Ovulation in horses is a physiological process involving the release of an ovum from the ovary, typically occurring during the mare's estrous cycle. This process is regulated by hormonal changes, primarily involving luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Ovulation is a key component of equine reproduction, influencing breeding management and fertility outcomes. The timing and detection of ovulation are critical for optimizing breeding strategies, often involving techniques such as ultrasound examination and hormone assays. This page compiles peer-reviewed research studies and scholarly articles that investigate the mechanisms, detection methods, and implications of ovulation in equine reproductive health.
Raz T, Carley SD, Green JM, Card CE.Reliable methods for regulating oestrus and superovulation in equine embryo transfer (ET) programs are desirable. The objective in this study was to compare two oestrus synchronization methods combined with equine follicle-stimulating hormone (eFSH) treatment in an ET program. In the progesterone and estradiol-17β (P&E) group, mares (n=12) were given progesterone and estradiol-17β, daily for 10 days, followed by prostaglandin (PG)F(2α) on the last day. In the PG group, mares (n=12) were given PGF(2α) 5 days post-ovulation. In both groups donor mares were allocated to eFSH therapy, and were...
Gastal MO, Gastal EL, Beg MA, Ginther OJ.The objective of this study was to evaluate the effect of short-term feed restriction on characteristics of the preovulatory follicle and on concentrations of systemic hormones (leptin, follicle-stimulating hormone [FSH], luteinizing hormone [LH]) and follicular fluid hormones and growth factors (leptin, estradiol, inhibin-A, activin-A, free insulin-like growth factor-1 [IGF1], insulin-like growth factor binding protein 2 [IGFBP2], vascular endothelial growth factor [VEGF]). Mares were submitted to a short-term (48 h) feed restriction when the expected ovulatory follicle was > or =27 mm (Hour ...
Sharma S, Davies Morel MC, Dhaliwal GS.Decreased reproductive performance due to summer stress is a well known phenomenon in farm livestock. Whether this occurs in the mare and specifically how this might affect postpartum reproductive activity and performance, especially at Foal Heat (FH), is unknown. This study, therefore, aims to investigate this and the factors that might affect postpartum reproductive activity. Reproductive records of 228 Thoroughbred mares (694 mare years) bred in subtropical north-western India were retrospectively analysed. Overt oestrous activity occurred within 21 d postpartum in 92.94% (645/694) of mares...
Jacobson CC, Choi YH, Hayden SS, Hinrichs K.Oocytes may be collected from live mares from either the stimulated preovulatory follicle or from all visible immature follicles. We evaluated the yield of mature oocytes, and of blastocysts after intracytoplasmic sperm injection (ICSI), for both follicle types. In Experiment 1, mares were assigned to Progesterone (1.2g biorelease progesterone weekly) or Control treatments. Transvaginal aspiration of all follicles was performed every 14 d. Overall, 596 follicles were aspirated, with a 54% oocyte recovery rate. There was no difference between treatments in number of follicles punctured (9.0 to ...
Rojer H, Aurich C.Recently, successful treatment of mares with a history of persistent mating-induced endometritis (PMIE) with dexamethasone has been reported. As systemic treatment of horses with glucocorticoids should be handled with caution, we tested the hypothesis that treatment with the non-steroid anti-inflammatory drug (NSAID) vedaprofen, an inhibitor of cyclooxygenase-2, may have comparative, positive effects on fertility. Barren mares with a history of repeated PMIE were treated with vedaprofen (n = 8; initially 2 mg/kg bodyweight followed by 1 mg/kg orally twice daily) from 1 day before the first ins...
Mozzaquatro FD, Verstegen JP, Douglas RH, Troedsson MH, DeLaCorte FD, Silva CA, Rubin MI.Ultrasonic-guided transvaginal follicle aspiration was performed in 58 crossbreed mares in order to determine whether aspiration of various dominant follicle diameters resulted in luteal tissue capable of producing progesterone (P(4)). The mares were randomly assigned to three groups according to follicular diameter (25-29 mm; 30-35 mm and >35 mm). Mares that had ovulations naturally served as controls. The serum progesterone (P(4)) concentrations in the aspirated mares were greater (P < 0.0001; r(2) = 0.6687; CV = 21.52) in mares with natural ovulation compared to mares with aspirated follicl...
Checura CM, Beg MA, Parrish JJ, Ginther OJ.The functional relationships among intrafollicular free insulin-like growth factor 1 (IGF1), circulatory gonadotropins, and development of the dominant follicle were studied in 40 mares in two experiments. A GnRH antagonist (Acyline) was given i.m. at the expected beginning of follicular deviation (largest follicle or F1> or =20mm; Day 0) alone (Acyline group) or in combination with intrafollicular treatment of F1 with rhIGF1 (Acyline/IGF1 group). In Experiment 1, blood samples, follicular-fluid samples, and diameter of F1 were taken on Days 1 and 2. In Experiment 2, daily follicular diamet...
