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.
Brück I, Anderson GA, Hyland JH.The influence of different maternal plasma progesterone concentrations on embryonic glucose metabolism was studied. Uterine flushes were obtained after treating ovariectomized mares (n = 3) with 0 (control), 100 or 200 mg progesterone daily for 7 d. A group of progesterone-induced proteins (PIP) of Mr approximately 20,000 were identified in flushes from progesterone treatments by SDS-PAGE but were not observed in control flushes. Progesterone-induced proteins were removed from half the pooled flush in each treatment group by Sepharose blue CL-6B. In a 3 x 2 factorial (progesterone treatments, ...
Choi SJ, Anderson GB, Roser JF.In vitro production of free estrogens and estrogen conjugates by intact Day 12.5, 13.5 and 14.5 equine embryos was measured at 2-h intervals over a 24-h culture period. Production of free estrogens was higher for Day 14.5 than Day 12.5 embryos. Differences in production of conjugated estrogens were not significant, but a trend toward increased production with increased age of embryo was apparent. No trend toward increased free and conjugated estrogen production per cell was observed with age. Embryo diameter and number of cells increased with age but varied considerably within groups. The amou...
Kirkpatrick JF, Turner JW, Liu IK, Fayrer-Hosken R, Rutberg AT.Non-lethal management methods are required for wild equids that are protected by law and for deer inhabiting areas where lethal controls are not legal or safe. Single or multiple inoculations of porcine zona pellucida (PZP) vaccine have been delivered to wild horses and deer by means of darts. Contraceptive efficacy in horses after two inoculations ranged from 90% to 100%, and after a single inoculation ranged from 19% to 28%. Mares given a controlled-release form of the vaccine had foaling rates ranging from 7% to 20%. No detectable changes in social organization or behaviours among treated h...
Giger R, Meier HP, Küpfer U.In a retrospective study the gestation lengths of two groups, each consisting of 193 "Freiberger" mares, were compared. The mares of the first group were bred by a donkey, those of the second group by a stallion of the "Freiberger" breed. On average, the gestation length of mares with "Freiberger" foals lasted 336.5 days, and that of mares with mule foals 343.1 days. The difference between both groups was significant (p < 0.001). The shortest and longest observed gestation length of mares with "Freiberger" foals was 307 and 361 days, and that of mares with mule foals 315 and 369 days, respecti...
Meier HP, Gertsch U, Kohler S.Twin pregnancies are a serious problem in stud medicine as they terminate in most cases in abortion, stillbirth or the delivery of dead or weak and deformed foals. In recent years, the introduction of sonography has greatly improved the management of mares with twin conceptuses, in particular monitoring the phenomenon of spontaneous embryo reduction to a single vesicle. This allows supervision of pregnancy with relatively little expenditure and loss of time. We document the spontaneous reduction to single vesicles of unilateral twin pregnancies in a draught- and a warmblood-mare. In both mares...
Sharp DC, Thatcher MJ, Salute ME, Fuchs AR.The effect of transcervical endometrial biopsy on the concentrations of plasma immunoreactive oxytocin and 15-keto-13,14-dihydro-prostaglandin F2 alpha (PGFM) was studied in 18 pony mares on days 8, 12 and 14 after ovulation, days 12 and 14 of early pregnancy and at oestrus. Five biopsy specimens were taken within 15 min and consecutive specimens from each mare were pooled two (A) and three (B) together for measurement of the number of oxytocin receptors. Blood samples were collected at intervals of 5 min for 15 min beginning just before the initial biopsy. Biopsy procedure elicited prompt oxy...
Crossett B, Allen WR, Stewart F.Large quantities of an unusual 19 kDa protein (p19) are secreted into the lumen of the uterus of the mare (Equus caballus) during the oestrous cycle and early pregnancy. p19 associates strongly with the acellular capsule that surrounds the young horse conceptus and is believed to be important in maintaining pregnancy. Here we report the complete cDNA sequence encoding p19, its expression patterns in horse tissues and a Southern blot analysis of the gene in horse DNA. The predicted amino acid sequence of the p19 cDNA demonstrated a signal peptide of 18 residues and a mature protein of 162 resid...
