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.
Klewitz J, Krekeler N, Ortgies F, Heberling A, Linke C, Sieme H.To assess pregnancy and live foaling rates after reduction of twin pregnancy via transvaginal ultrasound-guided aspiration (TUA) in mares and evaluate effects of gestational period, localization of conceptuses, fluid aspiration volume, and combination of TUA with embryonic or fetal puncture on these outcomes. Methods: Clinical trial. Methods: 44 mares pregnant with twins (25 to 62 days of gestation). Methods: TUA was performed in all mares and combined with embryonic or fetal puncture in 13. Follow-up ultrasonographic examinations were performed by referring veterinarians. Effects of gestation...
Carter AM, Enders AC.Epitheliochorial placentation is a derived condition and has evolved separately in strepsirrhine primates and laurasiatherians (pangolins, whales, and hoofed mammals). Usually it is associated with a long gestation period, small litters, and precocial young. Oxygen transfer is facilitated by indenting of the uterine and trophoblast epithelia by maternal and fetal capillaries, respectively. Histotrophic nutrition is important, and adaptations include areolas and hemophagous regions. In pigs and horses, for example, iron is transported as uteroferrin secreted from the uterine glands and taken up...
Antczak DF, de Mestre AM, Wilsher S, Allen WR.A remarkable feature of equine pregnancy is the development of the invasive trophoblast of the chorionic girdle and its formation of the gonadotrophin-secreting endometrial cup cells in early gestation. The details of this process have been revealed only slowly over the past century, since the first description of the endometrial cups in 1912. This centennial presents an opportunity to review the characteristics of the cells and molecules involved in this early, critical phase of placentation in the mare. The invasiveness of the chorionic girdle trophoblast appears to represent an atavistic at...
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...
Binanti D, Livini M, Riccaboni P, Sironi G.A 16-year-old primiparous mare aborted an apparently normal fetus at 240 days of gestation. A large, oval mass, measuring approximately 20 cm × 30 cm × 20 cm, was detected attached to the umbilical cord of the fetus. On the cut surface, the mass showed multifocal cystic structures, foci of mineralization, and diffuse hemorrhages. Histological examination of the mass revealed haphazardly arranged cartilage, bone, mesenchymal stroma, adipose tissue, vascular structures, smooth muscle, ciliated epithelium, squamous cornifying epithelium, and undifferentiated germ cells with areas of necrosis an...
Palm F, Walter I, Nowotny N, Budik S, Helmreich M, Aurich C.In most mammalian species, progestins have a major function in maintaining pregnancy. In humans, the physiologic initiation of parturition bears similarities with inflammatory processes and anti-inflammatory effects of progestins have been suggested to postpone birth until term. To examine if comparable effects exist in the horse, mares were treated with the synthetic progestin altrenogest from day 280 of gestation until parturition (N = 5) or were left untreated as controls (N = 7). Tissue from the amnion (AMN), allantochorion (AC), and endometrium (EM) was collected at foaling and mRNA expre...
Vander Heyden L, Lejeune JP, Caudron I, Detilleux J, Sandersen C, Chavatte P, Paris J, Deliège B, Serteyn D.Osteochondrosis (OC) is the most common developmental orthopaedic disease in horses and represents a major problem to the horse industry. The complete mechanism of this multifactorial disease is not yet elucidated, but it is accepted that OC lesions are the result of intrinsic genetic and external factors. The aim of the present work was to evaluate the relationship between breeding management and OC. Breeding conditions were recorded, and a radiological examination was performed in 223 foals. Feeding practice and housing management were analysed in a multivariate model to determine risk facto...
Drumm NJ, Embertson RM, Woodie JB, Ruggles AJ, Hopper SA, Fimmers R, Handler J.Clinical experience has suggested that foaling rates following colic surgery in the pregnant mare are influenced by days of gestation. This premise has not been supported in previous studies. We also aimed to determine the effects of other potential influencing factors. Objective: To determine the influence of age of gestation on foaling rates in pregnant mares following colic surgery and evaluate the relationships between other factors and foaling rates. Methods: Medical records of Thoroughbred mares, which had colic surgery performed from 1993 to 2007 at the Rood and Riddle Equine Hospital, ...