Cuervo-Arango J, Newcombe JR.The association between use of hormone treatments to induce estrus and ovulation and the incidence of hemorrhagic anovulatory follicles (HAFs) was studied in a mixed population of mares (Equus caballus) during two breeding seasons in a commercial breeding clinic. Mares treated with cloprostenol (CLO) were more likely to develop HAFs than were mares with spontaneous cycles (P0.05) from that of mares with ovulatory cycles (10.5+/-1.5 yr).
Cuervo-Arango J, Clark A.The mare is a seasonally polyestrus breeder. In early spring, the mare enters a "transition period" between the anovulatory season and the first ovulation of the year. This period is characterized by irregular estrus cycles and high incidence of regressing dominant follicles. There is a belief that pregnancy rates resulting from the first ovulation of the season is lower than in subsequent ovulations, however this has never been studied critically. Progestagens are often used as an aid to manage the transition period. The objective of this study was to compare pregnancy rates of mares from the...
Sessions DR, Vick MM, Fitzgerald BP.Matrix metalloproteinases (MMP) and tissue inhibitors of MMP (TIMP) regulate tissue remodeling events necessary for ovulation. Thus, changes in MMP and TIMP expression and protein enzyme activity were examined in vivo and in vitro during follicular development and atresia in the horse. Equine granulosa cells and follicular fluid from medium (15 to 29 mm) healthy and atretic follicles and from large (>30 mm) healthy and preovulatory follicles were collected by transvaginal aspiration. The cells were either snap-frozen (in vivo study) or cultured for 48 h (in vitro study) to determine gene ex...
Cuervo-Arango J, Newcombe JR.Prostaglandin F(2α) and its analogues (PGF) are widely used in equine reproductive practice. The interval from PGF treatment to ovulation (ITO) varies greatly with a range from 2 to 16 days. Clinical observation suggests that mares mated and ovulated soon after PGF treatment may have poor fertility. Reproductive records of 329 cyclic Thoroughbred mares were analysed retrospectively. The following parameters were analysed: (i) use of cloprostenol; (ii) ITO and (iii) number of ovulations per cycle. According to these parameters, mares were classified into four groups. (i) mares with spontaneous...
Ginther OJ, Gastal EL, Gastal MO, Duarte LF, Beg MA.The effect of the ovarian follicles on plasma concentrations of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) before versus after the expected emergence of the ovulatory follicular wave was studied on Days 0 to 18 (Day 0=ovulation) in four groups of mares (n=6/group). In addition to a control group, all follicles >/=6mm in diameter were ablated on Days 0.5, 6.5, or 12.5 in a herd of mares with reported emergence at 6mm of the future ovulatory follicle on mean Day 10.5. Concentrations of FSH were not different between the Day-0.5 or Day-6.5 ablation groups and the correspon...
Ginther OJ, Siddiqui MA, Beg MA.Responses to intravenous treatment of mares with prostaglandin F2alpha (PGF) 8 d after ovulation were studied in three groups (n=4/group): control (no treatment), bolus (single treatment with 2.5 mg PGF), and infusion (0.1 mg PGF during 2 h). Infusion resulted in a 13,14-dihydro-15-keto-PGF2alpha (PGFM) concentration (559+/-44 pg/mL) that was not different from the mean concentration for the major portion of a natural PGFM pulse associated with luteolysis (569+/-45 pg/mL; n=5). Progesterone in the bolus group increased (P<0.03) between 0 (17.8+/-3.5 ng/mL) and 2 min (25.3+/-4.8 ng/mL), peak...
Kimura J, Kakusho N, Yamazawa K, Hirano Y, Nambo Y, Yokota H, Himeno R.The 3D internal structure microscopy (3D-ISM) was applied to the equine ovary, which possesses peculiar structural characteristics. Stereolithography was applied to make a life-sized model by means of data obtained from 3D-ISM. Images from serially sliced surfaces contributed to a successful 3D reconstruction of the equine ovary. Photopolymerized resin models of equine ovaries produced by stereolithography can clearly show the internal structure and spatial localizations in the ovary. The understanding of the spatial relationship between the ovulation fossa and follicles and/or corpora lutea i...
