Ovarian follicles in horses are structures within the ovaries that contain the developing oocyte, or egg, and are essential for reproduction. These follicles undergo a series of growth stages, from primordial to preovulatory, influenced by hormonal changes within the mare's reproductive cycle. The development and maturation of ovarian follicles are regulated by hormones such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Monitoring follicular development is integral to understanding reproductive physiology and managing breeding in equine practice. This page compiles peer-reviewed research studies and scholarly articles that explore the physiology, development, and clinical management of ovarian follicles in horses.
Hinrichs K.In vitro embryo production is not yet successful in the horse, largely due to low rates of fertilization in vitro. However, methods to produce embryos from isolated oocytes have been developed. Oocytes may be recovered from living mares by aspiration of the dominant preovulatory follicle by trans-abdominal puncture, and from both preovulatory and immature follicles by trans-vaginal ultrasound-guided puncture. Transfer of in vivo-matured oocytes to the oviducts of bred recipient mares has resulted in good pregnancy rates (75-85%). Little work has been done on transfer of horse oocytes matured i...
Kerban A, Doré M, Sirois J.In contrast to other species, the histology of the equine follicle during ovulation has not been described. Preovulatory follicles were isolated during oestrus at 0, 12, 24, 30, 33, 36 and 39 h (n = 5-6 follicles per time point) after an ovulatory dose of hCG to characterize the cellular and vascular changes associated with ovulation in mares. Pieces of follicle wall were formalin-fixed and processed for light microscopy to evaluate the general follicular morphology and quantify selected parameters. Marked changes were observed in the histology of equine follicles in the hours before ovulation...
Aurich C, Parvizi N, Brunklaus D, Hoppen HO, Aurich JE.The effects of dopaminergic and opioidergic systems on LH and prolactin release in Pony mares were investigated. Experiments were performed in intact mares during the non-breeding and the breeding seasons and in ovariectomized mares in November, March and May. Mares were treated with the dopamine D2-antagonist sulpiride, the opioid antagonist naloxone and naloxone plus sulpiride and saline. Naloxone alone and in combination with sulpiride increased plasma LH concentrations in intact anovulatory mares and in cyclic luteal phase mares, whereas sulpiride alone had no effect. None of the treatment...
Telfer EE, Watson ED.The aims of this study were to evaluate the use of collagenase treatment to isolate preantral follicles from mare ovaries and to assess the effect of this treatment on follicular morphology. Intact mare ovaries were chopped into pieces, incubated individually with 1, 3 or 5 mg collagenase (type 1A) ml(-1) in a shaking waterbath at 37 degrees C for up to 2 h and passed through a series of stainless steel filters with pore size 50-300 microm to remove large clumps and stromal cells. The samples were prepared for histological analysis and sections were examined by light microscopy. Isolated folli...
Kanitz W, Alm H, Becker F, Nürnberg G, Kurth J, Hinrichs K.Cumulus-oocyte complexes (COCs) recovered from ovaries of mares killed at abattoirs or after in vivo collection have heterogeneous morphologies and meiotic competence as follicles of variable quality are used. It is thought that it should be possible to recover more uniform COCs, with respect to morphology and nuclear maturation, by repeated follicle aspiration. Therefore, the influence of repeated follicle aspiration on the number and diameter of follicles > or =5 mm in diameter, the morphology and recovery rate of COCs, and the chromatin configuration in oocytes was investigated. Repeated...
Nequin LG, King SS, Roser JF, Soderstrom BL, Carnevale EM, Neumann KR.The reproductive activity of light horse mares (n=12) was monitored each day from 3 September until 29 January, or until the mares entered anoestrus, by behaviour evaluation, ultrasonography and blood sampling. Follicles, corpora lutea and ovulation, as well as oestradiol, progesterone, and LH and FSH concentrations, were analysed to determine a reproductive profile for the transition into anoestrus. The results of the present study indicate that light horse mares progress through four phases during the autumn transition into anoestrus: (i) normal cycles; (ii) aberrant cycles; (iii) anovulatio...
Tanaka Y, Nagamine N, Nambo Y, Nagata S, Nagaoka K, Tsunoda N, Taniyama H, Yoshihara T, Oikawa M, Watanabe G, Taya K.In mares, circulating immunoreactive inhibin concentrations increase during the follicular phase and decrease at the start of the LH surge. Thereafter, sharp increases in circulating immunoreactive inhibin concentrations, the 'ovulatory increase', are observed during ovulation. In the present study, the cellular sources and molecular form of ovarian inhibin were investigated to determine the mechanism responsible for this unique ovulatory increase. Three sizes of ovarian follicles (small, 30 mm in diameter) were selected. Inhibin alpha-subunit was localized by immunohistochemistry to the gran...
