Reproduction in horses encompasses the biological processes and mechanisms involved in the breeding and development of equine offspring. This includes the study of reproductive anatomy, physiology, and endocrinology in both mares and stallions. Key areas of interest include the estrous cycle, ovulation, conception, gestation, and parturition. Researchers also examine factors influencing fertility, reproductive technologies such as artificial insemination and embryo transfer, and management practices that impact reproductive success. This page compiles peer-reviewed research studies and scholarly articles that explore the physiological, genetic, and environmental aspects of equine reproduction.
Thomas PG, Ignotz GG, Ball BA, Miller PG, Brinsko SP, Currie B.Oviduct epithelial cells (OEC) increasingly are used to support embryonic development and to study gamete interactions with the female reproductive tract in vitro. This series of experiments was designed to characterize monolayers derived from oviduct epithelium. Epithelial cells harvested from the isthmus and ampulla of the oviducts of five estrous mares were cultured with or without the basal lamina extract, Matrigel. Within each group OEC were cultured in the presence of either estradiol-17 beta or a carrier control. All groups were subcultured three times. Epithelial cell morphology and fu...
Jöchle W.Ovuplant (deslorelin STI), when used in estrous mares with a follicle > or = 30 mm, reliably causes acceleration of ovulation and assurance that > 80% of the treated mares will ovulate within 48 hours. Time to ovulation is reduced by 30 hours or more. Treatment with Ovuplant had no adverse effects on pregnancy rates and did not increase the rate of early twin pregnancies. Treatment did not cause local or systemic side effects beyond short-term local irritation. Mares can be treated repeatedly without the development of tolerance or the loss of effectiveness. These studies have shown that...
Silvia PJ, Meyer SL, Fitzgerald BP.Twelve horse mares were used in a repeated-measures design consisting of 3 replicates of 4 mares each. On Day 6 following ovulation, luteolysis was initiated with an i.m. injection of prostaglandin F2 alpha (PGF2 alpha; Lutalyse, 10 mg). Either 12 (-12) or 36 (-36) h before PGF2 alpha (PRE), blood samples were collected simultaneously from the intercavernous sinus (ICS) and jugular (JUG) vein at 10-min intervals for an 8-h period. Pituitary capacity to exogenous GnRH (2 micrograms/kg BW, i.v.) was evaluated at the alternate time point within this period. Frequent sampling and GnRH challenge we...
Guerin MV, Deed JR, Kennaway DJ, Matthews CD.Plasma melatonin was measured at the winter and summer solstices and the autumn and spring equinoxes in four mares held under natural conditions at 35 degrees S. At all seasons the onset of the nightly elevated melatonin was coincident with or after the time of sunset and the melatonin offset after the time of sunrise. The duration of elevated melatonin was not different from the duration of natural scotophase for each season, with the duration of elevated melatonin longer in winter than the other seasons. Immediately following each 24 hr sampling two mares were resampled in acutely extended d...
Chopineau M, Stewart F, Allen WR.The coding regions of the horse (Equus caballus) and donkey (E. asinus) luteinizing hormone (LH) beta-subunit transcripts were cloned from pituitary gland RNA, in order to investigate their relationships to the corresponding equine chorionic gonadotropin (CG) beta-subunits and to further understand the unusual receptor-binding properties of equine LH and CG. The horse and donkey LH beta-subunit sequences were very similar (97% identity at the nucleotide (nt) level; 93% at the amino acid (aa) level), confirming their very close evolutionary linkage and also indicating that the C-terminal extens...
Milliken JE, Paccamonti DL, Shoemaker S, Green WH.A pseudohermaphrodite horse with aggressive stallion-like behavior and ambiguous external genitalia was gonadectomized. The hypoplastic gonads removed from the abdomen were confirmed by histologic examination to be testes. Examination of blood and fibroblasts revealed a 64,XX karyotype.
Wang X, Kole AR, Greenwald GS.This study was designed to determine whether the major site of eCG neutralization by an antiserum to the hormone is at the peripheral or ovarian level. Hamsters hypophysectomized at oestrus were injected s.c. with 25 iu eCG. Three days later, preovulatory follicles were dissected and cultured for 5 h and the medium was changed every hour. At the end of the first hour of incubation, oestradiol and androstenedione accumulation was high, with a sharp drop over the next 4 h, whereas progesterone concentrations did not change over the entire period. Addition of eCG antiserum to the incubated follic...
