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.
Hillman RB.Thirty-seven induced parturitions involving thirty-one mares were studied over a 2-year period using various doses of oestrogen and oxytocin. The time of appearance and degree of expression of the major clinical signs of parturition, and the time for completion of delivery and the passage of the placenta were significantly influenced by increasing doses of oxytocin. Oestrogen was useful in softening and relaxing the cervix when it was tight, but was not essential to induction when the cervix was already soft and dilating. Fertility was not adversely affected by induced parturition.
Klug E, Treu H, Hillmann H, Heinze H.Artificial insemination using deep-frozen semen was performed on 116 mares in 1973 using twelve ejaculates from eight stallions of the Hanoverian breed. Despite the fact that the quality of the semen used was poor, the majority of the mares inseminated were subfertile and some mares were inseminated during one oestrus only, 44% nevertheless conceived and gave birth to live foals. Of a small group of ten mares inseminated in the same year with fresh semen, seven conceived.
Belonje PC, van Niekerk CH.Attention is drawn to the beneficial effect of improved nutrition during winter and early spring on the ovarian activity of mares. Furthermore, the necessity of an adequate plane of nutrition during early pregnancy to prevent embryonic resorption is stressed.
Allen WR, Rowson LE.Surgical and non-surgical methods used for the recovery and transfer of fertilized horse eggs are described. Sixteen of the twenty-three zygotes recovered surgically between Days 1 to 6 after ovulation from thirty donor mares were transferred surgically to synchronized recipients; seven pregnancies resulted. Seven of the eleven zygotes recovered non-surgically between Days 6 to 8 after ovulation from twenty-eight donor mares were transferred non-surgically to synchronized recipients; five pregnancies resulted.
Short RV.The infertility of the mule has proved a continuing challenge to scientific thought. Since the chromosomal differences between the two parental species are so great as to render normal meiosis impossible, it is postulated that all mules and hinnies are sterile. The problem now is to explain how mules and hinnies can occasionally produce spermatozoa or ova. The appearance of the mule was sufficient to persuade the ancients that both parents, not just the male, must contribute to the make-up of the offspring. The mule has also taught us that, when the number of oocytes in the ovary is reduced, t...
Jeffcott LB.The mechanism of transfer of maternal immunity to the foal is reviewed. Maximal efficiency of macromolecular absorption by specialized cells of the small intestine exists soon after birth. The absorptive cells are progressively replaced by more mature-looking cells incapable of taking up large molecules and the rate of absorption is reduced in a linear decline and ceases completely within 24 hr. Passive antibody levels fall rapidly in the first 4 weeks of life to less than half their original values and have usually completely disappeared by 6 months of age. The foal shows immunological compet...
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...
Arvidson G, Astedt B, Ekelund L, Rossdale PD.Phospholipids in embryonic lung tissue, pulmonary washings and amniotic fluid were measured to study the development of lyng surfactant in the horse. A significant increase in the concentration of total phospholipids in lung tissue and a concomitant rise in the amount of dipalmitoyl lecithin in amniotic fluid between 100 and 150 days of gestation indicated the initial formation of surfactant in the fetal lung during this period.
Douglas RH, Ginther OJ.Prenatal specimens from mares with known breeding dates were used to characterize morphological changes in the fetus and placenta of pony mares. Prenatal characteristics and the day on which each was first found and weights of different components of the equine conceptus are summarized.
Parker WG, Sullivan JJ, Larson LL.The diagnostic value of rectal palpation and immunological assay of PMSG was tested at different stages of pregnancy in mares inseminated with frozen semen in three separate studies. The results were based on foaling success and particular attention was paid to the numbers of inconsistent results obtained by the two tests. Generally, the number of false positive diagnoses was lower for the immunological assay than for palpation in early pregnancy (Days 40 to 60) and the relationship became reversed later in gestation.
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 ...