King SS, Douglas BL, Roser JF, Silvia WJ, Jones KL.There is a well-documented increase in luteolytic failure, resulting in spontaneously prolonged corpus luteum (SPCL) function, during estrous cycles of horses in autumn. The cause of this phenomenon may be due to seasonal alterations in PGF(2alpha) and/or in prolactin (PRL) secretion around luteolysis. To investigate this, progesterone (P4), 13, 14-dihydro, 15-keto PGF(2alpha) (PGFM) and PRL concentrations were compared between summer and autumn estrous cycles during natural luteolysis and luteolysis induced by benign uterine stimulation. A single estrous cycle from mares in June-July (n=12) w...
Ginther OJ, Almamun M, Shahiduzzaman AK, Beg MA.The mechanism for a reported temporal association between ovulation and a transient disruption in the periovulatory increase in LH concentrations was studied in nine mares treated with human chorionic gonadotropin when the preovulatory follicle was >/=32mm. Examinations for ovulation detection and blood collection were done at 2-h intervals and the results were retrospectively centralized to ovulation (Hour 0). Concentrations of LH began to increase (P<0.03) rapidly at Hour -18, decreased (P<0.04) between Hours 0 and 6, and again increased (P<0.0001) after Hour 12. A progressive de...
Raz T, Card C.Reliable methods of regulating estrus and stimulating superovulations in equine embryo transfer programs are desirable. Our objectives were to investigate the efficacy of a progesterone and estradiol-17beta (P&E) estrus synchronization regimen in mares with and without subsequent equine follicle-stimulating hormone (eFSH) treatment and to examine the effects of eFSH on folliculogenesis and embryo production. Cycling mares were treated with P&E daily for 10 d. On the final P&E treatment day, prostaglandin F(2alpha) was administered, and mares were randomly assigned to one of two treatment group...
Raz T, Carley S, Card C.The objective was to compare the effects of eFSH and deslorelin treatment regimes on ovarian stimulation and embryo production of donor mares in early spring transition. Starting January 30th, mares kept under ambient light were examined by transrectal ultrasonography. When a follicle > or =25 mm was detected, mares were assigned to one of two treatment groups, using a sequential alternating treatment design. In the eFSH group, mares (n=18) were treated twice daily with eFSH (12.5mg im) until they achieved a follicle > or =35 mm; hCG was given 36 h later. In the deslorelin group, mares (n=18) ...
El-Maaty AM, Gabr FI.Sixteen Arab lactating mares belonging to Al-Zahraa Arab Horse Stud underwent two ultrasound examinations at 3 weeks interval starting from the day of demonstration of foaling heat. In addition, daily blood samples were collected from parturition until after exhibiting first postpartum estrus (day 11) with daily observation of estrous signs. Both leptin and estradiol hormones were assayed. Mean day of foaling heat was 8.9+/-0.9 day. Most mares came in foaling heat during days 9 and 10 had high conception rate compared to those who came in estrus earlier or later. Estradiol levels were high aft...
Cuervo-Arango J, Aguilar J, Newcombe JR.Embryonic vesicle growth in the mare is easily monitored by ultrasound. Apart from pregnancy diagnosis, assessment of the embryonic vesicle in practice is also useful to evaluate its viability. Although subject to individual variation, embryo growth rate follows a constant pattern in the early stages of development in relation to embryonic age. Previous studies have shown a significant effect of some factors routinely used in practice, such as post-ovulation insemination and embryo transfer, on embryonic growth and the time in which the vesicle is first detected. This study attempts to confirm...
Jennings MW, Boime I, Daphna-Iken D, Jablonka-Shariff A, Conley AJ, Colgin M, Bidstrup LA, Meyers-Brown GA, Famula TR, Roser JF.The efficacy of a recently engineered single chain recombinant equine follicle stimulating hormone (reFSH) was investigated in estrous cycling mares whose gonadotropins and follicular activity had been suppressed by concurrent treatment with progesterone and estradiol (P&E). Time of estrus was synchronized in 15 estrous cycling mares during the breeding season with prostaglandins F(2alpha) (PGF(2alpha)). The day after ovulation, mares were treated once daily with P&E for 14 days. Mares received a second injection of PGF(2alpha) on day 6 of the synchronized estrous cycle to induce luteolysis. O...
Raz T, Amorim MD, Stover BC, Card CE.The objective of this study was to compare the efficacy of purified equine- and porcine-FSH treatment regimes in mares in early vernal transition. Mares (n = 22) kept under ambient light were examined ultrasonographically per-rectum, starting January 30th. They were assigned to one of two treatment groups using a sequential alternating treatment design when a follicle >or= 25 mm was detected. In the eFSH group, mares were treated twice daily with equine-FSH, and in the pFSH group mares were treated twice daily with porcine-FSH; treatments were continued until follicle(s) >or= 35 mm, and 24 h l...
