Progesterone is a steroid hormone produced primarily by the ovaries in mares and plays a significant role in the reproductive system of horses. It is involved in the regulation of the estrous cycle and the maintenance of pregnancy. Progesterone levels fluctuate throughout the reproductive cycle, influencing reproductive behavior and physiology. In veterinary medicine, measuring progesterone levels can aid in diagnosing reproductive conditions and managing breeding programs. This page compiles peer-reviewed research studies and scholarly articles that explore the production, regulation, and clinical applications of progesterone in equine reproductive health.
Ousey JC, Houghton E, Grainger L, Rossdale PD, Fowden AL.Progesterone (P4), pregnenolone (P5) and their metabolites are present in maternal plasma in pregnant mares. It is believed that one of these progestagens may maintain myometrial quiescence. The aims of this study were to identify specific progestagens in pregnant mares' plasma and determine whether these differed between mares with healthy or compromised pregnancies. Jugular blood samples were collected between 243 and 351 days gestation from 19 healthy Thoroughbred mares and 14 mares with placental pathology, including placentitis, and other clinical problems (uterine torsion/rupture, colic,...
Youngblood RC, Filipov NM, Rude BJ, Christiansen DL, Hopper RM, Gerard PD, Hill NS, Fitzgerald BP, Ryan PL.Consumption of wild-type (toxic) endophyte-infected tall fescue (E+) by horses during late gestation is known to adversely affect pregnancy outcome; however, little is known of the potential disruptive consequences of E+ consumption by mares during the critical phases of placentation and fetal development in early pregnancy. The objective of this study was to evaluate the detrimental effects of feeding E+ to mares during early gestation. Mares (n = 12) paired by stage of gestation (d 65 to 100) were assigned to diets (six per diet) consisting of endophyte-free (E-) or E+ tall fescue seed (50% ...
Brown-Douglas CG, Firth EC, Parkinson TJ, Fennessy PF.There is little information on age, weight and time of year of puberty in Thoroughbred horses, and the interpretation of such data is difficult due to the wide variety of descriptions of the onset of puberty. Objective: To examine the age, bodyweight and date of onset of puberty in Thoroughbreds born in spring and autumn. Methods: Bodyweight data and blood samples were collected in 59 pasture-raised Thoroughbred horses. Five autumn-born and 18 spring-born colts and 3 autumn-born and 33 spring-born fillies were examined from birth to age 13 and 17 months. A testosterone concentration >2 s.d. ab...
Sessions DR, Reedy SE, Vick MM, Murphy BA, Fitzgerald BP.Peripheral insulin resistance is the failure of proper cellular glucose uptake in response to insulin. Insulin resistance and hyperinsulinemia are associated with several disease states in the horse and reproductive function disturbances in humans, including polycystic ovarian syndrome. To test the hypothesis that insulin resistance (IR) and hyperinsulinemia disrupt the estrous cycle in mares, two experiments were conducted to first develop a model to induce IR and to then examine the effect of this model on the duration of the estrous cycle. In Exp. 1, a hyperinsulinemic-euglycemic clamp (HEC...
Ousey JC.The endocrine profiles in the periparturient mares are dominated by increasing concentrations of progestagens and decreasing oestrogens. These hormones are produced by precursors from the foetus, metabolized by the placenta and act primarily on the maternal uterus. The circulating concentrations of hormones in maternal plasma, generally, represent a small proportion of those metabolized by the foetus and utero-placental tissues. There is clear evidence that the foetal hypothalamo-pituitary-adrenal (HPA) axis initiates the process of foetal maturation and the hormonal cascade which culminates i...
Briant C, Ottogalli M, Guillaume D.With the objective of controlling the day of ovulation, 40 mares were assigned to a control or three treated groups: A3d, A4d, and A5d. The treated groups received antarelix (Teverelix 0.01 mg/kg, i.v., twice a day) for 3, 4, or 5 days from the day the dominant follicle (F1) reached 28 mm (=D0), and one injection of hCG (1600 IU, i.v.) on D1, D2, or D3, respectively. Control mares received one injection of hCG when F1 reached 35 mm. Plasma LH, FSH, progesterone, and total estrogens were assayed. In the A3d, A4d, and A5d groups, 9 (90%), 6 (60%), and 5 (50%) out of 10 mares, respectively, ovula...
Glazar BS, McCue PM, Bruemmer JE, Squires EL.Practical estrus synchronization schemes are needed for mares. The Ovsynch synchronization protocol for cattle involves the administration of gonadotropin-releasing hormone (GnRH) to induce ovulation or luteinization of dominant follicles during the luteal phase and prostaglandin 7 days later to cause regression of any luteal tissue and development of a preovulatory follicle. An Ovsynch-type synchronization program potentially could be developed for horses if luteinization or ovulation of diestrous follicles occurred in response to GnRH treatment. The objective of this study was to determine i...
