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.
Roberts MA, London K, Campos-Chillón LF, Altermatt JL.An equine embryo produced by intracytoplasmic sperm injection (ICSI) was trans-cervically transferred to a recipient mare and pregnancy was confirmed via ultrasound examination on days 11, 12 and 15. On days 20 and 22, a single embryonic proper with a heartbeat was observed. On day 29, two embryos proper appeared during ultrasound examination, each possessing a heartbeat. Subsequent examinations on days 35 and 39 revealed continued viability and development of both embryos proper. On day 49, demise of both fetuses was present. Although no DNA analysis or post-partum examinations were performed...
de Ruijter-Villani M, Stout T.Implantation is a pivotal step in the establishment of mammalian pregnancy. Although implantation strategies vary between species, many aspects of conceptus-maternal signalling necessary to induce uterine receptivity to implantation are conserved. The temporal 'window' for the initiation of implantation is short and precisely controlled by endocrine, paracrine and autocrine factors. An invariable prerequisite for the development of uterine receptivity to implantation is continuous exposure of the endometrium to progesterone which, after a species-specific interval, downregulates progesterone r...
Lotstra RJ, van den Broek J, Power T, Marr CM, Wijnberg ID.Atrial fibrillation is a common equine arrhythmia. Quinidine alone, or with digoxin are common treatments. Studies on outcome in Warmblood populations in which duration of the AF is often unknown are limited. Objective: To identify the factors that are associated with the success of full treatment cardioversion with oral medication, and establish whether there are differences in these factors between institutions. Methods: Retrospective case series using patient records of Equine University Clinic of Utrecht University and Rossdales Equine Hospital, Newmarket. Methods: Forty-nine horses treate...
Ferreira JC, Canesin HS, Ignácio FS, Rocha NS, Pinto CR, Meira C.The present experiment was divided into three studies to investigate the effect of age and endometrial degeneration on uterine blood flow of mares. In study 1, the influence of semen infusion and conception was evaluated using noninseminated (non-AI), inseminated nonpregnant (AI-NP), and inseminated pregnant (AI-P) mares (n = 7 mares/group). In study 2, the effect of age was investigated using young (≤6 years), adult (from 8 to 12 years), and old (≥15 years) pregnant mares (n = 7 mares/group). In study 3, uterine blood flow was also characterized in pregnant mares (n = 7 mares/group) with ...
Cuervo-Arango J, Aguilar JJ, Vettorazzi ML, MartÃnez-Bovà R.The present study characterizes the relationship between the levels of eCG, ovarian morphology, resumption of cyclicity, and fertility in postaborted embryo transfer recipient mares. A total of 32 pregnant recipient mares carrying a male fetus were aborted at approximately 65 days of gestation by single transcervical administration of cloprostenol. In addition, 25 gestation age-matched mares were used as nonaborted controls. The concentration of progesterone, but not of eCG, differed significantly between controls and aborted mares 48 hours after abortion. Of treated mares, 84.4% (27 of 32) ex...
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...
de Ruijter-Villani M, Deelen C, Stout TA.Leukaemia inhibitory factor (LIF) plays a critical role in blastocyst development and implantation in several species. The present study investigated mRNA and protein expression for LIF, as well as the low-affinity LIF receptor (LIFR) and interleukin-6 signal transducer (IL6ST), in equine endometrium, trophoblast and histotroph during early pregnancy and in the endometrium during the oestrous cycle. Endometrial LIF mRNA expression was upregulated after Day 21 of pregnancy, whereas LIF immunoreactivity increased in the endometrium on Day 28. Expression of LIF mRNA in the yolk sac membrane incre...
Hemberg E, Einarsson S, Kútvölgyi G, Lundeheim N, Bagge E, Båverud V, Jones B, Morrell JM.This study investigated the relationship of the health of the newborn foal and (1) number of polymorphonuclear leukocytes (PMNLs) in the amniotic fluid, (2) bacteria present in the amniotic fluid and the venous umbilical blood, and (3) bacteria present in the uterus of the newly foaled mare. A further aim was to investigate relationships between the bacteriologic findings in the amniotic fluid, umbilical blood, and uterus postpartum. Samples were taken from 50 Standardbred trotter foaling mares from a well-managed stud in Sweden. Parturition was spontaneous in all cases. Length of pregnancy, p...