Mari G, Morganti M, Merlo B, Castagnetti C, Parmeggiani F, Govoni N, Galeati G, Tamanini C.Since results with using sulpiride and domperidone are conflicting and since both have not been tested at the same time, the aim of this study was to compare the efficacy of these substances for the induction of ovulation in deep anestrous mares in the same experimental conditions and to determine their fertility after artificial insemination (AI) at the induced estrus. Twenty-six non-pregnant, non-lactating standardbred anestrous mares were randomly assigned to three groups and treated daily for 25 days (from February 3rd to February 28th) with either sulpiride (1mg/kg of body weight im SID, ...
Raz T, Hunter B, Carley S, Card C.The objective was to compare the reproductive performances associated with the first (Cycle-1), second (Cycle-2), and mid-season (MS-Cycle) ovulations of the breeding season in donor mares that were treated with equine-FSH (eFSH) in the early vernal transition. Mares (n=15) kept under ambient light were examined ultrasonographically per-rectum starting January 30. When an ovarian follicle > or =25mm in diameter was detected, twice daily eFSH treatments were initiated. The eFSH treatments ceased when a follicle > or =35mm was detected, and 36h later hCG was administered. Thereafter, mares were ...
Ginther OJ, Gastal MO, Gastal EL, Jacob JC, Beg MA.A follicular wave and luteolysis were induced in mares by ablation of follicles > or =6 mm and treatment with prostaglandin F(2alpha) (PGF) on Day 10 (where ovulation = Day 0). The incidence of haemorrhagic anovulatory follicles (HAFs) in the induced waves (20%) was greater (P < 0.007) than in preceding spontaneous waves (2%). Hormone and follicle dynamics were compared between induced follicular waves that ended in ovulations (ovulating group; n = 36) v. HAFs (HAF group; n = 9). The day of the first ovulation or the beginning of HAF formation at the end of an induced wave was designated as po...
Ginther OJ, Gastal MO, Gastal EL, Jacob JC, Siddiqui MA, Beg MA.The effects of age (young: 5-6 years; intermediate: 10-14 years; old: > or =18 years) on follicle and hormone dynamics during an interovulatory interval (IOI; n = 46) and on preovulatory oocytes and concentrations of follicular fluid factors (n = 44) were studied in mares. Old mares were not approaching senescence, as indicated by regular lengths of the IOI (19-27 days) during the period May-October. The IOI was 1 day longer (P < 0.05) in the old group than in the two younger groups and was associated with a slower (P < 0.05) growth rate of the ovulatory follicle. The old group had di...
Raz T, Gray A, Hunter B, Card C.Superovulatory treatment may potentially increase the embryo recovery rate and the per-cycle pregnancy rate in normal or subfertile mares that are managed properly. However, some studies suggest a possible negative effect of superovulatory treatment on ovarian follicular maturation and embryo viability. Objectives of the present study were to investigate the early effects of eFSH treatment in reproductively normal mares in terms of: folliculogenesis, pregnancy rate, early embryonic development, reproductive tract parameters (tone and edema), and serum estradiol-17beta and progesterone concentr...
Ginther OJ, Gastal MO, Gastal EL, Jacob JC, Beg MA.An ovulatory follicular wave was induced by ablation of follicles > or =6mm and treatment with prostaglandin F2alpha (PGF) on Day 10 (ovulation=Day 0). Follicle and hormone dynamics of the induced waves were compared among three age groups: young (5-6 y, n=14 waves), intermediate (10-14 y, n=16), and old (> or =18, n=15). During the common-growth phase of the induced wave (Days 12-17), diameter of the future ovulatory follicle was not different among ages, but the young group had more (P or =10mm. The number was correlated (r=+0.7; P<0.0001) within mares between consecutive interovula...
Ginther OJ, Jacob JC, Gastal MO, Gastal EL, Beg MA.Ablation of follicles > or = 6 mm in diameter and treatment with PGF2alpha 10 days after ovulation were used to induce the development of ovulatory waves. Comparisons were made between induced waves with one (33 waves, 72%) and multiple (13 waves, 28%) ovulatory follicles. Diameter deviation was defined as the separation of follicles into dominant and subordinate categories. Multiple ovulatory follicles were preceded by more (p or = 20 mm at the beginning of deviation, higher LH preceding deviation (approached significance, p < 0.08), lower (p < 0.05) concentrations of FSH on the day...