Handler J, Wüstenhagen A, Schams D, Kindahl H, Aurich C.In the present study, the kinetics of the prostaglandin F2alpha (PGF2alpha)-metabolite 15-keto-13,14-dihydro-PGF2alpha after a single intramuscular application of various doses of the natural PGF2alpha dinoprost at Day 7 of the cycle in the mare were investigated. Effects of low doses on estrous cycle length and life span of corpus luteum were examined, because release of PGF2alpha is still under discussion to have detrimental influence on success rates of transcervical transfer of equine embryos. Eight Shetland pony mares were each randomly assigned to each of four treatments: (a) 0.8 mg/100 ...
Viñoles C, Quintans G, Paiva N, Cavestany D.The ovarian responses of anoestrus beef cows to a combined treatment with medroxy-progesterone acetate (MAP) sponges and oestradiol benzoate or equine chorionic gonadotrophin (eCG) were evaluated. Forty-five suckling Hereford cows were allocated to three equal groups. Group 1 received a MAP sponge for seven days plus an injection of 2 mg oestradiol benzoate when the sponge was inserted (day 0) and 1 mg when the sponge was withdrawn; group 2 received identical treatment until day 7, when a dose of 400 iu of eCG was administered, and group 3 were left untreated as control animals. From day 0 to ...
Bollwein H, Weber F, Steffen S, Stolla R.In previous studies, transrectal color Doppler sonography was used to demonstrate an increase in genital blood flow resistance in subfertile mares. The objectives of the present study were to determine the effects of an anticoagulant (acetylsalicylic acid) and a vasodilator (captopril) on uterine and ovarian perfusion and plasma progesterone concentrations in cycling mares. From Day 1 to 11 of an estrous cycle (Day 0=day of ovulation following prostaglandin-induced luteolysis), five Trotter mares were given 2500 mg lactose, 2500 mg ASA, or 50 mg captopril twice daily in their feed (one compoun...
Nagy P, Huszenicza G, Reiczigel J, Juhász J, Kulcsár M, Abaváry K, Guillaume D.Factors influencing plasma progesterone concentration were investigated in seven mares. Two-phase logistic curves were fitted (r=0.98) to plasma progesterone concentrations of blood samples collected once daily. In addition to the effect of time (P<0.001), there were differences (P<0.01) among mares in the peak height of the progesterone plateau and in the (area under the curve) AUC. Plasma progesterone concentrations were higher (P<0.001) after a multiple versus single ovulation. There was an effect of season (P<0.001), but no significant effect of luteal morphology. The retrospec...
Camillo F, Vannozzi I, Rota A, Di Luzio B, Romagnoli S, Aria G, Allen WR.Mules, hybrids resulting from the mating of a horse mare (Equus caballus, 2n = 64) to a Jack donkey (E. asinus, 2n = 62), are generally infertile. Five horse embryos were transferred non-surgically to two cyclic and one acyclic recipient mules. In the mares and cycling mules, oestrus and ovulation were induced with, respectively, d-cloprostenol and human chorionic gonadotrophin (hCG). The acyclic mule, on the other hand, received oestradiol benzoate when the embryo donor was showing oestrus and progesterone after the donor had ovulated and until pregnancy diagnosis. Non-surgical embryo collect...
Guillaume D, Chavatte-Palmer P, Combarnous Y, Duchamp G, Martinat N, Nagy P, Daels PF.The aim of this study was to compare the effects of treatment with repeated injections of sulpiride (a dopamine D2 antagonist) on prolactin secretion and induced lactation in ovariectomized and intact adult mares and to verify if this induction was possible at the beginning and at the end of the birth season. Two experiments were carried out in September [experiment (expt) 1], and in March (expt 2), in France (48 degrees N). In expt 1, three groups of five mares were tested: intact-control, intact-treated and ovariectomized-treated mares. In expt 2, mares previously subjected to artificial pho...
Nie GJ, Johnson KE, Wenzel JG, Braden TD.Mares (n = 30) were treated in the post-ovulatory period with saline, oxytocin, or cloprostenol (Clo). Dose, administration frequency and treatment day (Day 0, 1 or 2 post-ovulation) were evaluated. Interovulatory interval of control cycles was 22.7 (+/-0.36) days with a range of 20.6 (+/-1.44) to 23.8 (+/-1.39) days among all treatment groups. Mares treated with two micro-doses of cloprostenol on Day 2 post-ovulation had the shortest interovulatory interval. This group also had the lowest mean circulating progesterone concentrations on Days 3-7 and 13, and was the slowest group to reach conce...
