Fetal health in horses encompasses the study of the development and well-being of the equine fetus during gestation. This area of research focuses on understanding the physiological processes that occur from conception to birth, including fetal growth, placental function, and maternal-fetal interactions. Factors influencing fetal health can include genetics, nutrition, environmental conditions, and maternal health status. Monitoring fetal health is important for identifying potential complications such as developmental abnormalities or pregnancy loss. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms, assessment methods, and implications of fetal health in equine reproduction.
Tervit HR.Recent advances in reproductive physiology offer ways for exploiting superior, female cattle and for manipulating physiological events such as parturition. The techniques involved in these advances and their associated hazards are the subject of this review.
Hafs HD.Often in developing hormone assays, hormones that may interfere with the assay by cross-reaction are not available for testing the validity of the assay. For example, horse TSH was unavailable to test for cross-reaction in an LH radioimmunoassay (RIA). The authors devised an indirect means of accomplishing the same goal, and the evidence from the indirect test of cross-reaction was at least as persuasive as a direct test might have been. Other examples are given of experiments where extensive effort was devoted to validation of steroid RIA, but there were substantial quantitative differences i...
Matheka HD, Coggins L, Shively JN, Norcross NL.EIA virus was purified from equine fetal kidney cell cultures by PEG-precipitation, two sucrose-gradient sedimentations (5-30 per cent) and (25 to 60 per cent) centrifugation, using the immunodiffusion test to follow the procedure. Purified EIA virus had a density (20 degrees C) of 1.162 and a sedimentation constant of S20w=656. electron microscopy revealed a particle of about 100 nm in diameter with a very flexible but usually spherical shape. The dense core may be at various locations inside the membrane bound particle.
Sharma OP.The concentrations of PGF-2alpha in the peripheral blood of five foaling mares were measured by radioimmunoassay. Low levels of PGF-2alpha were detected as early as 1 week before foaling in two of the mares. These levels increased steadily, reaching a peak (1-74 +/- 0-44 ng/ml) during fetal expulsion. A relatively high PGF-2alpha level was found in samples collected 60 min after foaling.
Verberne LR, Mirck MH.The toxicity of parbendazole in different doses was investigated with 52 horses and 16 ponies, in twelve groups. Side effects observed with the anthelmintic were laxation (soft dung, diarrhoea), anorexia, and listlessness. The seriousness of these symptoms depended greatly on the dose used. Half the therapeutic dose of parbendazole (2.5 to 3.75 mg/kg) administered on two consecutive days led, as a rule, to only slight toxic symptoms and proved highly effective with regard to gastro-intestinal nematodes occurring in horses and ponies. The utilisation of "standard powders" (not commercially avai...
Silver M, Comline RS.Mares and fetuses with indwelling catheters in the umbilical and uterine vessels have been used to monitor transplacental blood gas tensions, pH, O2 affinities and the concentration of various metabolites in fetal and maternal blood during late gestation. Measurements of umbilical and uterine blood flows and arterio-venous differences enabled the uptake of O2 and glucose by the fetus and the uterus to be estimated. The present findings are compared with those from other species in comparable conditions.
Spincemaille J, Bouters R, Vandeplassche M, Bonte P.Two females of heterosexual pairs of chimaeric horse twins were fertilized by their co-twin brother and PMSG production examined during gestation. Four pregnancies developed in one mare and two in the other. The levels of PMSG were high in both mares and remained detectable in the peripheral blood until 220 and 265 days of gestation. The fetal membranes of one mare contained remnants of cup secretion with PMSG activity at term. The findings support the thesis of Allen & Moor (1972) that the endometrial cups are of fetal origin and that they are destroyed by immunological mechanisms.
Deanesly R.A histological study of the developing germinal epithelium in the fetal horse ovary shows an enormous wastage of oocytes during the meiotic phase, between Days 73 and 150 of pregnancy. The first groups of oocytes to enter this phage undergo mass degeneration and eventually disappear; few, if any, oocytes develop to primordial follicles. Peripheral oogonia, dividing by mitosis, give rise to more oocytes which pass through the same changes and are also reduced by degeneration, but by Day 150 primordial follicles are fairly common.
