallion sperm. The fertility of sex-sorted, cryopreserved stallion sperm must be improved for the sex-sorting technology to be applied commercially. Objective: To optimise the conditions used to liquid store stallion sperm prior to sex-sorting and assess the fertility of sperm following sex-sorting and cryopreservation. Methods: Both in vitro experiment and randomised controlled trial in healthy, client-owned mares. Methods: Stallion ejaculates (n = 9) were diluted in either a skimmed milk (KMT) or BSA (I-BSA) based media to 25 × 106 sperm/ml directly (+SP25) or washed to remove seminal plasma and diluted t...
The period of the follicular phase during which the uterus of mares shows estrus-like echotexture influences the subsequent pregnancy rate. The interval from both spontaneous and prostaglandin (PGF)-induced luteolysis to ovulation is greatly variable in mares. Several reports have shown a positive association between the length of the interval from PGF treatment to ovulation (ITO) and the subsequent pregnancy rate (PR). However, it is not known whether this association also occurs in estrous cycles with spontaneous luteolysis. The main objective of this study was to determine the effect of the duration of estrus-like echotexture of the uterus during the follicular phase on the subsequent PR in both spontaneous and PGF-induced cycl...
Proteome of equine oviducal fluid: effects of ovulation and pregnancy. The equine oviduct plays a pivotal role in providing the optimal microenvironment for early embryonic development, but little is known about the protein composition of the oviducal fluid in the horse. The aim of the present study was to provide a large-scale identification of proteins in equine oviducal fluid and to determine the effects of ovulation and pregnancy. Four days after ovulation, the oviducts ipsilateral and contralateral to the ovulation side were collected from five pregnant and five non-pregnant mares. Identification and relative quantification of proteins in the oviducal fluid ...
Embryo-maternal communication during the first 4 weeks of equine pregnancy. The first month of equine pregnancy covers a period of rapid growth and development, during which the single-cell zygote metamorphoses into an embryo with a functional circulation and precursors of many important organs, enclosed within extraembryonic membranes responsible for nutrient uptake and gaseous exchange. After exiting the oviduct, the conceptus must influence uterine physiology to ensure adequate nutrition and preparation for implantation, while continued development results in the chorioallantois superseding the yolk sac as the primary interface for maternal interaction and exchange...
The role of relaxin in mare reproductive physiology: A comparative review with other species. Relaxin is a peptide hormone best known for its action during the latter half of pregnancy, in particular for its softening effect on pelvic ligaments that aids in preparation of the birth canal for the impending delivery of the fetus. The source of relaxin during early pregnancy varies across species, with the CL being the main source in a number of species. The main source of relaxin during late equine pregnancy is the placenta. In mares with impaired placental function, circulating relaxin levels decline before abortion. During early pregnancy, relaxin promotes endometrial angiogenesis thro...
Review of the reproductive endocrinology of the pregnant and parturient mare. Analytical advancements, especially methods using gas or liquid chromatography tandem mass spectrometry, have allowed more specific and reliable measurement of multiple steroid hormones in the plasma of mares throughout gestation and the periparturient period. Data such as these will form the central focus of this review. The comprehensive analyses possible with liquid chromatography tandem mass spectrometry illuminate the key physiological and developmental transitions that make equine gestation unique. Weeks 6 to 20 encompass endometrial cup formation and equine chorionic gonadotropic secret...
Serum levels of mitochondrial uncoupling protein 1, leptin, and lipids during late pregnancy and the early postpartum period in mares. The aim of this study was to investigate the changes of serum mitochondrial uncoupling protein 1 (UCP1) and leptin levels as well as of lipid and lipoprotein profiles in mares during the peripartum period. Ten pregnant mares (group A) were monitored from 15 ± 3 days of pregnancy until 15 days after foaling, and 10 nonpregnant nonlactating mares constituted the control (group B). In group A, blood sampling was performed on Days 15 ± 3 and 7 ± 3 before foaling, on the day of foaling, and on Days 7 and 15 after foaling. In group B, blood sampling was performed on the same days as in gr...
Development of a new fertility prediction model for stallion semen, including flow cytometry. Several laboratories routinely use flow cytometry to evaluate stallion semen quality. However, objective and practical tools for the on-field interpretation of data concerning fertilizing potential are scarce. A panel of nine tests, evaluating a large number of compartments or functions of the spermatozoa: motility, morphology, viability, mitochondrial activity, oxidation level, acrosome integrity, DNA integrity, "organization" of the plasma membrane, and hypoosmotic resistance, was applied to a population of 43 stallions, 33 of which showing widely differing fertilities (19%-84% pregnancy rat...
Polarisation of equine pregnancy outcome associated with a maternal MHC class I allele: Preliminary evidence. Identification of risk factors which are associated with severe clinical signs can assist in the management of disease outbreaks and indicate future research areas. Pregnancy loss during late gestation in the mare compromises welfare, reduces fecundity and has financial implications for horse owners. This retrospective study focussed on the identification of risk factors associated with pregnancy loss among 46 Thoroughbred mares on a single British stud farm, with some but not all losses involving equid herpesvirus-1 (EHV-1) infection. In a sub-group of 30 mares, association between pregnancy ...