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...
Spoormakers TJ, Graat EA, ter Braake F, Stout TA, Bergman HJ.Previous surveys have reported that mare and foal survival after correction of uterine torsion (UT) varies from 60 to 84% and from 30 to 54%, respectively. Furthermore, resolution via a standing flank laparotomy (SFL) has been associated with better foal, but not mare, survival. Objective: To compare the success of SFL with other correction methods (e.g. midline or flank laparotomy under general anaesthesia; correction per vaginam). Methods: Retrospective analysis of clinical records. Methods: Data on correction technique, stage of gestation, degree of rotation, survival and subsequent fertili...
Baska-Vincze B, Baska F, Szenci O.Monitoring fetal heart rate (FHR) and fetal heart rate variability (FHRV) helps to understand and evaluate normal and pathological conditions in the foal. The aim of this study was to establish normal heart rate reference values for the ongoing equine pregnancy and to perform a heart rate variability (HRV) time-domain analysis in Lipizzaner mares. Seventeen middle- and late-term (days 121-333) pregnant Lipizzaner mares were examined using fetomaternal electrocardiography (ECG). The mean FHR (P = 0.004) and the standard deviation of FHR (P = 0.012) significantly decreased during the pregnancy. ...
Klewitz J, Struebing C, Rohn K, Goergens A, Martinsson G, Orgies F, Probst J, Hollinshead F, Bollwein H, Sieme H.Color Doppler sonography has become routine for the evaluation of high-risk pregnancies in human medicine. Previous studies documenting uterine blood flow parameters in the pregnant mare have found a decrease in peripheral blood flow resistance in the first pregnancy weeks and an increase in uterine blood flow, especially in the last trimester of pregnancy. However, these studies involved only a small number of mares. No naturally occurring pregnancy abnormalities occurred that would allow blood flow changes to be retrospectively examined and analyzed. The objective of the present study was to...
Silva ES, Scoggin KE, Canisso IF, Troedsson MH, Squires EL, Ball BA.The objective of this study was to compare expression of estrogen receptor alpha (ER-α), β (ER-β), progesterone receptor (PR), as well as prostaglandin E2 type 2 (EP2) and 4 (EP4) receptors in the equine myometrium and endometrium during estrus, diestrus and early pregnancy. Tissues were collected during estrus, diestrus, and early pregnancy. Transcripts for ER-α (ESR1), ER-β (ESR2), PR (PGR), EP2 (PTGER2) and EP4 (PTGER4) were quantified by qPCR. Immunohistochemistry was used to localize ER-α, ER-β, PR, EP2 and EP4. Differences in transcript in endometrium and myometrium were compared ...
Jenner F, van Osch GJ, Weninger W, Geyer S, Stout T, van Weeren R, Brama P.Articular cartilage regeneration is the focus and goal of considerable research effort. Since articular chondrocytes descend from a distinct cohort of progenitor cells located in embryonic nascent joints (interzones), establishing the timing of equine interzone formation is an essential first step towards understanding equine joint and articular cartilage development. Objective: To establish the time frame during which the equine femorotibial interzone forms. Methods: Descriptive anatomical study. Methods: Equine embryos were harvested at 37 (E37), 40, 42, 45, 50 and 65 days' gestation. The fe...
Aguilar JJ, Cuervo-Arango J, Santa Juliana L.It is scientifically demonstrated that lunar cycles have important effects on several biological events. Controversy exists about the lunar influence on human and animal parturition. In addition, in the horse industry, especially in Polo Horse breeders of Argentina and around the world there is a higher demand for female offspring than for males. The objective of this study was to determine whether there is a significant association between the lunar phase at the time of mating and the sex ratio at birth in horses. The Argentinean Stud Book provided information related to all matings registere...