Goudet G, Belin F, Młodawska W, Bézard J.The effect of epidermal growth factor (EGF) on the in vitro maturation rate of equine oocytes was examined. Oocytes were collected from an abattoir (Expt 1) or using ultrasound-guided follicular puncture in vivo (Expt 2). All oocytes with a compact or expanded cumulus at recovery were cultured for 30 h in: medium 1 (TCM199 + fetal calf serum (FCS) + crude equine gonadotrophin (CEG) + oestradiol + antibiotics); medium 2 (TCM199 + EGF); medium 3 (medium 1 without FCS + EGF); or medium 4 (medium 1 without CEG + EGF). In Expt 1, 84% (37/44) and 87% (40/46) cumulus expansion (P > 0.05), and 39% (22...
Hinrichs K, Betschart RW, McCue PM, Squires EL.Mares with preovulatory follicles >33 mm in diameter were administered hCG and were randomly assigned for aspiration of the dominant follicle at 24 h or 35 h after hCG administration. Oocytes recovered at 24 h were cultured for 12 h before transfer and oocytes recovered at 35 h were cultured for 1 h. Oocytes were transferred by flank laparotomy to the oviduct of the same mare, or to the oviduct of another oocyte donor. Recipient mares were inseminated before and after transfer. The oocyte recovery rates at 24 h and 35 h after hCG administration were not significantly different (10/15 (66%) and...
Gerstenberg C, Allen WR.Branched tubular endometrial glands are key features of the uterine lining in mares. The epithelium in the neck regions of the glands is similar to that lining the lumen of the uterus, whereas the epithelium in the deeper, coiled portions of the glands secretes protein rich histotrophe or 'uterine milk' during dioestrus and pregnancy. The present study was performed to characterize endometrial histology in perinatal and peripubertal fillies and to investigate the influences of specific steroid treatments on endometrial gland development in the prepubertal period. Uteri obtained from equine fet...
Pedersen HG, Watson ED, Telfer EE.During the oestrous cycle follicles grow and either ovulate or regress. Regressing follicles undergo atresia and in many species apoptosis has been identified as the underlying mechanism in this process. The aims of this study were to establish whether equine granulosa cells degenerate via an apoptotic mechanism and whether the presence of apoptotic cell death in granulosa cells is correlated with oocyte quality. Ovaries from mares at unknown stages of the oestrous cycle were obtained from an abattoir. In Expt 1, follicles (n=352) from 37 mares were processed. DNA was extracted from granulosa ...
Bergfelt DR, Adams GP.Two experiments were performed to determine the efficacy of ultrasound-guided transvaginal follicle ablation for synchronizing ovarian function in mares. The experiments were initiated at random stages of the oestrous cycle in control (nonablated) and follicle-ablated mares. On day 0, all follicles > or =10 mm in diameter were punctured, aspirated and curettaged in ablated mares, and, on day 4, two doses of PGF2alpha were administered with a 12 h interval between the doses to both ablated and nonablated (control) mares. In Expt 1, hCG was administered to the ablated mares on the first or se...
Schmid RL, Kato H, Herickhoff LA, Schenk JL, McCue PM, Chung YG, Squires EL.In Expt 1, compact cumulus oocyte complexes (COCs) were matured in: (i) control medium (Hepes-buffered TCM-199 with 10% oestrous cow serum (OCS) + oestradiol, LH and FSH); (ii) Hepes-buffered TCM-199 with 20% follicular fluid; or (iii) control medium containing 250 ng progesterone ml(-1). Mature oocytes were collected by transvaginal aspiration as a positive control for the in vitro maturation (IVM) treatments. Oocytes were fertilized by ICSI and cultured in Menezo's B2 + 5% fetal calf serum (FCS). There were no significant differences among IVM treatments. In Expt 2, oocytes with expanded COC...
Witkowski M, Tischner M.The aim of the present study was to determine the effect of prolonged photoperiod during late pregnancy on subsequent ovarian activity and fertility in mares. Pregnant mares (n=13) due to give birth in January and February were stimulated by a fixed photoperiod (16 h light: 8 h dark) from 15 November (during the last 2-3 months of gestation) until up to 1 month after parturition. A control group of mares (n=9) due to give birth at the same time were kept in the same stable and management regimen, but under natural light conditions. Light-treated mares ovulated during foal oestrus approximately...