Lovell JD, Stabenfeldt GH, Hughes JP, Evans JW.The levels of progesterone and total progestins increased during late pregnancy and then fell dramatically during the last few days before parturition, although birth occurred in the presence of significant amounts of plasma progesterone. Oestrogen levels decreased slowly but insignificantly until birth occurred, and then remained at a low level until the post-partum oestrus 10 to 12 days later. Total 11beta-hydroxycorticosteroids were unchanged from Day 45 before to Day 15 after birth. The endocrine pattern of one ovariectomized pregnant mare during the last month of gestation was similar to ...
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.
Raeside JI, Liptrap RM.Urine collections (24 hr) were made at weekly intervals from four Pony mares from the 3rd or 4th month of pregnancy until parturition. Separation of oestrogens on Celite columns was followed by Kober measurements of oestrone and equilin. Individual differences were noted in peak amounts of total oestrogens excreted (200 to 800 mg/day), when oestrone constituted 80 to 95% at the 6th to 7th months. Although equilin increased in later gestation, oestrone remained the major product. Total oestrogen values decreased rapidly from the peak and then more gradually towards the end of pregnancy. During ...
Burns SJ, Fleeger JL.Plasma progestagens were measured in eighteen pregnant mares to establish normal levels in the first and last 90 days of gestation. Progestagens increased from 25 ng/ml at 90 days before birth to 60 ng/ml at 10 days before birth, decreased to 58 ng/ml at 5 days before, and were 3 ng/ml or less by 5 days after perturition. During the first 90 days of pregnancy, progestagens reflected luteal activity with an increase in plasma levels from Day 30 to Day 60.
Onuma H, Ohnami Y.Genital tracts from 227 mares slaughtered in various reproductive states were investigated to study egg retention in the oviducts. Eggs were found in 88-2% of 212 non-pregnant mares; the number/mare ranged from 0 to 21, and averaged 4-34. Retained eggs were twice as common in heavy as in light breeds and were found more frequently in early than in late pregnancy. Eggs were not found in the oviducts of two anovulatory post-partum mares. A few globular masses, probably consisting of desquamated tubal mucosa, were frequently lodged in the distal region of the ampulla and appeared, to some extent ...
Squires EL, Ginther OJ.Examination of the ovaries of mares at various stages of pregnancy and after hysterectomy, together with measurement of progesterone concentrations in the peripheral plasma of pregnant and hysterectomized mares and in uterine and ovarian venous plasma of pregnant mares, demonstrated that the primary CL of pregnancy remains functional until at least Day 160 of gestation. The results showed that primary and secondary CL, and the placenta or uterus, all contribute to the total progesterone pool in mares during pregnancy. Similarities and differences in ovarian function observed between pregnant a...
Samuel CA, Allen WR, Steven DH.The various cell types in the adult anterior pituitary may be distinguished at the ultrastructural level of the sizes of the secretory granules within the cytoplasm. In the fetal adenohypophysis, with the exception of prolactin-producing cells, all types may be identified after Day 100 of gestation. Morphological evidence suggests that they are producing and secreting trophic hormones. The three constituent layers of the adrenal cortex are also discernible by Day 100 of pregnancy. The cells of the zona glomerulosa have large numbers of darkly stained inclusions within the cytoplasm. The zona f...
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.
Hernández-Jáuregui , González-Angulo A.Electron microscopy and immunofluorescence techniques were used to study the various epithelial cells in the endometrial cups of ten pregnant mares, and in the uterine epithelium of one non-pregnant mare. Evidence was obtained which suggested that epithelial gland cells within the endometrial cups, as distinct from the hypertrophied decidual-like cells in the cup, may synthesize PMSG. The suggestion does not agree with the findings of other workers in the fetal origin (chorionic girdle cells) of this gonadotrophin.
Nishikawa Y.Retention of high motility of horse spermatozoa preserved at 4 degrees C was improved by a semen extender. Raw semen preserved for 2 to 8 hr at 4 degrees C gave an average conception rate of 67-3% but preservation for 1 to 2 days gave an extremely low conception rate. The conception rate from deep-frozen semen during 8 years was 56-3%.
