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Topic:Ovulation
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.
Relationship between estrus endometrial edema and progesterone production in pregnant mares two weeks after ovulation. Progesterone plays a crucial role in the maintenance of pregnancy from conception to about 100-120 days of gestation when placenta becomes the main source of gestagens. The aim of the study was to test progesterone concentration 14 days after ovulation in pregnant mares and relate it to peak estral endometrial edema and the presence of intrauterine fluid (IUF) after artificial insemination (AI), the number of treatments against IUF, and the time from AI to the day when the uterus was found free of fluid. Results: Mares were divided into two groups: group A (n = 13; age 10.8 ± 4.5 y...
Metabolic profiling of preovulatory follicular fluid in jennies. Follicular fluid is formed from the transudation of theca and granulosa cells in the growing follicular antrum. Its main function is to provide an optimal intrafollicular microenvironment to modulate oocyte maturation. The aim of this study was to determine the metabolomic profile of preovulatory follicular fluid (PFF) in jennies. For this purpose, PFF was collected from 10 follicles of five jennies in heat. Then, PFF samples were analysed by nuclear magnetic resonance (NMR) and heteronuclear single quantum correlation (2D H/C HSQC). Our study revealed the presence of at least 27 metabolites i...
Equine chorionic gonadotropin administered on day 5 of a 7-days fixed-time artificial insemination program improves ovulation synchrony and corpus luteum function in anestrous beef cows. In order to assess the effect of equine chorionic gonadotropin (eCG) administered on Day 5 or 7 of a fixed-time artificial insemination protocol (FTAI) in anestrous suckled beef cows, two experiments were performed to determine the following endpoints: Experiment 1 (n = 22), preovulatory follicle (POF) diameter, ovulation time, corpus luteum (CL) area, estradiol (E2) and progesterone (P4) concentrations; and Experiment 2 (n = 676), a field trial to evaluate conception rate using the same experimental design. In both experiments, a synchronization protocol using estradiol benzoate (EB) (Day...
The post-ovulatory rise in progesterone is lower and the persistence of oestrous behaviour longer during the first compared with the second cycle of the breeding season in mares. 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...
Endocrine and ovarian responses to combined estradiol benzoate-sulpiride in seasonally anovulatory mares treated with kisspeptin. 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 ...
Ovarian and Uterine Dynamics During the Estrous Cycle in Criollo Breed Mares. After having been brought to America 400 years ago, the Criollo horse reproduced freely for centuries in the southern part of the American continent. Roughness, resistance, and endurance are typical characteristics of this breed of horses. Although the natural selection that occurred over the centuries may have positively influenced the fertility and longevity of this breed, information regarding ovarian function and other reproductive aspects of Criollo breed mares under natural or controlled management conditions is scarce. The objectives of the present study were to (1) characterize the fol...
The Correlation of Endogenous Progesterone Concentration in Diestrus on Early Pregnancy Rate in Thoroughbred Mares. The aim of this project was to test the hypothesis that progesterone concentration 5 days after ovulation did not differ between pregnant and nonpregnant Thoroughbred mares on stud farms located in the Waikato region of New Zealand. A prospective cohort study was performed involving five stud farms in the Waikato region of New Zealand during the 2018 breeding season. A total of 275 mares were enrolled in the study. Mares were served by 34 individual stallions. Blood samples were taken from each mare 5 days after ovulation (D0) and measured for progesterone concentration. Early pregnancy was co...
Effect of day of estrus cycle at time of transvaginal follicle aspiration for oocyte recovery on rates of in vitro maturation and blastocyst production after intracytoplasmic sperm injection. 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...
Luteal Tissue Area and Immunoreactive Concentration of Progesterone in Plasma of Bred and Non-bred Mares. Progesterone is pivotal to maintain pregnancy in the first trimester and low concentration ( .05). Multiple ovulations were associated with greater progesterone concentration and luteal tissue area (P = .0001). There was a moderate positive association between the number of ovulations and luteal tissue area (r = 0.54; P = .0001). The lack of change in the progesterone concentration and luteal tissue area between bred and non-bred mares suggests that horse seminal plasma does not affect luteal function in mares. As all mares had progesterone above 4 ng/mL after 5-days post-ovulation; it i...