Morrell JM, Richter J, Martinsson G, Stuhtmann G, Hoogewijs M, Roels K, Dalin AM.A successful outcome after artificial insemination with cooled semen is dependent on many factors, the sperm quality of the ejaculate being one. Previous studies have shown that spermatozoa with good motility, normal morphology, and good chromatin integrity can be selected by means of colloid centrifugation, particularly single layer centrifugation (SLC) using species-specific colloids. The purpose of the present study was to conduct an insemination trial with spermatozoa from "normal" ejaculates, i.e., from stallions with no known fertility problem, to determine whether the improvements in sp...
Ali A, Alamaary M, Al-Sobayil F.The aim of this study was to evaluate the reproductive performance of the Arab mares in the Kingdom of Saudi Arabia (KSA). Methods: Managers of 26 studfarms containing 1014 Arab mares at five districts were asked to complete a questionnaire on the reproductive efficiency of their mares. Results: The mean age at first mating was 3.06 ± 0.5 years. Mares were mated equally in winter and all over the year. Natural mating was mostly used (76.9%). The means of estrus duration and estrus interval were 6.58 ± 1 days and 19.57 ± 1.8 days, respectively. The means of first service and over- all pregna...
Rodrigues MN, Carvalho RC, Franciolli AL, Rodrigues RF, Rigoglio NN, Jacob JC, Gastal EL, Miglino MA.Since the horse has a highly precocial reproductive strategy, most organs are functionally well developed at birth and thus, embryonic and fetal life is interesting. Data on the development of important organs are very limited. Here, we detailed macroscopically and histologically the equine digestive system, focusing on the first third of gestation. At 21 days, the oral cavity was an empty space, and the liver contained proliferating endodermal cells. At 25 days, a fusiform stomach and the pancreatic bud were present. At 28 days, a small tongue and the esophagus occurred. At 30 days, primary a...
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...
Bostedt H, Sieme H, Bartmann CP, Handler J, Sobiraj A, Wehrend A.This review describes stepwise the recto-manual and transrectal ultrasonographic evidence of early pregnancy detection in the horse. The morphological and physiological conditions in the individual phases of early pregnancy are presented in correlation to the potential clinical findings. The importance of embryonic and early foetal losses is presented. Communication and documentation of findings are also addressed. The final section is devoted to the evaluation of the examination effort. In this regard, it is emphasized that the gynaecological examination for the evaluation of the pregnancy st...
Murase H, Endo Y, Tsuchiya T, Kotoyori Y, Shikichi M, Ito K, Sato F, Nambo Y.It has not been common to perform regular ultrasound examination of the fetus in equine practice, due to the increasing volume of the uterus caused by fetal development. The convex three-dimensional transducer is bulb-shaped and is able to observe wide areas. In addition, its operation is simple, making it easy to create appropriate angles for various indices using a transrectal approach. The aim of this study was to measure Thoroughbred fetal growth indices throughout gestation using a convex transducer and to clarify the detectable period of some indices for clinical use. We demonstrated cha...
Scholtz EL, Krishnan S, Ball BA, Corbin CJ, Moeller BC, Stanley SD, McDowell KJ, Hughes AL, McDonnell DP, Conley AJ.One of the most widely accepted axioms of mammalian reproductive biology is that pregnancy requires the (sole) support of progesterone, acting in large measure through nuclear progesterone receptors (PRs) in uterine and cervical tissues, without which pregnancy cannot be established or maintained. However, mares lack detectable progesterone in the latter half of pregnancy. Instead of progesterone, several (mainly 5α-reduced) pregnanes are elevated and have long been speculated to provide progestational support in lieu of progesterone itself. To the authors' knowledge, evidence for the bioacti...
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...
Herrera C, Morikawa MI, Bello MB, von Meyeren M, Centeno JE, Dufourq P, Martinez MM, Llorente J.Preimplantation genetic diagnosis (PGD) allows identifying genetic traits in early embryos. Because in some equine breeds, like Polo Argentino, females are preferred to males for competition, PGD can be used to determine the gender of the embryo before transfer and thus allow the production of only female pregnancies. This procedure could have a great impact on commercial embryo production programs. The present study was conducted to adapt gender selection by PGD to a large-scale equine embryo transfer program. To achieve this, we studied (i) the effect on pregnancy rates of holding biopsied e...