Osborne VE.Foaling figures for Thoroughbred mares in Australia show a puzzling disparity between conception and foaling rates in the second half of the 22 years of official data collection between 1950 and 1972. In the first 9 years of the survey, the live foal percentages rose in parallel with conception rates, but then a divergence of the figures occurred with the conception rate continuing to improve by 6-25% while the foaling rate improved by only 0-01% over the same period. An hypothesis supported by data from two studs is considered that stress factors additional to those experienced by mares in th...
Mitchell D, Allen WR.Reproductive performance was studied in 137 yearling mares run with stallions in small groups for 3 months between June and August in 1968 to 1971 (four breeding seasons). Pregnancy diagnosis by repeated rectal palpation and qualitative tests for PMSG, showed that ninety-five mares conceived of which forty-four aborted spontaneously between Days 30 and 160 of gestation. Laboratory examination of twenty-one aborted fetuses failed to show any infectious agents. Serial quantitative and qualitative tests for PMSG in aborting animals gave results similar to those observed in mares with normal pregn...
Platt H.Many infections of the equine placenta and fetus result from ascending spread along the cervical canal. Most abortions due to infection occur during the later stages of pregnancy and the possible effects of intrauterine infection on the developing fetus and young foal are discussed.
Parker WG, Sullivan JJ, First NL.Fifty mares were inseminated on Days 2, 4, 7, 11 or 17 of the oestrous cycle with spermatozoa from one of three stallions to observe the distribution of the spermatozoa in various parts of the reproductive tract 12 hr later (Days 3, 5, 8, 12 and 18). Only 0-06 to 2-21% of inseminated spermatozoa were recovered from the tract. More (P less than 0-05) spermatozoa were recovered from the cervix and uterus on Day 12 than on Days 3, 5, 8 and 18. The mean number of spermatozoa recovered from either or both oviducts was significantly greater (P less than 0-10) on Days 5 and 8 than on Days 3, 12 and 1...
Holtan DW, Nett TM, Estergreen VL.Peripheral plasma progestagens were quantified by a competitive protein-binding assay throughout pregnancy. The level of progesterone increased significantly between Days 0 and 8 (P less than 0-05) and again between Days 28 and 44 and reached a maximum on Day 64. Subsequently, it fell slowly until about Day 300 and then rose again during the last 30 days before reaching a minimum on the day after foaling. Very low concentrations of 17alpha-hydroxyprogesterone were found except between Days 40 and 120 and during the last 30 days before birth. Two unidentified compounds, one eluting slightly bef...
Allen WE.The ovaries of twenty pregnant mares were examined daily, per rectum, for the first 4 months of gestation and note was made of their estimated size and follicular content. Serial blood samples from sixteen of the mares were assayed for PMSG. A marked seasonal effect was noted on ovarian size, follicular content and ovulation rate during pregnancy but there was no such effect on PMSG production. It is concluded that PMSG is synergistic with gonadotrophins of pituitary origin and that the latter hormone are the primary stimulus on the ovary of the pregnant horse.
Rogers PA, Fahey GC, Albert WW.Serum amino acid profiles and other serum characteristics of broodmares and their foals wee studied. Compared with mares, foals had significantly higher concentrations of serum leucine, threonine, aspartic acid, asparagine, glutamic acid, glutamine, proline and tyrosine, glucose, cholesterol, creatinine and phosphorus. Foals had significantly less serum histidine, glycine, cystine, taurine, protein and urea nitrogen. Lysine and/or methionine supplementation of pregnant and lactating broodmare diets were conducted. Changes in serum amino acid profiles caused by dietary amino acid supplemented w...
Yurdaydin N, Tekin N, Gülyüz F, Aksu A, Klug E.An Arab broodmare herd of 30 mares age ranging from 4 to 12 years was grouped into 3 groups (group A, B, C) with 10 mares each and exposed to three different methods of cycle synchronisation. Group A mares received two PGF2 alpha injections 14 days apart. Group B mares got additionally 2,500 IU of hCG 5 days after second prostaglandin application. Group C consisted of mares which had foaled in a synchrony of one week and got a PGF2 alpha injection 3 weeks after parturition. All the mares responding to synchronisation were inseminated closely to ovulation detected by serial rectal palpations wi...