Nie GJ, Johnson KE, Wenzel JG, Braden TD.Mares (n = 37) were treated from 4h after breeding through 2 days post-ovulation with oxytocin or cloprostenol. Oxytocin (20 units i.m.) was administered every 6 h and cloprostenol (250 mcg i.m.) daily. Luteal function was impaired for several days following treatment, however, lower progesterone levels among cloprostenol treated mares in this study did not result in decreased pregnancies. Pregnancy outcome at 15 days post-ovulation was not different between the oxytocin (13/18) and cloprostenol (13/19) treatment groups, respectively (P = 0.80). The results of this study indicate cloprostenol ...
Pinto CR, Paccamonti DL, Eilts BE, Venugopal CS, Short CR, Gentry LR, Thompson DL, Godke RA.In the present study, follicular fluids of estrous mares treated with saline solution (Control) or nitric oxide synthase (NOS) inhibitors were analyzed for nitric oxide (NO), estradiol-17beta (E2) and progesterone (P4) concentrations before and 36h after administration of human chorionic gonadotropin (hCG). Follicular fluids obtained before (0h) hCG administration from control mares had lower concentrations of NO than those obtained 36h after administration of hCG (58.3+/-17.8 micromol versus 340.4+/-57.7 micromol; P<0.05). A similar pattern was also noted for intrafollicular P4 in control ...
Stecco R, Paccamonti D, Gutjahr S, Pinto CR, Eilts B.Oxytocin is released in response to teasing during both estrus and diestrus in mares, and at least during estrus, teasing results in an increase in electromyographic activity in the uterus. Exogenous oxytocin causes an increase in intrauterine pressure and prior studies have shown that this response is correlated to the day of the estrous cycle. To determine if teasing causes an increase in intrauterine pressure and if this response varies by day of the cycle, intrauterine pressure was measured while mares were teased with a stallion 2 days before ovulation, on the day ovulation was detected a...
Briant C, Ottogalli M, Morel M, Guillaume D.The GnRH antagonist antarelix (Teverelix) was administered to mares (0.01 mg/kg, i.v., twice a day) during the periovulatory period. In Experiment 1, 20 mares were divided into a treated (A3d-) and a control (Control-) group. A3d- mares received antarelix for 3 days from the day when the dominant follicle (F1) reached 32 mm (D0). In Experiment 2, 10 mares were divided into a treated (A6d+) and a control (Control+) group. A6d+ mares received antarelix for 6 days from D0 and hCG was injected in all animals (1600 IU, i.v.) on D1. Pregnancies were determined 13 days after ovulation. In both experi...
Ousey JC, Forhead AJ, Rossdale PD, Grainger L, Houghton E, Fowden AL.In pregnant mares during late gestation, little, if any, progesterone (P4) is found in the maternal circulation. Hence, quiescence of the equine uterus is believed to be maintained by metabolites of pregnenolone and P4 known as progestagens, which are produced by the uteroplacental tissues. However, little is known about the ontogeny, distribution, or actual rates of uteroplacental progestagen production in pregnant mares and their fetuses during the second half of pregnancy. Therefore, the present study measured the rates of uteroplacental uptake and output of eight specific progestagens in c...
Handler J, Königshofer M, Kindahl H, Schams D, Aurich C.We conducted the present study to establish a standardized method for cervical stimulation without affecting the endometrium, and to investigate the effect on estrous cycle pattern and concentrations of progesterone, oxytocin and PGF2alpha-metabolite of cervical dilatation in the mare. Six healthy Haflinger mares underwent three different treatments (control, insertion, dilatation) on Days 5 and 7 of the cycles in different orders according to a Latin square design. During dilatation, the balloon of the catheter was inflated stepwise every 30s with warm physiological saline to a maximum of 50 ...
Rathi R, Colenbrander B, Stout TA, Bevers MM, Gadella BM.Progesterone (P(4)) is a physiological inducer of the acrosome reaction (AR) in stallion spermatozoa. However, the capacitation-dependent changes that enable progesterone binding, and the nature of the signaling cascade that is triggered by progesterone and results in induction of the AR, are poorly understood. The aim of the current study was, therefore, to investigate the protein kinase dependent signaling cascades involved in progesterone-mediated induction of the AR in stallion spermatozoa. In addition, we aimed to determine whether bicarbonate, an inducer of sperm capacitation, acted via ...
Watson ED, Thomassen R, Steele M, Heald M, Leask R, Groome NP, Riley SC.Dominant and subordinate follicles were collected from mares on the day after the dominant follicle reached 30 mm in diameter, to investigate regulation of folliculogenesis during spring transition and the breeding season. Concentrations of oestradiol-17beta, progesterone and inhibin A, but not inhibin isoforms with pro- and alpha C-immunoreactivity, were significantly higher in preovulatory follicles than in dominant anovulatory transitional follicles. Steroidogenic activity was regained gradually in the dominant follicles of successive anovulatory waves through spring transition. The dominan...