Turner RM, McDonnell SM, Hawkins JF.Ejaculation was pharmacologically induced in a 13-year-old Quarter Horse stallion with a spiral fracture of the radius. The owners desired to have semen from the stallion frozen prior to euthanatizing the horse, but because of the debilitating injury, standard methods of semen collection could not be used. With the stallion standing quietly in a stall, a plastic collection bag was positioned over the stallion's penis, and clomipramine hydrochloride (2.2 mg/kg of body weight, IV) was administered. Fifty-five minutes later, xylazine hydrochloride (0.5 mg/kg, IV) was administered. The stallion ej...
Tannus RJ, Thun R.A total of 259 normally fertile mares were examined gynecologically by means of rectal palpation and ultrasonography in order to record the presence of uterine cysts and pregnancy. The incidence of endometrial cysts was 22.4%. Of the 95 cysts observed during the trial, 87.4% were located in the middle and posterior segments of both uterine horns. The size of all endometrial cysts ranged between 3 and 48 mm. When all mares were assigned to three age groups, A 14 years (n = 26), a significant (P < 0.01) increase in the number of endometrial cysts was observed with advancing age (4.3%, 29.1% ...
Klonisch T, Ryan PL, Yamashiro S, Porter DG.To determine the site of relaxin gene expression in equine placentae, a set of degenerate oligonucleotide primers was made according to the published amino acid sequence of the A- and B-chain of equine relaxin (eRXN). Total cellular RNA (tcRNA) from equine placentae at about 120 and 300 days of pregnancy was subjected to reverse transcriptase-polymerase chain reaction (RT-PCR) with use of these primers. A single amplification product of approximately 430 bp was detected in each case by agarose gel electrophoresis. The PCR product was ligated into Bluescript plasmid and sequenced to confirm the...
Belz JP, Glatzel PS.Because of the mare's ability to conceive very soon post partum a thoroughly performed control of the puerperal period is of particular importance. Cytological examinations of uterine content and histological examinations of uterine biopsy specimens provide more detailed information than microbiological examinations of uterine swabs. Uterine content and uterus biopsy specimens of 55 mares were examined histologically on days 3, 6 and 9 post partum. We observed a heavy polymorphonuclear reaction of the endometrium following disturbed puerperal processes especially in cases of retained placenta....
Clemmons AJ, Thompson DL, Johnson L.Gross observation of testicular parenchyma of 1.5- to 2-yr-old horses reveals both light and dark regions. If this gross, differential shading reflects quantitative differences in the development of spermatogenesis and interstitial cell populations, the horse may prove to be a useful model for study of the paracrine relationships associated with initiation of spermatogenesis. The objective of this study was to characterize seminiferous tubules and interstitium of testes with gross, differential shading. Testes with both light and dark regions of parenchyma were obtained from horses 1.5-2 yr ol...
Almadhidi J, Seralini GE, Fresnel J, Silberzahn P, Gaillard JL.Estrogens are the major steroids produced by equine gonads. To identify the cells responsible for estrogen synthesis, an antiserum against purified equine testicular cytochrome P450 aromatase was produced in rabbits. The reactivity and specificity of the antiserum were assessed by ELISA, immunoblot analysis, and immunoneutralization studies. Immunofluorescence microscopy demonstrated that in the male gonad, cytochrome P450 aromatase (P450arom) was localized in the interstitial tissue, whereas, under the experimental conditions used, the Sertoli and germ cells did not show any specific staining...
Berghuis GA, Wesselink HG.Twenty nine mares with retained fetal membranes were treated IV with an oxytocine infusion. Within two hours the placenta released in 24 mares (83%). Twenty six (90%) mares got pregnant during the same season.
Del Campo MR, Donoso X, Parrish JJ, Ginther OJ.Equine oocytes (n = 537) were collected from slaughterhouse ovaries (n = 118 mares) by scraping the internal follicular wall. Preculture record was made of the appearance of oocyte investments (no cumulus, corona radiata only, compact cumulus, expanded cumulus), appearance of cytoplasm (homogeneous, condensed heterogeneous/fragmented), and nuclear maturation stages (germinal vesicle, germinal-vesicle breakdown, metaphase I, metaphase II, degenerated). There was no difference between follicles > 30 mm and follicles < or = 30 mm in the preculture frequency distribution among the 5 nuclear stages...
