The equine placenta is a vital organ that facilitates nutrient and gas exchange between the mare and the developing fetus during pregnancy. It plays a role in hormone production and immune modulation to support fetal development. The placenta in horses is classified as a diffuse, epitheliochorial type, characterized by the widespread attachment of the chorionic villi to the endometrium. Research on the equine placenta encompasses studies on its structure, function, and the physiological processes involved in its development and maintenance. This page compiles peer-reviewed research studies and scholarly articles that explore the morphology, function, and clinical implications of the placenta in equine reproduction and health.
Christie GA.Carbohydrate (particularly glycogen), lipid and RNA were among the substances earliest to be described in the placenta. The papers of Wislocki and his associates (1946a, b, c, 1948) have been supplemented by studies in several species (Hafez, 1964). Recently the distribution of glycogen has been re-examined using modern specific techniques (Christie, 1966a) and some correlation between the distribution of glyco-gen and certain specific alkaline phosphatases has been made (Christie, 1967a). Many enzymes relevant to the metabolism of glycogen, lipid and RNA can be demonstrated histochemically, a...
Visutakul P, Bell ET, Loraine JA, Fisher RB.Human chorionic gonadotrophin (HCG), pregnant mare serum gonadotrophin (PMSG) and human menopausal gonadotrophin (HMG) were incubated with varying concentrations of urea at different temperatures for different times.
The luteinizing hormone (LH) activity of HCG was progressively destroyed with increasing concentrations of urea. The degree of inactivation was greater at higher temperatures but the time of incubation did not affect the results.
The follicle-stimulating activity of PMSG was reduced at high urea concentrations; the time of incubation was without effect.
Under the experime...
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...
Jalali GR, Rezai A, Underwood JL, Mowbray JF, Surridge SH, Allen WR, Matthias S.We have shown that most of the IgG present on term syncytiotrophoblast, membrane, microvesicles is bound to an 80 kDa protein antigen (R80K). Methods: Microvesicles were prepared from term human placenta, and the IgG eluted at pH3. Results: When IgG antibody was eluted at pH3 and reacted with acid-treated vesicles of other placentae, the alloantibody always bound to the preparation from which it was obtained, but only to about 10% of acid-treated preparations from other placentae. A similar polymorphic protein found in association with IgG antibody was found in term horse placentae. Cross-reac...
Arai KY, Tanaka Y, Taniyama H, Tsunoda N, Nambo Y, Nagamine N, Watanabe G, Taya K.In this study, the expression patterns of inhibins, activins, insulin-like growth factor-I (IGF-I) and steroidogenic enzymes in equine placentae recovered during the latter two-thirds of gestation were examined. Concentrations of inhibin A and inhibin pro-alphaC in endometrial and fetal placental tissue homogenates were very low during the period examined, whereas these tissues contained high concentrations of activin A. In both maternal endometrial and fetal placental tissues, activin A levels decreased as pregnancy progressed. Expression of inhibin alpha-subunit was not observed in the place...
Magalhaes HB, Canisso IF.This study aimed to establish normal ranges and determine variables affecting the duration of gestation, placental and fetal eyeball measurements in donkeys. Jennies (n = 121) were submitted to transrectal ultrasonography at 15-day-intervals from 120 days of gestation until parturition. During each examination, variables assessed included: the combined thickness of uterus and placenta (CTUP), fetal eyeball diameter, amniotic membrane thickness, allantoic and amniotic fluids echogenicity, and chorioallantois edema. Parametric data were analyzed with t-test, linear regression, mixed models, AN...
Poonacha KB, Donahue JM, Giles RC, Hong CB, Petrites-Murphy MB, Smith BJ, Swerczek TW, Tramontin RR, Tuttle PA.Leptospirosis was diagnosed in 51 equine fetuses and 16 stillborn foals with gestational ages from 3 1/2 to 11 months. Diagnosis was based on one or more of the following: positive fetal antibody titer, positive fluorescent antibody test, demonstration of spirochetes in kidney and/or placental sections stained by the Warthin-Starry technique, high leptospiral titers in aborting mares, or isolation of Leptospira spp. from fetal organs. Gross lesions were observed in 80.3% of the fetuses, stillborn foals, and placentas. Gross placental lesions included nodular cystic allantoic masses, edema, are...
McFarlane JR, Coulson SA, Papkoff H.This study describes the presence of immunoactive and bioactive eCG-like material in full-term placentas of both domestic horses and zebras. Term placental extracts were immunoreactive in an LH monoclonal antibody RIA, and methods successfully used previously for the purification of eCG and eLH were employed to further concentrate the immunoreactive materials to the point where additional characterization studies could be performed. Sufficient equine material was obtained to perform a final fractionation on a concanavalin A Sepharose column yielding an unadsorbed fraction, e17A, and an adsorbe...
