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.
Dhakal P, Tsunoda N, Nambo Y, Taniyama H, Nagaoka K, Watanabe G, Taya K.Although equine gestation is unique from the standpoint of fetal gonadal enlargement and regression, the activator of this process is still unknown. The present study aimed to show a possible role of activin during equine gestation. In the first experiment, weekly plasma samples from six pregnant mares were used to measure activin A. In the second experiment, eight pregnant mares carrying female (gestational days 110, 140, 180, and 270) and male fetuses (gestational days 120, 180, 225, and 314) were used for immunohistochemistry of activin receptors (IA, IB, IIA, IIB), and their intracellular ...
Araki M, Ohtaki T, Kimura J, Hobo S, Taya K, Tsunoda N, Taniyama H, Tsumagari S, Nambo Y.Immunohistochemical investigations of the expression of surfactant protein A (SP-A) and surfactant protein D (SP-D) in the uterine and placental tissues of 13 pregnant mares were performed using anti-horse monoclonal primary antibodies. Strong positive reactions for both SP-A and SP-D were observed in the trophoblasts in the microcotyledons of the placentae at 182 to 314 days of gestation; in uterine glandular epithelial cells, faint-to-weak reactions were observed during gestation. This study describes, for the first time, the changes in the SP-A and SP-D expression levels in the endometrium ...
Magalhaes HB, Canuto LEF, Canisso IF.The objectives of this study were to determine (i) the usefulness of serial assessment of mammary gland electrolytes concentrations and correspondent pH to detect impending parturition in jennies; and (ii2) the associations between mammary gland secretions, and gestation length, foal sex, maternal, placental, and foal birth weights. Multiparous jennies (n = 37) were monitored daily from 350 to 355 days of gestation until parturition. The pH of mammary gland secretions was assessed daily with a hand-held device. Aliquots of mammary secretions were frozen daily and then retrospectively assesse...
Dini P, Kalbfleisch T, Uribe-Salazar JM, Carossino M, Ali HE, Loux SC, Esteller-Vico A, Norris JK, Anand L, Scoggin KE, Rodriguez Lopez CM, Breen J....Most autosomal genes in the placenta show a biallelic expression pattern. However, some genes exhibit allele-specific transcription depending on the parental origin of the chromosomes on which the copy of the gene resides. Parentally expressed genes are involved in the reciprocal interaction between maternal and paternal genes, coordinating the allocation of resources between fetus and mother. One of the main challenges of studying parental-specific allelic expression (allele-specific expression [ASE]) in the placenta is the maternal cellular remnant at the fetomaternal interface. Horses () ha...
Abraham M, Bauquier J.The peripartum period is critical in equine medicine for maintaining healthy mares, and ensuring the delivery of healthy neonatal foals. The field of perinatal mortality in horses is continuously evolving, with several advances being recently made in causes of perinatal fetal and foal loss. This review details the main causes of perinatal loss in horses, through late pregnancy, parturition and the neonatal period. Recent advances in identification of infectious organisms and indicators of survival in neonatal foals will be discussed. Continued advances in reproductive and neonatal medicine wil...
Robles M, Hammer C, Staniar B, Chavatte-Palmer P.Forage availability should cover most needs for mares bred during spring and summer. Out-of-season breeding, lack of access to pasture, or good quality forage calls for nutritional supplementation. Current evaluations of broodmare needs are based on fetoplacental tissue requirements, but do not consider endocrine changes or that the maternal diet quality affects long-term foal health. This article reviews pregnant mares' current nutritional recommendations. Secondly, fetoplacental developmental stages during gestation are outlined, defining critical periods in the context of the developmental ...
Bradbery AN, Coverdale JA, Hartz CJ, Millican AA, Goehring MS, Fikes KK, Picking E, Hammer CJ, Dunlap KA, Cardoso RC, Wickersham TA, Leatherwood JL....Results from previous studies indicate that maternal overnutrition during late gestation predisposes foals to metabolic disease, however, specific mechanisms resulting in disease remain unknown. Quarter Horse mares (n = 16), were randomly assigned to dietary treatments, beginning on gestational day 235, and consisted of a control group (CON- diet meeting nutrient requirement; n = 8) or an overfed diet (HIGH; n = 8) where mares received an additional 40 % above CON. On gestational days 285 and 315, an intravenous glucose tolerance test (FSIGTT) was conducted. Following parturition, foals were s...