Johnston GM, Taylor PM, Holmes MA, Wood JL.The Confidential Enquiry into Perioperative Equine Fatalities (CEPEF-1) is an observational multi-institutional prospective study of recovery outcome at 7 days post operatively, as called for by Steffey (1991). Data from 6,255 general anaesthetics (February 91-March 93) were submitted confidentially by 62 clinics. The outcomes of 333 cases which were subjected to euthanasia and which were not classified 'alive' or 'died' at 7 days, were excluded from the analysis. The remaining 5922 cases were analysed to identify risk ratios (RR) between survivors and nonsurvivors for a variety of factors. Th...
Guillaume D, Rio N, Toutain PL.The aims of the present study were to determine basic kinetic parameters and the nycthemeral production rate of melatonin in the horse. Seven pony mares were used for the kinetic studies. Five other pony mares were used under long and short days for the production rate studies. Melatonin was administered by intravenous, oral, and intragastric routes at different dose levels. The plasma melatonin clearance was 1.02 +/- 0.31 l.kg-1.h-1, and the volume of distribution was 0.89 +/- 0.53 l/kg for the 0.4 microgram/kg melatonin dose. The systemic availability after oral and intragastric administrati...
Heilkenbrinker T, Schubert TS, Oetjen J, Pózvári M, Frerking H.In this thesis the influence of pneumo-vagina on the microbiological colonization of the genital tract and their manifestation in cytological smears was examined. For mares with poor vulval conformation a comparison of the bacterial growth before and after plastic surgery of the vulva and vestibulum was carried out, as well as the registration of conception rates after operation and insemination. The biggest reduction of the bacterial content in the reproductive tract was found between vestibulum and cranial section of the vagina. The increased number of contaminant bacteria in the cranial sec...
Schumacher J, Varner DD, Schmitz DG, Blanchard TL.A urethral defect, presumed to communicate with the corpus spongiosum penis, caused hematuria in seven geldings and hemospermia in three stallions. Hematuria in geldings occurred at the end of urination. Hematuria was not observed in stallions with hemospermia. A linear urethral defect was identified, by endoscopic examination, on the convex surface the urethra at the level of the ischial arch of each horse. Cause of the defect was not determined. Two stallions were successfully treated for hemospermia, one by temporary subischial urethrostomy combined with sexual rest for 10 weeks, and the ot...
Hinrichs K, Martin MG, Schmidt AL, Friedman PP.Two experiments were conducted to evaluate the effect of follicular components on the maintenance of meiotic arrest in horse oocytes. In Expt 1, oocytes were incubated for 24 h with follicular fluid, or with granulosa cells suspended either in medium or in follicular fluid at 25 x 10(6) cells ml-1. None of the treatments resulted in significant maintenance of the germinal vesicle stage over that of non-suppressive control. Culture with follicular fluid plus granulosa cells resulted in a significantly higher proportion of oocytes at metaphase I compared with controls. In Expt 2, oocytes were di...
Stock AE, Emeny RT, Sirois J, Fortune JE.It is not known whether the equine preovulatory follicle produces oxytocin or is a target tissue for oxytocin, as has been reported for other species, especially ruminants. Bovine granulosa cells secrete oxytocin, and oxytocin modulates the production of progesterone by granulosa cells in vitro. We examined whether oxytocin plays a comparable role in the equine preovulatory follicle. To test the hypothesis that the equine preovulatory follicle produces oxytocin during estrus and that its production increases in late estrus, preovulatory follicles were isolated during early (Days 1 to 2; n = 4)...
Hernández-Avilés C, Ramírez-Agámez L, Love CC, Friedrich M, Pearson M, Kelley DE, Beckham AMN, Teague SR, LaCaze KA, Brinsko SP, Varner DD.Under in vitro conditions, stallion sperm might preferentially use energy substrates that primarily undergo mitochondrial metabolism. The present study sought to determine the effects of glucose, pyruvate, lactate, or their combinations on the quality of stallion sperm subjected to cooled storage at different temperatures, when using a skim milk-based semen extender. In Experiment 1, no substrate (Control), glucose (40 mM; Glu-40), pyruvate (2 mM, 19.8 mM; Pyr-2, Pyr-19), lactate (2 mM, 19.8 mM; Lac-2, Lac-19, respectively), or their combinations (G/P/L-2 or G/P/L-19, respectively) were ...