Follicular-fluid proteomics during equine follicle development. The complex composition of the follicular fluid (FF), the intimate proximity to the oocyte, and the continual changes in their composition have a major effect on folliculogenesis and oogenesis. To date, the profiling of FF proteomes during follicle selection, development, and ovulation has not been comprehensively investigated. Therefore, a shotgun proteomics approach and bioinformatics analyses were used to profile the proteomes of equine FF harvested in vivo from follicles at the following development stages: predeviation (18-20 mm), deviation (22-25 mm), postdeviation (26-29 mm), preo...
The Kisspeptin analogue C6 induces ovulation in jennies. 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...
Emergence and selection of the dominant follicle and gonadotropin dynamics in postpartum lactating versus non-postpartum cycling mares. Among female livestock, the mare has the shortest interval from parturition to first ovulation. Due to the scarcity of research on postpartum mares, little progress has been made on the characterization of the resumption of ovarian cyclicity after parturition. This study compared follicular and gonadotropin dynamics during follicle emergence and deviation in postpartum lactating (PP Lactating) versus non-postpartum cycling (N-PP Cycling) mares. On the day of parturition, every PP Lactating mare was paired with a N-PP Cycling mare. Comparisons were made by considering the partum-ovulation inter...
Suppression of reproductive behaviour and gonadal function in female horses-An update. The behaviour of mares is often detrimental to their performance resulting in frequent demand for methods to suppress gonadal function. In addition, prevention of unintended reproduction especially in feral horse populations may require methods for suppression of gonadal function. Surgical ovariectomy is a safe method but not an acceptable approach in feral mares and undesired in mares where future breeding is considered. There are different approaches for artificial prolongation of the luteal phase resulting in transient inhibition of oestrus and ovulation. Among those, treatment with natural...
Success rate in a clinical equine in vitro embryo production program. In vitro embryo production (IVEP) via Ovum Pick-Up (OPU) and Intracytoplasmic Sperm Injection (ICSI) has become a popular breeding technique in Warmblood mares because of the high success rate and several practical advantages. IVEP offers a solution for a variety of reproductive issues including, but not limited to, sub-fertility in stallions or mares, poor quality or scarce frozen semen, difficulty in synchronizing donor and recipient mares, and inefficient use of recipient mares. In 515 OPU-ICSI sessions performed in our facility in 2021, a mean of 25.9 antral follicles were aspirated yield...
Effect of short-term artificial light and transvaginal progesterone device on first ovulation in late transitional mares. In study I, plasma progesterone concentrations were evaluated in anoestrous mares that received an intravaginal progesterone release device (IPRD) for 10 days. Mares were divided into 3 groups based on the dosage of progesterone (0 g, n=3; 1.38 g, n=5; and 1.9 g, n=5). No statistical differences were found in plasma progesterone concentrations between the two doses tested. In study II, the effects of a protocol based on a short program of artificial light combined with an IPRD containing 1.38 g of progesterone on oestrous behaviour and onset of ovulation were evaluated. IPRDs were inserted int...
Ovulatory response to GnRH agonist during early and late fall in mares. This study aimed to assess the ovulatory response of deslorelin acetate during the fall and the response to PGF2α 8 d post-ovulation. One hundred estrous cycles from 22 mares kept in 40° latitude were evaluated. Mares were checked by transrectal ultrasonography until a preovulatory follicle was detected and ovulation induced with deslorelin acetate. Ovulation was confirmed by ultrasonography performed at 24, 36 h post-induction and then repeated at 2-h intervals post-induction. Serum progesterone concentrations and luteal tissue area were determined daily to assess CL function. A dose of P...