Castro T, Jacob JC, Stefani G, Domingues RR, Ginther OJ.The concentrations of progesterone (P4) and a metabolite of PGF2α (PGFM) in mares were compared between the interovulatory interval (IOI; n = 8) and the corresponding days of pregnancy (n = 9). In daily blood samples, P4 increased between the day of ovulation (Day 0) and ∼Day 6 and then gradually decreased until the beginning of luteolysis in the IOI group. Before the beginning of luteolysis, there were no significant differences in P4 concentrations between the IOI and early pregnancy. In the IOI, PGFM concentration on the day before the beginning of luteolysis began to increase (P <Â...
Macpherson ML, Giguère S, Pozor MA, Burden CA, Berghaus LJ, Berghaus RD, Varner JC, Hayna JT, Benson SM, Randell SA, Lyle SK, Kelleman AA, Hart KA....Minimal evidence exists supporting therapeutic selections for equine placentitis. The goal of this study was to characterize the anti-inflammatory effects of firocoxib when administered to mares with placentitis. Mares (gestation D270-300) were assigned to: INFECT (n = 6; placentitis, no treatment), FIRO (n = 6; placentitis, firocoxib, 0.1 mg/kg, PO, daily), and NORM (n = 6; no infection/treatment). Allantoic fluid (8 hours, 24 hours, birth) and amniotic fluid (birth) were collected from mares after infection. Concentrations of IL-1β, IL-6, TNF-α, IL-10, PGF , and PGE in fluids were...
Rivera Del Alamo MM, Katila T, Palviainen M, Reilas T.Intrauterine devices block luteolysis in cyclic mares, but the underlying mechanism is unknown. To clarify the mechanisms, the protein profile of the endometrial secretome was analyzed using two-dimensional difference gel electrophoresis (2D-DIGE). Twenty-seven mares were classified according to whether they were inseminated (AI) or had an intrauterine device (IUD), a water-filled plastic sphere, inserted into the uterus on Day 3 after ovulation. Uterine lavage fluids were collected on Day 15 from pregnant inseminated mares (AI-P; n = 8), non-pregnant inseminated mares (AI-N; n = 4), and m...
Liao Q, Li Z, Han Y, Deng L.The purpose of this study was to investigate the profile change of serum trace and major elements, and biochemical and hematological parameters in jennies during late pregnancy and early lactation. Twenty-five healthy Chinese Liaoxi jennies were used in late pregnancy and early lactation. Results showed that the levels of Fe, total protein (TP), and aspartate aminotransferase (AST) were highly variable interindividual among the jennies. Early lactating jennies showed significantly lower serum levels of K, Se, AST, total cholesterol (TC), and triglyceride than late pregnant jennies (P < .05)...
Li N, Yu J, Yang F, Shao Y, Wu S, Liu B, Li M, Wang T, Li J, Zeng S.The aim of this study was to evaluate the effects of L-proline on the extender quality of frozen and post-thawed jackass semen. Jackass (n = 6) semen samples were collected and cryopreserved in gradient concentrations (0-80 mM) of L-proline in extenders; post-thawed semen samples were cultured in L-proline medium for 10 hours at 37°C. For cryopreservation experiment I, the motile parameters, mitochondrial membrane potential (MMP), and plasma membrane, acrosome, and chromatin structure integrities of post-thawed semen were assessed. For culture experiment II, additional ROS contents were ana...
Fedorka CE, El-Sheikh Ali H, Walker OF, Scoggin KE, Dini P, Loux SC, Troedsson MHT, Ball BA.Ascending placentitis is a leading cause of abortion in the horse, but adaptive immune response to this disease is unknown. To evaluate this, sub-acute placentitis was experimentally-induced via trans-cervical inoculation of S. zooepidemicus, and endometrium and chorioallantois was collected 8 days later (n = 6 inoculated/n = 6 control). The expression of transcripts relating to Th1, Th2, Th17, and Treg maturation was assessed via RNASeq. IHC of transcription factors relating to each subtype in the same tissues (Th1: TBX21, Th2: GATA3, Th17: IRF4, Treg: FOXp3). An immunoassay was utili...