Roser JF, Chang YS, Papkoff H, Li CH.A specific and sensitive homologous radioimmunoassay has been developed for equine prolactin, suitable for measuring prolactin concentrations in serum of horses. The sensitivity of the assay ranged from 0.4 to 0.6 ng/ml and the intra- and inter-assay coefficients of variation averaged 6.9 and 15.4%, respectively, for five doses of hormone. Cross-reactivity with other mammalian and nonmammalian prolactins and growth hormones was less than 20 and 0.3%, respectively. Cross-reactivity with equine growth hormone was less than 0.07%. Equine serum and pituitary extracts showed parallel dilution-respo...
Del Campo MR, Donoso X, Parrish JJ, Ginther OJ.Equine oocytes (n = 537) were collected from slaughterhouse ovaries (n = 118 mares) by scraping the internal follicular wall. Preculture record was made of the appearance of oocyte investments (no cumulus, corona radiata only, compact cumulus, expanded cumulus), appearance of cytoplasm (homogeneous, condensed heterogeneous/fragmented), and nuclear maturation stages (germinal vesicle, germinal-vesicle breakdown, metaphase I, metaphase II, degenerated). There was no difference between follicles > 30 mm and follicles < or = 30 mm in the preculture frequency distribution among the 5 nuclear stages...
Maurel MC, Ban E, Bidart JM, Combarnous Y.In the present study we have established an immunochemical mapping of equine Chorionic Gonadotropin (eCG/PMSG) using three monoclonal antibodies (mAbs), namely the antibodies ECG01, E10 and D7, raised against the native hormone. These antibodies do not bind to reduced, alkylated hormone, suggesting that they recognize discontinuous rather than continuous epitopes. We have also assessed the reactivity of mAbs towards human CG, and ovine, porcine, equine and bovine LH and FSH. The antigenic determinant recognized by ECG01 is localized on the alpha-subunit of equine gonadotropins and of human CG ...
Guillaume D, Duchamp G, Nagy P, Palmer E.Classical photostimulation of winter anoestrous mares consists of a light treatment with 14.5-16.0 h white light (100 lux), starting near the time of the winter solstice and ending around the time of the summer solstice. Cyclicity is obtained typically after about 70 days of treatment. The aim of the present study was to establish the minimum number of days of treatment, the lowest light intensity and the duration of light required per day to advance the onset of ovarian activity in winter anoestrous mares. In Expt 1 it was demonstrated that a 35 day exposure to a photoperiod (14.5 h light: 9....
Choi YH, Chung YG, Seidel GE, Squires EL.The objective was to compare culture media for in vitro maturation of equine oocytes and for in vitro culture of zygotes produced from IVF of partially zona-removed oocytes. Cumulus-oocyte complexes from slaughterhouse-derived ovaries were washed in m-Dulbecco's PBS and cultured in TCM-199, F10-DMEM or c-F10-DMEM (50% F10-DMEM + 50% F10-DMEM conditioned medium from culture of an equine trophoblast monolayer for 3 or 4 days). All media included FSH, LH, E2, and 10% FCS. After 28 to 30 h maturation, cumulus expansion was scored from 0 (no expansion) to 4 (fully expanded). Oocytes with a 1st pola...
Robinson CS, Wylie CE, Compston PC, Payne RJ.To describe a technique of canaliculosinostomy into the caudal maxillary sinus to alleviate epiphora secondary to nasolacrimal duct obstruction and to report the long-term outcome in 5 horses. Methods: Case series. Methods: Five client-owned horses. Methods: Case records of all horses presented for chronic epiphora to a single equine hospital that underwent surgical treatment were reviewed. All included horses had a Jones test or dacryocystography to confirm nasolacrimal duct obstruction. All horses were anesthetized and canaliculosinostomy was created from the medial canthus of the eye into t...
Donahue JM, Williams NM, Sells SF, Labeda DP.Over the course of the past decade, actinomycetes have been isolated from the placentas of horses diagnosed with nocardioform placentitis. The incidence of this infection has generally been low, with typically no more than 30 animals affected in most years, but the incidence increased through 1999, with placentas from 144 mares found to be infected. Approximately half of the cases result in loss of the foal. A typical actinomycete with branching mycelium was isolated from placental lesions, and a comparison of the sequence of the 16S rDNA gene against the public databases indicated a relations...