Reilas T, Katila T.Uterine lavage fluids from postpartum and nonparturient mares were compared to determine when the normal secretory capacity of the postpartum uterus is restored. Lavage fluids were obtained from cyclic nonparturient mares on the second, fourth or fifth day of oestrus, and 3, 8, or 14 days after ovulation (seven mares/sampling day). Twelve intact postpartum mares were sampled 1 to 28 days postpartum (group A: 1, 6, 12 and 20; group B: 2, 8, 14 and 24; group C: 4, 10, 16 and 28 days postpartum; four mares/group). Three ovariectomized (OVX) postpartum mares were sampled as mares in group C. Sampl...
Evans MJ, Kitson NE, Alexander SL, Irvine CH, Turner JE, Perkins NR, Livesey JH.We wish to use a gonadotrophin-releasing hormone (GnRH) antagonist in the mare as a tool for investigating the control of the oestrous cycle. The aim of this study was to test the effectiveness of the antagonist cetrorelix by testing both in vitro, using perifused equine anterior pituitary cells, and in vivo in seasonally acyclic mares. Pituitary cells were prepared and after 3-4 days incubation, loaded onto columns and given four pulses of GnRH (at 0, 30, 60 and 90 min; dose-response study). After the second GnRH pulse, infusion of cetrorelix began (0, 100, 1000 and 2000 pmol/l) and continued...
Porter RH, Duchamp G, Nowak R, Daels PF.An attempt was made to elicit maternal behavior in non-parturient Welsh pony mares through a combination of hormonal treatment and vaginal-cervical stimulation (VCS). Lactation was induced in 16 nonpregnant, non-parturient mares via a combination of estradiol, progesterone and a dopamine antagonist (sulpiride). During the adoption trials, each lactating mare was confined behind a padded bar and a newborn foal was held near her head. Eight of the mares received two 3-min periods of VCS when the foster foal was introduced. Following VCS, the foal was released and its interactions with the adopti...
Chopin JB, Chopin LK, Knott LM, de Kretser DM, Dowsett KF.An 8-year-old mare, with a foal at foot, was inseminated on foal heat with frozen semen, with the resultant pregnancy lost between days 34 and 41. The right ovary developed a large anovulatory follicle that was non-responsive to multiple doses of ovulating agents. The follicle eventually appeared to luteinise, although plasma progesterone concentrations did not reflect this. Another follicle developed, responded to GnRH and resulted in a pregnancy from frozen semen that went to term with a healthy foal. When the mare was examined after foaling, the structure on the right ovary appeared to be a...
Gérard N, Loiseau S, Duchamp G, Seguin F.Follicular development and ovulatory processes in mammals involve local biochemical changes as a result of substantial modifications in cellular metabolism, the most well known of which is steroid variation. In the present study, the intrafollicular variation of several other components was studied using proton nuclear magnetic resonance ((1)H NMR). This approach made it possible to demonstrate that the intrafollicular biochemical content changes during follicular growth and maturation. Follicular fluid was aspirated by ovarian puncture of the dominant follicle at various physiological stages ...
Henson KL, Alleman AR, Kelley LC, Mahaffey EA.Immunohistochemical techniques were used to examine 29 cases of equine lymphoma for estrogen receptor (ER) and progesterone receptor (PR) expression. The lymphomas examined included T-cell-rich large B-cell lymphomas, B-cell neoplasms, and T-cell lymphomas. The individual cases were also classified according to the anatomic location of the tumors. One normal equine lymph node was also examined for ER and PR expression. All of the cases of equine lymphoma and the normal lymph node were negative for Er. A total of 16/29 (55%) PR-positive lymphomas were identified. Seven of the 12 (58%) T-cell-ri...
Diel de Amorim M, Bramer SA, Rajamanickam GD, Klein C, Card C.Our objectives were to examine changes in endometrial and luteal gene expression during estrus, diestrus, pregnancy and treatments to induce luteolysis and putatively induce luteostasis. Groups were: Diestrus (DIEST), Estrus (ESTR), Pregnant (PREG), Oxytocin (OXY), Carbetocin (CARB), and Meclofenamic acid (MFA). Blood was obtained from day (D)12 to D15 for measurement of oxytocinase, also referred to as leucyl-cysteinyl aminopeptidase (LNPEP) and progesterone. Luteal biopsies were obtained on D12 and D15 and an endometrial biopsy on D15. Real-time RT-PCR was performed for the following genes: ...