Barnes RJ, Nathanielsz PW, Rossdale PD, Comline RS, Silver M.Normal Thoroughbred and catheterized Pony mares and their fetuses were used. Fetal oestrogen and progestagen concentrations in late gestation were much higher than maternal values. A major feature of the umbilical steroid concentrations was a large venous-arterial difference in progestagens and total oestrogens throughout late gestation which may indicate a metabolic cycle in the fetus between progesterone and other steroid metabolites. Metabolites of 20alpha-dihydroprogesterone were present in high concentrations in maternal and fetal plasma. In Thoroughbreds, and to a lesser extent in Pony m...
González-Angulo A, Hernández-Jáuregui P, Martínez-Zedilo G.Light and electron microscopic studies of the gonads of the fetal horse have shown that, in their hypertrophic condition which begins during the 3rd month, the interstitial cells contain large amounts of smooth endoplasmic reticulum, suggesting a secretory activity. Hydroxylating activity which was cytochrome P-450-dependent was observed in the fetal testis and may be involved in steroid biosynthesis.
Samuel CA, Allen WR, Steven DH.Microcotyledons, which are a distinctive feature of the mature equine placenta, are fully formed by Day 150 of gestation. The fetal component of each microcotyledon is developed from several primary folds of trophoblast which become elaborately subdivided as gestation proceeds. These changes are reflected in the structure of the maternal crypts, which receive the fetal villi. Between Days 60 and 150 of gestation the maternal epithelium is greatly reduced in height. No such change occurs on the fetal side of the placenta, but between Days 100 and 250 a progressive indentation of the epithelium ...
Marrable AW, Flood PF.A sequence of ten known-age embryos recovered from Dartmoor Ponies during the first 4 months of gestation is described. Changes in size, shape and vascularity of the conceptus are recorded, as well as the growth and decline of the yolk-sac and the succeeding establishment of the allantochorion. The progress of equine somatogenesis is compared with that of the pig which it lags on average of about 4 days. Some quantitative data are presented.
Morgan DO, Bryans JT, Mock RE.The foal is born without detectable antibody and except for small amounts of IgM is devoid of immunoglobulins. Intrafetal administration of either Venezuelan equine encephalomyelitis virus (VEE-TC83) or ovine erythrocytes elicited IgGa, IgGb and a trace of IgG(T). The fetal blood VEE-TC83 neutralization titre was higher than the neutralization titre elicited by the same preparation in older horses.
Kitchen H, Bunn HF.Studies were made of the O2 affinities of fetal and maternal haemoglobins in the horse, and correlations were found with erythrocytic levels of 2,3-diphosphoglycerate.
Steven DH, Samuel CA.The study of the equine placenta, which began in Venice in 1598, has a long but discontinuous history. Early observations were purely morphological, but new techniques have stimulated a broader and more functional approach. Histological and ultrastructural observations at various stages of pregnancy have shown that the fetal side of the placenta comes to acquire certain features in common with the air-blood barrier of the mammalian lung. These changes may reflect the increasing O2 requirements of the fetus as gestation proceeds.
Moor RM, Allen WR, Hamilton DW.Biochemical and morphological studies were carried out to determine the origin and histogenesis of endometrial cups in mares. A wide range of fetal and maternal tissues were cultured in vitro and their ability to secrete gonadotrophin (PMSG) was monitored. High levels of PMSG were produced in culture only by cells from the restricted area of the equine trophoblast known as the chorionic girdle which is an annular band of highly specialized cells at the junction of the allantois and the regressing yolk sac. The morphological appearance of girdle cells after cultivation in vitro and after alloge...
Allen WR.The influence of fetal genotype upon gonadotrophin (PMSG) and progestagen production in mares and donkeys during the first half of pregnancy was examined. The production of PMSG was greatly reduced in mares carrying mule conceptuses and greatly increased in donkeys carrying hinny conceptuses. Fetal genotype had no obvious influence upon progestagen production in mares, but donkeys carrying hinny conceptuses showed extremely high peripheral plasma progestagen concentrations when serum PMSG levels were elevated. Fetal genotype profoundly influences the intensity and rate of success of the matern...
