Pregnancy in horses, or equine gestation, is a physiological process that involves the development of a foal within the mare over approximately 11 months. This period is characterized by distinct stages, including fertilization, embryonic development, and fetal growth. Throughout gestation, mares undergo various physiological and hormonal changes to support the developing fetus. Monitoring pregnancy in horses involves assessing fetal health and mare well-being through veterinary examinations and diagnostic tools such as ultrasound. This page compiles peer-reviewed research studies and scholarly articles that explore the physiological processes, management practices, and health considerations associated with equine pregnancy.
SAVARD K.The urinary ketonic estrogens were studied at monthly intervals in five pregnant mares. Estrone and equilin appear to be the principal components and equilenin a minor constituent of the mares’ estrogens. The levels of equilin rise from the 4–5th months to equal and in some instances exceed those of estrone in the late months of pregnancy. A partition chromatographic method for the separation of the ketonic phenolic steroids of pregnant mares’ urine is described.
Morrissey J, Pinsky T, Roy MF.Pregnancy loss after Day 40 in mares usually results in the expulsion (abortion) of the fetus and placental membranes. However, fetal retention within the uterus is also a possible outcome, leading to either fetal mummification or maceration. Fetal maceration is septic decomposition of fetal tissues within the uterus following failure of expulsion. It requires the presence of bacteria and oxygen within the uterus, likely originating from an open cervix, and results in tissue autolysis, leaving only fetal bones remaining in the mare. Fetal maceration is a rare complication of pregnancy in mares...
Delchiaro SB, Oliveira PVLF, Júnior RJP, Gonçalves GD, Morotti F, Seneda MM.Mares (n = 77) were evaluated by antral follicle count (AFC) and selected as embryo recipients. Cyclic recipients received embryos between days 4-6 after ovulation. The acyclic recipients received an intramuscular (i.m.) protocol with 5mg of estradiol benzoate (EB) on the day of donor ovulation (D0; D-4 recipient), 3mg of EB on the following day (D1; D-3 recipient), and 3mg of EB (D2; D-2 recipient). Furthermore, 1500mg of progesterone (P4) i.m. given on D0 of the recipient (D4 donor) followed by 1500mg of P4 on the day of ET (D4-6 recipient). On the ET day, the AFC and animals' weight, body c...
Sielhorst J, Baade S, Neudeck KC, Tönissen A, Rohn K, Hollinshead F, Sieme H.Transvaginal ultrasound-guided aspiration (TUA) is used for post-fixation twin reduction in mares. However, there is limited information regarding factors that influence pregnancy outcome after TUA. Objective: To evaluate the effect of day of gestation on which TUA is performed, aspiration volume, puncture of the conceptus, medication administered before and after TUA, embryo location, mare age and parity and operator experience on pregnancy and foaling rates after TUA. Methods: Retrospective case series. Methods: Data were collected from case records of 464 TUAs performed by 14 operators in 4...
Smith L, Moran AW, Al-Rammahi M, Daly K, Shirazi-Beechey SP.Studies carried out in several species have demonstrated that detection of low-calorie sweeteners in the lumen of the intestine, by the sweet receptor, T1R2-T1R3, initiates a signaling pathway leading to enhanced expression and activity of intestinal Na/glucose cotransporter 1, SGLT1. This results in an increased gut capacity to absorb glucose, sodium chloride and water, the basis for oral rehydration therapy. Horses express T1R2, T1R3 and downstream signaling elements in the intestinal tissue. As such, the potential of sweetener-stimulation of T1R2-T1R3 leading to upregulation of SGLT1 allows...
Kovacsy S, Ismer A, Funes J, Hoogewijs M, Wilsher S.Equine embryos >300 μm require puncture before vitrification. Protocols that do not require pre-puncture would make vitrification easier and allow for its widespread use. Objective: To design a successful vitrification protocol for embryos >300 μm without puncture as a pre-treatment. Methods: Experimental in vivo study. Methods: Thirty-eight embryos were divided into 3 groups (G1: ≤300 μm, n = 11; G2: >300-500 μm, n = 20; G3: >500 μm, n = 7). Embryos were vitrified using a human vitrification kit. Following a 15 min exposure to equilibration solution ...
Cardiovascular changes have been reported in late pregnancy in mares. However, there are no data on changes in peripheral blood flow. Doppler ultrasound represents a sensitive method for assessing the blood flow directed to the hoof. The aims of this study were to evaluate the blood flow parameters of the lateral palmar digital artery (LPDA) in pregnant mares and to assess intra- and interrater agreement between two observers with different levels of experience. The LPDAs of pregnant Italian Standardbred mares were examined. The vessels were located with B-mode ultrasound and analyzed with col...