No increase in pregnancy rate of mares after preovulatory deep uterine horn application of misoprostol. A potential source of fertility loss in mares is oviductal dysfunction, potentially caused by masses or debris in the lumen, that may prevent either sperm from reaching the fertilization site or the embryo from reaching the uterus. Recently a novel therapeutic method leading to increased pregnancy results was described by infusing misoprostol, a synthetic prostaglandin E, in the uterus of mares with unexplained fertility problems. In this study, we aimed, after examining the compatibility of misoprostol with semen, to evaluate the pregnancy rate after routine preovulatory deep uterine horn app...
Dominant follicle and gonadotropin dynamics before ovulation in postpartum lactating mares. The aim of this study was to compare the dominant follicle (DF) and gonadotropin dynamics for 9 days before ovulation in postpartum lactating (PP Lactating) versus non-postpartum cycling (N-PP Cycling) mares. Every PP Lactating mare on the day of parturition was paired with a N-PP Cycling mare, and the data analyses considered the partum-ovulation interval (POI) and the postpartum interovulatory interval (PPIOI) in PP Lactating mares and two interovulatory intervals in N-PP Cycling mares. The results of the present study revealed several novel and unique aspects of DF development and FSH and L...
Assessment of anti-Müllerian hormone in mares’ transitional period and in relation to fertility in elderly mares. Anti-Müllerian Hormone (AMH) has been linked to reproductive tract abnormalities in mares and stallions. This study aimed at evaluating AMH as a biomarker for two reproductive conditions in mares. In the first part of this study, plasma AMH was evaluated as an early indicator of the onset of cyclicity in mares in the transitional period from the anovulatory phase during winter anoestrus to the cyclic phase during the breeding season. Ten mares between 8 and 17 years old were included in the experiment which lasted from mid-February until the end of April. Ovarian activity was monitored with u...
Interrelationship between reproductive hormones and acute phase proteins during estrous cycle and pregnancy in Spanish purebred broodmares. In some species, female steroid hormones modify the profile of acute phase proteins (APPs) during the estrous cycle and pregnancy, according to the ovulation, embryonic implantation and placental development; however, nowadays there's no experimental evidence for equine species. Objectives of this study were: to compare the serum amyloid A (SAA), haptoglobin (Hp) and C-reactive protein (CRP) concentrations between cyclic and pregnant mares, and to analyze the influence of estradiol-17β (E) during estrous cycle or estrone sulfate (E) during pregnancy, and progesterone (P) on these proteins to ...
Variables Affecting Veterinary Students’ Ability to Accurately Interpret Ovulation in Live Mare Palpation. In a veterinary medicine curriculum, students' hands-on practice is essential but is still considered one of the major deficiencies in veterinary schools in Europe. After theoretical and basic practical training, students, under the control of experienced veterinarians (supervisors), monitored the reproductive cycle of embryo recipients by transrectal palpation and ultrasound. To evaluate the skills of students, the question "Has she ovulated?" was posed when a dominant follicle ≥ 35 mm was recorded in the previous day's examination and a score of 1 or 0 was assigned in the case of a correct...
Systemic and Intrafollicular Androgen Concentrations in Cycling Mares. The evidence that androgens regulate the folliculogenesis supports the hypothesis that intrafollicular testosterone (T), androstenedione (A) and dehydroepiandrosterone (DHEA) could be modified along follicular growth. The objective of this study was to evaluate the changes and related relationships between systemic and intrafollicular T, A and DHEA in post-deviation and impending ovulation follicles. Sixty ovaries were taken after the slaughter of 30 clinically healthy mares. In according to the sizes, the follicles were classified in 3 different categories, as small (20-30 mm), medium (31-40 ...
Spatial distribution of Gasterophilus pecorum (Diptera) eggs in the desert steppe of the Kalamaili Nature Reserve (Xinjiang, China). The dominant Gasterophilus species in the desert steppe (Xinjiang, China) Gasterophilus pecorum poses a serious threat to the reintroduced Przewalski's horses. We investigated the distribution pattern of G. pecorum eggs in June 2017. Two sampling methods, transect and grid, were used, and the results were analyzed via geostatistics by semivariance. The nest quadrat was used to determine the optimal quadrat size. Eggs were found in 99 quadrats (63.1%) and 187 clusters (1.5%) of Stipa caucasica on the steppe. The mean oviposition count of a cluster was 3.8 ± 1.6. Three-eggs is the mode of w...