Watson ED, Thomson SR.Aromatase P-450 (P-450arom) is a crucial regulatory enzyme that is necessary for conversion of androgens to oestrogens. Corpora lutea and follicles were obtained from the ovaries of cyclic mares and from mares at day 20 and days 40-70 of pregnancy. The presence of P-450arom within specific cell types was investigated by immunostaining to determine potential sites of oestrogen synthesis. Immunoreactivity for P-450arom was confined to the granulosa layer of non-atretic follicles > 5 mm in diameter and to corpora lutea at all stages of the oestrous cycle and during pregnancy. These findings co...
Rasch K, Schoon HA, Sieme H, Klug E.The aim of this field study was to examine the influence of the uterotonic substance oxytocin in 2 different therapeutic dosages of 15 and 25 i.u., respectively on the uterine drainage of oestrous mares and on their fertility. In addition endometrial biopsies of mares with and without intrauterine fluid accumulations around the time of ovulation were evaluated histomorphologically regarding the aetiology of susceptibility to uterine infection. A population of 59 Hanoverian Warmblood mares was used in this study. The mares were divided into Group A (mares with intrauterine fluid accumulations [...
Gastal MO, Gastal EL, Kot K, Ginther OJ.The temporal relationships among day of conceptus fixation (cessation of mobility), conceptus diameter, uterine tone, uterine contractility, and myometrial and endometrial thickness of the middle and caudal segments of the uterine horns were assessed in 13 pony mares with fixation in the caudal segment of a uterine horn. The mean day of fixation (14.9 +/- 0.3) was established by 2-h mobility trials. Uterine tone increased (P < 0.0001) gradually over Days 11 to 21, whereas uterine contractility decreased (P < 0.0001) between Days 14 and 18. The diameter of the spherical embryonic vesicle ...
Hochi S, Maruyama K, Oguri N.The present study was designed to examine the suitability of ethylene glycol as a cryoprotectant for equine embryos. Blastocysts recovered nonsurgically from Day 6 donor mares were cryopreserved by conventional 2-step freezing in the presence of 10% ethylene glycol (EG), 10% glycerol (Gly), or 10% ethylene glycol + 0.1M sucrose (EG + Suc). After thawing, the EG and Gly were removed by a 6-step manner, and the EG + Suc was diluted to one fourth in the freezing straw. The postthaw blastocysts were transferred nonsurgically into the uteri of recipient mares on Days 4 to 7 after ovulation. Pregnan...
Daels PF, Besognet B, Hansen B, Mohammed H, Odensvik K, Kindahl H.To determine the role of progesterone in the regulation of endogenous prostaglandin F2 alpha (PGF2 alpha) secretion during cloprostenol-induced abortion and to investigate use of progestins to prevent prostaglandin-associated abortion. Methods: 16 pregnant mares. Methods: To induce abortion, cloprostenol (250 micrograms/d) was administered daily until fetal expulsion or for up to 5 days. In experiment 1, 8 mares, 98 to 153 days' pregnant, received progesterone (300 mg/d) at 24-hour intervals for 5 days, starting 18 hours after the first cloprostenol administration. In experiment 2, 8 mares, 93...
Besognet B, Hansen BS, Daels PF.We have previously demonstrated that daily administration of the dopamine D2 antagonist, sulpiride, during seasonal anoestrus, effectively advances the mean time of onset of the breeding season in mares. The purpose of this study was to examine the effect of sulpiride administration on pulsatile FSH and LH secretion in seasonally anoestrous mares, follicular development, time of first ovulation and the fertility at the first ovulation. Fourteen anoestrous mares were selected based on progesterone concentrations < 1 ng ml-1 for 3 weeks and largest follicle diameter < 20 mm. Starting 30 Ja...