Naylor RJ, Luis-Fuentes V, Livesey L, Mobley CB, Henke N, Brock K, Fernandez-Fuente M, Piercy RJ.Type 1 polysaccharide storage myopathy (PSSM1), an equine glycogen storage disorder caused by a gain of function mutation (R309H) in the gene encoding glycogen synthase (GYS1), is associated with the accumulation of amylase-resistant alpha-crystalline polysaccharide inclusions within skeletal muscle. Several glycogenoses in humans have a cardiac phenotype, and reports exist of horses with PSSM and polysaccharide inclusions in cardiac muscle. Objective: To investigate the hypothesis that horses with PSSM1 display a cardiac phenotype. Our objectives were to compare plasma cardiac troponin I (cTn...
Wilsher S, Gower S, Allen WR.A polyclonal human mucin-1 (MUC1) antibody was used to stain immunohistochemically for the presence of MUC1 on the endometrium and fetal membranes in mares between 20 and 309 days of gestation. Western blot analysis demonstrated the presence of a protein equivalent in size to a human MUC1 isoform, MUC1/Y, in equine endometrium, allantochorion and amnion. At all stages of gestation examined immunoreactivity to the MUC1 antibody was detected on the apical surface of the lumenal epithelium of the endometrium and the epithelium lining the mouths and apical regions of the endometrial glands. Furthe...
Waelchli RO, Betteridge KJ.Twin ovulations are common in horses, but twin pregnancies are rarely carried to term. Theories of how one or both twins is/are naturally eliminated in early pregnancy, termed 'embryo reduction', have been based on ultrasonographic, not morphological, studies. Here we describe conceptuses recovered transcervically between Days 15 and 28 from 31 twin and two triplet pregnancies. Signs of contact between conceptuses were deduced from those seen in one pair that remained attached by their capsules on Day 18. Signs were found on capsules in two of 10 pairs before or during fixation (immobilisation...
Hanlon DW, Stevenson M, Evans MJ, Firth EC.To describe the reproductive performance of a population of Thoroughbred mares on stud farms in the Waikato region of New Zealand. Methods: A prospective cohort study was performed involving five stud farms in the Waikato region of New Zealand during three consecutive breeding seasons (2006-2008). A total of 1,482 individual mares contributed 2007 mare years and 3,402 oestrous cycles over the three breeding seasons. Mares were served by 87 individual stallions. Results: The mean first-cycle pregnancy rate (FCPR) was 53.6%, the end-of-season pregnancy rate (SPR) was 85.3% and the foaling rate w...
Cross DL, Reinemeyer CR, Prado JC, Donnell RL, Bond KG, Farr H, Longhofer SL.The objective was to evaluate the efficacy of domperidone in the prevention of reproductive complications of fescue toxicosis in periparturient mares. Pregnant mares at ≤310 days of gestation were fed ≥200 μg ergovaline per kg diet daily in endophyte-infected fescue hay and seed, starting ≥30 days before their expected foaling date (EFD: 340 days after breeding). Thirty-five mares were randomized to a treatment group to receive either domperidone gel (n = 20, 1.1 mg/kg, PO, once daily) or placebo (n = 15). Treatment was initiated 10 to 15 days before the EFD and continued for 5 days aft...
Langlois B, Blouin C, Chaffaux S.The files for ultrasound diagnosis of gestating mares belonging to the French equine herd recorded for 3 consecutive years were joined with the files for foal birth of these same mares, allowing the statistical analysis of factors of pregnancy loss. For 28 872 positive diagnoses of gestation, 2898 losses were recorded, that is, a global rate of gestation interruption of 9.12%. The etiology of these interruptions is mainly extrinsic: the year and month of insemination, as well as region for climatic reasons. The intrinsic causes that are implicated are breed of the father (heavy breeds except t...