Reproductive patterns and follicular waves in postpartum lactating versus non-postpartum cycling mares. This comparative study between postpartum lactating (PP Lactating) and non-postpartum cycling (N-PP Cycling) mares aimed to characterize reproductive patterns, types and frequencies of follicular waves, corpus luteum and endometrial echotexture dynamics, and the influence of season and body condition. Mares from each group were paired considering the day of parturition of a PP Lactating mare. The partum-ovulation interval (POI) and the postpartum interovulatory interval (PPIOI) were evaluated for PP Lactating mares, and 2 IOIs were evaluated for N-PP Cycling mares. The following observations w...
Assessment of Age Effects on Ovarian Hemodynamics Using Doppler Ultrasound and Progesterone Concentrations in Cycling Spanish Purebred Mares. In equine reproduction, accurate and timely detection of the moment of ovulation is of great importance. Power Doppler ultrasound technology is a non-invasive method that enables to assess the morpho-echogenic features and blood flow changes during the estral cycle in mares. The objective of the present study was to evaluate the influence of age on ultrasonographic parameters (follicular diameter, follicular blood flow-FBF, corpus luteum (CL) area and corpus luteum blood flow-CLBF) and blood plasma progesterone concentrations in cycling Spanish Purebred mares (15 less than 8 years old and 15 e...
The Proteome of Equine Oviductal Fluid Varies Before and After Ovulation: A Comparative Study. 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°...
Anti-Müllerian Hormone and OPU-ICSI Outcome in the Mare. Anti-Müllerian hormone (AMH) reflects the population of growing follicles and has been related to mammalian fertility. In the horse, clinical application of ovum pick-up and intracytoplasmic sperm injection (OPU-ICSI) is increasing, but results depend largely on the individuality of the mare. The aim of this study was to assess AMH as a predictor for the OPU-ICSI outcome in horses. Therefore, 103 mares with a total follicle count above 10 were included in a commercial OPU-ICSI session and serum AMH was determined using ELISA. Overall, the AMH level was significantly correlated with the number...
The Combination of hCG and GnRH Analog to Hasten Ovulation in Mares Does not Change Luteal Function and Pregnancy Outcome in Embryo Recipient Mares. Equine practitioners often prescribe the combined use of hCG and GnRH to hasten ovulation due to presumed synergistic effects. Therefore, this study aimed to test whether the combination of hCG and deslorelin acetate to hasten ovulation in mares would show any effect in inducing ovulation more efficiently than when either drug is used by itself, and to verify whether this association would affect progesterone concentrations; corpus luteum (CL) diameter and blood flow; and pregnancy outcome in recipient mares after embryo transfer (ET). Seventeen mares had the ovulation hastened (≥35 mm folli...
Sperm migration, selection, survival, and fertilizing ability in the mammalian oviduct†. In vitro fertilization (IVF) gives rise to embryos in a number of mammalian species and is currently widely used for assisted reproduction in humans and for genetic purposes in cattle. However, the rate of polyspermy is generally higher in vitro than in vivo and IVF remains ineffective in some domestic species like pigs and horses, highlighting the importance of the female reproductive tract for gamete quality and fertilization. In this review, the way the female environment modulates sperm selective migration, survival, and acquisition of fertilizing ability in the oviduct is being considered...
Deslorelin Slow-Release Implants Delay Ovulation and Increase Plasma AMH Concentration and Small Antral Follicles in Haflinger Mares. There is an increasing interest in the manipulation of ovarian follicular populations in large domestic animals because this could prove beneficial for assisted reproductive techniques such as ovum pick-up (OPU). The aim of the present study was to evaluate the effects of deslorelin slow-release implants (SRI) on the interovulatory interval, antral follicle count (AFC), number of follicles of different size ranges and plasma anti-Muellerian hormone (AMH) concentration in mares. To synchronize their estrous cycles, Haflinger mares (n = 12) were treated twice with a PGF2α analogue. One day afte...