Comline RS, Hall LW, Lavelle R, Silver M.Methods developed for the insertion of catheters into the umbilical artery and vein and the uterine vein of the pregnancy mare are described. The technique requires careful anaesthesia and the maintenance of normal blood gas tensions, pH and arterial blood pressure. Fetal survival was variable: three mares delivered live foals and six fetuses survived more than 15 days with a maximal period of 41 days. The erythrocytes sedimentation rate (ESR) of the fetal foal was always very low at operation but subsequently increased slightly; a sudden large rise in ESR usually indicated imminent fetal deat...
Nathanielsz PW, Rossdale PD, Silver M, Comline RS.Fetal plasma cortisol concentrations (mean +/- S.E.M.) in ten animals with indwelling umbilical catheters ranged from 13-9 +/- 1-5 ng/ml (227 to 244 days) to 18-1 +/- 2-2 ng/ml (290 to 310 days). Maternal values did not change over this period (15-9 +/- 1-7 ng/ml). Fetal cortisol production rates in two fetuses were 3-6 and 3-8 mg/kg/day at 291 days; there was little placental transfer of cortisol. In three fetuses (319 to 321 days) plasma cortisol values 1 to 10 days before birth were higher (30 to 50 ng/ml) than in any other group, and at birth the values were comparable with those found in ...
Flood PF, Marrable AW.The distribution of several hydroxysteroid dehydrogenases (HSD) was examined in a variety of equine placental and fetal tissues. The main points of interest were: (a) the lack of dehydrogenase activity in the gonad, (b) the appearance of a variety of HSDs in the trophoblast as early as 13 days of gestation, (c) the histochemical similarity between the cells of the trophoblast and the endometrial cup, and (d) the restriction of the strong endometrial 17beta-HSD reaction to those parts of the uterine epithelium directly apposed to the trophoblast.
Drew B, Barber WP, Williams DG.On a thoroughbred stud four foals were born with greatly enlarged thyroids and leg weakness. Two foals died within 18 hours of birth, the others subsequently recovered. An enlarged thyroid was also evident in one of the resident mares. The thyroids from the dead foals were hyperplastic. Feed analyses showed that the mares had an iodine intake of about 83 mg daily, 8-8 ppm of the dietary dry matter, due almost entirely to the high iodine content of a proprietary compound horse nut which had been fed at the daily rate of 12 lb per head. It was concluded from the histology of the thyroids, the hi...
Whitwell KE, Jeffcott LB.Of 211 consecutive thoroughbred foalings, 145 satisfied a set of criteria for normal parturition and foal viability. The fetal membranes from these and from 10 pony foalings have been systematically examined morphologically and quantitatively and the findings compared to those of other authors. Five sites on the allantochorion were consistently devoid of villi. Expulsion usually occurred with the non-villous side outermost. In 24 per cent of allantochorions the non-pregant horn was of equal length or longer than the pregnant horn. These placentae tended to be shed with the villous side outermo...
Bhavnani BR, Martin LJ, Baker RD.A mixture of 1-14C-isopentenylpyrophosphate and 3H-dehydroisoandrosterone was injected into a horse fetus intramuscularly during laparotomy, after which maternal urine was collected for 4 days. Steroid conjugates in the urine were extracted with Amberlite XAD-2 resin, hydrolysed and separated into phenolic and neutral fractions. From the phenolic fraction estrone, 17alpha-estradiol, equilin and equilenin were isolated. Only estrone and 17alpha-estradiol contained both 3H and 14C, while the ring B unsaturated estrogens contained only 14C. From the neutral fraction 14C-labeled 3beta-hydroxy-5alp...
Lanci A, Ingallinesi M, Morini M, Freccero F, Castagnetti C, Mariella J.Hydramnios is an excessive accumulation of fluid within the amniotic compartment. It is a rare condition in mares, often associated with fetal anomalies. Hydrops of fetal membranes predisposes to the rupture of the prepubic tendon, and many authors suggest the induction of parturition to preserve mare's reproductive career. This report presents the case of a 15-year-old multiparous Quarter Horse mare, referred at 268 days of gestation for suspected hydrops. Repeated ultrasonographic exams confirmed an increase in the depth of the amniotic fluid and reduced fetal viability. During the hospitali...