Garcia-Muñoz A, Valldecabres-Torres X, Newcombe JR, Cuervo-Arango J, Garcia-Rosello E.The objective of this study was to determine the effect of exogenous progesterone administration at ovulation and during the early development of the CL, on its future sensitivity to a single administration of PGF2a in mares and cows. Horse Retrospective reproductive data from an equine clinic in the UK during three breeding seasons were used. Mares were divided into: control group, cycles with single ovulations; double ovulation group cycles with asynchronous double ovulations; and PRID group: cycles with single ovulations and treatment with intravaginal progesterone device (CIDR) immediately...
Kareskoski M, Vakkamäki J, Laukkanen K, Palviainen M, Johannisson A, Katila T.Matrix metalloproteinase (MMP)-2 and MMP-9 are gelatinases that take part in several reproductive processes. The aim of this study was to measure levels of MMP-2 and MMP-9 in fractionated stallion ejaculates, and to evaluate the association between these components and semen quality, and sperm longevity during cooled storage. Semen quality were assessed separately for sperm-rich fractions (HIGH), sperm-poor fractions (LOW), and whole ejaculate samples (WE) from 33 stallions. After cooled storage with SP either present or removed, sperm motility and DFI were determined. The relative activity of...
Runcan EE, Pozor MA, Zambrano GL, Benson S, Macpherson ML.The acrosome is a highly specialised region of the spermatozoon that is essential for fertilisation. Defects or dysfunction of this structure have been associated with fertility problems in man and various domestic species including stallions. Current methods of evaluating the acrosome of stallion spermatozoa are time consuming and require specialised equipment, which is cost prohibitive to the average practitioner. Objective: To evaluate 2 conventional stains (Dip Quick and Spermac) and determine their usefulness in assessing acrosome integrity in stallions as compared with specific acrosomal...
McFarlane JR, Czekala NM, Papkoff H.Six samples of pregnant zebra (z) serum from the first and second trimesters of pregnancy were analyzed by RIA and shown to have chorionic gonadotropin levels comparable to that of the mare (0.9-5.3 micrograms/ml); first trimester levels in most cases were higher than second trimester levels. A pool of the sera (10 ml) was fractionated by methods previously employed for the purification of equine (e) and donkey (d) chorionic gonadotropin to achieve a concentration of the zebra chorionic gonadotropin (zCG). A yield of 1.0 mg of glycoprotein was obtained. HPLC analysis of the material indicated ...
Dini P, Weiland A, Boakari Y, Scoggin KE, Esteller-Vico A, Daels P, Ball BA.The goal of this study was to develop a safe, effective, and economical method for permanent sterilization of mares based upon tubo-ovarian ligation performed via colpotomy. In this study, we evaluated the application of a nylon cable tie (zip-tie) to the ovarian pedicle and oviduct of mares to induce ovarian ischemia and tubal ligation without removal of ovaries. Initially, efficiency of zip-ties on the ovarian pedicle was tested in vitro and in vivo. Based on the absence of leakage through the zip-tie ligated vessels in anatomic specimens, we confirmed the potential efficacy of the technique...
Pérez-Marín CC, Vizuete G, Vazquez-Martinez R, Galisteo JJ.Few studies have been published about cryopreservation and embryo assessment in horses and donkeys. Objective: To evaluate the viability of embryos collected from mares and jennies that were cryopreserved by slow freezing or by vitrification. Methods: Randomised controlled experiment. Methods: Horse (n=19) and donkey (n=16) embryos (≤300 μm) were recovered on days 6.5-7.5 post-ovulation and assigned to control or cryopreservation protocols of slow freezing or vitrification. For slow freezing, 1.5 mol/L ethylene glycol (EG) was used. For vitrification, horse embryos were exposed to 1.4 mol/L...
Fitzgerald BP, Affleck KJ, Barrows SP, Murdoch WL, Barker KB, Loy RG.Two groups of mares were exposed to an abrupt, artificial increase or a natural increase in daylength. In both groups, mean LH pulse frequency increased with time of year and was accompanied by a reciprocal decrease in LH pulse amplitude. A non-pulsatile pattern of LH secretion was observed in some mares sampled close to the day of ovulation. Maximum mean LH pulse frequency and the onset of the breeding season occurred earlier in those mares exposed to an abrupt artificial increase in daylength. In blood samples collected frequently, mean serum LH concentrations increased in relation to time o...