Raz T, Amorim MD, Stover BC, Card CE.The objective of this study was to compare the efficacy of purified equine- and porcine-FSH treatment regimes in mares in early vernal transition. Mares (n = 22) kept under ambient light were examined ultrasonographically per-rectum, starting January 30th. They were assigned to one of two treatment groups using a sequential alternating treatment design when a follicle >or= 25 mm was detected. In the eFSH group, mares were treated twice daily with equine-FSH, and in the pFSH group mares were treated twice daily with porcine-FSH; treatments were continued until follicle(s) >or= 35 mm, and 24 h l...
Williams GL, Amstalden M, Blodgett GP, Ward JE, Unnerstall DA, Quirk KS.Three experiments were conducted during the operational breeding season to confirm that continuous, subcutaneous infusion of low-dose GnRH would not disrupt established estrous cycles (Experiment 1), and test the hypotheses that a similar treatment would stimulate secretion of LH and induce development of ovulatory follicles in persistently anovulatory mares (Experiments 2 and 3). Treatment with GnRH (5 microg/h) increased (P<0.001) serum P4 during the luteal phase (7.7+/-0.5 versus 6.4+/-0.5 ng/mL), tended to increase serum LH (2.6+/-0.27 versus 1.9+/-0.25 ng/mL), and did not modify intero...
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...
Cougouille-Gauffreteau B, Jussiaux M, Trillaud C.The androgenization of a more belonging to a social group where it held a stable hierarchic rank, or a mare recently admitted to this group, increases their status in the hierarchic order and the position acquired is subsequently maintained; in some cases, they continue to rise in the hierarchic order long after the injections of male hormones has been stopped. Some elements of the social behaviour of a stallion appear during the treatment; these elements may persist long after the mares have regained their female hormone balance, corroborated by the establishment of a standard pregnancy.
Lantz KC, Enders AC, Liu IK.In addition to the unique feature of retention of unfertilized ova, the oviducts of mares frequently contain large intraluminal masses with a fibrillar component and some cells. The aim of this study was to identify the cells and examine their relationship to the extracellular components of these masses. Intraluminal masses were examined both in situ and flushed from the oviducts. The nature of the contained cells and their relationship to the fibrils were examined by light microscopy and by transmission and scanning electron microscopy. In some mares the large masses distended the oviduct, bu...
Dos Reis WVA, de Braga D, Júnior MV, Gheller JM, de Deco-Souza T, da Costa E Silva EV, Sampaio BFB, Macedo GG.Dispersed ovulation at the breeding (BS) and anestrus at non-breeding season (NBS) are major impediments to embryo transfer and insemination programmes. The present study aimed to evaluate a hormonal P4/E2-based synchronisation protocol in mares during both the BS and the NBS on ovarian/follicle behaviour. Mares underwent a hormone protocol to synchronise their ovulation during the BS (n = 8) and NBS (n = 10), starting (D0) with the insertion of an intravaginal device containing 1 g of P4 and 7 mg Estradiol Benzoate IM. (EB). On D9, the device was removed and injected with 0.25 mg o...
Fedorka CE, Ali HE, Troedsson MHT.Galectins are proteins that bind to glycans in targeted cells and function in cell-to-cell signaling throughout the body. Galectins have been found to be involved in various reproductive processes, including placental dysfunction, but this has not been investigated in the horse. Therefore, the objective of this study was to assess alterations in galectin expression of the abnormal placenta in pregnant mares. Next-generation RNA sequencing was performed on the postpartum chorioallantois of two placental pathologies following clinical cases of ascending placentitis (n = 7) and focal mucoid place...