Silva ES, Frade SC, Ignácio FS, Pantoja JC, Puoli Filho JN, Meira C.The present study evaluated the effect of altrenogest treatment during 70 or 120 days of gestation on pregnancy maintenance in non-cyclic recipient mares and correlated the hormonal interruption findings with number, supplementary corpora lutea (SCL) formation period, and plasma progesterone (P4). Twenty five mares were used as recipients during anestrus, transitional or ovulatory phase and were assigned into groups according to altrenogest treatment period (70ALT, 120ALT or Control groups) or reproductive status at beginning of treatment (Anestrus, Transition or Cyclic/Control groups). Mares ...
de Ruijter-Villani M, van Boxtel PR, Stout TA.Uterine-derived growth factors and cytokines play essential roles in regulating preimplantation conceptus development. In several species, fibroblast growth factor-2 (FGF2) promotes embryogenesis, trophoblast cell migration, and adhesion. This study investigated mRNA expression for FGF2, its receptors (FGFR1-4), the activating factor FGF binding protein (FGF-BP) in equine endometrium and trophectoderm during early pregnancy and the estrous cycle, and localized FGF2 protein in both endometrium and conceptus tissues. FGF2, FGFRs1-4, and FGFBP mRNAs were expressed in endometrium throughout the es...
Winsco KN, Coverdale JA, Wickersham TA, Lucia JL, Hammer CJ.Thirty pregnant mares (538 to 695 kg BW; 4 to 19 yr of age) were used to evaluate the effects of plane of nutrition on DMI of hay and mare performance (BW, BCS, and rump fat) during the last third of pregnancy. Mares were divided into 4 blocks by their expected foaling date and randomly assigned within block to either a hay or concentrate plus hay diet (concentrate fed at 0.75% BW, as-fed basis) with 15 mares per treatment. Treatments began 110 d before expected foaling date (230 d of gestation) and terminated at parturition. Mares were housed by block and allowed ad libitum access to coastal ...
Binanti D, Zani DD, De Zani D, Turci T, Zavaglia G, Riccaboni P.Congenital anomalies in horses are very rare, and contracted foal syndrome is one of the most commonly reported. This malformation is characterized by contraction of the joints of the forelimbs and/or hindlimbs. In addition, the syndrome can be characterized by vertebral column malformations, such as scoliosis or torticollis, and cranial deformity. The present report describes the radiological and necroscopical findings of multiple rare malformations in two foals. Both foals showed skeletal abnormalities and fenestration of the abdominal cavity. Other pathological findings include a interventr...
Fanelli D, Tesi M, Ingallinesi M, Camillo F, Panzani D.This study retrospectively analysed the effects of different environmental factors such as the photoperiod, temperature/humidity index of 19Â years of a commercial embryo transfer programme performed in central Italy. From 340 donors of different breeds and aged between 2 and 25Â years, 576 embryos of an excellent or good quality were obtained by uterine flushing on days 7-8 after ovulation. The embryos were transferred to 259 recipients, aged between 2 and 16Â years, and belonging to different breeds. Both the donors and the recipients were employed for several cycles/years. At the time of tr...
Goff AK, Leduc S, Poitras P, Vaillancourt D.The objective of this study was to determine if changes in steroid synthesis occurred in the horse blastocyst about the time of maternal recognition of pregnancy. Embryos collected between days 7.5 and 14.5 were incubated for 8 hr in vitro in HAM's F10 containing radiolabelled pregnenolone. The steroid metabolites in the incubation medium were separated by reverse phase HPLC and the major peaks expressed as a percentage of total metabolites. It was found that there were no major changes in the profile of metabolites throughout the period of study, although there was increased conversion as the...
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...
Lanci A, Castagnetti C, Ranciati S, Sergio C, Mariella J.In the mare, foaling is a critical unpredictable event due to a wide range of gestational length and the absence of clear signs of impending parturition. To predict foaling, pH, inversion sodium potassium and increase of calcium concentration in mammary secretions are used. The aim of this study was to find how many days are left until parturition knowing mare's age (A) and parity (P) combined with ultrasonographic measurements of the fetal orbit in Standardbred mares with normal pregnancy. Eighty healthy Standardbred mares with normal pregnancy were hospitalized for attended delivery. Informa...