Roach JM, Foote AK, Smith KC, Verheyen KL, de Mestre AM.Pregnancy loss after Day 70 of gestation manifests as abortion, stillbirth or perinatal death. While previous studies have reported the diagnoses of laboratory submissions, none have quantified the incidence and causes of abortions, stillbirths and perinatal mortality at a population level. Objective: To report the incidence and causes of pregnancy loss after Day 70 of gestation in a cohort of Thoroughbreds. Methods: Retrospective cohort study. Methods: Outcomes of Day 70 pregnancies were collected from eight Thoroughbred farms over the 2013-2017 breeding seasons. Stud, veterinary and laborato...
Stasiak K, Dunowska M, Rola J.Equid herpesvirus 1 (EHV-1) infections are endemic worldwide, including Poland. Many are subclinical, but some are associated with respiratory disease, abortion, neonatal foal death, or neurological disease. We describe an outbreak of abortions in Arabian mares at a well-managed State stud farm in Poland. Methods: Eight of 30 pregnant mares aborted and one gave birth to a weak foal that died within 72 h after birth. EHV-1 was isolated from all fetuses as well as from the diseased foal. All viruses belonged to the N variant based on the predicted open reading frame (ORF) 30 amino acid sequenc...
Nagel C, Melchert M, Aurich C, Aurich J.Equine fetomaternal monitoring is based on endocrine and cardiac parameters which may differ among small, medium-size, and full-size horses. Therefore, Shetland ( = 6), Haflinger ( = 8), and Warmblood pregnancies ( = 9) were studied during late gestation and at foaling. Weight of mares, foals and placenta, plasma progestin and cortisol concentration, heart rate and heart rate variability (HRV) were determined. Foal weight always approximated 10% of mare weight but relative placenta weight was highest in full-size mares ( < 0.05). Progestin ( < 0.001) and cortisol ( < 0.05) concentrati...
Sgorbini M, Freccero F, Castagnetti C, Mariella J, Lanci A, Marmorini P, Camillo F.Induction of parturition in horses is still not well accepted due to the potential peripartum complications for mares and newborn foals. We assessed differences after spontaneous and induced parturition with low doses of oxytocin (OX) in 1) incidence of peripartum complications in mares; 2) viability, behavioral, physical, and venous blood gas analyses in foals. In this study 61 mares were included; 45/61 were enrolled in the spontaneous foaling group (SF) and 16/61 in the induced foaling group (IF). In the IF group, when the calcium in mammary secretion reached concentrations of ≥250 ppm, ...
Beachler TM, Scott Bailey C, Gracz HS, Morgan DR, Von Dollen KA, Ellis KE, Gadsby JE, Lyle SK.The amniotic and allantoic fluid compartments in the mare serve essential roles throughout pregnancy and parturition. Although the global metabolomic profile of amniotic fluid in women has been extensively characterized, current data for equine fetal fluids are limited. Therefore, the goal of this study was to characterize the global metabolomic profile of equine allantoic and amniotic fluid through nuclear magnetic resonance spectroscopy. Fetal fluids were collected between 270 and 295Â days of gestation from 12 pregnancies through ultrasound-guided transabdominal puncture. A total of 24 samp...
Bucca S, De Oliveira IRS, Cunanan JC, Vinardell T, Troedsson MHT.Assessment of pregnancy viability in the equine patient is currently based on gestational profiles of limited prognostic value. In recent years Doppler technology has been applied to uterine and umbilical arteries of pregnant mares to monitor fetal responsive haemodynamics, suggestive of compromise. To date, uterine artery Doppler indices failed to provide sufficient evidence of pregnancy viability and the umbilical cord of the equine fetus is inconsistently visualized past 250 days gestation. The objectives of this study were to: i) evaluate intracranial blood flow impedance by Doppler examin...
