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.
Bhavnani BR, Short RV, Solomon S.A mixture of 14C-sodium acetate and 3H-cholesterol was injected into the umbilical circulation of a pregnant mare in the 3OOth day of gestation. The abdomen was closed and urine was collected for 3.5 days. The mare delivered a normal live foal 23 days later. Steroid conjugates present in the maternal urine were hydrolyzed and separated into neutral and phenolic fractions. From the phenolic “sulfate” fraction estrone, 17α-estradiol, equilin, equilenin, and 17α-dihydroequilenin were isolated. Only estrone and 17α-estradiol contained both 3H and 14C, while the ring-B unsaturated estrogens ...
Vandeplassche M, Podliachouk L, Beaud R.A study has been made of 44 cases of twin pregnancy in mares. The fetuses, foals, fetal membranes and blood groups of parents and foals were examined in order to determine the incidence of chorio-vascular anastomosis, blood chimaerism and freemartinism. All of the twins proved to be dizygotic and 33 of the 34 pregnancies were bicornual. Fusion of the chorion was seen in 14 of 22 placentas and macroscopic choriovascular bridges were observed in five of these, although blood chimaerism was diagnosed in 11 of 25 cases (44 per cent) examined. This would indicate a high incidence of microchoriovasc...
Loux SC, Conley AJ, Scoggin KE, El-Sheikh Ali H, Dini P, Ball BA.Steroid production varies widely among species, with these differences becoming more pronounced during pregnancy. As a result, each species has its own distinct pattern of steroids, steroidogenic enzymes, receptors, and transporters to support its individual physiological requirements. Although the circulating steroid profile is well characterized during equine pregnancy, there is much yet to be explored regarding the factors that support steroidogenesis and steroid signaling. To obtain a holistic view of steroid-related transcripts, we sequenced chorioallantois (45 days, 4 months, 6 months, 1...
Bigler NA, Gross JJ, Baumrucker CR, Bruckmaier RM.This review discusses endocrine and functional changes during the transition from late gestation to lactation that are related to the production of colostrum in different mammalian species. Species covered in this article include ungulate species (cattle, sheep, goats, pigs, horses), rodents (rat, mouse), rabbits, and carnivores (cats, dogs), as well as humans. An immediate availability of high quality colostrum for the newborn after birth is crucial in species where a transfer of immunoglobulins (Ig) does not or only partially occur via the placenta during pregnancy. Declining activity of ges...
Galli C, Colleoni S, Duchi R, Lagutina I, Lazzari G.Development of assisted reproductive technologies in horses has been relatively slow compared to other domestic species, namely ruminants and pigs. The scarce availability of abattoir ovaries and the lack of interest from horse breeders and breed associations have been the main reasons for this delay. Progressively though, the technology of oocyte maturation in vitro has been established followed by the application of ICSI to achieve fertilization in vitro. Embryo culture was initially performed in vivo, in the mare oviduct or in the surrogate sheep oviduct, to achieve the highest embryo devel...
Wehrenberg WB, Fowler S, Kurhajec J, Hutz RJ.Forty-four female ranch mink, maintained out-of-doors under standard conditions, were exposed to natural photoperiod supplemented with a period of artificial light from approximately 2300 hr to 0300 hr from early January to mid February. Breeding was initiated on March 1. After repeated attempts to breed the animals, it was determined that the likelihood of their breeding was very low, presumably due to the artificial and asynchronous long-day photoperiod. In an attempt to induce breeding, the mink were randomly assigned to one of four treatment groups: saline, 25 International Units (IU) PMSG...
Govaere JL, Hoogewijs MK, De Schauwer C, De Vliegher S, Van Soom A, Duchateau L, de Kruif A.Deep intra-uterine insemination is commonly accepted as a routine procedure for artificial insemination in horses. The motives and principles of deep insemination are well described, but the equipment used may differ. In this trial, the efficiency of two different insemination pipettes for deep intra-uterine insemination in the mare was compared with insemination into the uterine body using commercially available frozen-thawed semen of two stallions of proven fertility. These inseminations were performed using two different doses. The semi-flexible Minitube pipette was compared with a newly de...
Heiskanen ML, Hilden L, Hyyppä S, Kangasniemi A, Pirhonen A, Mäenpää PH.The first (1 to 3) sperm-rich fractions of the ejaculate were collected from 4 stallions using an open-ended vagina. The volume of the collected fractions was 12 +/- 8 ml with a density of 475 +/- 200 million spermatozoa/ml. Before freezing, the semen was diluted with a skim-milk based extender 1:1 to 1:8 (volume of semen: volume of extender), depending on the initial sperm concentration to achieve a final concentration of 100 million/ml. The total number of spermatozoa in an insemination dose ranged from 0.7 to 1 billion spermatozoa. Within 12 h after ovulation, 48 mares were inseminated in 7...