Bristol F.Oestrus was synchronized in 220, 300 and 272 mares in 1983, 1984 and 1985 respectively. Mares were given two injections of 250 micrograms fenprostalene 15 days apart except in 1983 and 1984 when 56 and 53 of the synchronized mares were given 1-10 daily injections of 150 mg progesterone and 10 mg oestradiol-17 beta to delay and synchronize post-partum oestrus. At 2 days after the second PG injection or 7 days after the last progesterone + oestradiol treatment, mares were divided into groups of 15-21, and each group was placed in a separate pasture with a stallion for 7 weeks. Pregnancy rates we...
Camacho CA, Estradé MJ, Cazales N, Caballeros JE, Fiala-Rechsteiner SM, Neves AP, Mattos RC.This experiment aimed to verify if the proteins present in a 13 day conceptus induce changes in the equine endometrial ultra-structure, histology, and vascularization, two days after its infusion. Ten healthy cyclic mares were used. Once estrus was confirmed, mares were examined daily to detect ovulation (day 0). After ovulation, mares were examined daily until day seven by transrectal palpation and B-mode and Doppler ultrasonography. In this first cycle, intrauterine biopsies were collected at day seven after ovulation, constituting the Cyclic group (n = 10). In the second cycle, the same mar...
Poradowski D, Chrószcz A.The study consisted of the immunohistochemical analysis of fundic and pyloric mucosa in the equine stomach between the 4th and 11th month of gestation. The accessible material was classified into three age groups using the CRL method. The adult reference group was used to define potential differences between foetal and adult populations of gastric APUD cells. The samples were preserved, prepared, and stained according to the standard protocols. The immunohistochemical reaction was assessed using the semi-quantitative IRS method. The results were documented and statistically analysed. The most ...
Rodrigues LT, Segabinazzi LG, Oliveira SN, Frasson M, Papa FO.Pregnancy rates after embryo transfer (ET) are disappointing in donkey species. This study aims to report two successful ET of mini-donkey embryos using Brazilian Northeastern jennies as recipients. Eighteen embryo flushes were performed 9 days post-ovulation in two non-pregnant mini-donkeys jennies (11 and 7 cycles per jenny). Eleven embryos (61%, 11/18) were collected and transferred to Brazilian Northeastern jennies 4-6 days post-ovulation by conventional (n = 6) or an alternative (n = 5) technique. The alternative method consisted of inserting a Polansky equine vaginal speculum smear...
Giguère S, Macpherson ML, Benson SM, Cox S, McNaughten JW, Pozor MA.Pregnancy induces several physiologic changes that might impact the bioavailability, distribution, metabolism, and excretion of drugs. The objective of this study was to determine the effects of pregnancy on the disposition of oral firocoxib in mares. Seven pony mares received oral firocoxib paste at a dose of 0.1 mg/kg during late pregnancy and again 12 to 33 days postpartum. Firocoxib concentrations were measured in plasma by HPLC with ultraviolet detection. Maximum plasma concentrations were significantly lower in pregnant (50.0 ± 21.8 ng/mL) than in postpartum (73.7 ± 25.6 ng/mL) mares. ...
Voss JL, Pickett BW.The effect of rectal palpation of fertility of non-lactating, normal cyclic mares was studied over 3 years. During the first year (1971), the conception rates in mares after daily paplaption during oestrus only, and during oestrus and the first 50 days of pregnancy, were not significantly lower (P greater than 0-05) than the conception rates recorded in mares not palpated. No abortions could be attributed to palpation. Oestrus lasted longer (P less than 0-05) in non-palpated than palpated mares. During the second year (1972), first-cycle pregnancy rates in two groups of mares palpated daily du...
Berlin D, Steinman A, Raz T.The aim of this prospective study was to investigate possible endocrine components to foal rejection behaviour in post-partum Arabian mares. Arabian mares were divided into two groups based on their maternal behaviour: (1) mares with normal post-parturient behaviour (8 mares); and (2) mares that demonstrated foal-rejecting behaviour post-partum (15 mares). Most mares were visited and sampled twice, in the first and third days post-partum. Serum samples were used for measurement of progesterone, oestradiol and prolactin concentrations. There were no statistically significant differences in oest...