Ginther OJ, Williams D, Curran S.Transrectal ultrasonic examinations were made in 31 pregnant pony mares once a week during Months 6 to 11. Each uterine horn was divided into 3 approximately equal segments (caudal, middle, cranial). The percentage of examinations with cranial fetal presentation increased (P<0.05) progressively from 58% at Month 6 to 99% at Month 9 and was followed in all mares by entry of the fetal hind limbs into one uterine horn. The mean number of uterinehorn segments with limb parts increased (P<0.05) between each set of consecutive months from Month 6 to Month 10. Initially (Months 7 and 8), retrac...
Cohen ND, Carey VJ, Donahue JG, Seahorn JL, Harrison LR.Epidemiological and pathological findings of 433 late-term abortions associated with the mare reproductive loss syndrome (MRLS) in central Kentucky were identified by reviewing the records of the University of Kentucky Livestock Diseases Diagnostic Center. The distribution of dates of abortion was clustered during a brief period of time, presumably from a simultaneous environmental exposure. The most common pathological findings were microscopic pulmonary lesions consisting of squamous epithelial cells present in alveoli with or without concurrent infiltration of inflammatory cells (neutrophil...
Roberts SJ, Myhre G.Equine twinning, related abortion and progestogen plasma concentrations during the gestation period were reviewed. The supplemental administration of exogenous progesterone apparently prevented impending twin abortions in three mares after midgestation. A single viable twin and a mummified fetus were delivered at term by the mares.
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...
Vandeplassche M, Simoens P, Bouters R, De Vos N, Verschooten F.In 214 cases of severe dystocia in mares, of which 141 (66 per cent) were Draught horses, deviation of the head and neck, with or without torticollis, malformed head and limbs were found to be the cause of dystocia. No evidence of a genetic lethal factor was found and torticollis was often combined with scoliosis of the head and, frequently, with malformation of one or more limbs. This is considered evidence of a common aetiology and pathogenesis of the syndrome of malformation. The malformations were found to be associated with an increased incidence of caudal and, particularly, transverse pr...
Mutoh K, Watanabe S, Wakuri H.The glands of pelvis renalis in adult and fetal horses were examined by histochemically. The glandular terminal was divided into two types, intraepithelial gland (IE) and extraepithelial gland (EE) by their locations and histochemical characters. Both glands were composed of mucous cells. The former lay in the transitional epithelium and were stained reddish with galactose oxidase-Schiff (GOS) and mild oxidation-Schiff (MOS), bluish purple with periodic acid-cold thionine Schiff-NaOH-PAS (PCP). The latter distributed in the lamina propria, but was not discovered in the fetus. They were stained...
Kadivar A, Rashidzadeh H, Davoodian N, Nazari H, Dehghani Tafti R, Heidari Khoei H, Seidi Samani H, Modaresi J, Ahmadi E.Accurate diagnosis of foetal sex in pregnant mare is helpful for many breeders, both for private or commercial purposes. In this study, in order to pre-natal foetal sexing in equine, we used TaqMan duplex real-time PCR to detect the specific regions of SRY and TSPY genes on extracted cell-free foetal DNA from maternal blood. Peripheral blood samples from 50 pregnant Arabian mares with singleton foetuses were collected. Cell-free foetal DNA was extracted from maternal plasma, and duplex real-time PCR assays were performed with TaqMan probes and primers. Amplification of glyceraldehyde-3-phospha...
Steven DH, Jeffcott LB, Mallon KA, Ricketts SW, Rossdale PD, Samuel CA.Post-partum placentae and uterine biopsy samples from mares after normal and abnormal foalings are described. After normal delivery there is little damage to fetal or maternal tissues. The villous epitheliochorial palcenta separates cleanly at the maternal-fetal interface and the afterbirth consists almost exclusively of fetal tissue. Uterine involution is well advanced by the 3rd and 4th days post partum and the changes are usually complete by the oestrus 7--10 days after parturition. Placental separation and involution of the uterus appear to proceed normally in malpresented foals and in oth...
Pascoe DR, Stover SM.Twenty-one pregnant mares with single or twin conceptuses between 41 and 65 days of gestational age were allotted to 5 treatment groups. A ventral median celiotomy was performed in all mares. In group-1 mares (3 mares, single conceptus), the uterus and fetus were palpated for 5 minutes. In group-2 mares (3 mares, single conceptus, flunixin meglumine), 250 ml of sterile placental fluid was injected into the nongravid uterine horn. In group-3 mares (4 mares, unicornuate twin conceptuses), group-4 mares (3 mares, unicornuate twin conceptuses, flunixin meglumine), and group-5 mares (8 mares, bicor...