Klein C, Troedsson MH.Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine expressed by a wide range of tissues, which has been implicated to be involved in reproduction. Relative abundance of MIF mRNA in conceptus and endometrial tissue was assessed using real-time RT-PCR. Western blot analysis and immunohistochemistry were used to detect MIF protein expression. MIF transcript abundance was lowest in conceptuses obtained 16 days after ovulation, while the remaining stages of conceptus development that were analysed showed relatively constant expression levels. Migration inhibitory factor expressi...
Budik S, Palm F, Walter I, Helmreich M, Aurich C.Oxytocin (OT) and arginine vasopressin (AVP) have been detected in the yolk sac of the pre-attachment equine conceptus. Therefore, we have assessed the presence of OT and AVP receptors in equine conceptuses between Days 10 and 16 of pregnancy by qualitative PCR, quantitative PCR and immunohistochemistry. Expression of OT receptor and of the AVP receptors V1aR and V2R could be verified after sequencing the RT-PCR products of the expected length. The size of conceptuses used for quantitative PCR significantly increased with day of pregnancy (P<0.01) as did their quantitative expression of OTR...
Becvarova I, Buechner-Maxwell V.The nutrition and nutritional status of the mare, as well as foal's nutrient intake from colostrum, milk and creep feed, are critical factors that are known to influence the growth period of the foal. Long-term effects of mare and foal nutrition are not well recognised or understood in the horse but may have the greatest impact on the animal's health and use when mature. Both under- and overfeeding can negatively influence important characteristics such as bone development and neurological function The risk of developing debilitating diseases such as metabolic syndrome may also be increased by...
Wilsher S, Allen WR.The development of the equine placenta involves a series of stage-specific events which ensure that the fetus is nourished throughout its 11 months of gestation. Initially, placental exchange to the developing embryo is histotrophic, via the yolk sac but, as the allantochorion develops and microcotyledons form, haemotrophic nutrition plays the major role in sustaining the increasing demands of the growing fetus. This review describes the development of the allantochorionic placenta of the mare and discusses some of the factors that influence its growth, size and functions and, hence, its contr...
Fowden AL, Forhead AJ, Ousey JC.In adapting to life ex utero, the foal encounters a number of physiological challenges. It has to assume the nutritional, respiratory and excretory functions of the placenta and activate full regulatory control over its own internal environment for the first time. To achieve this, there must be structural and functional changes to a wide range of tissues including several endocrine glands. In most species, including the horse, these maturational changes begin in late gestation and continue into the first few days of neonatal life. Consequently, during this perinatal period, there are major cha...
McCue PM, Ferris RA.An understanding of the normal events of foaling, causes of dystocia and clinical outcomes is important for equine practitioners. Objective: The goals of the present study were to: 1) evaluate factors that influence gestation length; 2) report duration of Stage II labour; 3) determine the frequency of dystocia and premature placental separation; and 4) determine the relationship between problems at foaling and foal survival. Methods: Foaling records of 1047 mare births were evaluated. Results: The average gestation length was 342.7 days [corrected] +/- 0.4 days, with no effect of mare age or b...
Johnson AK, Roberts JF, Hagan A, Wilborn RR, Dujovne G, Sells SF, Donahue JM.A 25-year-old pregnant American Quarter Horse mare presented with a 1-week history of progressively worsening vaginal discharge. Transrectal ultrasound revealed increased thickness of the combined uterus and placenta with evidence of chorioallantoic edema but no placental separation. A thickened amnion was visible on transabdominal ultrasound. Abortion occurred 2 days after presentation despite medical treatment. At necropsy, the chorioallantois had variable but diffuse thickening with focally extensive browning of the chorionic surface in the right horn and adjacent body. There were fluid-fil...
Jacobson CC, Sertich PL, Mc Donnell SM.To investigate effects of a 5-day oral misoprostol regimen recommended for use in horses as a gastrointestinal mucosal cytoprotectant during colic on mid-gestation pregnancies. Objective: To monitor cervical tone, ultrasonographic characteristics of the uterus, cervix and conceptus, as well as serum progesterone and oestrone sulphate concentrations, and observations of general health, behaviour and comfort of mid-gestation mares given a 5-day course of misoprostol or control treatment. Methods: Eleven light horse and pony mares with known breeding dates were administered 5 µg/kg bwt misoprost...