Brück I, Hyland JH.The contributions of 2 biochemical pathways to the total metabolism of glucose (the Embden-Meyerhof pathway [EMP] and the pentose phosphate pathway [PPP]), were assessed for equine embryos recovered on Day 4.5, 7.5 and 11.5 post ovulation. At all developmental stages studied, glucose was metabolized through both pathways. Through the EMP, the amounts of glucose metabolized per nl embryo volume per hour were 4.0, 9.9 and 3.1 pmol, whereas via the PPP, amounts were 0.9, 1.7 and 0.07 pmol for Day-4.5, -7.5 and -11.5 embryos, respectively. The ratio of EMP:PPP with age was 9.7 for Day -4.5 embryos...
Moslemi S, Silberzahn P, Gaillard JL.Explants of equine full-term placenta have been shown to synthesize 19-norandrogens from labelled androgens. Steroid metabolites were purified by silica-gel column chromatography then analysed and quantified by c18-reverse-phase HPLC coupled to a radioactive flow detector. 19-Norandrostenedione was subsequently recrystallized to constant specific activity, providing unequivocal evidence of its synthesis by the equine placenta. 19-Norandrostenedione synthesis appeared to be localized in the microsomal fraction. Regardless of the substrate used, formation of 19-norandrogens was far weaker than t...
Sigler DH, Ericson DE, Gibbs PG, Kiracofe GH, Stevenson JS.Lactating mares were assigned as controls or fed altrenogest (.044 mg.kg body wt-1.d-1) for 15 d after foaling. Mares (n = 6) fed altrenogest were inseminated during the first estrus after treatment and mares (n = 6) in the control group were inseminated during the second postpartum estrus. Ovulation during the estrus in which mares were inseminated occurred 26 +/- 1 d postpartum for treated mares and 36 +/- 1 d postpartum for control mares. The percentage of mares conceiving was not different for control (67%) and alternogest-treated (100%) mares. No differences were observed in tone and size...
Daels PF, Mohammed HO, Odensvik K, Kindahl H.To determine the relative role of endogenous prostaglandin F2 alpha (PGF2 alpha) secretion in cloprostenol-induced abortion in mares that no longer require luteal progesterone secretion for maintenance of pregnancy, and to evaluate the ability of a prostaglandin cyclooxygenase inhibitor (flunixin meglumine) to prevent cloprostenol-induced abortion. Methods: The effect of flunixin meglumine on PGF2 alpha secretion and outcome of pregnancy was compared between mares treated with cloprostenol only and mares treated with cloprostenol plus flunixin meglumine. Methods: Five pregnant mares, aged 4 to...
Ginther OJ, Scraba ST, Nuti LC.Pony mares (n=480) and 16 stallions were assigned to four herds of 60 mares and one stallion (large herds) and to 12 herds of 20 mares and one stallion (small herds). The stallions remained with the herds continuously for all of the large herds and seven of the small herds. In the five remaining small herds the stallion was put into a herd for three hours every two days for 12 observation periods. Pregnancy rates and day of ovulation were estimated by size of embryonal enlargements. Mean pregnancy rates of 51% and 54% were obtained in the small herds and 42% in the large herds during a 48-day ...
Annandale CH, Schulman ML, Kirkpatrick RD.Twelve pony mares were randomly assigned to either a control or a treatment group and inseminated with fresh, raw semen from a single stallion of known fertility in a cross-over trial design. Pregnancy was diagnosed by transrectal ultrasound 12-14 days post-ovulation and then terminated by administration of a luteolytic dose of cloprostenol. Treatment mares received a uterine instillation of 100 ml of electrochemically activated (ECA) saline 4-12 hours post-insemination. Control mares received no treatment post-insemination. Per cycle pregnancy rate was 58.3 % in the control group and 50 % in ...