Bartolome JA, Wallace SP, de la Sota RL, Thatcher WW.The objective was to evaluate the effect of equine chorionic gonadotropin (eCG) and hCG post artificial insemination (AI) on fertility of lactating dairy cows. In Experiment 1, cows were either treated with eCG on Day 22 post AI (400 IU; n = 80) or left untreated (n = 84). On Day 29, pregnant cows were either treated with hCG (2500 IU; n = 32) or left untreated (n = 36). Pregnancy and progesterone were evaluated on Days 29 and 45. In Experiment 2, cows (n = 28) were either treated with eCG on Day 22 (n = 13) or left untreated (n = 15) and either treated with hCG on Day 29 (n = 14) or left untr...
Tarko A, Fabová Z, Kotwica J, Valocký I, Alrezaki A, Alwasel S, Harrath AH, Sirotkin AV.The influence of environmental contaminant toluene and of plant fennel (Foeniculum vulgare Mill.) on reproduction are reported, but the mechanisms of their action and the protective effect of fennel on contaminant influence remain to be elucidated. In this study, we hypothesized that toluene and fennel directly affects basic ovarian cell functions, and that fennel can be used as an appropriate natural protective agent against the potential adverse effects of toluene. This study aimed to examine the action of toluene (20 μg/mL) and fennel extract (0, 1, 10, 100 μg/mL), and assess their comb...
Argo CM, Turnbull EB.Spherical (35 mm diameter) glass intra-uterine devices (IUDs) are commonly understood to modify sexual behaviour in performance mares. The effect of IUDs on the endocrinology (luteinising hormone, oestradiol, progesterone, testosterone), ovarian and uterine function, sexual and social behaviours associated with the ovarian cycle were evaluated during the natural breeding season in nine, nuliparous pony mares (4.6±0.5 years old, 230±12 kg bodyweight). Age and weight-matched groups were allocated to sham-treatment (n=5) or IUD-implantation (n=4) groups. Fifty complete ovarian cycles were evalu...
Toishi Y, Tsunoda N, Tagami M, Hashimoto H, Kato F, Suzuki T, Nagaoka K, Watanabe G, Tokuyama S, Okuda K, Taya K.Evaluation of a new chemiluminescent enzyme immunoassay, the PATHFAST assay system (PATHFAST), for measurement of circulating progesterone in mares was performed. Five mares at the mid-luteal stage were administrated a single i.m. injection of prostaglandin F2α analog (PGF2α; cloprostenol 250 μg/ml), and then blood samples were collected from the jugular vein at 0, 15, 30 and 45 min, at one-hour intervals until 24 and at 48 hr via a catheter in the jugular vein. To monitor the physiological changes in circulating progesterone in mares after induced luteolysis, concentrations of progesterone...
Oquendo PS, Silva ESM, Oquendo FMG, Cuervo-Arango J, Beletti ME.The effect of three different hormonal protocols to prepare anestrous recipient mares on embryo survival was evaluated. The first group consisted of only progesterone administration (NE) 4 days before embryo transfer, while the recipients from the other two groups received a single administration of 2.5 mg of oestradiol benzoate (SE) 2 days earlier or 8 mg of oestradiol split in increasing doses for 5 consecutive days (LE) ending 3 days before progesterone treatment. The likelihood of recovering an embryo 2 days after transfer was 46.1% (6/13), 62.5% (5/8) and 85.7% (6/7) for recipie...
Ginther OJ, Gastal EL, Gastal MO, Siddiqui MA, Beg MA.The effects of ultrasound morphology, vascularity, and follicular-fluid hormones of the preovulatory follicle on oocyte recovery rate and on follicle and oocyte maturity rates were studied for 60 spontaneous and solitary preovulatory follicles in mares. An ovulation-inducing dose of hCG was given when the follicle was >or=32 mm (Hour 0), and a procedure for oocyte recovery was done 30 h later (Hour 30). Between Hours 0 and 30, diameter of the follicle increased less and circulating estradiol (E2) concentrations decreased more in groups with successful versus nonsuccessful oocyte recovery an...
Pinto CR, Paccamonti DL, Eilts BE, Venugopal CS, Short CR, Gentry LR, Thompson DL, Godke RA.In the present study, follicular fluids of estrous mares treated with saline solution (Control) or nitric oxide synthase (NOS) inhibitors were analyzed for nitric oxide (NO), estradiol-17beta (E2) and progesterone (P4) concentrations before and 36h after administration of human chorionic gonadotropin (hCG). Follicular fluids obtained before (0h) hCG administration from control mares had lower concentrations of NO than those obtained 36h after administration of hCG (58.3+/-17.8 micromol versus 340.4+/-57.7 micromol; P<0.05). A similar pattern was also noted for intrafollicular P4 in control ...