Brosnahan MM, Miller DC, Adams M, Antczak DF.The invasive trophoblast cells of the equine placenta migrate into the endometrium to form endometrial cups, dense accumulations of trophoblast cells that produce equine chorionic gonadotropin between days 40 and 120 of normal pregnancy. The mechanisms by which the trophoblast cells invade the endometrium while evading maternal immune destruction are poorly defined. A gene expression microarray analysis performed on placental tissues obtained at day 34 of gestation revealed a >900-fold upregulation of mRNA encoding the cytokine IL-22 in chorionic girdle relative to noninvasive chorion. Quan...
Canisso IF, Beltaire KA, Bedford-Guaus SJ.Premature luteal demise or luteal insufficiency is not well characterised as a cause of pregnancy loss in domestic species, including horses. In this report, a mare inseminated with cooled-transported semen at our facility returned for a routine pregnancy diagnosis at 15 days post ovulation. Ultrasonography per rectum revealed endometrial oedema and the absence of visual indication of a corpus luteum on either ovary. Nonetheless, an embryonic vesicle small for the gestational age was identified. Daily oral altrenogest treatment was implemented immediately. Serum progesterone concentration was ...
Betteridge KJ, Waelchli RO, Christie HL, Raeside JI, Quinn BA, Hayes MA.To advance the understanding of early pregnancy and pregnancy failure in horses, this study determined how luteolysis induced by cloprostenol (an analogue of prostaglandin F2α) affects conceptus development. Mares were injected on Days 12, 14, 16 or 18 of pregnancy with either cloprostenol (treatment groups, total n=83 pregnancies) or saline (controls, n=81), and growth of the conceptuses was monitored and compared by daily ultrasonography until they were collected transcervically on Days 15-22, 1-4 days after the injections. The comparisons were extended in the recovered conceptuses by count...
Gee EK, Dicken M, Archer RM, Herdan CL, Pauwels FE, Drayton BM.A 14-year-old Thoroughbred mare was presented for evaluation of a rapidly enlarging ovary at 73 days gestation. The mare's owner reported behavioural changes in the mare since she returned from stud, notably aggression towards other horses. Results: Transrectal palpation and ultrasonography of the reproductive tract revealed a viable pregnancy, an enlarged, multiloculated right ovary, and a normal-sized left ovary with a corpus luteum present. Concentrations of inhibin and testosterone in serum were 13.8 ng/mL and 1,150 pg/mL, respectively, being markedly higher than reference ranges. Concentr...
Dicken M, Gee EK, Rogers CW, Mayhew IG.To examine the gestation lengths and occurrence of daytime foaling of Standardbred mares foaling outdoors at stud farms in Southland, New Zealand (latitude 45˚S). Methods: Data were collected prospectively at two commercial Standardbred stud farms (Farms A and B), during the 2008/9 and 2009/10 breeding seasons (October to February). For each foaling, the identity of the mare, date and time of foaling, gender of foal, time the mare passed the fetal membranes, time the foal stood, and foaling problems including dystocias, were recorded. The effect of farm, season, gender of foal, month of artif...
Kotoyori Y, Yokoo N, Ito K, Murase H, Sato F, Korosue K, Nambo Y.The objective was to assess the optimal procedure for real-time, three-dimensional (3D) ultrasound (US) imaging for assessing the equine fetus during the first half of gestation and the possibility of using 3D US imaging of the equine fetus in clinical applications. Seventeen pregnant mares were examined by 3D US between Days 35 and 180 of gestation. Abdominal and endo-vaginal real-time 3D transducers used in human medicine were used for transrectal and transvaginal examinations, respectively. Images were recorded by both 3D stationary and real-time movies. In a comparison of four methods, tra...
Davies Morel MC, Newcombe JR, Lauber M.To determine whether manually reduced multiple pregnancies (MPs) are at a greater risk of pregnancy loss than single pregnancy (SP) in mares, and to examine if a difference exists in the timing of pregnancy loss between manually reduced MPs and SPs, 1916 Thoroughbred mares were ultrasonically monitored every 2 days during oestrus to confirm ovulation, and up to Day 40 post-ovulation to confirm pregnancy. Ultimate pregnancy outcome was ascertained from the General Thoroughbred Stud book and classified as live foal (LF), early abortion (EA; Days 40-150), slipped foal (SF; Days 150-term), and bar...