Aurich C, Gerlach T, Aurich JE, Parvizi N.Modulation of reproductive functions is one of the multiple effects of growth hormone (GH). To investigate effects of reproductive functions on GH release in the horse, plasma GH concentrations in ovary-intact (n = 7) and ovariectomized (n = 8) mares during the anovulatory and breeding seasons and in pregnant mares (n = 6) at various stages of gestation were determined. To analyze an opioidergic regulation of GH release, repeated blood samples were taken over 3 h, and mares were injected with the opioid antagonist naloxone (0.5 mg/kg i.v.) or saline. GH was determined by RIA with an antiserum ...
Gastal EL, Bergfelt DR, Nogueira GP, Gastal MO, Ginther OJ.The effects of several doses of progesterone on FSH and LH concentrations were used to study the role of the gonadotropins on deviation in growth rates of the two largest follicles during the establishment of follicle dominance. Progesterone was given to pony mares at a daily dose rate of 0 mg (controls), 30 mg (low dose), 100 mg (intermediate dose), and 300 mg (high dose). All follicles > or = 6 mm were ablated at Day 10 (Day 0 = ovulation) to initiate a new follicular wave; prostaglandin F(2alpha) was given to induce luteolysis, and progesterone was given from Days 10 to 24. The low dose ...
Christman SA, Bailey MT, Wheaton JE, Troedsson MH, Ababneh MM, Santschi EM.To determine whether concentrations of dimeric inhibin (CaCA) are greater in plasma and tumor fluid from mares with granulosa-theca cell tumors (GTCT), compared with concentrations in plasma and equine follicular fluid (eFF) from control mares. Methods: 6 mares with GTCT and 12 clinically normal mares. Methods: The alphabetaA immunoradiometric assay used 2 antibodies, one against each subunit of inhibin (alpha and betaA subunits). Tumor tissue, tumor fluid, and a single blood sample were collected at the time of surgical removal of the GTCT. A single blood sample was collected from 7 control m...
Nagaoka K, Nambo Y, Nagamine N, Nagata SI, Tanaka Y, Shinbo H, Tsunoda N, Taniyama H, Watanabe G, Groome NP, Taya K.The relationship between a selective increase in circulating immunoreactive (ir)-inhibin and the time of ovulation was investigated in mares. Concentrations of plasma ir-inhibin were measured every 4 h during the periovulatory period. Inhibin pro-alphaC, a precursor protein of the inhibin alpha-subunit, was also measured. The changes in ir-inhibin and inhibin pro-alphaC in circulation were parallel. Concentrations of both ir-inhibin and inhibin pro-alphaC in the plasma increased at the same time when ovulatory follicles ruptured, and the peak levels of circulating ir-inhibin and inhibin pro-al...
Gerstenberg C, Allen WR, Stewart F.Immunohistochemical detection of the proliferation marker Ki-67 antigen was used to monitor mitotic activity in the endometrium of mares. The monoclonal antibody MIB1 was validated for use on equine tissues by demonstrating its reaction with activated peripheral blood lymphocytes, and endometrial biopsies were recovered from 26 non-pregnant mares at selected stages during the reproductive cycle. The proportion of positively stained nuclei was counted in five random areas on each histological section to determine the percentage and type of proliferating cells. Multiplication rates in the types ...
Boerboom D, Kerban A, Sirois J.Estradiol biosynthesis is a key biochemical trait of developing follicles. To study its regulation in equine follicles, the objectives of this study were to clone and determine the structure of equine cytochrome P450 aromatase (P450AROM), and characterize the regulation of P450AROM and P450 17alpha-hydroxylase/C17-20 lyase (P45017alpha) messenger RNAs (mRNAs) in vivo in equine preovulatory follicles isolated during hCG-induced ovulation. Two distinct P450AROM complementary DNAs (cDNAs) were isolated from an equine preovulatory follicle cDNA library. One clone was 2682 bp in length and included...