Morris L, Harteveld R, Gibb Z.Insemination of mares with frozen-thawed spermatozoa requires intensive management and results in 40%-60% per cycle pregnancy rates. Objective: To determine if satisfactory fertility is possible for frozen-thawed semen after processing it through a microfluidic device, followed by storage at 17°C for up to 24 h before fixed-time insemination. Methods: Uncontrolled field trials. Methods: A pilot study evaluated the motility of frozen-thawed spermatozoa after centrifugation and storage (17°C) in two different media for up to 48 h. Subsequently, the motility of frozen-thawed semen processed...
Melchert M, Aurich J, Ertl R, Reichart U, Walter I, Gautier C, Kaps M, Aurich C.Mares resume ovarian activity rapidly after foaling. Besides follicle-stimulating hormone (FSH) and luteinizing hormone (LH), the pituitary synthesizes prolactin and growth hormone which stimulate insulin-like growth factor (IGF) synthesis in the liver. We tested the hypothesis that follicular growth is initiated already antepartum, mares with early and delayed ovulation differ in IGF-1 release and that there is an additional IGF-1 synthesis in the placenta. Plasma concentrations of LH, FSH, IGF-1, IGF-2, activin and prolactin. IGF-1, IGF-2, prolactin and their receptors in placental tissues w...
Mattei DN, Harman RM, Van de Walle GR, Smith R, Grivel JC, Abdelalim EM, Vinardell T.Mesenchymal stromal cells (MSCs) have regenerative and immunomodulatory potential and may be used to treat injured tissues. Pregnancy has been associated with increased MSCs in the peripheral circulation in multiple species, but to date, there are no reports on this matter in horses. This study aimed to evaluate the effect of pregnancy on isolation efficiency and proliferation capacity of equine MSCs derived from the peripheral blood (PB) of mares. Venous blood samples were collected at the 11th month of gestation and 1 month after delivery from clinically healthy Arabian mares that presented ...
Pardié M, Kalpokas I, Freccero F, Castagnetti C, Meikle A.The aim of this study was to determine the effect of body condition score (BCS) on metabolic and endocrine parameters in pregnant Criollo mares (n=41), which were categorized according to their BCS as obese (7 to 9 BCS, n=26) or normal (5 to 7, n=15). Blood samples were taken during gestation in 3 periods: between 3.5 and 5 months (I), 8 and 9 months (II) and in the last month of gestation (III). The data was analyzed in the statistical model by mixed procedures, including BCS, gestational period and their interaction as fixed effects. BCS was only different in period I, as normal mares increa...
Cuccato M, Bertuglia A, Divari S, Brambilla E, Grieco V, Bollo E, Scaglione FE.An aborted female foal was submitted for necropsy. During the gross examination, the ovaries were pale, grayish, and enlarged (6 × 5 cm), with a well-developed vascular structure surrounding the external surface; the cut surface of the ovaries showed a brownish parenchyma with white follicular areas mainly localized in the peripheral region. The ovaries were fixed for histological investigations. The histological evaluation of the ovaries showed polygonal-shaped cells with abundant cytoplasm and round or oval nuclei, arranged in cords of single cells. The tissue architecture was characterized...
Martínez-Boví R, Gaber JTH, Sala-Ayala L, Plaza-Dávila M, Cuervo-Arango J.The effect of embryo reinsertion immediately after embryo flushing was studied. In Experiment 1, eight mares were used during 32 cycles (8 cycles in each group). For the first two groups, inseminated mares were flushed 8 days after ovulation and prostaglandin F2α was not administered: in group EF-ET (embryo flushing and embryo transfer) the embryo was reinserted in the same donor mare, while in the EF group, no further procedure was performed. In the third group (ET), non-inseminated mares (recipients) received a Day 8 embryo. Progesterone concentration was measured before EF/ET and 72 h afte...
Lindinger H, Wehrend A.In horses, parturition is characterized by the fact that any delays may rapidly result in the death of the foal. Therefore, birth monitoring and the rapid detection of dystocia are of great importance. For this purpose, the differentiation between behavior associated with physiological parturition and activities related to difficult parturition is important. The aim of this publication is to present the physiological behavior of mares during parturition on the basis of a literature review. The behavior of mares in the opening phase of parturition is highly individual. In general, it is charact...
Wagner LH, Aurich J, Claaßen S, Melchert M, Kaps M, Aurich C.Transrectal and transabdominal ultrasonography is an established method to monitor pregnancy, fetal growth and wellbeing in different species. Growth charts with multiple bio-morphometric parameters to estimate days of gestation and days before parturition exist in small companion animals, sheep and goats, riding type horses and large ponies but not in small horse breeds like Shetland ponies. The aim of this study was to apply fetal biometric assessment and detailed description of physiologic fetal development to mid and late term pregnancies in Shetland mares and to generate reference data fo...