Yamanouchi K, Hirasawa K, Hondo E, Hasegawa T, Ikeda A, Sugawara Y, Matsuyama S, Miyazawa K, Sawasaki T, Tojo H, Tachi C, Takahashi M.The expression of inhibin alpha-subunit mRNA in equine fetal gonads during pregnancy (Days 90 to 300) was examined by means of Northern blot analysis. In all samples examined, a single species of transcript was detected at the size of 1.5 kb. A digoxigenin-labeled antisense cRNA probe specific to equine inhibin alpha-subunit was synthesized and in situ hybridization analysis to locate the inhibin alpha-subunit mRNA positive cells was performed using frozen tissue sections of equine fetal ovary (day 150 of pregnancy) and equine fetal testis (day 180 of pregnancy). In the fetal ovary, positive c...
Mukaiya R, Kimura T, Ochiai K, Wada R, Umemura T.Equine herpesvirus-1 (EHV-1) infection was demonstrated in the lung tissue of seven aborted fetuses by immunohistochemical labelling and polymerase chain reaction. The placentas of the fetuses were also examined by non-isotopic in-situ hybridization for the EHV-1 glycoprotein B (gB) gene. Positive hybridization signals were observed in the cytoplasm of trophoblasts, especially in microcotyledons, of all seven placentas, and in villous epithelium of the allantochorion of six placentas. Despite the presence of EHV-1 RNA, EHV-1 antigens were not detected in placentas by immunohistochemical examin...
Glatzel PS, Kangasniemi A, Belz JP, Lange A.The investigations were done on 108 mares (78 warm-blooded horses, 25 cold-blooded horses and 5 trotters). To pursue the question in the title, progesterone and estradiol values in jugular vein-blood were examined starting from 30 days before the calculated date of parturition until 30 days after that event. In parallel to that Ca/Mg ratio was measured by means of a semiquantitative test-strip in the milk. Clinical signs of the birth, parturition itself and the post partum period were recorded. In respect to the P4 and E2 values it was that the P4:E2 ratio changed towards parturition in favour...
Ginther OJ.After the cessation of equine embryo mobility (fixation) on mean Day 16, the embryonic vesicle is rotated or oriented so that the pole with the embryo proper is opposite to the mesometrial attachment. Orientation involves massage of the vesicle by contractions of the turgid uterine horn and greater thickening of the vesicle at the pole with the embryo proper. Thickening of the dorsal endometrium (encroachment) especially on each side of the mesometrial attachment accounts for a guitar-pick shape of the vesicle when viewed in cross section of the uterine horn. On Days 21-40, the allantoic sac e...
Tsogtgerel M, Murase H, Moriyama H, Sato F, Nambo Y.Late-term fetal loss in horses is a major problem in the horse-breeding industry globally. Abnormal pregnancies should be diagnosed as early as possible to prevent abortions and other gestational problems. According to our previous longitudinal study in healthy pregnant mares, the plasma activin A concentration increases as pregnancy progresses. The aim of the present study was to compare plasma activin A concentrations in healthy pregnant Thoroughbred mares (n=40) with those in pregnant mares that suffered fetal loss or showed abnormal symptoms (n=30) during late gestation. This field study f...
Rook JS, Braselton WE, Nachreiner RF, Lloyd JW, Shea ME, Shelle JE, Hitzler PR.To document and determine changes in the mineral profiles of sera and mammary secretions from a population of periparturient mares. Methods: 18 clinically normal periparturient Arabian broodmares. Methods: Inductively coupled argon emission spectroscopy was used to measure Ca, Cu, Fe, K, Mg, Mn, Na, P, and Zn concentrations in sera and mammary secretions of periparturient mares. In addition, S was measured in mammary secretions. Results: Serum concentrations of Ca, Cu, Fe, K, Mg, Na, P, and Zn remained constant throughout late pregnancy and the first 7 days of lactation. Compared with values o...