Siddiqui MA, Gastal EL, Gastal MO, Beg MA, Ginther OJ.Follicle blood flow, follicular-fluid and plasma hormone concentrations, and oocyte quality were studied 30 h after an ovulation-inducing hCG treatment when the pre-ovulatory follicle was 32 mm. Mares were grouped as positive (n = 16) and negative (n = 44) for hCG antibodies before the experimental hCG treatment. Percentage of the follicle wall with blood flow signals was less (p < 0.05) in the antibody positive group than in the negative group. The concentrations of follicular-fluid oestradiol and free IGF1, and plasma oestradiol were greater (p < 0.001), and follicular-fluid progesterone (p ...
Douglas RH, Ginther OJ.Several experiments indicated that prostaglandin F2alpha (PGF2alpha) has luteolytic and abortifacient properties in mares. A single subcutaneous injection of 1-25 mg PGF2alpha on Day 6 of dioestrus was as effective as 10 mg PGF2alpha in inducing luteolysis. Oestrus and ovulation appeared to be synchronized when a single injection of 1-25 mg PGF2alpha was given on Days 7, 10 or 13 after ovulation but not on Days 1 or 4 after ovulation or on Day 2 of oestrus. Intramuscular administration was as effective as subcutaneous administration and 1-25 mg PGF2alpha was the minimal effective systemic dose...
Sirois J, Kimmich TL, Fortune JE.Ovulation in mares is preceded by a long and variable estrous period. The differentiation of equine preovulatory follicles with respect to steroidogenic capacity and responsiveness to equine gonadotropins was studied by culturing pieces of follicle wall (FW = theca + attached granulosa cells) from preovulatory follicles isolated during late diestrus (day 14 of cycle, n = 5 mares), early estrus (1st-2nd day of estrus, n = 6) or late estrus (4th or 5th day of estrus, n = 6). FW was cultured with or without equine LH, FSH, LH + FSH, or CG (10 or 100 ng/ml) and medium was collected and replaced at...
Blanchar TL, Brinsko SP, Rigby SL.A tendency for deslorelin implants to suppress subsequent follicular growth and delay return to estrus following induced ovulation has been documented in nonlactating mares. To investigate this phenomenon in lactating mares, 22 broodmares in southeast Texas were administered either deslorelin or hCG to induce ovulation in the first postpartum estrus during February and March 2001. Mares were teased daily and examined twice weekly (Tuesdays and Thursdays) by transrectal ultrasonography. When a follicle >35 mm diameter was detected on Tuesday, mares were treated with either 2,500 U hCG admini...
Griffin PG, Ginther OJ.Transrectal ultrasonography was used to quantitate uterine contractile activity during the estrous cycle and early pregnancy in pony mares (nonbred, n = 9; pregnant, n = 16). Continuous 1-min scans of longitudinal sections of the uterine body were videotaped, and uterine activity scores (1=minimal activity, 5=maximal activity) were assigned to each tape segment. There was a tendency (P<0.06) for a main effect of reproductive status (nonbred versus pregnant), a main effect of day (P<0.0001), and a reproductive status by day interaction (P<0.006). Uterine activity scores were higher (P&...
Fanelli D, Beltramo M, Conte G, Cerretini B, Lomet D, Rota A, Aucagne V, Camillo F, Panzani D.Kisspeptins (KPs) are the most potent stimulating neurotransmitters of GnRH release, and consequently KP administration triggers LH and/or FSH release. In small ruminants, KP or its analogs induced an LH surge followed by ovulation in both cyclic and acyclic animals, while in the mare KP only increased LH plasma levels but failed to induce ovulation. This study in jennies compares the endocrinological effects, ovulatory and pregnancy rates of the KP analog C6 and the GnRH analog buserelin acetate. The ovarian activity of nine Amiata jennies was monitored daily by transrectal ultrasound for thr...
Polasek TCM, Kozicki LE, Pedrosa VB, Weiss RR, Bertol MAF, Camargo CE, Talini R.This study aimed to correlate the inflammatory reaction (IR) caused by a progesterone-releasing intravaginal device (P4) with ovarian activity and pregnancy rate (PR) in embryo-recipient anestrus mares (to decrease the spring transitional period). 50 animals were assigned to three groups: GP4 (P4 group; n = 16), GP4OH (P4 + oxytetracycline hydrochloride and hydrocortisone sprayed onto the device; n = 14), and GNP4 (no intravaginal P4; n = 20). The administration protocol for GP4 was: Day 0, 750 mg P4 + ovarian examination by ultrasonography (US) + vaginal sample collection; Day 8, US;...