Becsek A, Schweizer A, Knutti B, Bollwein H.The aim of this study was to compare transrectal two-dimensional (2D) and three-dimensional (3D) ultrasound examination with regards to required time and accuracy of fetal sex determination in early pregnant mares. Methods: For this purpose 47 mares were examined transrectally once between days 58 and 115 of gestation. Initially, the fetal sex was determined by identifying the location of the genital tubercle (GT) or external genitalia using 2D-ultrasound. Subsequently, the ultrasound machine was switched to 3D-mode to obtain images for later computer-based evaluation. Results: The gestational...
Fraser NS, Wilborn RR, Johnson AK, Braden TD, Wiley AA, Canisso IF, Bartol FF.Equine uterine development, including endometrial histogenesis, begins prenatally and is completed postnatally. Little is known about this process in the horse. Uterine tissue was acquired from 38 foals, ranging in developmental age from gestational day (GD) 300 to postnatal day (PND) 180, for assessment of endometrial histogenesis. Patterns of endometrial cell proliferation were evaluated by multispectral imaging of uterine tissue sections stained immunofluorescently for Ki-67. Labeling index (LI, % labeled cells) for Ki-67 was calculated for each endometrial cell compartment (luminal epithel...
Wilsher S, Bowker A, Silva J, Allen WRT.A total of 127 normal placentas from Arabian mares resident in the United Arab Emirates were examined. The mean linear dimensions of the placenta were, on average, 84% of those previously recorded for the placentas of the Thoroughbred. Significant differences in the size of the allantochorion between primigravid and multiparous mares were seen only in the linear dimensions of the body portion. The pregnant horn was more commonly on the right than left side of the uterus (PÂ = .01; 74/127; 58%). Cord attachment was primarily at the base of the two placental horns (112/127; 88%), with the remain...
Clothier J, Small A, Hinch G, Brown WY.The long-term effects of gestational immaturity in the premature (defined as < 320Â days gestation) and dysmature (normal term but showing some signs of prematurity) foal have not been thoroughly investigated. Studies have reported that a high percentage of gestationally immature foals with related orthopedic issues such as incomplete ossification may fail to fulfill their intended athletic purpose, particularly in Thoroughbred racing. In humans, premature birth is associated with shorter stature at maturity and variations in anatomical ratios, linked to alterations in metabolism and timing of...
Loux SC, Conley AJ, Scoggin KE, El-Sheikh Ali H, Dini P, Ball BA.Steroid production varies widely among species, with these differences becoming more pronounced during pregnancy. As a result, each species has its own distinct pattern of steroids, steroidogenic enzymes, receptors, and transporters to support its individual physiological requirements. Although the circulating steroid profile is well characterized during equine pregnancy, there is much yet to be explored regarding the factors that support steroidogenesis and steroid signaling. To obtain a holistic view of steroid-related transcripts, we sequenced chorioallantois (45 days, 4 months, 6 months, 1...
Todd ET, Hamilton NA, Velie BD, Thomson PC.Horses produce only one foal from an eleven-month gestation period, making the maintenance of high reproductive rates essential. Genetic bottlenecks and inbreeding can increase the frequency of deleterious variants, resulting in reduced reproductive levels in a population. In this study we examined the influence of inbreeding levels on foaling rate, gestation length and secondary sex ratio in Australian Thoroughbred mares. We also investigated the genetic change in these traits throughout the history of the breed. Phenotypic data were obtained from 27,262 breeding records of Thoroughbred mares...
Parsons Aubone AM, Bisiau CM, McCue PM, Bouma GJ.Mammals have a circadian rhythm that is synchronized by a master clock located in the hypothalamic suprachiasmatic nucleus (SCN). The SCN regulates additional clocks located in peripheral tissues, including some involved in endocrine or reproductive functions. Studies in humans and mice report that molecular clocks also exist in the placenta. However, little is known about the presence of "Clock genes," namely Circadian Locomotor Output Cycles Kaput (CLOCK), Brain and Muscle Arnt-Like 1 (BMAL1), Period 1 (PER1), Period 2 (PER2), Cryptochrome 1 (CRY1), and Cryptochrome 2 (CRY2), in equine place...
Campos I, Batista B, Matos AC, Dutra F, Gomes G, Pinna A, Leite J, Ferreira A.The amnion is a layer of the foetal membrane that has mechanical protection function and allows expansion and growth. The diseases that affect amnion have rarely been reported in horses. Amnionitis and funiculitis have been implicated as components of abortions as observed in abortions caused by the mare reproductive loss syndrome. Here, we report an abortion at 240-day gestation of a 7-year-old Anglo-Arabian mare with a history of previous stillbirth. Blood samples from both mare and foetus were collected for serological testing. Fragments from the placenta were taken for macroscopic and hist...