Vagnoni KE, Schram BR, Ginther OJ, Lunn DP.Equine chorionic girdle cells are a subpopulation of highly invasive trophoblast cells that attach and invade the uterine epithelium on Day 35 (Day 0 = day of ovulation). These invading chorionic girdle cells form endometrial cups that are associated with a marked local maternal leukocytic response that may result in the demise of the cups at Day 120 of pregnancy. Once endometrial cups become established in the uterine wall they do not express MHC antigens, and therefore may only be susceptible to non-MHC restricted cytotoxic cells. The susceptibility of cultured chorionic girdle cells to LAK ...
Edens LM, Crisman MV, Toth TE, Ahmed SA, Murray MJ.The objectives of this study were to: (1) develop a technique to analyze the in vitro cytotoxic activity of lymphocytes from adult horses against equine herpesvirus-1 (EHV-1) infected allogenic equine dermal fibroblasts (EDF); (2) evaluate the ability of a 72-h in vitro incubation with interleukin-2 (IL-2) to enhance the lymphocytic cytolytic activity against EHV-1 infected EDF; (3) compare the cytotoxic activity of lymphocytes isolated from pregnant mares and non-pregnant mares against EHV-1 infected EDF; (4) ascertain if any correlations existed between the percent cytotoxicity and percentag...
Schutzer WE, Kerby JL, Holtan DW.Trilostane, a competitive inhibitor of 3 beta-hydroxysteroid dehydrogenase, was administered intravenously to pregnant mares (n = 3) between day 277 and day 282 of gestation to determine its effect on the progestin milieu. In addition, placental tissue from mares at mid-gestation (150-300 days) (n = 4) were exposed to either deuterium-labelled pregnenolone alone or deuterium-labelled pregnenolone and trilostane to examine the effect of trilostane on placental metabolism of pregnenolone. Blood samples were collected from indwelling jugular catheters at frequent intervals for 48 h after infusion...
Maher JK, Tresnan DB, Deacon S, Hannah L, Antczak DF.Down-regulation of major histocompatibility complex (MHC) genes by trophoblast cells is considered to be a primary mechanism preventing maternal immune rejection of the fetal-placental unit in mammalian pregnancy by rendering these cells, which form the primary barrier between mother and fetus, relatively non-antigenic. In situ hybridization with probes encoding human and horse MHC class I genes was used to characterize the pattern of MHC class I mRNA expression in the various forms of horse trophoblast. Strong hybridization signals were observed in the invasive trophoblast cells of chorionic ...
Enders AC, Meadows S, Stewart F, Allen WR.The mature preinvasive chorionic girdles of horse, mule, donkey and extraspecies donkey-in-horse conceptuses, and the very young endometrial cups on d 37 of gestation in mares carrying horse, mule and transferred donkey-in-horse conceptuses, were compared histologically and ultrastructurally to determine possible mechanisms underlying failure of endometrial cup development in the donkey-in-horse model of equine abortion. The progenitor chorionic girdle from the failing donkey-in-house pregnancy was similar in size to the normal donkey chorionic girdle but the trophoblast cells within the forme...
Barber JA, Troedsson MH.A 12-year-old Arabian mare with a history of repeated early embryonic losses gave birth to a mummified fetus. The fetus was not the result of a pregnancy with twins. The mare had been given a progestogen throughout gestation and expelled the mummified fetus at about 325 days of gestation, 2 weeks after progestogen treatment was discontinued. We estimate that the size of the fetus was consistent with a fetal age of 5 months. The mare and mummified fetus illustrated that progestogen administration after 100 days of gestation can promote retention of a nonviable fetus. When the fetoplacental unit...
Bracher V, Mathias S, Allen WR.Placentation between 80 and 220 days of gestation was studied by measurement of fetal dimensions and gross, light and transmission and scanning electron microscopic examinations of the allantochorion and endometrium from 4 fertile mares with no, or very mild, endometrial histopathology and 6 subfertile Thoroughbred mares suffering varying degrees of age-related chronic degenerative endometritis (endometrosis). Spontaneously occurring twin gestation was observed in 3 animals. Several of the subfertile mares had endometrial cysts which showed 2 distinct features during pregnancy: those located n...