Cuervo-Arango J, Claes AN, Stout TA.Asynchronous embryo transfer is an excellent tool to investigate how subtle differences in the uterine environment affect embryo development and survival. Progesterone secreted from the corpus luteum following ovulation is one of the main factors responsible for establishing endometrial receptivity for the pre-implantation embryo via complex alterations in the expression of genes involved in the secretion of the histotroph. The objective of this retrospective study was to determine whether the recipient's Day after ovulation and the number of CL at ET influence the pregnancy rates of IVP horse...
Ferris RA, McCue PM.Persistent mating induced endometritis is among the most common causes of infertility in the mare. Recently, improved pregnancy rates have been reported when corticosteroids were administered to 'problem mares' specifically, to modulate the post mating inflammatory response; however, the effect of treatment on pituitary and ovarian function requires further study. Objective: To evaluate the effects of prolonged treatment with glucocorticoids on pituitary and ovarian function. Methods: Eighteen cycling Quarter Horse mares in early oestrus were assigned randomly to one of 3 treatment groups: dex...
Watson ED, Thomassen R, Nikolakopoulos E.During spring transition, when estrus may be exhibited for prolonged periods, it is important for veterinarians and stud farm personnel to be able to predict whether a large follicle will ovulate or regress. It is thought that the presence of ultrasonically detectable uterine edema indicates that a follicle will ovulate, however, there is little evidence to support this. In the present study, 16 mares were regularly examined by transrectal ultrasonography to follow growth and regression of follicles from seasonal anestrus in February until second ovulation. Blood samples were collected daily f...
The present experiment aimed at determining whether the timing of the maternal recognition of pregnancy (MRP) was specific to individual mares by determining when luteostasis, a failure to return to oestrus, reliably occurred in individuals following embryo reduction. Singleton (n = 150) and synchronous twin pregnancies (n = 9) were reduced in 10 individuals (5-29 reductions/mare) at pre-determined time points within days 10 (n = 20), 11 (n = 65), 12 (n = 47), 13 (n = 12) or 14 (n = 15) of pregnancy. Prior to embryo reduction, the vesicle diameter was measured in 71% (106/150) of the singleton...
Peltier MR, Robinson G, Sharp DC.The effects of melatonin implant treatment over a 4 wk period at the summer solstice on the transition into and out of the following anovulatory season were evaluated in ovary-intact and ovariectomized mares. Melatonin implants tended to delay the timing of the final ovulation of the breeding season (P = 0.0797) in the ovary-intact mares. Although the decline in LH secretion associated with the end of the breeding season was parallel between treatments and ovarian statuses, the rate of LH secretion, as expressed by its mathematical accumulation, was lower in ovariectomized, melatonin-treated m...
Ginther OJ, Jacob JC, Gastal MO, Gastal EL, Beg MA.The characteristics of ovulatory follicular waves were studied for spontaneous waves and waves induced during the next estrous cycle by ovarian follicle ablations and administration of PGF2alpha 10 days after ovulation in 21 mares. In the induced group, both the days of the FSH surge and day of deviation were more synchronized, LH concentrations were greater before and after deviation, estradiol concentrations were greater after deviation, and the ovulatory follicle grew at a faster rate (3.4+/-0.2 compared with 2.7+/-0.1 mm/day). The frequency of two dominant follicles/wave was not different ...
Palmer E.The use of photoperiod, progestagen, prostaglandin and hCG treatments was investigated to obtain mating of mares at predetermined times. The objectives were: (1) synchronization of oestrus at an early time of the year, (2) simplification of treatment schedules by use of vaginal sponges, and (3) use of several controlled cycles by successive synchronization. The following conclusions were reached. First, after a 16 h photoperiod was applied beginning on 25 November, hormonal synchronization of oestrus and ovulation followed by cyclicity were obtained on 1 February; i.e. 2 months of light are es...
Koskinen E, Kurki E, Katila T.Sixty-four mares (27 foaling, 37 barren or maiden), mainly Finnhorses, were subjected to treatment with 14.5 h of light and 9.5 h of darkness, starting at the beginning of December. The onset of cycling in non-foaling mares was estimated by weekly serum progesterone determinations. All of the non-foaling mares cycled in the middle of March. They started to cycle on average in the middle of February, 11.1 weeks after the beginning of the trial. There were statistically significant differences in relation to breed (Finnhorses started to cycle 2 weeks later than warm blooded, p less than 0.02) an...
Bader H.A total of 23 mares were inseminated once within 0-6 h after clinical detection of ovulation, 14 with fresh and 9 with deep-frozen semen containing 0.1 x 10(9) to 4.7 x 10(9) motile spermatozoa. Within these two groups, the mares were slaughtered 2, 4 or 6 h after insemination and their genital tracts removed. The utero-tubal junction, isthmus and ampulla ipsilateral to the ovary in which ovulation occurred were flushed separately for sperm recovery. In 1 or 2 mares of each group, the uterine horn and corpus uteri, the cervix and vagina were also flushed. Tissue samples were collected from the...