Gastal EL, Gastal MO, Ginther OJ.A two-follicle model was used to study the nature of selection of the dominant follicle in mares by ablating neither or one of the two follicles on the day the larger follicle reached >/= 20 mm (Day 0). The larger follicle became the dominant follicle in all mares in which both follicles (n = 8) or only the larger follicle (n = 10) was retained. When only the smaller follicle (n = 9) was retained, it became dominant and ovulated in six mares and became atretic in three mares; the difference in diameter between the two follicles on Day 0 was less (p < 0.01) in mares in which the retained ...
Kaiser B, Koene M, Swagemakers J, Bader H, Hoppen HO.During the 1997 breeding season persistent follicles were diagnosed in 17 mares. In 16 of these mares a total of 17 follicles were transabdominally punctured and the steroids oestradiol, progesterone and testosterone were measured in the follicular fluid and in blood serum. In ten mares serving as a control group preovulatory follicles were punctured. The follicular fluid of the persistent follicles revealed a very high variability of the steroid concentrations. Depending on the steroid ratio within the follicles, eight follicles were rated as being intact, three follicles were undergoing atre...
Gastal EL, Gastal MO, Wiltbank MC, Ginther OJ.By definition, follicle deviation begins on the day the two largest follicles of a wave begin to differ in growth rates. The relationships between follicle deviation and intrafollicular and systemic estradiol concentrations were studied in ponies, using a two-follicle model in which all but the two largest follicles were ablated. A 20-microliter sample of follicular fluid was obtained from each of the two follicles by transvaginal ultrasonography. In experiment 1, the two follicles were sampled when the larger follicle reached 15 mm. No differences (p > 0.05) in post-sampling follicle chara...
Hess S, Gulati R, Peluso JJ.The present studies showed that sequential treatment with equine CG (eCG) and hCG not only induced an increase in ovarian weight, but also caused an estimated 4.6-fold increase in the number of ovarian surface epithelial cells. In addition, eCG-hCG treatment increased ovarian hepatocyte growth factor (HGF) messenger RNA levels. These studies also demonstrated that rat primary ovarian surface epithelial cells as well as a cell line derived from rat ovarian surface epithelium (i.e. ROSE-179 cells) do not express the LH (hCG) receptor. Both of these cells express c-Met, the receptor for HGF. To a...
Matthews NS, Hartsfield SM, Hague B, Carroll GL, Short CE.To evaluate propofol for induction and maintenance of anesthesia, after detomidine premedication, in horses undergoing abdominal surgery for creation of an experimental intestinal adhesion model. Methods: Prospective study. Methods: Twelve horses (424 +/- 81 kg) from 1 to 20 years of age (5 females, 7 males). Methods: Horses were premedicated with detomidine (0.015 mg/kg i.v.) 20 to 25 minutes before induction, and a propofol bolus (2 mg/kg i.v.) was administered for induction. Propofol infusion (0.2 mg/kg/min i.v.) was used to maintain anesthesia. The infusion rate was adjusted to maintain an...
Sugawara Y, Yamanouchi K, Naito K, Tachi C, Tojo H, Sawasaki T.A cDNA clone encoding equine follistatin was isolated from an equine ovarian cDNA library. Out of 1.2 x 10(5) independent clones screened, one positive clone was isolated and its cDNA sequence determined. The isolated clone, named EQ-FS-1, contained a complete open reading frame encoding 344 amino acid residues. The similarity of its deduced amino acid sequence to these of other mammalian species was greater than 95%. Although its expression level varied among the tissues examined, follistatin mRNA was detected in the equine uteroplacental tissues, follicles and corpora lutea by Northern blot ...
Ramirez S, Sedrish SA, Paccamonti DL, French DD.This report describes two mares presented for evaluation of anorexia, fever of unknown origin, and weight loss. Clinical examination, laboratory findings, and transrectal ultrasonographic images suggested ovarian abscessation. One mare was successfully treated medically. Because of financial considerations, the second mare was euthanatized and a postmortem examination was performed. At necropsy, there was an enlarged right ovary with an adhesion to the large colon. Microscopic findings were characteristic of an ovarian abscess.
Watson ED, Buckingham J, Björkstén TS.Oxytocin has been identified in the ovaries of many species
including ruminants (Wathes and Swann 1982; Rodgers et al.
1983), pigs (Jarry etal. 1990), sub-human primates (Khan-Dawood
1998), rats (Ho and Lee 1992) and women (Schaeffer et al. 1984).
In these species ovarian oxytocin has several roles, including
control of luteal regression (Fht and Sheldrick 1983) and possibly
luteinisation (Aladin Chandrase.kher and Fortune 1990; Eispanier et
al. 1997), and involvement in ovulation (viggiano et al. 1989).