Dordas-Perpinyà M, Normandin L, Dhier T, Terris H, Cochard A, Frilley C, Huiban F, Bruyas JF.The aim of this study was to assess the efficacy of different doses of buserelin acetate and another GnRH agonist, triptorelin acetate, in saline solution in a single subcutaneous injection, to induce ovulation of growing pre-ovulatory follicle in mare and compare it with the classical treatment of a single injection of hCG. The study is split into 3 experiments over different breeding seasons in the same stud with a random distribution of treatment. The first one was to compare the injection of 6 mg of buserelin with 1,500 IU of hCG; the second one consisted of comparing different doses of ...
Tanaka Y, Taniyama H, Tsunoda N, Shinbo H, Nagamine N, Nambo Y, Nagata S, Watanabe G, Herath CB, Groome NP, Taya K.Immunolocalization of the inhibin (a) and inhibin/activin (beta3A and betaB) subunit proteins in equine fetal testes was investigated to determine the ability of the fetal testis to produce inhibins at 120, 150, 200, and 250 days of gestation. In addition, concentrations of immunoreactive (ir)-inhibin, inhibin pro-aC, and inhibin A in both the maternal and fetal circulation were measured. It was found that plasma concentrations of ir-inhibin, inhibin pro-alphaC, and inhibin A were much higher (P < .05) in the fetal than in the maternal circulation at any stage of gestation examined. Similar...
Wilsher S, Allen WR.An opportunity to monitor equine chorionic gonadotrophin (eCG) production during 61 pregnancies in 25 Thoroughbred mares mated to the same Thoroughbred stallion was utilised in order to further knowledge regarding factors involved in the production of this hormone. Objective: To examine the effects of maternal body condition, exercise and parity on eCG production. Methods: In the first experiment, maiden mares were fed either a moderate (n = 9) or an excessive (n = 10) food intake throughout gestation. In the second experiment, 5 mares were exercised daily during pregnancy and eCG production r...
Nagel C, Melchert M, Aurich J, Aurich C.Cortisol is involved in the initiation of parturition and we hypothesized that increased maternal cortisol release advances the onset of foaling. Transport is a stressor for horses and induces an increase in cortisol release. To determine stress effects on the time of foaling, late-pregnant mares were transported by road for 3 hours (n = 12) or remained in their stable as controls (n = 4). Starting on day 325 of gestation, saliva and blood samples were taken for cortisol and progestin analysis, respectively. Fetomaternal electrocardiograms were recorded repeatedly. Mares were checked for im...
Loux SC, Scoggin KE, Bruemmer JE, Canisso IF, Troedsson MH, Squires EL, Ball BA.MicroRNAs (miRNAs) are small, non-coding RNAs which are produced throughout the body. Individual tissues tend to have a specific expression profile and excrete many of these miRNAs into circulation. These circulating miRNAs may be diagnostically valuable biomarkers for assessing the presence of disease while minimizing invasive testing. In women, numerous circulating miRNAs have been identified which change significantly during pregnancy-related complications (e.g. chorioamnionitis, eclampsia, recurrent pregnancy loss); however, no prior work has been done in this area in the horse. To identif...
Macpherson ML, Giguère S, Pozor MA, Burden CA, Berghaus LJ, Berghaus RD, Varner JC, Hayna JT, Benson SM, Randell SA, Lyle SK, Kelleman AA, Hart KA....Minimal evidence exists supporting therapeutic selections for equine placentitis. The goal of this study was to characterize the anti-inflammatory effects of firocoxib when administered to mares with placentitis. Mares (gestation D270-300) were assigned to: INFECT (n = 6; placentitis, no treatment), FIRO (n = 6; placentitis, firocoxib, 0.1 mg/kg, PO, daily), and NORM (n = 6; no infection/treatment). Allantoic fluid (8 hours, 24 hours, birth) and amniotic fluid (birth) were collected from mares after infection. Concentrations of IL-1β, IL-6, TNF-α, IL-10, PGF , and PGE in fluids were...