Cuervo-Arango J, Beg MA, Ginther OJ.The objective was to determine differences in follicle and reproductive hormone characteristics in mares with ovulatory and flunixin meglumine (FM)-induced anovulatory cycles. Estrous mares were given 1500 IU hCG when the follicle was ≥ 32 mm (0 h). In Experiment 1, control mares (n = 7) were not treated further. The remaining mares (n = 11) were given 1.7 mg/kg FM i.v. twice daily, from 0 to 36 h after hCG treatment. Blood samples and ultrasonographic examinations were performed every 12 h. All control mares ovulated normally between 36 and 48 h. In contrast, eight of 11 FM mares did not ov...
Daels PF, Stabenfeldt GH, Hughes JP, Odensvik K, Kindahl H.The role of decreased luteal activity in embryonic loss after induced endotoxemia was studied in mares 21 to 35 days pregnant. Fourteen pregnant mares were treated daily with 44 mg of altrenogest to compensate for the loss of endogenous progesterone secretion caused by prostaglandin F2 alpha (PGF2 alpha) synthesis and release following intravenous administration of Salmonella typhimurium endotoxin. Altrenogest was administered daily from the day of endotoxin injection until day 40 of gestation (group 1; n = 7), until day 70 (group 2; n = 5), or until day 50 (group 3; n = 2). In all mares, secr...
Newcombe JR, Wilsher S, Cuervo-Arango J.Mares are seasonally polyoestrous breeders. Therefore, the first ovulation of the season, following winter anoestrus, is the only cycle in which mares ovulate without the presence of an old CL from the previous cycle. The objective of this study was to compare the length of oestrous behaviour, and plasma progesterone concentrations during the early post-ovulatory period between mares after the first and second ovulation of the breeding season. Overall, 38 mares and 167 oestrous periods were used in the study. From those, 11 mares were used during the first and subsequent oestrous period to mea...
Weber JA, Causey RC, Emmans EE.To evaluate the technique of ultrasound-guided luteal injection in mares, PGF2alpha was administered under ultrasound guidance to horse mares (n = 7 to 9 per group) on Day 9 postovulation via either a systemic (i.m.; zero, 0.01, 0.1, or 5 mg/dose) route or a local intraluteal (i.l.; zero, 0.01 or 0.1 mg/dose) route. The luteolytic efficacy of each treatment was determined based on post-treatment decreases in progesterone concentration, interval to uterine edema (IE) and interovulatory interval (IOI). Local administration of PGF2alpha directly into the CL consistently induced luteolysis, at dos...
Taverne MA, van der Weyden GC, Fontijne P, Dieleman SJ, Pashen RL, Allen WR.Uterine electromyography was performed by means of chronically implanted surface electrodes in 3 Pony mares during spontaneous oestrous cycles and following luteolysis induced by a prostaglandin analogue (fluprostenol). Three distinct patterns were recognized during the oestrous cycle. (1) During oestrus well defined phases of activity with closely grouped high-amplitude spikes were separated by long periods (10-45 min) of complete inactivity. (2) During dioestrus more diffuse phases of activity with low-amplitude spikes were separated by variable periods of relative inactivity. (3) During lut...
Hunt B, Lein DH, Foote RH.Plasma and milk progesterone concentrations in 13 mares were determined 3 times a week for 5 months, beginning at parturition. The estrous cycle was divided into 2 phases. Estrus was considered to occur when the plasma progesterone concentration was less than 1 ng/ml, with diestrus occurring when plasma progesterone content was greater than or equal to 1 ng/ml. Based on this classification, the period of estrus averaged 8.9 days, diestrus averaged 13.9 days, and the estrous cycle averaged 22.8 days. During estrus, the progesterone concentration in plasma averaged 0.4 ng/ml and in milk averaged...
Walter I, Klein M, Handler J, Aurich JE, Reifinger M, Aurich C.To evaluate changes of glycoconjugate in uterine glands of endometrial tissues obtained from mares. Methods: adult mares. Methods: Uterine biopsy samples were collected during the breeding season and analyzed histologically for signs of chronic endometrial degeneration. Stage of the estrous cycle was established, using clinical examination and determination of hormonal status. Uterine tissue samples were analyzed, using lectin histochemical and immunohistochemical techniques (estrogen and progesterone receptors). Connective tissues were stained to determine alterations of ground substance in p...
Watson ED, Sertich PL.Corpora lutea (CL) were collected from mares during early (Day 4-5), mid- (Day 8-9), and late (Day 12-13) dioestrus. Dispersed cell suspensions were obtained by enzymic digestion of tissue. Two distinct luteal cell populations (large and small) were observed. The proportion of small luteal cells significantly increased as age of CL advanced. Cells (2 x 10(6)) from CL which were incubated for 24 h secreted prostaglandin (PG) F, PGE-2 and 6-keto-PGF-1 alpha (the stable metabolite of prostacyclin). Higher concentrations of all PGs were produced by cells from CL at early dioestrus than from those ...