In the mare, circulating oxytocin is reported to be high in
oestrus and early dio...
Goudet G, Belin F, Bézard J, Gérard N.The intrafollicular content of LH receptor, alpha-inhibin, and aromatase are known good indicators of follicular status. We investigated the amounts of these proteins in granulosa and cumulus cells in relation to oocyte competence for in vitro maturation, follicular growth, and estrous cycle stage in the mare. Follicular punctures were performed 34 h after an injection of crude equine gonadotropins, either during the follicular phase, at the end of the follicular phase, or during the luteal phase. The cumulus-oocyte complex, granulosa cells, and follicular fluid of follicles larger than 5 mm w...
Hanson CA, Galuppo LD.To describe a technique for laparoscopic bilateral ovariectomy in standing mares and report the outcome of 22 clinical cases. Methods: Prospective study. Methods: A total of 22 mares between 4 and 23 years of age, weighing between 360 and 600 kg. Methods: Mares with normal ovaries, as determined by palpation per rectum, were restrained in standing stocks and sedated with detomidine (0.01 to 0.02 mg/kg intravenously [i.v.]) and butorphanol (0.01 to 0.02 mg/kg i.v.). The laparoscope and instrument insertion sites were infiltrated with 2% lidocaine before incision. One laparoscope portal and two ...
Kanitz W, Alm H, Becker F, Nürnberg G, Kurth J, Hinrichs K.Cumulus-oocyte complexes (COCs) recovered from ovaries of mares killed at abattoirs or after in vivo collection have heterogeneous morphologies and meiotic competence as follicles of variable quality are used. It is thought that it should be possible to recover more uniform COCs, with respect to morphology and nuclear maturation, by repeated follicle aspiration. Therefore, the influence of repeated follicle aspiration on the number and diameter of follicles > or =5 mm in diameter, the morphology and recovery rate of COCs, and the chromatin configuration in oocytes was investigated. Repeated...
Squires EL, Ginther OJ.Examination of the ovaries of mares at various stages of pregnancy and after hysterectomy, together with measurement of progesterone concentrations in the peripheral plasma of pregnant and hysterectomized mares and in uterine and ovarian venous plasma of pregnant mares, demonstrated that the primary CL of pregnancy remains functional until at least Day 160 of gestation. The results showed that primary and secondary CL, and the placenta or uterus, all contribute to the total progesterone pool in mares during pregnancy. Similarities and differences in ovarian function observed between pregnant a...
Tate LP, Fogle CA, Bailey CS, Tate KB, Davis JW.To describe a technique for ovariectomy through a colpotomy using a chain écraseur with laparoscopic guidance and report outcome in 4 mares. Methods: Case series. Methods: After insertion of a laparoscope into the abdomen through the left flank, colpotomy was performed to allow introduction of an écraseur into the caudal aspect of the abdomen. Grasping and removal of the ovary and evaluation of the pedicle was observed via the laparoscope. The laparoscope was then inserted in the right flank for right ovariectomy. The colpotomy was closed in a continuous suture pattern using laparoscopic or ...
Collins SM, Zieba DA, Williams GL.We tested the hypothesis that continuous subcutaneous treatment with low-dose GnRH, administered to mares from late September/early October through March, would prevent the development of seasonal anovulation. Quarter Horse mares (n=20) were stratified by age and body condition score and assigned randomly to either a saline control (n=9) or a GnRH (n=11) treatment group. Gonadotropin-releasing hormone was delivered continuously via osmotic minipumps, with sham pumps placed in control mares. Initial pumps were inserted on Day 3 following ovulation or during the follicular phase if the next anti...
Joonè CJ, Nolan MB, Bertschinger HJ, Schulman ML.A sequence of studies is reviewed that reported the domestic horse (Equus caballus) mare as an appropriate and accessible research platform for recording clinical and laboratory data post-immunisation with anti- GnRH and -zona pellucida (ZP) immunocontraceptive vaccines. Experience with a native porcine ZP (pZP) vaccine in African elephant (Loxodonta africana) cows highlighted needs for improving vaccine formulations and more clearly defining associated ovarian effects and safety profiles. Initially, the efficacy, reversibility and safety of the GnRH vaccine Improvac® in mares was demonstrate...