Reef VB, Vaala WE, Worth LT, Sertich PL, Spencer PA.Mares with complicated pregnancies (illness, problems at parturition or delivery of an abnormal foal, n = 30) were scanned transabdominally from 298 days gestation to term in order to measure fetal size, evaluate fetal well-being and characterise the intrauterine environment. The results of the last scan obtained prior to parturition were compared to normal data obtained from fetuses of comparable gestational age to develop a biophysical profile specific for the equine fetus. Twelve mares produced a normal foal (positive outcome) and 18 mares delivered 19 abnormal foals (negative outcome). Bot...
Daels PF, Chang GC, Hansen B, Mohammed HO.We have characterized the testosterone secretion pattern during the first 80 d of pregnancy in mares and determined the sources that contribute to circulating testosterone levels during this period. Ten untreated, pregnant mares (Group 1), 10 altrenogest-treated, pregnant mares (Group 2), and 10 altrenogest-treated, pregnant mares in which the CL was eliminated by administration of PGF-2alpha on Day 16 (Group 3) were used in this study. Complete luteolysis occurred following PGF-2alpha administration in all mares in Group 3. Six of the 10 mares in Group 3 did not have an active CL until after ...
Pycock JF, Newcombe JR.The effects on pregnancy rate of three different treatments to remove intrauterine fluid were assessed in 1267 mares. The mares were mated and allocated, in strict rotation, to four treatment groups: 1) untreated controls, 2) intrauterine infusion of broad spectrum antibiotics, 3) intravenous injection of oxytocin, 4) intravenous injection of oxytocin followed by intrauterine antibiotics. The pregnancy status of the mares was determined 13 to 15 days and 27 to 30 days after ovulation by transrectal ultrasonography. The pregnancy rate of group 4 (72 per cent) was higher than that of group 2 (64...
Smith KC, Mumford JA, Lakhani K.Four Welsh Mountain pony mares at 3 months of gestation and one mare at 5 months were inoculated intranasally with equid herpesvirus-1 (EHV-1: Ab4 isolate) at doses of 10(5) to 10(6.6) TCID50. All five mares became infected, but no cases of paresis or abortion occurred. On days 8, 9, 11, 12 (3-month-pregnant mares) and 13 (5-month-pregnant mare) after infection, a detailed examination of the pregnant uterus was made. Small numbers of vascular lesions with EHV-1 antigen expression in endothelial cells were present in the uteri of the early gestational mares; thrombi were rare and foci of thromb...
Squires EL.Twinning is a major cause of abortion in mares. Although early management of twins is quite successful, twins that remain after 40 days are difficult to manage. This article reviews the current knowledge of the use of transvaginal ultrasound probe for elimination of twins. Several techniques are presented, as well as discussion on the best time during gestation for this technique to be used.
Stewart DR.Equine relaxin (eRlx) immunoactivity has previously been measured in the mare during pregnancy using the porcine relaxin (pRlx) RIA (pRlx-RIA). This was not the optimal system for measurement of eRlx because the dose-response curve obtained with equine plasma was not parallel to the pRlx standard curve. A homologous eRlx-RIA has been developed and used to measure relaxin immunoactivity during pregnancy and parturition in the mare. Highly purified eRlx was used for the generation of antiserum in rabbits, preparation of tracer, and as assay standards. A double antibody eRlx RIA (eRlx-RIA) was de...
Silberzahn P, Zwain I, Martin B.Blood testosterone levels were measured by RIA and gas chromatography-mass spectrometry in the pregnant mare. They were found to increase from the very beginning of pregnancy, reaching peak values 10 times higher than the basal values at the seventh month and then to return to basal values by the week after parturition. Testosterone binding by plasma proteins was investigated in nonpregnant and pregnant mares throughout gestation. Equilibrium dialysis and gel equilibration methods did not reveal any blood specific testosterone-binding activity at any gestational stage. Hence, blood testosteron...
Ginther OJ.Twenty-one pregnant pony mares were assigned to one of the following groups: 1) controls, 2) ovariectomy at Day 12, 3) ovariectomy at Day 12 plus daily progesterone treatment on Days 12 to 40, 4) PGF(2alpha) on Day 12, 5) PGF(2alpha) on Day 21, and 6) PGF(2alpha) on Day 30. Based on daily examinations by ultrasound, the embryonic vesicle was maintained to Day 40 in all control mares and in mares that were ovariectomized on Day 12 and given progesterone. The embryonic vesicle was lost in all mares of the other four groups. Administration of progesterone prevented the embryonic loss associated w...