Riley SC, Thomassen R, Bae SE, Leask R, Pedersen HG, Watson ED.Profound hormonally controlled tissue remodelling occurs in the equine ovary for follicle growth and development, and also for the alteration in follicle shape directed towards the ovulation fossa, the site where ovulation occurs. The aim of this study was to examine the spatial and temporal regulation of matrix metalloproteinases (MMP)-2 and MMP-9, important enzymes in tissue remodelling, during follicle growth, and ovulation. Using gelatin substrate zymography, we measured these MMPs in follicular fluid of large anovulatory follicles collected during spring transition, early dominant follicl...
Harada T, Nambo Y, Ishimaru M, Sato F, Nagaoka K, Watanabe G, Taya K.The effects of an extended photoperiod (EP) treatment (14.5 hr light, 9.5 hr dark) on Thoroughbred colts and fillies from December 25 at 7-9 months old to the following May at 12-14 months old on coat condition and gonadal functions were investigated. Coat condition was evaluated in April. The colts and fillies in the EP treatment group changed from winter to summer coats (molting of winter coats), whereas those in the control group did not. To determine the day of first ovulation, the plasma concentrations of progesterone were measured once a month in fillies. The day of first ovulation was a...
Gutjahr S, Paccamonti DL, Pycock JF, Taverne MA, Dieleman SJ, van der Weijden GC.To determine the effect of dose and day of oxytocin treatment on intrauterine pressure, 6 normal mares were treated with 10 or 25 IU oxytocin 2 days before ovulation, on the day of ovulation and 2 days after ovulation. Intrauterine pressure (IUP) was measured using micro-tip-catheters (one placed intrauterine, a second and third serving as reference sensors in the vagina and external to the mare) and transmitted by telemetry for 30 min to establish a baseline before saline was administered, iv, and for an additional 30 min after saline administration. Oxytocin was then given, iv, and IUP was r...
Snyder DA, Turner DD, Miller KF, Garcia MC, Ginther OJ.Observations of follicular and gonadotrophic changes were conducted on 14 Pony mares for 31-day periods beginning at the penultimate (second last) ovulation and at the last ovulation of the season. There were no main effects or interaction of day or period on the numbers of small follicles (less than 20 mm). Concentrations of FSH, numbers of large follicles (greater than 20 mm), and oestrous behaviour each showed an effect of day (P less than 0.01), but no effect of period. Concentrations of LH and diameter of the largest follicle each showed an interaction (P less than 0.01) between day and p...
Teixeira ACB, Valle GR, Riveros JAN, Diniz JHW, Wenceslau RR, Monteiro GA, Leme FOP, Oliveira LZ.The aim of this study was to evaluate the effect of equine chorionic gonadotropin (eCG) at the end of progesterone (P4) treatment on follicular and luteal characteristics during transition period (TP) and reproductive breeding season (RP). A total of 13 crossbred mares were distributed in two experimental groups in the spring and summer (n = 26). The animals received intravaginal P4 (1.9 g) releasing device from D0 to D10. On removal of P4 device, the mares received 400 IU of eCG (eCG group) or saline solution (control group). Human chorionic gonadotropin (hCG; 1.750 IU) was administered (Dh...
Fernández-Hernández P, Marinaro F, Sánchez-Calabuig MJ, García-Marín LJ, Bragado MJ, González-Fernández L, Macías-García B.Equine fertilization cannot be performed in the laboratory as equine spermatozoa do not cross the oocyte's zona pellucida . Hence, a more profound study of equine oviductal fluid (OF) composition at the pre-ovulatory and post-ovulatory stages could help in understanding what components are required to achieve fertilization in horses. Our work aimed to elucidate the proteomic composition of equine OF at both stages. To do this, OF was obtained postmortem from oviducts of slaughtered mares ipsilateral to a pre-ovulatory follicle ( = 4) or a recent ovulation ( = 4); the samples were kept at -80°...
Ferreira JC, Filho LFN, Boakari YL, Canesin HS, Thompson DL, Lima FS, Meira C.The aim of the current project was to characterize the luteal vascularity and the plasma concentrations of progesterone (P4), prolactin (PRL) and 13,14-dihydro-15-keto-PGF (PGFM) in mares with luteal disturbances during early and mid-diestrus. In Experiment 1, twenty-one mares were treated with 2 mL of 0.9% NaCl, or 1 mg Dinoprost, or 10 mg Dinoprost on day two after ovulation (Control-D2, 1/10PGF-D2 and PGF-D2 groups, respectively; n = 7 mares/group). In Experiment 2, similar treatments were performed eight days post-ovulation using a different cohort of 21 mares (Control-D8, 1/10PGF-D8 ...