Max MC, Silva CB, González SM, Lindquist AG, Búfalo I, Gomes RG, Morotti F, Costa CB, Barreiros T, Lisboa LA, Seneda MM.This study investigated the effects of different concentrations of FSH (10, 50, 100 and 200 ng/ml) in supplemented MEM+ on the development of equine pre-antral follicles that were cultured in vitro for 2 or 6 days. The ovaries (n = 5) from mares in seasonal anoestrus were collected from a local abattoir. Ten ovarian tissue fragments of approximately 3 × 3 × 1 mm were obtained from each animal. The fragments were cultured in situ for 2 days (D2) or 6 days (D6) in MEM+ or MEM+ supplemented with FSH at four different concentrations, establishing the following 11 groups: control (D0);...
Doyle LK, Hogg CO, Watson ED, Donadeu FX.The response of follicles to IGF1 was compared between the transition into the ovulatory season (transitional period) and the ovulatory season (ovulatory period) in eight mares using a cross-over experimental design within periods. Granulosa cells were collected from follicles 15-24 or 25-34 mm and expression of IGF1R, IGF2R, FSHR, LHCGR and PAPPA was determined by qPCR. In addition, 10 mg IGF1 or vehicle were injected into the largest follicle (transitional period) or the second largest follicle (ovulatory period) of a follicular wave before the beginning of diameter deviation between the two...
Bailey VN, Sones JL, Camp CM, Gomes VCL, Oberhaus EL.The objective of this experiment was to determine if incorporation of kisspeptin-10 (Kp10) into treatment with estradiol benzoate (EB) and sulpiride to induce early cyclicity would result in greater endocrine responses and a greater number of mares responding with either follicle(s) > 30 mm or ovulation within 25 days of treatment. Eighteen anestrous mares were blocked by breed, body condition, and age before random assignment to treatment or control. All mares received 50 mg EB before receiving osmotic minipumps containing either saline (n = 9) or Kp10 (50 μg/hour; n = 9) one day ...
Watson ED, Stokes CR, Bourne FJ.The function of blood and uterine luminal neutrophils from ovariectomized mares treated with ovarian steroids was investigated 18 h after intrauterine infusion of 1 X 10(9) Streptococcus zooepidemicus. Random migration of blood neutrophils under agarose was reduced by treatment with progesterone compared with that of neutrophils from oestradiol-treated and control mares. In-vitro addition of progesterone to blood neutrophils from acyclic ponies also reduced migration. Uterine neutrophils did not migrate under agarose which was probably an effect of bacterial phagocytosis. Hormone treatment had...
Nogueira GP, Ginther J.Follicle populations and concentrations of circulating gonadotropins were studied during age 2-10 months in 10 spring-born pony fillies. Blood sampling and ultrasound scanning were done every 4 days and daily for four 30 day periods. During 5-12 weeks, FSH concentrations were lower in 6 fillies with follicles > or = 6 mm (mean +/- s.e. 1.4 +/- 0.1 ng/ml) than in 4 fillies with follicles 10 mm and gonadotropin concentrations increased. Waves of follicular growth were identified during the 30 day periods by significant increases in the diameter of the 10 largest follicles. The waves did not ...
Tanaka Y, Nagamine N, Nambo Y, Nagata S, Nagaoka K, Tsunoda N, Taniyama H, Yoshihara T, Oikawa M, Watanabe G, Taya K.In mares, circulating immunoreactive inhibin concentrations increase during the follicular phase and decrease at the start of the LH surge. Thereafter, sharp increases in circulating immunoreactive inhibin concentrations, the 'ovulatory increase', are observed during ovulation. In the present study, the cellular sources and molecular form of ovarian inhibin were investigated to determine the mechanism responsible for this unique ovulatory increase. Three sizes of ovarian follicles (small, 30 mm in diameter) were selected. Inhibin alpha-subunit was localized by immunohistochemistry to the gran...
Kwong GPS, Klein C.Horses are long-day breeders and commence ovarian follicular activity during the spring. Evidence suggests that there is an endogenous circannual rhythm in mares, and it is uncertain whether hormonal manipulation during or immediately following the fall transition induces follicular development. The current study was designed to test the hypothesis that both deslorelin and naltrexone induce follicular development in late fall transitioning or anestrous mares. Five of six mares treated with deslorelin, and 4 of 6 mares treated with naltrexone, developed a pre-ovulatory-sized follicle and were i...