Evans TJ.During equine gestation, ergopeptine alkaloid exposure is not uncommon, and pregnant mares are particularly sensitive to the endocrine disruptive effects of these compounds on lactogenesis and steroidogenesis. Agalactia, prolonged gestation, abortion, dystocia, and placental and fetal abnormalities are all clinical manifestations of changes in the endocrine milieu induced by the ingestion of ergopeptine alkaloid-contaminated feedstuffs by mares during late gestation. An understanding of the endocrine disruptive effects of gestational exposure to ergopeptine alkaloids is necessary for the diagn...
Terqui M, Palmer E.Plasma total (conjugated + unconjugated) oestrogens were measured from Day 0 to 100 of pregnancy and compared with the levels found during the oestrous cycle. From Day 0 to 35 of gestation, the concentrations were similar to those during dioestrus. An increase in total oestrogens between Days 35 and 40 was followed by a plateau of 3 ng/ml between Days 40 and 60 which was slightly higher than preovulatory concentrations. This first increase in total oestrogen level was produced by the ovaries since values were suppressed after ovariectomy; stimulation may be due indirectly to PMSG causing folli...
Hong CB, Donahue JM.Abortion caused by Campylobacter fetus subsp fetus was diagnosed in a 7-month-old equine fetus. The fetus was small for its gestational age. Macroscopically, the proximal portion of the small intestine was hemorrhagic and its wall was thick. Histologically, the Brunner glands were distended with neutrophils, and the submucosa was thick, owing to fluid accumulation and/or cellular infiltrates. Curved bacteria were observed in the Brunner glands and intestinal glands. Campylobacter fetus subsp fetus was isolated from stomach contents, liver, and lungs, and was detected by dark-field microscopic ...
Langlois B, Blouin C, Chaffaux S.The files for ultrasound diagnosis of gestating mares belonging to the French equine herd recorded for 3 consecutive years were joined with the files for foal birth of these same mares, allowing the statistical analysis of factors of pregnancy loss. For 28 872 positive diagnoses of gestation, 2898 losses were recorded, that is, a global rate of gestation interruption of 9.12%. The etiology of these interruptions is mainly extrinsic: the year and month of insemination, as well as region for climatic reasons. The intrinsic causes that are implicated are breed of the father (heavy breeds except t...
Mari G, Iacono E, Merlo B, Castagnetti C.Diagnosis and management of twin pregnancies in the mare are an ongoing challenge in equine reproduction. Early detection of twin and manual crush of one vesicle are the main steps in the management of twins. Few studies were carried out about the use of transvaginal ultrasound-guided aspiration (TUGA) for reduction of twins in the mare. In this study, the efficiency of TUGA for management of twin pregnancies was investigated. Reduction of unicornuate twins between 16 and 25 days of gestation gave a success rate of 70.0% (14 viable foals/20 twin pregnancies); when reduction was performed after...
Lennard SN, Stewart F, Allen WR.Placentation in equids involves two types of trophoblast: a minor invasive component, the chorionic girdle, that gives rise to transient endocrine structures known as endometrial cups, and a major non-invasive component, the allantochorion, that forms the diffuse, microcotyledonary placenta. Growth factors are likely to be important in controlling these complex events at implantation and this study describes the use of in situ hybridization and northern blotting techniques to monitor expression of insulin-like growth factor II (IGF-II) in the fetus and placenta of the horse (Equus caballus), u...
Johnson AK, Roberts JF, Hagan A, Wilborn RR, Dujovne G, Sells SF, Donahue JM.A 25-year-old pregnant American Quarter Horse mare presented with a 1-week history of progressively worsening vaginal discharge. Transrectal ultrasound revealed increased thickness of the combined uterus and placenta with evidence of chorioallantoic edema but no placental separation. A thickened amnion was visible on transabdominal ultrasound. Abortion occurred 2 days after presentation despite medical treatment. At necropsy, the chorioallantois had variable but diffuse thickening with focally extensive browning of the chorionic surface in the right horn and adjacent body. There were fluid-fil...