Vincze B, Gáspárdy A, Kovács L, Albert E, Kézér L, Baska F, Szenci O.Transabdominal ultrasonography has been shown to be a useful and reliable method for assessing fetal well-being in horses and cattle. To test the applicability of fetal aortic diameter measurement in cattle, 44 late-term pregnant cows and heifers were examined 21 to 0 days prior to calving. Mean fetal aortic diameter was 2.07 ± 0.14 cm and mean fetal heart rate (FHR) was 109 ± 17 bpm. Three dead calves were dissected and their aortic diameter was measured in a water bath. The mean birth weight (n = 44) was 39.9 ± 5.8 kg. There was a significant negative correlation between FHR and fetal aor...
Burns SJ, Irvine CH, Amoss MS.This study was undertaken to determine if fertility could be improved by increasing the interval from foaling to breeding. Forty-two mares, not bred during normal post-partum oestrus, were injected with a prostaglandin analogue on Day 6 or 7 following ovulation. Mares were mated artifically with antibiotic-treated semen during the resulting oestrus and, if necessary, for the following 4 cycles. Their fertility was compared, by cycles/pregnancy and rate of fetal loss, to mares bred by the same methods on 86 normal post-partum oestrous periods. The interval from foaling to the onset of breeding ...
Mitchell ARM, Delvescovo B, Tse M, Crouch EE, Cheong SH, Castillo JM, Felippe MJB, Ainsworth DM, de Amorim MD.A 6-year-old Standardbred mare was presented at 339 days of gestation for investigation of abnormal abdominal distension and ventral edema. Transrectal palpation and ultrasound examination revealed the uterus to be enlarged with an excessive volume of fetal fluid, characteristic of hydrops. Gradual transcervical drainage of 55 L of allantoic fluid over 45 minutes, with concurrent intravenous fluid therapy followed by assisted vaginal delivery, resulted in the birth of a live foal with long-term survival. The birth and long-term survival of a foal from a mare with hydrallantois at term has not ...
Aureli G, Lauria A.The results of a study on interstitial cells of the horse gonads from foetal life to puberty are reported. The morphological (also ultrastructural) histochemical, histophysical and histoenzymological findings both in the organ and in monolayer cultures, clarify the problem of the ontogenesis of these cells showing that: --foetal interstitial cells give origin to "xanthochrome" cells; --"xanthochrome" cells in the prepuberal gonad are continuously renewed; --the same type of cells which in th prepuberal period undergo lipochromic degeneration, differentiate at puberty into Leydig cells in the t...
Allen AL, Myers SL, Searcy GP, Fretz PB.The Hematologic values of 19 equine fetuses between 202 and 238 days gestation were compared with those of their dams. The red blood cell (RBC) count, hemoglobin concentration, hematocrit, and mean corpuscular hemoglobin concentration were significantly lower in fetal blood, while the mean corpuscular volume, mean corpuscular hemoglobin, and red cell distribution width were significantly higher. Mares had a significantly higher nucleated blood cell count than fetuses, and all nucleated cells were leukocytes (WBC). Most WBC in mare blood were segmented neutrophils and lymphocytes. In contrast, ...
Morehead JP, Blanchard TL, Thompson JA, Brinsko SP.To determine features of an early fetal loss (EFL) syndrome and evaluate potential risk factors for EFL in Thoroughbred broodmares on 4 farms in central Kentucky. Methods: Retrospective study. Methods: 288 pregnant broodmares. Methods: Year-2001 breeding records for 288 Thoroughbred broodmares were examined. Early fetal loss was defined as loss of a fetus that was viable at > or = 40 days of gestation but was subsequently lost by 5 months of gestation. Results: Overall 2001 EFL rate was 25% (73/288), median gestational age at time of fetal loss was 77 days, and median date of loss was May 7...
The Journal of physiologyFebruary 9, 2006
Volume 572, Issue Pt 1 155-164 doi: 10.1113/jphysiol.2006.105635
O'Connor SJ, Ousey JC, Gardner DS, Fowden AL, Giussani DA.This study investigated, in vivo, the mechanisms underlying the development of cardiovascular function in the horse fetus, with particular relevance to baroreflex function and hind limb vascular arterial reactivity to constrictor agonists. Under general anaesthesia, vascular catheters were inserted and a Transonic flow probe was implanted around one of the metatarsal arteries of 13 horse fetuses, either at 0.6 of gestation (n= 6) or at 0.9 of gestation (n= 7, term approximately 335 days). At least 5 days after surgery, pressor, vasoconstrictor and cardiac chronotropic responses to exogenous bo...