Kindahl H, Daels P, Odensvik K, Daunt D, Fredricksson G, Stabenfeldt G, Hughes JP.Three different routes of administering Salmonella typhimurium endotoxin to mimic naturally occurring endotoxaemia were tried in the mare. Bolus injection, repeated bolus injections and continuous low-dose infusion were compared with prostaglandin F2 alpha release, leucocyte count and clinical response. A biphasic prostaglandin release and a pronounced leucopenia of almost identical patterns were seen in all models. Repeated bolus injections showed that the second injection initiated only a small prostaglandin release indicating the development of refractoriness to the treatment. A similar ref...
Fowden AL, Silver M.Epostane, a competitive inhibitor of 3 beta-HSD was administered intravenously to a pregnant mare between 292 and 330 days of gestation at doses of 1-3 mg/kg/min. Plasma progesterone concentrations fell rapidly during epostane infusion in both the artery and uterine vein and remained significantly depressed for 4-5 h after the start of infusion. The venous arterial (V-A) plasma concentration difference in progesterone across the uterus also decreased significantly in response to epostane infusion. There were no significant changes in plasma progesterone or in the V-A concentration difference i...
Grosskopf JF, Smuts EG.Blood was collected from 28 zebra mare (Equus burchellia antiquorum) immediately after being shot in the Kruger National Park. The serum was separated within two hours after collection and then stored at -15 degrees C for later assay. Of these, thirteen selected samples were tested for gonadotrophic activity. The stage of pregnancy was determined from a foetal growth curve. Blood samples from pregnant horse mares were collected by venipuncture. Nine mares were sampled. Seven blood samples at different stages of pregnancy were collected from one mare, four from another and only one sample each ...
Scherzer J, Fayrer-Hosken RA, Ray L, Hurley DJ, Heusner GL.Embryo transfer has been an inherent part of cattle breeding for more than 35 years and has also gained remarkable interest from the equine industry after several breeds allowed registration of more than one foal per year. In both large animal species, non-surgical embryo recovery and transfer are well-established techniques. However, success rates after superovulation and cryopreservation of embryos in horses are still lagging behind those of cattle, and more research is needed to address these areas. To address the problem of freezing large equine embryos, we offer a preliminary demonstratio...
Lloyd JW, Rook JS, Braselton E, Shea ME.A study was designed to model the fluctuations of nine specific element concentrations in mammary secretions from periparturient mares over time. During the 1992 foaling season, serial samples of mammary secretions were collected from all 18 pregnant Arabian mares at the Michigan State University equine teaching and research center. Non-linear regression techniques were used to model the relationship between element concentration in mammary secretions and days from foaling (which connected two separate sigmoid curves with a spline function); indicator variables were included for mare and mare ...
Tinel JB, Veras MM, Waked D, Alonso MA, Fernandes CB.Mules are derived from crossing horse mares with a donkey, in which the interest is due to gentleness and ability to work and equestrian sports. As the placenta is responsible for fetal development and maturation, knowing its typical microstructure allows us to understand how fetomaternal interactions occur in this interspecific pregnancy. Thus, the study performed a comparative stereological evaluation of volumetric composition and fetomaternal contact surface in the uterine body (UB), gravid uterine horn (GUH), and nongravid uterine horn (NGUH) of Mangalarga Paulista mare's term allantochori...
Jeffcott LB, Rossdale PD.The position, posture and presentation of the fetus were studied by serial radiography of the abdomen in 18 crossbred Pony mares near term and during first- and second-stage labour. In 3 mares the fetal position was assessed before and after induction of parturition with the synthetic prostaglandin, fluprostenol. In late gestation and up to the time of first-stage labour the fetus lay in ventral position with the forelimbs and poll flexed or partly flexed. At this time fetal movements were confined to flexion and extension of neck and forelimbs, but at parturition the head and limbs gradually ...
Wada R, Fukunaga Y, Kanemaru T, Kondo T.Five pregnant mares, at between 6 and 8 months gestation, were experimentally infected with the Bucyrus strain of equine arteritis virus (EAV). Of the five mares, four aborted and one died. The pathogenesis of the abortions was studied, using histopathologic techniques, tissue immunofluorescence and virus isolation. Common microscopic lesions in the maternal reproductive organs indicated myometritis with a degeneration of the myocytes and an infiltration of the mononuclear cells. Epithelial cells of the endometrial gland showed sporadic degeneration. Lesions in the fetal tissue included an atr...