Rodríguez H, Torres C, Valdés X, Guerra H, Pastor LM, Maccallini G, Bustos-Obregón E.In the female genital tract, spermatozoa must undergo capacitation and acrosome reaction prior to fertilization. A number of factors may induce physiological acrosome reaction assayed in vitro. The aims of this study are to determine the inductive effect of the preovulatory follicular fluid on the sperm acrosomal status in the equine, once some characteristics of the follicular fluid during folliculogenesis had been evaluated. The spermatozoa were obtained from cauda epididymes of adult stallion. Follicular fluid was taken from mare ovarian follicles classified according to their diameter. In ...
Irvine CH, Alexander SL.To study the mechanisms responsible for the unusually slow decline of the ovulatory LH surge in mares, secretion patterns of GnRH, LH and FSH were monitored in pituitary venous blood collected every 2 or 5 min for 10.5-18.0 h from five mares on the third (n = 4) or fifth day after ovulation (first sampling period). To determine the effectiveness of progesterone negative feedback, mares were then given a luteolytic dose of a prostaglandin analogue (PGF2 alpha) and pituitary venous sampling (every 2 or 5 min for 16 h) recommenced 20-22 h later (second sampling period). During the declining arm o...
Ginther OJ, Beg MA.The temporal associations of cortisol, estradiol-17β, and oxytocin with pulses of PGFM at the common hour of transition between preluteolysis and luteolysis was studied in plasma from hourly blood samples in mares (n=8). The transitional hour was determined from progesterone concentrations and occurred between 2PM and 2AM in all mares. Pulses of PGFM were grouped into those occurring at the last pulse of preluteolysis (preluteolytic pulse), at the hour of transition (transitional), and during luteolysis (luteolytic). The preluteolytic PGFM pulse (45±16pg/ml at peak) and transitional pulse (4...
Sato K, Miyake M, Yoshikawa T, Kambegawa A.Concentrations of progesterone and oestrogens were determined by radioimmunoassay in the peripheral blood of 22 Percheron and Breton breed mares from the 6th day of oestrus to the 150th day of pregnancy. Periodical variation patterns for the mean values of oestrone, oestradiol 17beta and total oestrogens in the cycling mares were found, with two peaks on the third day before and the 15th day after ovulation, and one depression on the 6th day of oestrus. In pregnant mares, the concentrations of oestrone and oestradiol 17beta increased rapidly (P less than 0.05) after Day 105 of gestation. Proge...
Rambags BP, van Rossem AW, Blok EE, de Graaf-Roelfsema E, Kindahl H, van der Kolk JH, Stout TA.Insulin is a pancreatic hormone that classically regulates carbohydrate and fat metabolism, but also appears to play a role in various reproductive processes. A preliminary study suggested insulin production by day 10 to 18 equine conceptuses. The aim of the present study was to examine the hypothesis that insulin is the conceptus signal responsible for maternal recognition of pregnancy (MRP) in the mare, or otherwise influences reproductive cyclicity during the MRP period. Six Warmblood mares were treated daily during days 7 to 17 after ovulation of two successive oestrous cycles with either ...
Kirkpatrick JF, Shldeler SE, Lasley BL, Turner JW.This study was carried out to develop an accurate, rapid and inexpensive method for diagnosing pregnancy in uncaptured feral horses by analysis of fecal steroid metabolites and to compare the accuracy of this method with diagnosis by urinary estrone conjugates (E(1)C). Paired urine and fecal samples were collected from 40 sexually mature feral mares during August and October. Urine samples were extracted directly from the soil and analyzed by enzymeimmunoassay (EIA) for E(1)C. Water extracts of fecal samples were assayed by EIA for E(1)C and nonspecific progesterone metabolites (iPdG). Urinary...
Macan RC, Camargo CE, Zielinski BL, Cardoso NGH, de Lara NSS, Bergstein-Galan TG, Weiss RR, Kozicki LE.Timed artificial insemination (TAI) has boosted the use of conventional artificial insemination (CAI) by employing hormonal protocols to synchronize oestrus and ovulation. This study aimed to evaluate the efficiency of a hormonal protocol for TAI in mares, based on a combination of progesterone releasing intravaginal device (PRID), prostaglandin (PGF2α ) and human chorionic gonadotropin (hCG); and compare financial costs between CAI and TAI. Twenty-one mares were divided into two groups: CAI group (CAIG; n = 6 mares; 17 oestrous cycles) and TAI group (TAIG; n = 15 mares; 15 oestrous cycle...