Botelho JH, Pessoa GO, Rocha LG, Yeste M.The present research sought to determine whether the administration of estradiol benzoate and long-acting progesterone to anovulatory recipient mares could maintain the pregnancy after embryo transfer during the autumn transitional phase. Recipient mares (n = 40) received the hormonal supplementation (treated group) whereas the other 36 served as a control. The control group consisted of mares having typical estrous cycles with ovulations, development of a viable corpus luteum and received one transferred embryo 5 days after ovulation. Hormonal administrations in the treated group started 8 da...
Miki W, Oniyama H, Takeda N, Kimura Y, Haneda S, Matsui M, Taya K, Nambo Y.We observed structural changes in the follicles and uterus of heavy draft mares during estrus and examined the effect of a single injection of the gonadotropin-releasing hormone analog buserelin on ovulation and endocrine profiles. Twenty-two heavy draft mares were divided into a buserelin-treated group (n=8) and a control group (n=14). Mares were given an intramuscular injection of 40 µg buserelin when they presented signs of estrus to a teaser stallion, had ≥45 mm diameter follicles, and presented decreased uterine edema compared with the previous examination. The follicles and uterus wer...
Martoriati A, Duchamp G, Gérard N.Paracrine factors have significant effects during folliculogenesis. Because of various morphological features, the mare is a convenient model to study in vivo the effects of factors involved in periovulatory events. In the present work, epidermal growth factor (EGF; experiment 1, n = 49 mares) and interleukin-1beta and interleukin-1RA (IL-1beta and IL-1RA, respectively; experiment 2, n = 80 mares) were injected intrafollicularly to evaluate the influence of these factors on in vivo maturation of equine preovulatory follicles. A transvaginal ultrasound-guided injection was performed when the di...
Walbornn SR, Felix M, Schnobrich MR, Bradecamp EA, Scoggin CF, Stefanovski D, Hinrichs K.To determine the effect of stage of estrus cycle (day after ovulation) at the time of transvaginal ultrasound-guided follicle aspiration (TVA) on parameters related to the success of in vitro equine embryo production. 14 healthy mares were used; 11 completed the study and were included for analysis. Mares underwent TVA of all follicles ≥ 5 mm diameter at each of 3 timepoints: 7 days after ovulation, 14 days after ovulation, and S-DSF (subordinate to a dominant stimulated follicle), during estrus at 24 hours after gonadotropin administration. The 3 treatments were assigned to each mare in ran...
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...
Douglas RH, Ginther OJ.In experiment 1, seven groups of pony mares (2 or 3/group) were given either no injections (controls), or 5 (5X) or 10 (10X) daily subcutaneous (SC) injections of 1.25 mg PGF2alpha beginning on days 1, 7 or 13 post-ovulation. Compared to controls (24.5 days), the interovulatory interval was longer (P less than ..05) for day 7, 10X (33.5 days) and day 13, 10X mares (49.0 days) but was not different for the remaining groups. In experiment 2, nine groups of pony mares (4/group) were given either no injections (controls) or 1 (1X) or 10 (10X) daily SC injections of 1.25 mg PGF2alpha beginning on d...
Korosue K, Murase H, Sato F, Ishimaru M, Harada T, Watanabe G, Taya K, Nambo Y.The purpose of this study was to demonstrate that a barren parous Thoroughbred mare with lactation induced by hormonal treatment can be introduced to an orphan foal at the same farm and that the mare can become pregnant after the end of the hormonal treatment. An additional purpose was to investigate the changes in the plasma concentrations of prolactin, estradiol-17β, progesterone, follicle-stimulating hormone, and luteinizing hormone before, during, and after hormonal treatment. The difference in body weight between the adopted foal and the control foals, which were at the same farm and rai...
Sharma S, Davies Morel MC, Dhaliwal GS.Decreased reproductive performance due to summer stress is a well known phenomenon in farm livestock. Whether this occurs in the mare and specifically how this might affect postpartum reproductive activity and performance, especially at Foal Heat (FH), is unknown. This study, therefore, aims to investigate this and the factors that might affect postpartum reproductive activity. Reproductive records of 228 Thoroughbred mares (694 mare years) bred in subtropical north-western India were retrospectively analysed. Overt oestrous activity occurred within 21 d postpartum in 92.94% (645/694) of mares...