Ono M, Akuzawa H, Nambo Y, Hirano Y, Kimura J, Takemoto S, Nakamura S, Yokota H, Himeno R, Higuchi T, Ohtaki T, Tsumagari S.A three-dimensional internal structure microscopy (3D-ISM) can clarify the anatomical arrangement of internal structures of equine ovaries. In this study, morphological changes of the equine ovary over the first 12 months of life were investigated by 3D-ISM in 59 fillies and by histological analysis in 2 fillies. The weight and volume of the paired ovaries initially decreased from 0 to 1 months to 2 to 3 months of age and then significantly increased at 8 to 12 months of age. The ovulation fossa was first observed around the 3rd month and became evident after the 6th month. The number of folli...
Gastal EL, Neves AP, Mattos RC, Petrucci BP, Gastal MO, Ginther OJ.Follicular dynamics were studied during 12 interovulatory intervals (IOIs) and 36 preovulatory periods in Miniature mares. The percentage of IOIs with the following follicle events was: ovulatory wave with only one follicle>or=10 mm (55%), diameter deviation similar to previous reports in larger mares (25%) and minor waves emerging before or after the ovulatory wave (55%). Follicle data were compared among Miniature ponies, large ponies and Breton horses (n=12 IOIs per breed). The IOI was longer (P<0.001) in Miniature ponies (23.3+/-0.9 days) and in large ponies (23.9+/-0.5 days) than in...
Becker F, Kurth J, Schneider F, Nürnberg G, Heinrich H, Kanitz W.The aim of this study was to prove if oxidation-reduction levels in the follicular fluid were new functional indices of follicular health and whether there was a high level of accordance with endocrinological parameters and with the growth stage as detected by ultrasound monitoring of individual follicles during the oestrous cycle in mares. Follicles were classified as growing and regressing follicles using ultrasonography. Altogether 48 follicles with a diameter from 20 to 56 mm were aspirated by transvaginal ultrasound guided follicular aspiration. Follicular concentration of oestradiol and ...
Viafara JAS, Portilho RV, Maculan R, Souza Júnior JF, Silva CM, Rodrigues PG, El Azzi MS, Souza JC.This study evaluated the presence of polyunsaturated fatty acids in circulating blood and in the ovarian follicular fluid of mares, after supplementation of the diet with linseed oil. Six Mangalarga Marchador mares, weighing 397.00±31.89 kg, were kept on native pasture, and assigned to the current study. In a switch over design, mares were randomly allocated to receive 150 ml of vegetable oil daily, containing polyunsaturated fatty acids n3 (62.23 g ALA, 20.34 g LA, 2.27 g EPA, 2.32 g DHA), (n=3) or no supplementation (n=3) in two replicates. Blood and follicular fluid samples were taken on t...
Turner DD, Garcia MC, Miller KF, Holtan DW, Ginther OJ.The influence of the ovaries and presence of a foal on periparturient concentrations of FSH and LH were studied in 19 Pony mares. In intact and ovariectomized mares, mean concentrations of FSH fluctuated between 1.1and 9.9 ng/ml on Days -14 to-1 before parturition (Day 0). A surge of FSH occurred in all mares in association with parturition. From Days 1 to 10, the high levels of FSH gradually decreased in the intact group to the minimal concentrations that occur during oestrus, but remained elevated in the ovariectomized mares. There were no significant pre-partum changes in LH in either type ...
Okólski A, Babusik P, Tischner M, Lietz W.Comparisons were made between 2 methods of oocyte recovery from the ovarian follicles of slaughtered mares: 500 oocytes (3 per mare) were obtained by aspiration of follicular fluid from ovaries of 162 mares, and 120 oocytes (8 per mare) by isolation and rupture of follicles from ovaries of 14 mares. In the oocytes recovered after rupture of follicles, 89.2% were morphologically unchanged, in comparison to 29.3% obtained by aspiration of follicular fluid. Stallion spermatozoa capacitated in vitro were tested on zona-free hamster oocytes. The stallion spermatozoa were washed in TCM-199 and prein...
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...
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...
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...
Oberhaus EL, Wilson KM, Camp CM, Sones JL.Sulpiride in vegetable shortening (VS) stimulates prolactin in horses for up to 10 days. Although effective, a pharmaceutical grade vehicle is needed for clinical application of sulpiride in horses. Sucrose acetate isobutyrate (SAIB), a hydrophobic polymer, may be an alternative to VS. Four in vivo experiments assessed the efficacy of SAIB for delivery of sulpiride, estradiol cypionate (ECP), and estradiol benzoate (EB). The first three studies utilized geldings to compare prolactin and luteinizing hormone (LH) concentrations between sulpiride delivered in VS and SAIB, and ECP or EB delivered ...