Gibson C, de Ruijter-Villani M, Rietveld J, Stout TAE.Glucose is the primary energy substrate for early conceptus development and, for the first 40 days of gestation, the equine conceptus depends solely on glucose available in the histotroph; thereafter, histotrophic glucose provision continues to support transport across the definitive placenta. To investigate glucose provision routes during early equine pregnancy we examined expression of glucose transporters in conceptus membranes and endometrium recovered on days 7, 14, 21 and 28 after ovulation. To further differentiate the contributions of maternal progesterone priming and conceptus-endomet...
Esteller-Vico A, Ball BA, Troedsson MHT, Squires EL.Equine pregnancy is characterized by very high circulating concentrations of estrogens. The physiological roles of estrogens during equine gestation are largely unknown, although some studies suggest a role in the regulation of uterine artery hemodynamics and a relationship between low circulating estrogen concentrations and late pregnancy loss. The objectives of this experiment were to evaluate the effects of estrogen suppression on uterine artery hemodynamics and on pregnancy outcome. Estrogen synthesis was suppressed using letrozole, a potent aromatase inhibitor. Twelve pregnant mares were ...
Allen AL, Townsend HG, Doige CE, Fretz PB.A case-control study was conducted to identify risk factors for the congenital hypothyroidism and dysmaturity syndrome of foals. A questionnaire was used during personal interviews of foal owners and farm managers to collect information on animal signalment, farm environment, and mare management. Information on 39 foals with the congenital hypothyroidism and dysmaturity syndrome were compared with 39 control foals. Foals with the syndrome had a significantly (P < 0.0001) longer gestation (357.6 d) than control foals (338.9 d). Pregnant mares that were fed greenfeed, did not receive any supplem...
Crossett B, Suire S, Herrler A, Allen WR, Stewart F.One of the major, progesterone-dependent proteins secreted into the uterine lumen of the mare is a 19-kDa lipocalin (P19). It associates strongly with the embryonic capsule that envelops the young horse conceptus in early gestation, suggesting that it may be involved in sustaining early development. However, it was not known whether the protein was transported through the capsule and/or trophoblast layer and into the yolk sac cavity. To address this question, polyclonal antisera were raised against a C-terminal peptide (based on the deduced amino acid sequence of P19) and a recombinant-derived...
Veronesi MC, Villani M, Wilsher S, Contri A, Carluccio A.The aim of the study was to compare horse and donkey placentae using stereological techniques. Term placentae were collected at spontaneous foaling from seven Thoroughbred mares, seven pony mares, and six jenny donkeys. Maternal and foal weights were recorded and the mass, volume, and gross area of each allantochorion was also recorded. Ten random biopsies were recovered and processed for light microscopy from which the surface density of the microcotyledons (S(v)) and the total microscopic area of fetomaternal contact were calculated stereologically. Gestation length was longer in the donkeys...
Klein C.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...
Schwarzenberger F, Möstl E, Bamberg E, Pammer J, Schmehlik O.Faecal samples were collected at weekly intervals from pregnant Lipizzan mares during Weeks 7-16 following mating and from Lipizzan, Trotter and Thoroughbred mares during the last 3 months of gestation. After parturition, samples were taken daily from the Thoroughbred mares for another 6 days. Non-pregnant mares served as controls. The concentrations of unconjugated oestrogens (Eg), 20 alpha-OH-progestagens (20 alpha-G) and 20 beta-OH-progestagens (20 beta-G) were measured by enzyme immunoassay. In the faeces of Lipizzan mares, immunoreactive progestagens were significantly (P less than 0.01) ...
Mesa AM, Warren LK, Sheehan JM, Kelley DE, Mortensen CJ.L-Arginine is an essential amino acid in many species that has been shown to influence reproduction. However, in horses a dose of 1% L-arginine of total dietary intake impaired absorption of other amino acids, whereas a dose of 0.5% did not. The objectives of this experiment were to evaluate postpartum parameters on mares supplemented with 0.5% L-arginine through the last 90d of gestation and 14d postpartum. Sixteen light-horse mares were randomly divided in two groups: 8 mares supplemented with 0.5% L-arginine and 8 mares fed an isonitrogenous equivalent. Gestation length, days to uterine cle...