El-Sheikh Ali H, Scoggin K, Murase H, Norris J, Menarim B, Dini P, Ball B.The equine chorioallantois (CA) undergoes complex physical and biochemical changes during labor. However, the molecular mechanisms controlling these changes are still unclear. Therefore, the current study aimed to characterize the transcriptome of equine CA during spontaneous labor and compare it with that of normal preterm CA. Placental samples were collected postpartum from mares with normal term labor (TL group, n = 4) and from preterm not in labor mares (330 days GA; PTNL group, n = 4). Our study identified 4137 differentially expressed genes (1820 upregulated and 2317 downregulat...
Heise A, Kähn W, Volkmann DH, Thompson PN, Gerber D.The use of epididymal stallion spermatozoa for routine artificial insemination can secure easy future use of valuable genetics after unforeseen death or injury of a valuable stallion. The aims of this study were to (1) directly compare pregnancy rates for fresh and frozen-thawed stallion epididymal and ejaculated spermatozoa after conventional artificial insemination and (2) to investigate the effect of seminal plasma on the fertility of epididymal spermatozoa after insemination. Twenty-one mares were randomly assigned to three stallions. Mares were inseminated at five consecutive oestrous per...
Lyle SK, Ferrer MS.The typical dose for insemination into the uterine body of the mare is > 300 x 10(6) progressively motile spermatozoa (PMS) and an insemination dose of > 200 x 10(6) PMS is recommended for frozen-thawed semen. Low-dose insemination techniques allow for a drastic reduction in the numbers of spermatozoa required to achieve pregnancy. Acceptable pregnancy rates can be achieved with doses ranging from 1 to 25 x 10(6) PMS in volumes ranging from 20 to 1000 microL. Two techniques have been described: hysteroscopic insemination and transrectally guided deep horn insemination using a pipette. Similar ...
Atayde L, Rocha A.It is important to get mares pregnant as early as possible after vernal transition and thus, identification signs of impending 1st ovulation of the year are warranted. To identify clinical indicators of an approaching first ovulation of the year, mares were teased with a stallion for oestrous detection starting January 3 and subjected to ultrasonographic examination. Day of first appearance of uterus oedema, follicular wall invagination, intrafollicular echogenicity, double contour of the follicle wall, increase in granulosa thickness, follicular wall hyperechogenicity and appearance of pear-s...
Bartošová J, Komárková M, Dubcová J, Bartoš L, Pluháček J.Lactation is the most energy demanding part of parental care in mammals, so parent-offspring conflict arises over milk provided by the mother. In some species females commonly become pregnant shortly after parturition of previous young. This further intensifies mother-offspring conflict due to concurrent pregnancy and lactation. In equids it has been well established that pregnant females wean their foals earlier than non-pregnant ones. Intensified mother-offspring conflict was presumed to associate with pregnancy also during the period of intensive lactation, i.e., before the weaning process ...
Maśko M, Zdrojkowski Ł, Wierzbicka M, Domino M.Determination of the pregnancy status is one of the most important factors for effective pregnancy management. Knowledge of the stage of pregnancy is important to interpret many of the reproductive hormones' concentrations, including progesterone (P4), estrone sulfate (E1S), 17-ß estradiol (E2), and relaxin (REL). However, it is limited in wildlife or captive equids that cannot be handled. Reproductive hormones affect regional blood flow, the proliferation of tissues, and local metabolism intensity. Therefore, this preliminary study aimed to assess changes in thermal features of the abdomen l...
Ferreira CSC, Morais RCL, de Andrade ABP, Balaro MFA, Ribas JAS, Gomes GM, Pinna AE.The aim of this study was to evaluate whether the RI and PI values would help in choosing the best embryo recipient, and observe whether CL vascularization would influence P4 production. During the breeding season 2018/2019, the study was conducted using 35 mares, which is used for reference to collect data for the project on the day of embryo transfer. The utilized mares were divided into five groups followed by the day after ovulation, with D0 being the day of ovulation. Therefore, the five groups are as follows: D4-mares that were on the 4th post-ovulation day; D5-mares that were on the 5th...