Renaudin CD, Troedsson MH, Gillis CL, King VL, Bodena A.The objective of this study was to determine normal variations in the utero placental thickness during mid- and late gestation in the mare. Normal, healthy pregnant mares (n = 9) were examined monthly from 4 mo of gestation until parturition by transrectal and transabdominal ultrasonography. At each examination, the combined thickness of the uterus and the placenta (CTUP) was measured at the placento-cervical junction (transrectally) and at the uterine body or the uterine horns (transabdominally). In addition, the echogenicity of the amniotic and allantoic fluids was evaluated by transrectal u...
Riera FL, Roldán JE, Espinosa JM, Fernandez JE, Ortiz I, Hinrichs K.Embryo biopsy for fetal sexing has clinical application, but few reports are available of its use within an active embryo transfer program. We evaluated results on biopsy of 459 embryos over one breeding season. There were no significant differences in pregnancy rate between biopsied and non-biopsied embryos (72% vs 73%) or for biopsied embryos recovered at the centre (73%) compared with those shipped overnight (72%). However, the pregnancy rate decreased significantly in shipped embryos biopsied ≥20h after collection. Overall, 86% of biopsies provided a sex diagnosis. The likelihood of a po...
Gupta T, Chatterjee A.Pregnant mare's serum gonadotropin (PMSG) of 10 IU on day 5 of pregnancy induced luteal demise and consequently an absolute resorption of fetuses and placentae resulted on day 16 of pregnancy. Simultaneous regimen of PMSG and indomethacin or cortisone was found to be consistently effective in preventing the luteolytic effect of PMSG. The growth of the fetuses, placentae as well as corpora lutea was found to be parallel to controls. Similarly, shortening of the duration of pseudopregnancy to 10--12 days in the bilaterally hysterectomized rat by PMSG and its retaining the normal duration of 18--...
Fowden AL, Forhead AJ, Ousey JC.Delivery of viable young requires co-ordination of fetal maturation with the onset of labour at term. In turn, this depends on a cascade of fetal and maternal endocrine events. The sequence of these events is broadly similar in most mammals but there are differences in placental hormone synthesis and in the timing and magnitude of key prepartum endocrine changes between species. In most farm animals, maternal progesterone (P4) levels decline and oestrogen levels increase in the last 5 - 10 days before delivery in response to activation of the fetal hypothalamicpituitary-adrenal (HPA) axis and ...
Johns IC, Del Piero F, Wilkins PA.An 11-year-old Thoroughbred broodmare was evaluated for suspected hepatic dysfunction. Clinical signs of hepatic encephalopathy were evident at admission. Hepatic ultrasonographic evaluation revealed an increase in hepatic size, rounded borders and normal echogenicity. There was no evidence of cholelithiasis or bile duct distention. Increased activity of hepatic enzymes, increased bile acid and bilirubin concentration and an increased ammonia concentration were supportive of a diagnosis of hepatic disease and hepatic encephalopathy. Histopathological evaluation of a liver biopsy specimen was c...
Webb PD, Steven DH.The adrenal cortex from twelve fetal foals (gestational ages from 61 to 300 days) was examined by light and electron microscopy. Adrenal glands from three newborn foals were also examined by light microscopy. Between 61 and 100 days of gestation the adrenal cortex became organised into two distinct regions, the zona glomerulosa and zona fasciculata, which grew steadily in thickness until the 300th day. Between 300 days and birth there was a dramatic increase in the width of the zona fasciculata. From 200 days a narrow band of compact cells marked the cortico-medullary border. Though these cell...
Hyland JH, Langsford DA.Foetal death was induced in 10 Standardbred mares at day 45 of gestation by injecting 20 to 45 ml of hypertonic (24% W/V) saline into the conceptus at surgery. Ten mares underwent sham treatment and acted as controls. Blood and urine samples were collected every other day between days 30 and 45 post ovulation and at 0, 3 and 6 h relative to the infusion of saline in the treated mares, or sham treatment in control mares. Blood and urine samples were then collected daily between days 46 and 55 post ovulation. Urine oestrone sulphate (E1S) concentrations, measured by radioimmunoassay, increased b...