Sales F, Ferreira-Silva J, Vieira J, Basto S, Filho P, Rocha J, Moura MT, Oliveira M.Post-diluents could potentially increase semen cryotolerance, but remain poorly explored in horses. The aim was to evaluate the efficiency of post-diluents on frozen-thawed semen viability of two stallions (S1-S2). The cryopreserved semen was thawed at 50°C for 40 seconds. Semen motility and acrosin activity (AA) were determined during the thermo-resistance test (TRT). Progressive motility of S2 semen decreased after 60 and 90 minutes of TRT (TRT60 and TRT90) on the control compared to both post-diluents. The total motility of both S1 and S2 decreased on TRT60 and TRT90 semen control versus b...
Klonisch T, Mathias S, Cambridge G, Hombach-Klonisch S, Ryan PL, Allen WR.In situ hybridization employing a cRNA probe derived from a 428-bp fragment of equine relaxin was used to localize relaxin mRNA, and immunocytochemistry was used to localize relaxin itself, in tissues of the placenta-endometrium interface recovered between 33 and 153 days of gestation from mares carrying intraspecific horse, interspecific mule and extraspecific donkey conceptuses. Immunocytochemical staining was also used to localize trophoblast-specific and class I major histocompatibility complex (MHC) antigens on some specimens. Relaxin mRNA and relaxin were both present in the single-cell ...
Ireland FA, Loch WE, Worthy K, Anthony RV.Pregnant pony mares in Group A (n = 4) received i.m. injections at 07:00 and 17:00 h of 0.8 mg bromocriptine/kg body weight 0.75 per day beginning on Day 295 of gestation and continuing until parturition. Group B (n = 4) was treated similarly, but perphenazine was administered orally at 0.375 mg/kg body weight twice a day beginning on Day 305 of gestation and continuing until parturition. Mares in Group C (n = 3) received i.m. injections of saline. Mean plasma prolactin and progesterone concentrations were greater (P less than 0.05) for mares in Group C than in Groups A and B from 295 to 309 d...
Ginther OJ.Recent findings on the origin and development of twins from ovulation (Day 0) to fixation (mean: Day 16) are reviewed. Available data show that almost all twins originate from multiple ovulations. Results of recent ultrasound studies indicate that the number of days between double ovulations does not affect the conception rate per ovum or embryo survival during the first 16 days after each ovulation. Embryo reduction is the natural elimination of excess embryos so that only one embryo enters the foetal stage. In two studies, embryo reduction before or on the day of fixation was not considered ...
Kato H, Seidel GE, Squires EL, Wilson JM.In vitro matured horse oocytes with a first polar body (n = 68) were each injected with a single spermatozoon and divided into 2 groups: Group 1 oocytes were treated with 10 microM calcium ionophore A23187 for 5 min while Group 2 oocytes received no activation treatment. After culture in vitro for 2 days, significantly more oocytes treated with A23187 (5/24, 21%) cleaved than oocytes without activation treatment (2/44, 5%, P<0.05). All 7 cleaved zygotes from both treatment groups were transferred to recipient mares but no pregnancies resulted.
Riera FL, Roldán JE, Gomez J, Hinrichs K.Transfer of donor oocytes to the oviducts of inseminated recipient mares (oocyte transfer, OT) presents a valuable method for production of foals from otherwise infertile mares. Little information is available, however, on factors affecting success of OT in a clinical setting. We report the findings over three breeding seasons in a commercial OT program developed at an equine embryo transfer center in Argentina. Overall, 25 mares were enrolled, and 197 follicle aspiration procedures were performed. The average mare age was 23 years. Follicle aspiration was performed with a needle placed throug...