Utt MD, Acosta TJ, Wiltbank MC, Ginther OJ.The acute effects of prostaglandin F(2alpha) (PGF) on circulating oxytocin and progesterone concentrations were characterized in mares during the mid- or late-luteal phase. Pony mares were randomly assigned to the following experimental groups based on treatment with PGF (2.5mg) or saline on Day 8 or Day 13 (Day 0=ovulation): PGF-8, PGF-13, saline-8, or saline-13 (n=7/group). Mares were fitted with indwelling, jugular vein catheters and two blood samples (-5 and 0 min) were collected prior to treatment. Treatments were administered into the jugular vein (0 min) and blood collection continued t...
Kaps M, Okada CTC, Gautier C, Aurich J, Scarlet D, Kuhl J, Aurich C.Behavior during the estrous cycle of mares can affect their performance and therefore inhibition of cyclical ovarian activity is indicated. We hypothesized that implants containing the GnRH analog deslorelin downregulate GnRH receptors and inhibit ovulation in mares. The estrous cycles of Shetland mares were synchronized with 2 injections of a PGF analog. One day after the second injection (day 0), mares received 9.4 (group D1, n = 6) and 4.7 mg deslorelin (D2, n = 5) as slow-release implants or 1.25 mg short-acting deslorelin as a control (C, n = 5). Ultrasonography of the reproductive trac...
Witt MC, Bollwein H, Probst J, Baackmann C, Squires EL, Sieme H.The aim of the present study was to investigate the effects of a gonadotropin treatment to induce superovulation on ovarian and uterine blood flow and its relationship with steroid hormone levels and ovarian response in mares, using color Doppler sonography. Each of six mares were examined sonographically in five cycles for 3 d (t1 to t3) during the follicular development phase (FDP) beginning at a follicle size of ≥ 22 mm, and for 4 d (D-4 to D-1; D0 = Ovulation) in the preovulatory phase (POP). After each examination, total estrogens (E(tot)) and progesterone (P(4)) levels were determined ...
Ababneh M, Ababneh H, Shidaifat F.Phospholipase A2 (PLA2) is a key enzyme for biosynthesis of PGF2α. Real-time RT-PCR and immunohistochemistry were used to determine transcription and cellular distribution of cytosolic PLA2 (cPLA2) in the equine endometrium during the oestrous cycle and early pregnancy. Endometrial biopsy and blood samples were collected from cycling mares on days (d) 8, 11, 15 and 18 (oestrus) (Day 0 = Day of ovulation; n = 5 for each day) and from pregnant mares (n = 4) on d15. Except for mares on d18 and some cyclic mares (n = 2) on d15 with low progesterone (P₄) concentrations (< 3.18 nm), P₄ conce...
Klein V, Müller K, Schoon HA, Reilas T, Rivera del Alamo MM, Katila T.Oestrous suppression by intrauterine devices (IUDs) is caused by prolongation of luteal function, but the biological mechanism is unknown. The aim of the study was to investigate mechanisms which could explain the action of IUDs. Thirty mares were age-matched and either inseminated (AI, n = 15) or fitted with an IUD (IUD, n = 15) and subsequently divided into four groups: AI-P, pregnant (n = 8); AI-N, non-pregnant (n = 7); IUD-P, prolonged luteal phase (n = 7); and IUD-N, normal luteal phase (n = 8). The median ages were 5.5 and 7 years in AI-P and IUD-P groups and 14 and 11 years in AI-N and ...
Jacobson CC, Sertich PL, Mc Donnell SM.To investigate effects of a 5-day oral misoprostol regimen recommended for use in horses as a gastrointestinal mucosal cytoprotectant during colic on mid-gestation pregnancies. Objective: To monitor cervical tone, ultrasonographic characteristics of the uterus, cervix and conceptus, as well as serum progesterone and oestrone sulphate concentrations, and observations of general health, behaviour and comfort of mid-gestation mares given a 5-day course of misoprostol or control treatment. Methods: Eleven light horse and pony mares with known breeding dates were administered 5 µg/kg bwt misoprost...
Gérard N, Monget P.The profiles of insulin-like growth factor-binding proteins (IGFBPs) in follicular fluid have been characterized in a number of mammals (rats, pigs, sheep, cattle, humans) and are good indicators of follicular status. We studied the IGFBP profiles of equine serum and ovarian follicular fluid recovered at various stages of the follicular phase. The levels of IGFBPs were related to the morphology and the steroidogenic activity of the follicles. Follicular fluids were recovered by ultrasound-guided follicular aspiration. In the first experiment, the dominant follicles of 10 mares were partly punc...