Saltiel A, Calderon A, Garcia N, Hurley DP.Ovarian activity, as measured by the presence of small (10-15 mm diam.), medium (15-30 mm) and large (greater than 30 mm) follicles, corpora haemorrhagica and corpora lutea (CL), was determined in a total of 3584 ovaries during 1 year using post-mortem specimens. There were significant correlations of the incidence of ovulated follicles (ovulations), large and medium follicles (P less than 0 . 001) and of the mean number of small follicles (P less than 0 . 05) per mare with respect to season. The yearly averages of ovulated, large and medium follicles were 30 . 1, 13 . 9 and 73 . 9%, respectiv...
Ginther OJ, Domingues RR, Dangudubiyyam SV, Araujo ER.Diameter deviation or follicle selection during a follicular wave begins with continuous growth rate of F1 (dominant or selected follicle; DF) and decreasing growth rate of F2 (largest subordinate). Intraovarian patterns based on presence or absence of the DF and CL are DF-CL, DF, CL, and devoid (neither DF nor CL). The DF and CL relationships in a pair of ovaries are ipsilateral (DF-CL pattern and devoid pattern) and contralateral (DF pattern and CL pattern). The effects of patterns and relationships on F1, F2, and FSH during deviation were determined in 21 mares. Diameters of F1 and F2 at ex...
Watson ED.Incubation of blood neutrophils with uterine flushings collected from ovariectomised mares treated with oestradiol, stimulated migration under agarose, whereas flushings from mares treated with progesterone or oily vehicle, inhibited migration. After intra-uterine infusion of bacteria, however, flushings from oestradiol-treated and vehicle-treated mares inhibited migration, whereas progesterone treatment stimulated migration. Migration of uterine-derived neutrophils under agarose was less than that of blood neutrophils and was not influenced by treatment with ovarian steroids. Uterine suscepti...
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...
Hinrichs K.In vitro embryo production is not yet successful in the horse, largely due to low rates of fertilization in vitro. However, methods to produce embryos from isolated oocytes have been developed. Oocytes may be recovered from living mares by aspiration of the dominant preovulatory follicle by trans-abdominal puncture, and from both preovulatory and immature follicles by trans-vaginal ultrasound-guided puncture. Transfer of in vivo-matured oocytes to the oviducts of bred recipient mares has resulted in good pregnancy rates (75-85%). Little work has been done on transfer of horse oocytes matured i...
Ginther OJ.Examples of research discoveries and first reports on mare reproduction by the O.J. Ginther team are (1) determined daily circulating concentrations of four hormones during the estrous cycle, (2) showed that mares can be induced to ovulate and superovulate by hormone treatment during both ovulatory and anovulatory seasons, (3) demonstrated that prostaglandin F2α was the luteolysin in mares, (4) described the mare's elaborate hormonal and biochemical mechanism for selecting the ovulatory follicle from a pool of like follicles, (5) developed the method for diagnosing fetal sex by Day 60 using l...
Finan SA, Lamkin EL, McKinnon AO.To investigate the comparative efficacy of BioRelease Deslorelin® (BRD) and Ovuplant® for induction of ovulation in cyclic mares in Australia. Methods: Ovarian follicular activity of 60 mares for a total of 95 cycles was monitored by ultrasonography until they developed a follicle ≥30 mm and a uterine oedema pattern of 3. Mares were then randomly allocated to one of three treatment groups: (1) treatment with 1.25 mg BRD, (2) a single Ovuplant pellet or (3) 1 mL compound sodium lactate control. Follicular activity was monitored with ultrasonography every 12 h until ovulation was detec...
Derar RI, Maeda Y, Hoque SM, Osawa T, Watanabe G, Taya K, Miyake Y.Two pony mares were immunized against recombinant porcine inhibin alpha subunit three times with 39 day intervals. Clinical findings and endocrinological changes before immunization were taken as the control. The first significant rise in the anti-inhibin titre (P<0.05) in the circulation was found 27 days after the first injection. Maximum binding activity was reached by the 12th day after the second booster dose. The number of small, medium and large sized follicles had increased significantly compared to before immunization (11.75 +/- 4.30, 2.75 +/- 0.69 and 2.51 +/- 0.63 vs 6.50 +/- 1.4...