Thompson DL, Reville SI, Walker MP, Derrick DJ, Papkoff H.To study the possible role of ovarian androgens in regulation of follicle stimulating hormone (FSH) secretion in the cycling mare, five mature, intact mares were treated with testosterone (20 micrograms/kg of body weight) daily during estrus; five control mares received safflower oil on the same schedule. Mares were teased for estrus and samples of jugular blood were drawn daily through one full estrous cycle. Concentrations of FSH in plasma were measured by a newly developed radioimmunoassay based on anti-ovine FSH serum and radioiodinated equine FSH. Testosterone treatment during estrus had ...
Arthur GH.The effect of intrauterine saline on reproductive function was studied by infusion of mares in anoestrus, dioestrus, oestrus and prolonged dioestrus. Anoestrous mares were unaffected except near the beginning and end of the breeding season when anovulatory heats were induced. Dioestrous mares infused between Days 5 and 9 returned to heat an average of 3-8 days earlier than expected, and infusions during dioestrus were followed by ovulatory heats of normal fertility. Three mares in prolonged dioestrus showed ovulatory heats within 3 to 9 days of infusion. Infusions during oestrus had no appreci...
Engle CE, Foley CW, Witherspoon DM, Scarth RD, Goetsch DD.Three experiments were conducted on the metabolism of stallion sperm. In experiment 1, whole and washed sperm were incubated under aerobic and anaerobic enviroments and analyzed before and after controlled incubation for motility, pH, lactic acid, glucose, fructose, and O2 comsumption. In experiment 2, whole and washed sperm were incubated aerobically and anaerobically with and without uterine tubal fluids. Experiment 3 was the same as experiment 2, except added substrates of glucose and lactic acid were studied. The same examinations were made in experiments 2 and 3 as for experiment 1. Motil...
Chevalier F, Palmer E.Ultrasonic echography in the mare allows pregnancy diagnosis as early as Day 14 after ovulation. In the 1980 and 1981 breeding seasons, a total of 7438 examinations of 4688 mares were performed on several farms with the same apparatus. The accuracy of positive pregnancy diagnosis was estimated to be greater than 95% and of non-pregnancy diagnosis greater than 84%. When abnormal pictures of vesicles are found, it has to be decided whether it is a conceptus or a cystic structure. Most small vesicles do not develop, whereas large ones, deformed shapes, presence of some echoes, or a division insid...
Watson ED, Stokes CR, Bourne FJ.Prostaglandins (PGs) F and E2 were measured in lavage fluid from the uterus of ovariectomised mares after experimental induction of uterine inflammation. Treatment with progesterone alone, or progesterone followed by oestradiol, significantly increased the concentrations of these PGs in the lavage compared with mares treated with oestradiol or control mares. Ovarian steroids, therefore, influenced uterine PG synthesis in response to an inflammatory stimulus. To determine whether the uterine lavage procedure might contribute to the concentrations of prostaglandins in the lavage, the procedure w...
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...
Sales FABM, Azevedo MV, Souza NM, Ferreira-Silva JC, Chaves MS, Junior VR, Rocha JM, Dos Santos Filho JP, Freitas VJF, Oliveira MAL.The aim of this study was to evaluate the correlation between the corpus luteum vascularization with the concentration of progesterone and the fertility of embryo recipient mares. Mangalarga Marchador mares (n = 33) were distributed into groups according to the days (D) after ovulation, as follows: D3 (n = 8), D4 (n = 8), D5 (n = 9), and D6 (n = 8). The evaluations of the corpus luteum, endometrium, and blood collection to quantify the progesterone concentration were carried out on D3, D4, D5, and D6. Among the parameters evaluated, only progesterone concentration on D6 differed from the other...
Kirkpatrick JF, Liu IM, Turner JW, Bernoco M.Twenty-six free-roaming feral mares were immunized against porcine zonae pellucidae (PZP) between February and May, 1988. Eight sexually mature mares received 2 inoculations 2 weeks apart, and 18 mares received 3 inoculations at intervals of 2 and 4 weeks. Analysis of urinary oestrone conjugates (E1C) and non-specific progesterone metabolites (iPdG) in samples collected in October, 1988, revealed that none of the 18 mares that received 3 and only 1 of the 6 mares that received two inoculations were pregnant, whereas 3 of 6 sham-injected control mares and 5 of 11 untreated mares were pregnant. ...