Silva ES, Frade SC, Ignácio FS, Pantoja JC, Puoli Filho JN, Meira C.The present study evaluated the effect of altrenogest treatment during 70 or 120 days of gestation on pregnancy maintenance in non-cyclic recipient mares and correlated the hormonal interruption findings with number, supplementary corpora lutea (SCL) formation period, and plasma progesterone (P4). Twenty five mares were used as recipients during anestrus, transitional or ovulatory phase and were assigned into groups according to altrenogest treatment period (70ALT, 120ALT or Control groups) or reproductive status at beginning of treatment (Anestrus, Transition or Cyclic/Control groups). Mares ...
Satué K, Domingo R, Redondo JI.The coordinated interaction of the components of the renin angiotensin aldosterone system (RAAS) with reproductive hormones such as progesterone, oestrogens and cortisol during pregnancy has been widely reported to play a vital role in foetal and placental development in various species, significantly influencing the proper achievement of pregnancy and foetal viability at birth. These interactions have not yet been clarified in mares. Thus, the purpose of the present research was to analyse the relationship between cortisol (CORT), progesterone (P4) and oestrone sulphate (OESTRONE), and the co...
Goretti RG, Araújo RR, Filho AN, Araújo GH, Lopes EP, Guimarães JD.The objective was to evaluate the effects of giving prostaglandin F₂(α) (PGF) to donor mares 48 h prior to embryo collection. Non-lactating donor mares (n = 20 estrous cycles in 10 mares), ranging from 2.5 to 10 y of age and 400 to 500 kg of body weight were used from September 2004 to February 2005 in the southern hemisphere (Brazil). Donor mares were randomly assigned in a cross-over design study. During a Treated cycle, 7.5 mg PGF was given 48 h prior to embryo collection, whereas in the Control cycle, 7.5 mg PGF was given at embryo collection. In Treated Cycles, serum progesterone conce...
Kwong GPS, Klein C.Horses are long-day breeders and commence ovarian follicular activity during the spring. Evidence suggests that there is an endogenous circannual rhythm in mares, and it is uncertain whether hormonal manipulation during or immediately following the fall transition induces follicular development. The current study was designed to test the hypothesis that both deslorelin and naltrexone induce follicular development in late fall transitioning or anestrous mares. Five of six mares treated with deslorelin, and 4 of 6 mares treated with naltrexone, developed a pre-ovulatory-sized follicle and were i...
Salem SE, Sinnott A, Roach JM, Verheyen KLP, de Mestre AM.Multiple pregnancies (MPs) are commonly diagnosed during breeding management of mares. Whilst some studies have reported on factors associated with the risk of MPs, few have utilised multivariable data analysis to control for confounding variables. A prospective cohort study of Thoroughbred broodmares was conducted with information collected on 27 factors. Mixed-effects logistic regression was used to determine risk factors for MPs. Mare, stallion, stud, and veterinarian were evaluated as random effects. The prevalence of MPs in 1754 mares and 2245 pregnancies was 16.06% (95% confidence interv...
Marshall DE, Gower DB, Silver M, Fowden A, Houghton E.Equine umbilicus was cannulated in utero and a series of cord plasma samples removed for analysis. After steroid extraction and derivatisation, gas chromatographic-mass spectrometric (GC-MS) analysis demonstrated large differences in steroid content between the plasma samples obtained from the umbilical artery and vein, the blood supplies leading to and from the placental surface, respectively. 3Beta-hydroxy-5,7-androstadien-17-one, dehydroepiandrosterone, pregnenolone, 3beta-hydroxy-5alpha-pregnan-20-one, 5-pregnene-3beta,20beta-diol and 5beta-pregnane-3beta,20beta-diol were identified as maj...
Parker NA, Bailey TL, Bowen JM, Ley WB, Purswell BJ, Dascanio JJ.Like the human female, the mare experiences reproductive tract pathology that may sometimes be circumvented by the use of assisted reproductive technologies (ARTs). One such technology, gamete intrafallopian transfer (GIFT), may be used in mares that exhibit ovulatory, oviductal, or uterine abnormalities that limit the use of common ARTs, such as embryo transfer. Homologous GIFT has been successfully performed in the horse; however, the logistics, costs, and associated risks of surgically transferring gametes to the oviducts of a recipient mare are considerably high. Use of a less costly speci...