Early pregnancy in the mare: old concepts revisited. "Maternal recognition of pregnancy" (MRP) is commonly used to describe the ongoing embryo-maternal communication during early pregnancy that culminates in prevention of luteolysis and ensures ongoing progestin support. The conceptus-derived pregnancy recognition signal has not yet been identified in the mare. Although equine conceptuses produce substantial amounts of estrogens, there is a lack of evidence that estrogens are the pregnancy recognition signal in mares. Conceptus mobility is integral to MRP and is driven by conceptus-derived prostaglandin production. Cessation of conceptus mobilit...
The outcome of the first stages of pregnancy on mares’ bloodstream thyroid hormones. The objective of this study was to compare in detail the total and free iodothyronines' pattern of mares from the first ovulation of the year over an extended period of 12Â weeks. A total of 20 mares were used in the study. The mares were classified into two groups: mares mated at the ovulation (n = 10) used as observational group and mares unmated at the ovulation (n = 10) used as control group. Serum total and free triiodothyronine (T3, fT3) and thyroxine (T4, fT4) levels were measured in baseline conditions at the first ovulation of year and once a week until 12Â weeks later. For the experi...
Changes in maternal androgens and oestrogens in mares with experimentally-induced ascending placentitis. While advanced stages of ascending placentitis can be diagnosed by transrectal ultrasonography and clinical signs, early stages can be missed. Thus, additional tools could enhance assessment of placental health. Objective: To characterise peripheral dehydroepiandrosterone sulphate (DHEA-S) and testosterone concentrations in mares carrying normal pregnancies (Study 1) and compare plasma concentrations of DHEA-S, testosterone, oestradiol 17-β (oestradiol) and oestrone sulphate (OES) in mares with or without placentitis (Study 2). Methods: Longitudinal cohort study of healthy mares (Study 1) and...
Micromanipulation of equine blastocysts to allow vitrification. Embryo cryopreservation presents an essential method for banking of valuable genetics. However, in equine species the cryopreservation of embryos is complicated by three interacting factors: (1) the late entry of the embryo into the uterus (~6 days after ovulation); (2) the rapid expansion of the blastocyst; and (3) the formation of the equine embryonic capsule, a glycoprotein membrane that forms between the embryo and zona. Efforts to freeze or vitrify equine expanded blastocysts were initially met with little success. In addition, it was thought that breaching the capsule led to loss of embr...
Effects of maternal dexamethasone treatment on pancreatic β cell function in the pregnant mare and post natal foal. Synthetic glucocorticoids are used to treat inflammatory conditions in horses. In other pregnant animals, glucocorticoids are given to stimulate fetal maturation with long-term metabolic consequences for the offspring if given preterm. However, their metabolic effects during equine pregnancy remain unknown. Objective: Thus, this study investigated the metabolic effects of dexamethasone administration on pregnant pony mares and their foals after birth. Methods: Experimental study. Methods: A total of 3 doses of dexamethasone (200 μg/kg bwt i.m.) were given to 6 pony mares at 48 h intervals beg...
Management of the pregnant mare and long-term consequences on the offspring. The study of early developmental conditioning of health and disease in adulthood is particularly relevant in the horse, which is bred mainly to perform in demanding sport challenges. On the basis of this concept, the management of the broodmare could be considered an effective means to produce animals with the desired features. Knowledge on the Developmental Origins of Health and Disease in the equine species remains relatively scarce, with some experimental studies and one single epidemiologic study. Data highlight the determinant role of the maternal environment for postnatal body conformati...
Key Factors Affecting Reproductive Success of Thoroughbred Mares and Stallions on a Commercial Stud Farm. To evaluate factors contributing to fertility of thoroughbred mares, data from 3743 oestrous periods of 2385 mares were collected on a large thoroughbred farm in Ireland. Fourteen stallions (mean age 8.3 years; range 4-15 years) had bred 2385 mares (mean age 9.4 years; range 3-24 years). Maiden mares accounted for 12%, mares with a foal at foot for 64%, and barren, slipped or rested mares for 24% of the total. The mean pregnancy rate per cycle was 67.8% (68.6% in year 1 and 66.9% in year 2). Backward stepwise multivariable logistic regression analysis was utilized to develop two models to eval...
The dynamic steroid landscape of equine pregnancy mapped by mass spectrometry. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) allowed comprehensive analysis of various steroids detectable in plasma throughout equine gestation. Mares (n=9) were bled serially until they foaled. Certain steroids dominated the profile at different stages of gestation, clearly defining key physiological and developmental transitions. The period (weeks 6-20) coincident with equine chorionic gonadotropic (eCG) stimulation of primary corpora lutea and subsequent formation of secondary luteal structures was defined by increased progesterone, 17OH-progesterone and androstenedione, all Î...