Martínez-Boví R, Zagrajczuk A, Donadeu FX, Skarzynski DJ, Piotrowska-Tomala K, Cuervo-Arango J.Haemorrhagic anovulatory follicles (HAFs) are the most common pathological anovulatory condition in the mare. To enhance understanding of the physiopathology of HAFs, the aim of the present study was to determine the effects of an induced-follicular wave on LH concentrations and follicular fluid factors relevant to the ovulatory process. Mares were allocated to treatment or control groups (n = 7/group) in a crossed over design during 14 oestrous cycles with a period of one cycle occurring when there were no treatments between the times when treatments were administered. In the treatment gr...
Grabowska A, Kozdrowski R.Progesterone plays a crucial role in the maintenance of pregnancy from conception to about 100-120 days of gestation when placenta becomes the main source of gestagens. The aim of the study was to test progesterone concentration 14 days after ovulation in pregnant mares and relate it to peak estral endometrial edema and the presence of intrauterine fluid (IUF) after artificial insemination (AI), the number of treatments against IUF, and the time from AI to the day when the uterus was found free of fluid. Results: Mares were divided into two groups: group A (n = 13; age 10.8 ± 4.5 y...
Hyland JH, Wright PJ, Clarke IJ, Carson RS, Langsford DA, Jeffcott LB.In Exp. 1, 30 Standardbred mares in deep seasonal anoestrus were divided into 3 equal groups and treated with 0, 50 (G50) or 100 (G100) ng GnRH kg-1h-1 for 28 days via osmotic minipumps. Ovulation occurred in 0/10, 3/10 and 7/10 mares respectively (P less than 0.05). Plasma GnRH profiles (Days -6, 0, 2, 6, 12, 20, 28 and 34 relative to pump insertion) were dose-dependent (P less than 0.01) and peaked on Day 12 of infusion. Mean daily plasma LH concentrations were biphasic in treated mares that ovulated, with LH peaks occurring around Day 6 and Days 16-20. By contrast, in treated mares that did...
Brosnahan MM, Silvela EJ, Crumb J, Miller DC, Erb HN, Antczak DF.Invasive trophoblast from Day 34 horse conceptuses survives in extrauterine sites in allogeneic recipients that are immunologically naive to donor major histocompatibility complex class I antigens. The ectopic trophoblast retains its in utero characteristics, including similar lifespan, physiologic effect of its secreted product (equine chorionic gonadotropin) upon the recipient's ovaries, and induction of host immune responses. Immunologic memory has not been considered previously in this experimental system. We hypothesized that primary exposure to ectopic trophoblast would affect the recipi...
Vandeplassche M, Podliachouk L, Beaud R.A study has been made of 44 cases of twin pregnancy in mares. The fetuses, foals, fetal membranes and blood groups of parents and foals were examined in order to determine the incidence of chorio-vascular anastomosis, blood chimaerism and freemartinism. All of the twins proved to be dizygotic and 33 of the 34 pregnancies were bicornual. Fusion of the chorion was seen in 14 of 22 placentas and macroscopic choriovascular bridges were observed in five of these, although blood chimaerism was diagnosed in 11 of 25 cases (44 per cent) examined. This would indicate a high incidence of microchoriovasc...
Samuel CA, Ricketts SW, Rossdale PD, Steven DH, Thurley KW.Endometrial biopsies obtained from mares at different stages of the oestrous cycle, during anoestrus and in various abnormal conditions were examined with the scanning electron microscope. Preliminary observations suggest that the patterns of secretory and ciliary activity in the uterine epithelium are similar to those observed by electron microscopical techniques in laboratory and other large domestic animals. The response of the epithelial cells to hormonal variations and infections is compared with that of the endometrium as seen with the light microscope.
Tortonese DJ, Gregory SJ, Eagle RC, Sneddon CL, Young CL, Townsend J.The intrahypophysial mechanisms involved in the control of gonadotrophin secretion remain unclear. In the horse, a divergent pattern of gonadotrophins is observed at different stages of the reproductive cycle in response to a single secretagogue (gonadotrophin-releasing hormone), and dramatic changes in fertility take place throughout the year in response to photoperiod. This species thus provides a useful model to investigate the regulation of fertility directly at the level of the hypophysis. A series of studies were undertaken to examine the cytological arrangements and heterogeneity of gon...