Turner RM, Love CC, McDonnell SM, Sweeney RW, Twitchell ED, Habecker PL, Reilly LK, Pozor MA, Kenney RM.An 8-year-old stallion was evaluated because of recurrent urinary tract infections and chronic intermittent urospermia. After extensive diagnostic testing, it was hypothesized that the stallion had a reflex dyssynergia of the bladder and urethral sphincter. Initial attempts to manage the urospermia included semen fractionation, semen collection after voluntary urination, and use of semen extenders. None of these efforts reliably yielded a quality ejaculate. Administration of imipramine hydrochloride (1.2 mg/kg of body weight, PO, 4 hours prior to semen collection) was initiated in an attempt t...
Hyland JH, Bristol F.Oestrus was synchronized in 116 mares by means of an i.m. injection of prostaglandin F-2 alpha (Day 0) and of fluprostenol (a PG analogue) on Day 16. Mares were then randomly divided into three groups. Group A mares (N = 30) were given 2500 i.u. hCG I.M. ON Day 20 and artificially inseminated on Day 21 without detection of oestrus. Group B mares (N = 32) were given 2500 i.u. hCG i.m. on Day 20 and inseminated on Days 21 and 23, also without oestrus detection. Group C mares (N = 54) were teased on Days 18, 19, 21, 23 and 25 and inseminated on Days 19, 21, 23 and 25 while they were in oestrus. S...
Ginther OJ, Griffin PG.The extent and nature of fetal mobility (presentation and location changes) were studied in 10 pony mares by ultrasonic examinations each week during the fetal stage (Day 40 to term). The percentage of examinations with cranial fetal presentation was 35 to 43% during Months 2 to 5 (no significant differences among months); a significant increase occurred between Months 5 and 6 reaching 100% at Month 7. With only 3 transient exceptions, the fetus was in cranial presentation during all examinations from Month 7 to term. The frequency of presentation changes between successive examinations decrea...
Fernandes CB, Loux SC, Scoggin KE, Squires EL, Troedsson MH, Esteller-Vico A, Ball BA.The cervix is a dynamic structure that undergoes dramatic changes during the estrous cycle, pregnancy and parturition. It is well established that hormonal changes, including estrogens, progestogens and prostaglandins, regulate the expression of key proteins involved in cervical function. The arachidonic acid cascade is important in the remodeling and relaxation of the cervix in the days preceding parturition. Despite the complexity of this mechanism, regulation of cervical function has received little study in the mare. Therefore, the objective of this study was to compare the expression of e...
Newcombe JR, Paccamonti D, Cuervo-Arango J.Data were analysed retrospectively from fourteen breeding seasons at an Equine Fertility Clinic for the effect of interval between pre- and postovulatory examinations for immediate postovulatory insemination on pregnancy rate (PR) and embryo loss rate (ELR). Mares of various breeds and ages were examined at intervals which varied from 0.5 to 15h between the pre- and postovulatory period over 867 cycles. When ovulation was detected they were inseminated with a single dose of commercial frozen-thawed semen. All mares were treated in the post-insemination period with intrauterine antibiotics and ...
Morris LH, Allen WR.The need for relatively high numbers of spermatozoa for artificial insemination limits our application of recently available technologies such as sex-sorted semen. The fertility of two different methods of low dose insemination using fresh, frozen and sex-sorted semen are compared in this overview. Satisfactory conception rates are described using very low doses of spermatozoa inseminated by either hysteroscopic or deep uterine insemination methods, proving the stallion is fully fertile. The hysteroscopic method appears to give higher conception rates when inseminating fewer than 5 x 10(6) spe...
Stewart DR, Stabenfeldt GH, Hughes JP.Plasma relaxin concentrations were measured hourly by radio immunoassay in 4 pregnant mares from 11 days before until 4 days after natural foaling. Pre-partum levels ranged from 4 to 7 ng/ml without any surge until the second stage of labour when they increased rapidly to about 11 ng/ml. In 3 of these mares, relaxin activity declined immediately after the expulsion of the placenta and was below detectable levels within 36 h. In the other mare relaxin activity did not fall until after the mechanical removal of the placenta 7 h after foaling. Eight mares were induced to foal by the administratio...