Forhead AJ, Broughton Pipkin F, Taylor PM, Baker K, Balouzet V, Giussani DA, Fowden AL.Blood pressure, heart rate and the plasma concentrations of cortisol and components of the renin-angiotensin system were measured in chronically catheterized Pony mares (n=15) and their fetuses during the second half of gestation (day 153-336 of gestation; term is normally between day 320 and day 340 of gestation). Fetal blood pressure increased towards term with the prepartum surge in plasma cortisol concentration, and there was a correlation between fetal blood pressure and both gestational age (r = 0.88, P < 0.0005) and plasma cortisol concentration (r = 0.88, P < 0.0005). Plasma concentrat...
Todd ET, Hamilton NA, Velie BD, Thomson PC.Horses produce only one foal from an eleven-month gestation period, making the maintenance of high reproductive rates essential. Genetic bottlenecks and inbreeding can increase the frequency of deleterious variants, resulting in reduced reproductive levels in a population. In this study we examined the influence of inbreeding levels on foaling rate, gestation length and secondary sex ratio in Australian Thoroughbred mares. We also investigated the genetic change in these traits throughout the history of the breed. Phenotypic data were obtained from 27,262 breeding records of Thoroughbred mares...
Leith GS, Ginther OJ.Intrauterine mobility patterns of the embryonic vesicle were characterized on Days 9 to 17 after ovulation in pony mares using real-time ultrasonography (n=5 or 7 mares per day). The location of the vesicle was determined by dividing the uterus into right horn, left horn, and body. Each uterine horn was further divided into three approximately equal portions (cranial third, middle third, caudal third), yielding seven segments (body plus three portions of each horn). Location of the vesicle within the uterus was recorded every five minutes for two consecutive hours (25 location determinations p...
The Journal of physiologyNovember 1, 1974
Volume 242, Issue 3 805-826 doi: 10.1113/jphysiol.1974.sp010735
Comline RS, Silver M.1. Blood gas tensions, pH, PCV, O(2) affinity and red cell 2,3-diphosphoglycerate (DPG) levels have been measured in uterine and umbilical blood in conscious cows and mares with indwelling vascular catheters and in sows under sodium pentobarbitone anaesthesia.2. Large P(O2) gradients (20-24 mmHg) were observed between the uterine and umbilical venous blood in the cow and pig, while in the mare the corresponding P(O2) difference was only 2.7 +/- 1.7 mmHg. Alterations in maternal arterial P(O2) did not affect the large vein-to-vein P(O2) difference in either ruminant or pig.3. In the cow the pre...
Cudd TA, LeBlanc M, Silver M, Norman W, Madison J, Keller-Wood M, Wood CE.Fetal maturation and the timing of parturition in both sheep and primates are thought to be controlled by the hypothalamic-pituitary-adrenal axis but little is known about the endocrinology of the equine fetus. We investigated the ontogeny of plasma concentrations of adrenocorticotropic hormone (ACTH), cortisol and corticosteroid binding capacity in the late-gestation fetal horse. We also wished to determine whether there is ultradian rhythmic release of ACTH and cortisol in fetal horses and we compared fetuses to maternal and non-pregnant adult horses. Six fetuses, 278-304 days gestation (ter...
Legacki EL, Scholtz EL, Ball BA, Stanley SD, Berger T, Conley AJ.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...
Fedorka CE, El-Sheikh Ali H, Walker OF, Scoggin KE, Dini P, Loux SC, Troedsson MHT, Ball BA.Ascending placentitis is a leading cause of abortion in the horse, but adaptive immune response to this disease is unknown. To evaluate this, sub-acute placentitis was experimentally-induced via trans-cervical inoculation of S. zooepidemicus, and endometrium and chorioallantois was collected 8 days later (n = 6 inoculated/n = 6 control). The expression of transcripts relating to Th1, Th2, Th17, and Treg maturation was assessed via RNASeq. IHC of transcription factors relating to each subtype in the same tissues (Th1: TBX21, Th2: GATA3, Th17: IRF4, Treg: FOXp3). An immunoassay was utili...