Silver M, Fowden AL.In the present study, ten insulin challenge tests were carried out on nine chronically catheterized fetal foals between 253 and 314 days gestation (term > 320 days). Changes in fetal plasma concentrations of glucose, catecholamines, cortisol, ACTH, free fatty acid (FFA) and lactate were measured before and after a bolus dose of insulin (0.5-2.0 u/kg I.V.). Fetal blood gases, pH, haemoglobin levels and heart rate were measured throughout the 2-3h experimental period. The fetuses fell into two distinct groups on the basis of proximity to delivery and basal plasma cortisol and catecholamine level...
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...
Duggan VE, Holyoak GR, MacAllister CG, Cooper SR, Confer AW.The objective of this study was to investigate the protein, amyloid A3 (AA3), in equine colostrum and early milk. We hypothesized that AA3 was consistently present in equine colostrum and early milk, that no correlation existed between serum and colostrum concentrations of this protein in individual mares at parturition and that colostrum/milk concentrations of this mammary protein may be affected by age, breed, length of gestation and/or induction of parturition. Thirty-eight peripartum mares and seven non-pregnant, non-lactating mares were included in the study. Mean serum concentrations of ...
Chaney KP, Holcombe SJ, LeBlanc MM, Hauptman JG, Embertson RM, Mueller PO, Beard WL.Anecdotal speculation suggests that prognosis for survival of mares and foals following correction of uterine torsion has improved over the past 30 years. Objective: To determine statistically the outcome of uterine torsion according to duration of clinical signs, stage of gestation, parity, physical examination findings, method of correction, prognosis for survival and reproductive health of the mare, and prospects for the foal within the neonatal period. Methods: This retrospective study combined cases from 4 equine referral hospitals. Results: The stage of gestation at which uterine torsion...
Kuhl J, Stock KF, Wulf M, Aurich C.Maternal lineage influences performance traits in horses. This is probably caused by differences in mitochondrial DNA (mtDNA) transferred to the offspring via the oocyte. In the present study, we investigated if reproductive traits with high variability-gestation length and fetal sex ratio-are influenced by maternal lineage. Data from 142 Warmblood mares from the Brandenburg State Stud at Neustadt (Dosse), Germany, were available for the study. Mares were grouped according to their maternal lineage. Influences on the reproduction parameters gestation length and sex ratio of offspring were anal...
Ewert M, Lüders I, Böröcz J, Uphaus H, Distl O, Sieme H.The aim of the present study was to analyze the effects of stallion and mare, their ages, and maternal lineage on the gestation length (GL) in Thoroughbreds. In addition, additive genetic effects of the dam, stallion and fetus were analyzed. Data were taken from 1993 through 2009, and included 16,226 pregnancies from 5959 Th oroughbred mares mated with 290 different stallions. All analyses were performed using linear mixed models. The GL ranged from 306 to 390 days, with a mean length of 347.0 ± 14.4 days. Mating of mares with stallions aged 17 years and older resulted in a significantly ...
Saint-Dizier M, Chopineau M, Dupont J, Daels PF, Combarnous Y.Luteal steroids are necessary to maintain the first 70-90 days of pregnancy in the mare. At 35 days postovulation, the resurgence of the primary corpus luteum (CL) coincides with the secretion of the fetal hormone eCG. In order to study the responsiveness of the primary CL to eCG, we have examined levels of luteal equine LH/CG receptors (eLH/CG-R) mRNAs by Northern blot analysis and measured concentrations of eLH/CG binding sites on luteal membranes using 125I-eLH saturation binding assays at three stages of gestation: before the onset of eCG secretion (Days 14-31), from onset to maximum eCG s...
Hinrichs K, Sertich PL, Palmer E, Kenney RM.Pregnancy was established and maintained after embryo transfer in 3 ovariectomized mares treated with progesterone only. Four ovariectomized mares were used as recipients, and 7 transfers were performed. Progesterone in oil, 300 mg i.m. daily, was given starting 5 days before transfer of a 7-day embryo. If the mare was pregnant at 20 days, progesterone treatment was continued to 100 days of gestation. The 3 pregnant mares carried to term and delivered live foals with normal parturition, lactation and maternal behaviour. No differences were seen between pregnant and non-pregnant ovariectomized ...