Stabenfeldt GH, Daels PF, Munro CJ, Kindahl H, Hughes JP, Lasley B.A direct enzyme immunoassay was developed to measure conjugated oestrogens in the plasma of pregnant mares. The antibody was produced in rabbits using oestrone-3-glucuronide (E1G) conjugated to bovine serum albumin. The enzyme conjugate was E1G conjugated to horseradish peroxidase. A sharp increase in plasma E1G concentrations occurred between Days 35 and 40 of gestation. Values declined slightly to Day 45, remained relatively constant to around Day 70 and rose sharply thereafter. Fetal death before Day 35 had no effect on plasma concentrations of E1G. Fetal death after Day 35 in conjunction w...
Artiushin S, Timoney JF, Fettinger M, Fallon L, Rathgeber R.Enterocolitis caused by Clostridium difficile (C. difficile) is a serious, sometimes fatal, disease of neonatal foals and older horses. Toxins A and B (TcdA and B) produced by C. difficile are important virulence factors. Immunisation of mares with receptor binding domains of toxins may prevent or reduce the severity of C. difficile colitis in foals. Objective: To determine whether antibodies generated in the pregnant mare to the binding regions of TcdA and B will neutralise TcdA and B toxicity. Methods: Sequences encoding the binding domains of each toxin were isolated by PCR amplification fr...
Bucca S.Equine fetal gender can be easily determined by ultrasound between Days 120 and 210. A combination of transrectal and transabdominal ultrasound examinations can visualise fetal sex organs up to 8 months of gestation. Early equine fetal sexing techniques, performed between approximately Days 58 and 70, are aimed at identifying the position of the genital tubercle. A wider diagnostic window, a diagnosis based on several parameters, and the ease of identification of fully developed fetal primary sex organs make gender diagnosis in mid- to advanced-gestation a preferable technique.
Vincze B, Baska F, Papp M, Szenci O.Prepartum fetal surveillance techniques have been widely used in both human and veterinary obstetrics, although these tests differ in their sensitivity for the assessment of fetal well-being. In equine reproduction, the 'gold standard' examination technique is the equine biophysical profile (EBP) described by Virginia Reef in 1995. Although this fetal assessment has many benefits, its accuracy, sensitivity and specificity have not been evaluated so far. In this study, 129 late-term pregnant mares were scanned twice in their last month of gestation using two different protocols (the EBP and a n...
Panzani D, Rota A, Pacini M, Vannozzi I, Camillo F.One year old fillies are able to conceive but, usually, not to give birth to a living foal. Although embryo transfer allows the production of foals from mature mares with repeated pregnancy losses, no reports are available on the use of one year old fillies as embryo donors. To evaluate this possibility, eleven 12-16 months old Haflinger mares were inseminated with fresh semen and subjected to embryo recovery. Some of the recovered embryos were non-surgically transferred into synchronized mature recipients. Pregnancies were terminated using PGF2alpha at day 25. Fillies' embryo recovery rate an...
Steven DH, Samuel CA.The study of the equine placenta, which began in Venice in 1598, has a long but discontinuous history. Early observations were purely morphological, but new techniques have stimulated a broader and more functional approach. Histological and ultrastructural observations at various stages of pregnancy have shown that the fetal side of the placenta comes to acquire certain features in common with the air-blood barrier of the mammalian lung. These changes may reflect the increasing O2 requirements of the fetus as gestation proceeds.
Pennington PM, Splan RK, Jacobs RD, Chen Y, Singh RP, Li Y, Gucek M, Wagner AL, Freeman EW, Pukazhenthi BS.Insulin resistance (IR) is characterized by an increase in biomarkers of systemic inflammation and susceptibility to laminitis in horses. Impacts on reproduction include a lengthened interovulatory period in horses. Dietary omega-3 (docosahexaenoic acid [DHA]) promotes anti-inflammatory processes, has been implicated in health benefits, and can reduce cytokine secretion. This preliminary study investigated the impact of IR as well as the influence of dietary supplementation (DHA) on the uterine fluid proteome in early pregnant horses. Mares were artificially inseminated; uterine fluid and embr...