Hinrichs K, Betschart RW, McCue PM, Squires EL.Mares with preovulatory follicles >33 mm in diameter were administered hCG and were randomly assigned for aspiration of the dominant follicle at 24 h or 35 h after hCG administration. Oocytes recovered at 24 h were cultured for 12 h before transfer and oocytes recovered at 35 h were cultured for 1 h. Oocytes were transferred by flank laparotomy to the oviduct of the same mare, or to the oviduct of another oocyte donor. Recipient mares were inseminated before and after transfer. The oocyte recovery rates at 24 h and 35 h after hCG administration were not significantly different (10/15 (66%) and...
Nett TM, Shoemaker CF, Squires EL.High concentrations of estrogens in the peripheral circulation during late gestation inhibit synthesis of LH and markedly reduce pituitary content of LH at the end of pregnancy in most domestic species. Because blood concentrations of estrogen peak shortly before mid-gestation in the mare and then gradually decrease until parturition, we hypothesized that pituitary content of LH may increase during late gestation. To test this hypothesis 10 horse mares were challenged with a maximally stimulatory dose (2 micrograms/kg) of GnRH on d 240 and 320 of gestation and d 3 after parturition. A separate...
Lapin DR, Ginther OJ.A crude equine pituitary ethanol extract (EE) was used to induce single and miltiple ovulations in seasonally anovulatory pony mares 3-15 years of age. 12 mares were injected daily for 14 days with EE; 6 of the EE-treated mares were also treated with human chorionic gonadotropin (HCG), and 6 control mares received saline vehicle only. In a 2nd experiment designed to determine if EE treatment could induce multiple ovulations in seasonally ovulatory mares, 7 mares were treated during diestrus, 7 mares were treated beginning on Day 1 of estrus, and 7 remained untreated. The results of experiment ...
Lindsey AC, Bruemmer JE, Squires EL.Mares are generally inseminated with 500 million progressively motile fresh sperm and approximately 1 billion total sperms that have been cooled or frozen. Development of techniques for low dose insemination would allow one to increase the number of mares that could be bred, utilize stallions with poor semen quality, extend the use of frozen semen, breed mares with sexed semen and perhaps reduce the incidence of post-breeding endometritis. Three low dose insemination techniques that have been reported include: surgical oviductal insemination, deep uterine insemination and hysteroscopic insemin...
Sirois J, Betteridge KJ, Brault A.Embryo transfer was used in an equestrian teaching center in order to produce as many foals as possible from their preferred mares during a single breeding season. Embryo collection by uterine lavage was attempted in five donor mares on 25 occasions 6.5 days after ovulation. Sixteen of the collection attempts (64%) yielded a total of 17 blastocysts. Of these 17 embryos, 13 were immediately transferred transcervically into recipient mares that had ovulated within two days of the time of ovulation in the donors, three were frozen for later transfer, and one was lost. Eight of the freshly transfe...
Torres-Boggino F, Sato K, Oka A, Kanno Y, Hochi S, Oguri N, Braun J.Seminal characteristics, fertility and the response to semen preservation (liquid storage and cryopreservation) were evaluated in 4 Draft stallions (Percheron 2, Breton 2). Seminal characteristics (gel-free volume, sperm concentration, sperm morphology, percentage of motile spermatozoa) were assessed in 5 ejaculates from each of the 4 stallions. The fertility of the stallions was calculated retrospectively as the accumulated pregnancy rate over 3 breeding seasons. Five ejaculates from each of the stallions were subjected to liquid storage at 5 degrees C. The percentage of motile spermatozoa (P...
Gånheim A, Gånheim A, Jöchle W.In a blinded trial, the effectiveness and safety of 2.2 mg of the GnRH analog deslorelin acetate, administered in a short-term implant (STI) to normally cycling mares in estrus with a dominant ovarian follicle of 30 mm in diameter or larger, were evaluated, using a placebo implant as a negative control. A total of 39 mares received treatments at admittance with pre-randomized implants containing either 2.2 mg or 0 mg deslorelin. Mares were teased daily and examined rectally with ultrasound at 24 h intervals to determine time to ovulation and duration of estrus. The number of breedings and the ...
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...