Campos-Chillòn LF, Suh TK, Barcelo-Fimbres M, Seidel GE, Carnevale EM.The objectives of this study were to: (1) determine an optimal method and stage of development for vitrification of bovine zygotes or early embryos; and (2) use the optimal procedure for bovine embryos to establish equine pregnancies after vitrification and warming of early embryos. Initially, bovine embryos produced by in-vitro fertilization (IVF) were frozen and vitrified in 0.25mL straws with minimal success. A subsequent experiment was done using two vitrification methods and super open pulled straws (OPS) with 1- or 8-cell bovine embryos. In Method 1 (EG-O), embryos were exposed to 1.5M e...
Macpherson ML, Reimer JM.Twin pregnancy in the mare causes economic loss. Early transrectal ultrasonographic detection of twins and manual crush of one embryonic vesicle is the method of choice for managing equine twins (90% success rate). Transcutaneous and transvaginal ultrasound-guided twin reduction techniques are described for twin pregnancies that advance beyond 25 days of gestation. Reported success rates for the ultrasound-guided procedures are 50% and 20%, respectively.
Gaivão MM, Rambags BP, Stout TA.Experimental studies and field surveys suggest that embryonic loss during the first 6 weeks of gestation is a common occurrence in the mare. During the first 2 weeks of development, a number of important cell differentiation events must occur to yield a viable embryo proper containing all three major germ layers (ectoderm, mesoderm, and endoderm). Because formation of the mesoderm and primitive streak are critical to the development of the embryo proper, but have not been described extensively in the horse, we examined tissue development and differentiation in early horse conceptuses using a c...
Todhunter KH, Cawdell-Smith AJ, Bryden WL, Perkins NR, Begg AP.Six pregnant Standardbred mares aged between 6 and 14 years were gavaged with 50 g or 100 g of suspended emulsified whole Processionary caterpillars (Ochrogaster lunifer) for 5 days during 2 experiments undertaken to study the etiology of equine amnionitis and fetal loss (EAFL). The 6 treated mares and 1 untreated mare were between 128 and 252 days gestation. Mare 1 (untreated) was euthanized on day 5 of the treatment period, while the treated mares were euthanized on days 2, 4, 8, 10, 12, and 24 days from their first treatment. Caterpillar setae were not found in the untreated mare. Setal fra...
Schöniger S, Gräfe H, Richter F, Schoon HA.The enzyme indoleamine 2,3-dioxygenase 1 (IDO1) acts immunomodulatory and restricts bacterial growth. In the uterus of women and mice, it likely contributes to tissue homeostasis and disease pathogenesis. Pregnancy failure in mares is often caused by endometritis and endometrosis. The pathogenesis of nonsuppurative endometritis and endometrosis is still uncertain. To the authors' knowledge, no information on IDO1 expression in the equine endometrium is published. Aim of this study was to examine the presence of IDO1 as transcripts and proteins in the healthy and diseased endometrium of 25 mare...
George LA, Staniar WB, Cubitt TA, Treiber KH, Harris PA, Geor RJ.To characterize the effects of pregnancy on insulin sensitivity (SI) and glucose dynamics in pasture-maintained mares fed supplemental feeds of differing energy composition. Methods: Pregnant (n = 22) and nonpregnant (10) healthy Thoroughbred mares. Methods: Pregnant and nonpregnant mares underwent frequently sampled intravenous glucose tolerance tests at 2 times (period 1, 25 to 31 weeks of gestation; period 2, 47 weeks of gestation). Following period 1 measurements, mares were provided a high-starch (HS; 39% starch) or high-fat and -fiber (14% fat and 70% fiber) supplemental feed. From a sub...
Allen WR, Gower S, Wilsher S.Implantation and placentation in the mare does not commence until as late as day 40 after ovulation. The reasons for this and the growth factors and/or hormones which drive placentation when it does finally occur are of considerable academic and practical interest. Placental interface tissues recovered from 11 accurately aged and perfused-fixed horse uteri between 20 and 68 days of gestation were stained immunocytochemically for Epidermal Growth Factor (EGF), its specific receptor (EGF-R) and for the steroid hormone enzyme, aromatase. EGF was present in endometrial gland and lumenal epithelia ...