Ginther OJ.Recent findings on the development and natural outcome of twins from Day 17 (immediately after fixation) to Day 40 are reviewed. Incidence of embryo reduction was increased significantly when the vesicles became fixed unilaterally, rather than bilaterally, and when the vesicles were unequal in diameter. Of 68 mares with twins on the day of fixation, post fixation embryo reduction occurred in 41 (60 per cent). The incidence of reduction was 41 of 48 (85 per cent) following unilateral fixation; reduction occurred in all of 22 mares with vesicles of dissimilar size (4 mm or more difference in dia...
Wynn MAA, Esteller-Vico A, Legacki EL, Conley AJ, Loux SC, Stanley SD, Curry TE, Squires EL, Troedsson MH, Ball BA.During the latter half of gestation in mares, there is a complex milieu of pregnanes in peripheral blood. Progesterone concentrations are often assessed by immunoassay during late gestation as a measure of pregnancy well-being; however, interpretation of results is complicated by the numerous cross-reacting pregnanes present in high concentrations during late gestation. Further, many mares are supplemented with an exogenous progestin, altrenogest, which may also cross-react with existing assays and further confound interpretation. The objectives of this study were: 1) to compare differences in...
Ousey JC, Freestone N, Fowden AL, Mason WT, Rossdale PD.Progesterone or progestagens are thought to maintain myometrial quiescence in pregnant mares, although this has not been proven. In the present study, the contractility of the equine myometrium was tested in vitro using samples collected from pregnant mares (n=33) between day 68 and day 340 of gestation. Myometrial samples were equilibrated in aerated Krebs buffer and subjected to one or more of these treatments: (i) oxytocin only; (ii) initial oxytocin treatment followed by combined oxytocin and progesterone or another progestagen; and (iii) initial oxytocin treatment followed by Krebs buffer...
Vegas AR, Podico G, Canisso IF, Bollwein H, Fröhlich T, Bauersachs S, Almiñana C.During initial maternal recognition of pregnancy (MRP), the equine embryo displays a series of unique events characterized by rapid blastocyst expansion, secretion of a diverse array of molecules, and transuterine migration to interact with the uterine surface. Up to date, the intricate transcriptome and proteome changes of the embryo underlying these events have not been critically studied in horses. Thus, the objective of this study was to perform an integrative transcriptomic (including mRNA, miRNAs, and other small non-coding RNAs) and proteomic analysis of embryos collected from days 10 t...
Camillo F, Marmorini P, Romagnoli S, Cela M, Duchamp G, Palmer E.The aim of this study was to test whether low dose oxytocin i.v. injection once a day to mares diagnosed as being ready for birth by mammary secretion calcium strip test measurements could be used as a reliable method to induce parturition and/or predict the mare would not foal during the following night if parturition did not occur within 2 h of treatment. Fifty-one near-term Haflinger mares were used and a single injection of 2.5 iu oxytocin was given between 1700 and 1900 h, including 10 mares used as controls which were administered a placebo. Administration of oxytocin resulted in the del...
Baska-Vincze B, Baska F, Szenci O.Monitoring fetal heart rate (FHR) and fetal heart rate variability (FHRV) helps to understand and evaluate normal and pathological conditions in the foal. The aim of this study was to establish normal heart rate reference values for the ongoing equine pregnancy and to perform a heart rate variability (HRV) time-domain analysis in Lipizzaner mares. Seventeen middle- and late-term (days 121-333) pregnant Lipizzaner mares were examined using fetomaternal electrocardiography (ECG). The mean FHR (P = 0.004) and the standard deviation of FHR (P = 0.012) significantly decreased during the pregnancy. ...
Fowden AL, Silver M.With the use of [U-14C]glucose tracer methodology, the rates of umbilical uptake, utilization, oxidation, and production of glucose were determined in nine chronically catheterized fetal foals in the fed state between 268 and 325 days of gestation (term approximately 335 days). At the same time, the rates of umbilical O2 and lactate uptake were measured in all nine fetuses by Fick principle. The mean fetal rates of umbilical glucose uptake, glucose utilization, and CO2 production from glucose carbon were 36.9 +/- 2.5, 36.4 +/- 1.7, and 117.7 +/- 17.4 mumol.min-1.kg fetal body wt-1, respectivel...