Allen WR, Bowen JM, Frank CJ, Jeffcott LB, Rossdale PD.This short review article describes the various techniques currently available for artificial insemination in the horse. The collection and use of raw and extended semen is discussed together with the more recent developments in freezing semen. The expected conception rates with both fresh and frozen semen are quoted. The possible benefits in disease control and stud management are discussed, as well as the difficulties in controlling the use of A.I. from the Breed Registration Authorities point of view.
Kirkpatrick JF, Shldeler SE, Lasley BL, Turner JW.This study was carried out to develop an accurate, rapid and inexpensive method for diagnosing pregnancy in uncaptured feral horses by analysis of fecal steroid metabolites and to compare the accuracy of this method with diagnosis by urinary estrone conjugates (E(1)C). Paired urine and fecal samples were collected from 40 sexually mature feral mares during August and October. Urine samples were extracted directly from the soil and analyzed by enzymeimmunoassay (EIA) for E(1)C. Water extracts of fecal samples were assayed by EIA for E(1)C and nonspecific progesterone metabolites (iPdG). Urinary...
de Vries PJ, van der Holst W.The reliability of determination of the plasma progesterone level within approximately eighteen days after ovulation in the pregnancy diagnosis of mares is examined in the present study. Studies were done in seventy-five mares, a number of which were served or inseminated during several cycles so that a total number of eighty-seven blood samples were obtained. On the analogy of other authors, the progesterone level above which mares were believed to be pregnant and below which they were assumed to be non-pregnant, was set at 2 ng/ml. The twenty-five mares in which the level was below 2 ng/ml. ...
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...
Stonehouse O, Stefanovski D, Bowman B, Sertich PL, Demchur J, Lewis GM, Turner RM, Turner RMO.Nocardioform placentitis (NP) has been associated with mid to late pregnancy loss in mares. To date, disease outbreaks have been described only in central Kentucky, although sporadic, isolated cases have been reported globally. This study describes a series of cases of NP that occurred in a sample population of 299 mares foaling in southeastern Pennsylvania and northeastern Maryland in 2020. These cases coincided with an outbreak of NP that occurred in Kentucky that same year. On farms that reported information on both normal and abnormal foalings, nocardioform organisms/DNA were isolated from...
Macan RC, Camargo CE, Zielinski BL, Cardoso NGH, de Lara NSS, Bergstein-Galan TG, Weiss RR, Kozicki LE.Timed artificial insemination (TAI) has boosted the use of conventional artificial insemination (CAI) by employing hormonal protocols to synchronize oestrus and ovulation. This study aimed to evaluate the efficiency of a hormonal protocol for TAI in mares, based on a combination of progesterone releasing intravaginal device (PRID), prostaglandin (PGF2α ) and human chorionic gonadotropin (hCG); and compare financial costs between CAI and TAI. Twenty-one mares were divided into two groups: CAI group (CAIG; n = 6 mares; 17 oestrous cycles) and TAI group (TAIG; n = 15 mares; 15 oestrous cycle...
Renaudin CD, Gillis CL, Tarantal AF.Gender determination of the equine fetus using transabdominal ultrasonography was studied in 20 mares. One group of 10 research mares was scanned repeatedly every 2 weeks from 100 days gestation to parturition, while the second group of 10 client mares was subjected to echography once during mid-gestation. In males, the penis and/or prepuce was observed on 71 occasions from 102 days to 258 days gestation. On cross-sectional views, the male external genitalia had a round shape with parallel linear echogenic foci up to approximately 140 days gestation and then appeared triangular. Fetal testes w...
Webb PD.The pituitary glands of 4 horse embryos (41-55 days of gestation) were examined by light microscopy, and the pars distalis from 10 fetal foals (75-300 days) was examined by electron microscopy. At Day 41 the development of Rathke's pouch and the saccus infundibuli was advanced; the former had almost lost its connection with the stomodaeum and the latter had started to differentiate into infundibular process and infundibular stalk. By Day 43 Rathke's pouch was completely dissociated from the stomodaeum and its walls were beginning to show uneven growth. The ventral wall of the pouch, the future...
Inoue Y, Sekiguchi M.Therapeutic techniques for oviductal obstruction in the mare are limited. Nonsurgical and retrograde flushing may be an attractive alternative to current treatment methods for oviductal blockage. Objective: To evaluate hysteroscopic selective hydrotubation as a treatment option for presumptive equine oviductal blockage. Methods: Retrospective case series. Methods: A quantity of 10 mL of saline was flushed through the oviducts in 28 standing sedated mares, which had reproductive histories of unexplained subfertility, by inserting a catheter into the uterotubal junction under endoscopic guidance...