Hülskötter K, Aurich C, Köhne M, Baumgärtner W, Wohlsein P.Adenomatous hyperplasia of the equine allantoic epithelium (EAAH) is an infrequently observed nodular or plaque-like change in the placenta of the mare which is presented as a case description. EAAH is most frequently diagnosed in cases of aborted fetuses and is associated with inflammatory changes of the placenta. Histologically, different degrees of EAAH may be distinguished; however, these are not associated with specific clinical signs, degree of inflammation, a particular pathogen, or the frequency of abortions. It is assumed that EAAH represents a secondary, reactive change and has per s...
Stewart DR, Papkoff H.It has been previously determined that the equine placenta is the sole significant source of relaxin during pregnancy and that relaxin immunoactivity is also present in term placentas. Therefore, placentas obtained at the time of foaling were selected for starting material for purification of equine relaxin. Frozen whole placentas were ground and then extracted with 0.5 N HCl-85% acetone. Relaxin was precipitated by raising the acetone concentration to 97%. Equine relaxin was further purified by stepwise elution ion exchange, gel filtration, and gradient elution ion exchange chromatographies a...
Lanci A, Merlo B, Grandis A, Mariella J, Castagnetti C, Iacono E.Wharton's jelly (WJ) is fundamental for the well-being of the fetus, binding to the umbilical vessels and protecting them from twisting and compression. Gross and microscopic studies have been undertaken on the umbilical cord (UC) of human placentae in both normal and high-risk pregnancies, however there is limited research on equine UC. The aim of this study was to describe microscopically and immunohistochemically the equine UC in normal pregnancies, with particular attention to WJ. Forty-seven healthy mares, with no complications during pregnancy, admitted to the hospital for attending deli...
Skopakoff C.The development of the chewing, lacerative and omnivorous dentition type was confirmed on the base of the author's studies on the dentition of placentalia representatives. The use of vegetable food by the rodents and herbivorous mammals induces an efficient development of molars, absence or reduced number of incisors and canines of the upper jaw and increased number of incisors and absence of canines of the lower jaw, resulting into the proposal of an alteration of the dentition formula for rabbits and for the rest of the rodents (Simplicidentata), for herbivorous and for horses. In beasts of ...
Visutakul P, Bell ET, Loraine JA, Fisher RB.Human chorionic gonadotrophin (HCG), pregnant mare serum gonadotrophin (PMSG) and human menopausal gonadotrophin (HMG) were incubated with varying concentrations of urea at different temperatures for different times.
The luteinizing hormone (LH) activity of HCG was progressively destroyed with increasing concentrations of urea. The degree of inactivation was greater at higher temperatures but the time of incubation did not affect the results.
The follicle-stimulating activity of PMSG was reduced at high urea concentrations; the time of incubation was without effect.
Under the experime...
Ellerbrock M, Wehrend A.Dystocia represents a life-threatening condition for mare and foal. Morbidity and mortality rates due to a difficult birth, as well as the influence on fertility of the mare were analyzed, based on a review of publications. This was aggravated by the fact that no standardized diagnostic code was used and that most publications do not clearly describe how extensively the examinations were performed beforehand. Retentio secundinarum is the most common complication caused by dystocia. Other complications are injuries to the soft birth canal and the colon. These occur more frequently after surgica...
Lawson JM, Shilton CA, Lindsay-McGee V, Psifidi A, Wathes DC, Raudsepp T, de Mestre AM.Excessive inbreeding increases the probability of uncovering homozygous recessive genotypes and has been associated with an increased risk of retained placenta and lower semen quality. No genomic analysis has investigated the association between inbreeding levels and pregnancy loss. Objective: To compare genetic inbreeding coefficients (F) of naturally occurring Thoroughbred Early Pregnancy Loss (EPLs), Mid and Late term Pregnancy Loss (MLPL) and Controls. The F value was hypothesised to be higher in cases of pregnancy loss (EPLs and MLPLs) than Controls. Methods: Observational case-control st...
Sielhorst J, Koether K, Volkmann N, Blanco M, Vicioso R, Baade S, Kemper N, de Mestre AM, Sieme H.Little is known about the incidence and outcome of high-risk pregnancies in equine practice and clinical studies on spontaneous occurring placentitis cases and treatments are missing. Therefore, the aims of this retrospective field study were to (1) describe the incidence and severity of ultrasonographic assessed placental abnormalities (UPA) in 4,192 pregnancies on a large commercial warmblood stud farm in 2017 - 2019 and (2) characterize these UPA cases and their pregnancy outcome. UPA severity (Placental abnormality score (PSc) 1-3; low to high), nine treatment regimens (TM1-9) used in UPA ...