Ricard RM, Wobeser B. is a reported cause of infertility and endometritis in sheep, cattle, and pigs; however, the association between uterine disease and is poorly understood in horses. Recently, a high prevalence of in equine aborted chorioallantoises was reported in horses in western Canada. Based on this high prevalence, investigation into the effects of on infertility and endometritis in western Canadian mares is prudent. We examined 98 formalin-fixed, paraffin-embedded endometrial biopsies from western Canada submitted between 2014 and 2022 using a -specific 16S rRNA PCR test; 40 samples tested positive f...
Lindinger H, Wehrend A.Various systems are available for birth monitoring in horses, whereby a distinction must be made between methods for more accurate prediction of the date of birth in order to intensify monitoring of the mare in a timely manner as well as methods for detecting individuals that are in labor. Basically, it should be noted that there are almost no studies that compare different methods on the same population of mares. As the time of birth approaches, physiological parameters of mare and fetus change, but their variability is too high to predict the exact parturition time point prospectively. The b...
Kikuchi M, Murase H, Urata K, Ishige T, Nagata SI, Tozaki T, Kakoi H, Ishiguro-Oonuma T, Kizaki K.Circulating microRNAs (miRNAs) are stable in body fluids and can serve as biomarkers for various diseases and physiological states. Although pregnancy-related miRNAs have been identified in various mammals, studies on parturition-related circulating miRNAs in mares are limited. Therefore, this study aimed to identify parturition-related miRNAs and examine their potential applications in the prediction of parturition date. miRNAs were extracted from the plasma of Thoroughbred mares 30 days (295-326 days pregnant) and 5 (323-352 days pregnant) - 0 (328-357 days pregnant) days before parturition,...
Del Prete C, Vastolo A, Pasolini MP, Cocchia N, Montano C, Cutrignelli MI.The peripartum period constitutes a delicate physiological moment in mares showing a transient state of oxidative stress. Diet supplementation with antioxidants during pregnancy in women appears to have a beneficial effect on mother and neonate health. The aim of this work was to evaluate the effects of diet supplementation with a commercial product containing a mix of antioxidants (Oxyliver®, Candioli) on the length of gestation, weight, and haemato-biochemical parameters in Italian Salernitano mares and their newborn foals. Eight late-term pregnant mares were randomly divided into two group...
Terpeluk ER, Schäfer J, Finkler-Schade C, Rauch E, Rohn K, Schuberth HJ.The quality of equine colostrum is typically defined by refractometry or the concentration of maternal antibodies. However, the activity of other equine colostral bioactive molecules has not yet been investigated. This study analyzed whether the administration of a fermentation product (SCFP) influences the biological activity of mare colostrum and whether the biological activity of colostrum has a lasting immunomodulating effect for foals. A total of fourteen pregnant mares received 20 g/day of a SCFP for a period of twelve weeks prior to the calculated date of birth (SCFP-group). Twelve pre...
Canisso IF, Amorim GBAG, Magalhaes HB.The objectives of this study were (i) to determine pH and electrolyte concentrations in MGS collected prepartum and at parturition, (ii) to characterize mare milk pH during the first week postpartum, and (iii) to evaluate pre-foaling MGS pH at three storage temperatures. This study outlined two hypotheses: (i) all mares exhibit acidic pH, increased calcium, magnesium, and potassium, and reduced sodium concentrations regardless of prepartum pH and electrolytes; (ii) pre-foaling MGS pH varies with storage temperature and time in an initial value-dependent manner. Twenty-three multiparous mares w...
Agerholm JS, Damborg P, Christoffersen M.Streptococci are well-known opportunistic bacterial abortifacients in mares. Colonization of the pregnant uterus is considered to happen after transcervical migration of bacteria from the lower genital tract mucosa. Streptococcus ovis is a pathogen mainly associated with inflammatory lesions in sheep. This species has not been reported in association with disease in horses. In the present case, S. ovis was isolated in monoculture from the lung of an 8-months-old equine fetus and was associated with development of acute suppurative bronchopneumonia, umbilical cord cellulitis and placentitis in ...
Derbala MK, Abu-Seida AM, El-Metwally AE, Asfour HAE.Embryo transfer (ET) is regarded as one of the reproductive methods for genetic improvement initiatives in the horse business. The current study aimed to increase the success rate of ET by re-flushing and re-transferring of embryos from contaminated recipient mares into second healthy recipients. The study involved 25 recipient mares that demonstrated embryonic vesicles inside intraluminal fluid (ILF) on ultrasound scanning 2 ± 0.5 days after ET. Seven recipient mares were left without re-flushing and re-transferring of embryos (control group) and 18 recipient mares (treated group) were subje...