Ginther OJ.Fixation and orientation of the conceptus within the uterine lumen of 40 barren mares were examined by ultrasound daily on days 11-21 and at three-day intervals thereafter until day 48. The growth curve of the in situ conceptus had a distinct plateau between days 17-24, as determined by measurements of the width and area of conceptuses on the ultrasound images. The vesicle expanded at an average daily rate of 3-4 mm before the plateau and 2-3 mm after the plateau. Dramatic changes occurred in the shape of conceptus. The predominant shapes were approximately as follows: days 11-16, spherical; d...
Giger R, Meier HP, Küpfer U.In a retrospective study the gestation lengths of two groups, each consisting of 193 "Freiberger" mares, were compared. The mares of the first group were bred by a donkey, those of the second group by a stallion of the "Freiberger" breed. On average, the gestation length of mares with "Freiberger" foals lasted 336.5 days, and that of mares with mule foals 343.1 days. The difference between both groups was significant (p < 0.001). The shortest and longest observed gestation length of mares with "Freiberger" foals was 307 and 361 days, and that of mares with mule foals 315 and 369 days, respecti...
Silver M, Fowden AL, Taylor PM, Knox J, Hill CM.Blood amino acids were measured in twelve chronically catheterized mares and fetuses between 250 and 310 days gestation. The concentrations of the majority of individual amino acids were similar in maternal and fetal arterial blood and no gestational changes were detected. Only methionine, phosphoserine, 3-methyl-histidine and glutamine were consistently higher in the fetus than the mare, whilst certain other amino acids were higher in the maternal blood. Fasting the mares for 36 h led to significant falls in plasma glucose and rises in urea and maternal free fatty acids (FFA). Small but signi...
Allen WE, Porter DJ.Milk and plasma samples were obtained every 48 hours from eight pony mares for 40 days after foaling. Progestogen concentrations in milk and plasma were measured using an enzyme-linked immunoassay (ELISA) and compared with radioimmunoassay of the plasma. In general the three assays showed similar trends in progestogen concentration changes but absolute values varied considerably. Difficulty could occur in interpreting the results from single samples taken at times when progestogen concentrations were either rising (ie, after ovulation) or falling. ELISA could be used on plasma obtained by allo...
Fowden AL, Giussani DA, Forhead AJ.In many species, the pattern of growth and physiological development in utero has an important role in determining not only neonatal viability but also adult phenotype and disease susceptibility. Changes in fetal development induced by a range of environmental factors including maternal nutrition, disease, placental insufficiency and social stresses have all been shown to induce adult cardiovascular and metabolic dysfunction that often lead to ill health in later life. Compared to other precocious animals, much less is known about the physiological development of the fetal horse or the longer-...
Bradbery AN, Coverdale JA, Hammer CJ, Dunlap KA, Leatherwood JL, Satterfield MC.Skeletal muscle plays an integral role in the ability of a horse to perform at high levels. Shifts in skeletal muscle development in response to maternal plane of nutrition may have substantial and lasting impacts on athletic performance and whole-body metabolism. Therefore, sixteen Quarter Horse mares were used in a completely randomized design and maintained at a body condition score (BCS) 6 until start of third trimester. On d 235 of gestation, mares were randomly assigned to receive one of two dietary treatments with a diet formulated to meet requirements during late gestation (CON; n = ...
Holtan DW, Nett TM, Estergreen VL.Peripheral plasma progestagens were quantified by a competitive protein-binding assay throughout pregnancy. The level of progesterone increased significantly between Days 0 and 8 (P less than 0-05) and again between Days 28 and 44 and reached a maximum on Day 64. Subsequently, it fell slowly until about Day 300 and then rose again during the last 30 days before reaching a minimum on the day after foaling. Very low concentrations of 17alpha-hydroxyprogesterone were found except between Days 40 and 120 and during the last 30 days before birth. Two unidentified compounds, one eluting slightly bef...