Manning AW, Rajkumar K, Bristol F, Flood PF, Murphy BD.The variation in the quantity of circulating chorionic gonadotrophin (CG) and its follicle-stimulating hormone (FSH) and luteinizing hormone (LH) activity in rodent bioassay systems was investigated. A portion of the variability in total CG could be attributed to the stallion that sired the pregnancy and it was possible to select sires and mares to increase CG production. It was further demonstrated that FSH activity per unit of CG was greater at Days 71 and 104 of gestation than at Day 39. LH activity per unit of CG varied with the sire, but no effect of day of gestation could be shown. It wa...
Fowden AL, Ralph MM, Silver M.Prostaglandins (PGs) are produced by a variety of uteroplacental tissues during pregnancy and are released into the fetal fluid sacs and both the uterine and umbilical circulations. Uterine PG output increases towards term and is enhanced by maternal undernutrition in pregnant ewes and mares. In both species, withdrawal of food but not water for 30-48 h increases uterine venous PG levels and the uterine venous arterial concentration differences in PGE and 13, 14, dihydro-15-keto-prostaglandin F2 alpha (PGFM), the stable metabolite of PGF2 alpha. The increments in uterine V-A concentration diff...
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...
Ellerbrock RE, Canisso IF, Roady PJ, Rothrock LT, Zhong L, Wilkins P, Dirikolu L, Lima FS, Honoroto J.In selective cases, enrofloxacin may be an alternative antibacterial agent to treat unresponsive infections in pregnant mares. Supratherapeutic doses of enrofloxacin are toxic to adult horses and also to newborn foals, however, it is unknown if enrofloxacin crosses the equine placenta or if it is toxic to the fetus. Objective: To assess the diffusion of enrofloxacin and its metabolite to fetal fluids and its effects on fetal cartilage when administered to pregnant mares. Methods: In vivo and terminal controlled experiment. Methods: Healthy mares at 260 days of gestation were allocated into thr...
Taylor PM, White KL, Fowden AL, Giussani DA, Bloomfield M, Sear JW.To characterize propofol anaesthesia in pregnant ponies. Methods: Fourteen pony mares, at 256 ± 49 days gestation, undergoing abdominal surgery to implant fetal and maternal vascular catheters. Methods: Pre-anaesthetic medication with intravenous (IV) acepromazine (20 µg kg), butorphanol (20 µg kg) and detomidine (10 µg kg) was given 30 minutes before induction of anaesthesia with detomidine (10 µg kg) and ketamine (2 mg kg) IV Maternal arterial blood pressure was recorded (facial artery) throughout anaesthesia. Arterial blood gas values and plasma concentrations of glucose, lactate, cort...
Wilsher S, Allen WR.There is a paucity of information on factors that influence placental development in the horse. Objective: Changes in nutrition, particularly around the time of proliferative placental growth, can affect development of the placenta and fetal growth. Objective: To investigate the effects of 2 planes of nutrition and an unforeseen infection-mediated nutritional insult on placental and fetal development in the mare. Methods: Twenty maiden Thoroughbred fillies, age 3 or 4 years, mated to one Thoroughbred stallion, were maintained on either High or Moderate food intake throughout pregnancy. In mid-...
Glade MJ.Skeletal homeostasis during late gestation, lactation, and the post-lactational recovery period is poorly understood. In an experiment using an animal model (the horse), metacarpal breaking strengths (MBS) estimated via transmission ultrasonics were examined during the last 12 weeks of gestation and for 40 weeks after parturition. MBS increased during the last 6-10 weeks of gestation in mares fed amounts of calcium (Ca) recommended by the National Research Council; maximum MBS coincided with the week of parturition. In contrast, MBS in mares fed 20% less Ca remained relatively constant during ...