Ellerbrock M, Krohn J, Büttner K, Wehrend A.Dystocia is rare in horses, but is life-threatening for mares and foals. Therefore, veterinary research depends on up-to-date data to optimise equine dystocia management. In addition, knowledge of the prognosis of equine dystocia is necessary to advise animal owners. This retrospective study of equine dystocia aimed to enrich existing datasets with up-to-date information. For the first time, the focus was on the causes of dystocia that occurred alone or in combination. Over a period of 10 years, 72 cases of dystocia were analysed using a standardised, predetermined diagnosis code. Results: Of ...
Arroyo E, Whitelock LM, Stanton ME, Stevenson V, de Aguiar LH, Kelleman A.Hydropsical conditions in domestic animals are characterized by abnormal fluid accumulation. While their complete pathophysiology remains unclear, factors such as changes in chorioallantoic membranes, placentitis, or fetal abnormalities may contribute. Hydrops present as a medical emergency that can cause complications for the mare. Early diagnosis and treatment are crucial for the mare's prognosis, as fetal survival is often poor. This report describes a case of hydroallantois in a 9-year-old pregnant Quarter mare at 271 days of gestation, leading to dystocia of a non-viable foal with multipl...
Brito PHS, Ferreira MA, Rusch E, Arantes JA, Carregaro AB, Valadão CAA, Ghantous GF, Dória RGS.Submitting late-term pregnant mares to anesthesia for non-obstetric surgery raises concerns about the survival of the mother and fetus. This study aimed to evaluate and describe transient maternal and fetal hemodynamic changes during general inhalation anesthesia in mares during the last month of gestation. Nine adult mares in the last month of gestation were subjected to general inhalation anesthesia and dorsal recumbency for 90 minutes. Trans-anesthetic vital parameters, arterial hemogasometry, cardiac output, pulmonary arterial pressure, central venous pressure, and fetal heart rates were a...
Sala-Ayala L, Cuervo-Arango J, Martinez-Bovi R.The case report discusses the implications of using different volumes of flushing media during embryo flushing (EF) procedures in a single donor mare that experienced multiple unintended pregnancies following negative EF outcomes. The study involved two sets of EF experiments over two years on a non-lactating Spanish purebred mare. The initial experiments (group 1, n=6) used 1L of flushing medium (Ringer´s Lactate), and subsequent tests (group 2, n=5) increased the volume to 2L, to assess whether a larger volume could enhance embryo recovery rates. After every EF procedure, no PGF2α was admi...
Peere S, Van den Branden E, Broothaers K, Polfliet E, Smits K, Govaere J.Transfer of in vitro-produced (IVP) equine embryos is associated with a higher incidence of monozygotic multiple pregnancies, but this remains a rarity. The outcome of monozygotic twin gestation is poor, and good management techniques are lacking. In addition, hydrops conditions are exceptional in horses, with hydroallantois occurring more frequently than hydramnion. Most hydrops conditions will lead to compromise or death of the foal and mare. A 6-year-old multiparous standardbred recipient mare, 332 days pregnant, diagnosed with a monozygotic twin and hydrops with a dead co-twin, gave birth ...
Silva GC, Nogueira CEW, Scalco R, Pizzi GLBL, Leite TA, Bastos R, Curcio BR.Gestation length (GL) in horses varies widely, influenced by multiple variables, including maternal, fetal, and environmental factors. This study aimed to investigate and quantify the relative contributions of climatic (photoperiod and temperature-humidity index - [THI]), maternal (age and parity), fetal (sex) and environmental (year and month of foaling) variables influencing gestation length in Thoroughbred mares. Retrospective data encompassing 704 pregnancies across nine breeding seasons in tropical and subtropical Brazilian climates were analyzed. Stepwise regression analysis identified f...
Gonzalez SW, Espy BMK, Stefanovski D, Turner RM.Monitoring gestation and predicting parturition in mares with unknown breeding dates is challenging, especially in pasture bred herds of bucking horses. Transrectal ultrasonographic measurement of fetal vitreous body length is a validated predictor of foaling dates, but previous research suggested a need for breed-specific parameters to develop accurate indices for respective breeds. This study aimed to develop a scale associating fetal vitreous body length with days before parturition (DBP) in bucking horses. Biannual data collection over 2 years identified 199 pregnancies out of 240 reproduc...
Debes L, Venner M, Koether K, Vervuert I, Blanco M, Sieme H, Sielhorst J.Little is known about the health status of foals born alive from mares treated for placental disease. The aims of the present study were (1) to compare the neonatal health status and health development during the rearing period of foals born from mares treated for ultrasonographically assessed placental abnormalities (UPA) to age-matched healthy foals from the same warmblood stud and (2) analyze the influence of mare's placental health on colostrum quality. Foals (n = 127) born from mares with UPA (UPA group; P) in 2017-2019 were compared to 127 foals born from healthy mares (control group; ...