McCue PM, Fleury JJ, Denniston DJ, Graham JK, Squires EL.A technique was developed for oviductal insemination of mares, in which a small number of motile spermatozoa are deposited directly into the oviduct. Pregnancy rates in mares inseminated by traditional intrauterine artificial insemination were compared with rates in mares inseminated by oviductal insemination. Fifteen mares were inseminated with 5 x 10(8) progressively motile spermatozoa by intrauterine artificial insemination, and 14 mares were inseminated with 5 x 10(4) progressively motile spermatozoa by oviductal insemination. Pregnancy rates in mares inseminated by intrauterine artificial...
Lea RG, Stewart F, Allen WR, Ohno I, Clark DA.Endometrial tissue from the gravid uterine horn of pregnant mares was examined by northern analysis and in situ hybridization for mRNA that hybridized to cDNA and RNA probes generated from a mouse TGF-beta 2 1.2 kb cDNA clone. The mouse cDNA probe hybridized to characteristic TGF-beta 2 mRNA transcripts on a northern blot of total RNA isolated from horse endometrium collected at day 45 of gestation. Two major 4.0 and 3.5 kb transcripts and possibly a minor 1.6 kb transcript were observed, consistent with specific hybridization to equine TGF-beta 2 mRNA. By in situ hybridization, riboprobes tra...
Turner DD, Garcia MC, Miller KF, Holtan DW, Ginther OJ.The influence of the ovaries and presence of a foal on periparturient concentrations of FSH and LH were studied in 19 Pony mares. In intact and ovariectomized mares, mean concentrations of FSH fluctuated between 1.1and 9.9 ng/ml on Days -14 to-1 before parturition (Day 0). A surge of FSH occurred in all mares in association with parturition. From Days 1 to 10, the high levels of FSH gradually decreased in the intact group to the minimal concentrations that occur during oestrus, but remained elevated in the ovariectomized mares. There were no significant pre-partum changes in LH in either type ...
Goudet G, Leclercq L, Bézard J, Duchamp G, Guillaume D, Palmer E.This study reports the follicular growth and oocyte competence for in vitro maturation and fertilization under the influence of circulating eCG. Three to 7 successive ultrasound-guided follicular punctures were performed on 4 pregnant mares from Day 23 until Day 75 of pregnancy and on 5 control mares whose embryonic vesicle was crushed on Day 22. All follicles larger than 5 mm were punctured 24 h after the largest follicle reached 18 mm. Expanded cumulus oocyte complexes (COCs) were stained at recovery to analyze the nuclear stage. Compact COCs were cultured in vitro for 46 h and either staine...
Huhtinen M, Reilas T, Katila T.The pregnancy rate is lower in mares inseminated at the first post-partum (p.p.) oestrus (40-50%) compared with pregnancy rates in subsequent oestrous cycles (55-65%). The causes of the lowered pregnancy rate are not fully understood. The aim of the present study was to examine if embryonic defects could be one of the reasons for lowered pregnancy rate. A total of 23 p.p. and 14 non-lactating control mares were flushed 7 days after detection of ovulation. Embryo recovery rate was 48% and 71% in p.p. and control mares, respectively (p = 0.16). Embryos were photographed, measured, graded and sta...
Gibb Z, Grupen CG, Maxwell WM, Morris LH.The fertility of sex-sorted, cryopreserved stallion sperm must be improved for the sex-sorting technology to be applied commercially. Objective: To optimise the conditions used to liquid store stallion sperm prior to sex-sorting and assess the fertility of sperm following sex-sorting and cryopreservation. Methods: Both in vitro experiment and randomised controlled trial in healthy, client-owned mares. Methods: Stallion ejaculates (n = 9) were diluted in either a skimmed milk (KMT) or BSA (I-BSA) based media to 25 × 106 sperm/ml directly (+SP25) or washed to remove seminal plasma and diluted t...