Bucca S.Identification of a compromised pregnancy in the mare requires the exhaustive collection of a database that includes past and recent reproductive and medical histories and a variety of parameters indicating fetal distress and possibly suggesting neonatal compromise.Judicious interpretation of findings and serial recording of data throughout gestation may help in the early detection of abnormal fetomaternal exchange pathways. Some sources of compromise may be identified, and the impact on fetomaternal well-being maybe calculated. Appropriate preventive or corrective measures may then be impleme...
Cottrill CM, Jeffers-Lo J, Ousey JC, McGladdery AJ, Ricketts SW, Silver M, Rossdale PD.One hundred twenty-four horse placentas were evaluated according to gross appearance, weight and surface area. Grossly abnormal placentas were photographed, and histological sections were taken from abnormal appearing areas, and from representative areas (pregnant horn, non-pregnant horn, body and cervical pole) in both normal and abnormal placentas. Information about the resulting foals was obtained and correlations examined. Histological sections were reviewed and related to the resulting foals. Four normal fresh placentas were infused with dyes to ascertain the blood supply to various areas...
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...
Arar S, Chan KH, Quinn BA, Waelchli RO, Hayes MA, Betteridge KJ, Monteiro MA.During the second and third weeks of pregnancy, the equine conceptus expands rapidly while it is enclosed within a glycan capsule. Around day 16 of gestation, the conceptus loses its mobility in the uterus by a process termed 'fixation', coinciding with various changes in the capsule. Here, we compared the structure of the carbohydrate moieties expressed by the capsule during pre- and post-fixation periods. The glycan structures were studied by chemical analyses in combination with mass spectrometry. Capsule material from conceptuses collected before fixation (days 13-16) was observed to carry...
Silver M, Barnes RJ, Comline RS, Fowden AL, Clover L, Mitchell MD.The concentrations of the primary prostaglandins (PG) F-2alpha and E-2 and the metabolite 13,14-dihydro-15-oxo-prostaglandin (PGFM) in maternal and fetal plasma and in allantoic fluid were measured in chronically catheterized mares and fetuses. A gradual rise in all 3 PGs occurred with increasing gestational age. PGE-2 and PGF-2 alpha levels were highest in the allantoic fluid and lowest in the maternal plasma, whereas PGFM concentrations were greatest in maternal plasma. Significant venous-arterial plasma differences in PGFM concentration were detected across the uterine circulation between 1...
El-Sheikh Ali H, Legacki EL, Loux SC, Esteller-Vico A, Dini P, Scoggin KE, Conley AJ, Stanley SD, Ball BA.The current study aimed to elucidate the mechanisms underlying myometrial activation during equine placentitis related to progestogens and the progesterone receptor signaling pathways. Placentitis was induced via intracervical inoculation with Streptococcus equi ssp zooepidemicus in mares at approximately 290 days of gestation (placentitis group; n = 6) with uninoculated gestationally matched mares as controls (n = 4). Mares in the placentitis and control groups were euthanized, and myometrial samples were collected from two regions: region 1-parallel to active placentitis lesion with plac...
Smith S, Marr CM, Dunnett C, Menzies-Gow NJ.Birthweight of Thoroughbred foals has increased in recent years. It is unknown whether this is associated with increased broodmare obesity or endocrine dysfunction. Objective: To determine insulin, leptin and triglyceride concentrations in Thoroughbred mares throughout gestation and investigate their association with obesity and foal birthweight. Methods: Cohort study. Methods: A total of 66 mares were included from 40 days post-breeding. Body condition score (BCS), weight and blood samples were obtained every 60 days throughout gestation. Serum/plasma insulin, leptin and triglyceride concentr...
Gerstenberg C, Allen WR, Stewart F.Placentation involves considerable growth and reorganization of both maternal and fetal tissues. In this investigation, immunohistochemical localization of the proliferation marker Ki-67 antigen was used to monitor cell division during placentation in mares. Endometrial biopsies were obtained from eight mares between day 14 and day 26 of pregnancy and from eight anoestrous mares that had been treated with various combinations of progesterone and oestrogen. Samples of endometrium and fetal membranes were obtained from 19 mares carrying normal horse conceptuses between day 30 and day 250 of gest...
