Reproduction in horses encompasses the biological processes and mechanisms involved in the breeding and development of equine offspring. This includes the study of reproductive anatomy, physiology, and endocrinology in both mares and stallions. Key areas of interest include the estrous cycle, ovulation, conception, gestation, and parturition. Researchers also examine factors influencing fertility, reproductive technologies such as artificial insemination and embryo transfer, and management practices that impact reproductive success. This page compiles peer-reviewed research studies and scholarly articles that explore the physiological, genetic, and environmental aspects of equine reproduction.
Holtan DW, Nett TM, Estergreen VL.Jugular vein plasma from 13 mares was extracted with diethyl ether and chromatographed on Sephadex LH-20 columns (.5 × 9 cm) after which progesterone and 17α-hydroxyprogesterone (170HP) were quantified by a competitive protein binding radioassay. During pregnancy, progesterone increased (P < .05) from 1.1 ± .4 ng/ml (mean ± SE) on day 0 to 7.5 ± 1.2 ng/ml on day 8 followed by a transient (nonsignificant) decrease to 4.8 ± .4 ng/ml on day 28. From days 28 to 44 progesterone again increased (P < .05) attaining a maximum concentration of 15.2 ± 1.4 ng/ml on day 64. Thereafter progesterone ...
Pickett BW, Sullivan JJ, Byers WW, Pace MM, Remmenga EE.The effect of centrifugation of diluted and undiluted semen on equine and bovine spermatozoan motility and fertility was examined, as was the effect of seminal plasma and dilution on stallion spermatozoa during incubation before and after freezing. Centrifugation at 370 g or 829 g was not detrimental (P greater than 0.05) to prefreeze or postfreeze motility if a final concentration of 10% seminal plasma was present. A reduction of seminal plasma from 10% to 2% significantly (P smaller than 0.05) reduced motility. A centrifugal force of 956 g significantly reduced prefreeze but not postfreeze m...
Engle CC, Foley CW.Uterine tubal fluids were collected twice a day from mares for 5 consecutive estrous cycles between March 15 and September 1. Follicular fluids were aspirated from the follicles of exteriorized ovaries of 3 mares between days 2 and 5 of estrus. Uterine tubal fluid and follicular fluid were analyzed for osmolarity, dry matter, total lipids, total free fatty acids, glucose, fructose, and lactic acid. Blood samples were collected (jugular venipuncture) throughout the estrous cycle, and the same physical and biochemical analyses were made on blood plasma. A difference (P less than 0.01) was found ...
Allen WE.Ten pregnant Welsh pony mares were each treated with a series of three intravenous injections of 2000 iu human chorionic gonadotrophin (HCG) on alternate days. In four mares the first dose was given before the 39th day of gestation and conceptual loss followed treatments in all mares. The other six mares were first treated between the 40th and 97th days. No conceptual loss occurred despite five of the mares being given a fourth dose of HCG. Two mares first treated on days 36 and 38 of pregnancy subsequently produced PMSG although foetal death had occurred.
Douglas RH, Ginther OJ.Nine groups of pony mares (3/group) were used in a 3 times 3 factorial experiment. The factors were dose of PGF-2 alpha (0, 0.25 of 1.25 mg and route of administration (im, iu or il). Mares were laparotomized and treated on day 7 postovulation. Jugular blood was collected for progesterone RIA at 0 (pretreatment) and 1,6,12,24,48, and 72 hr posttreatment. In mares given either 0.25 mg or 1.25 mg PGF-2alpha, progesterone concentrations were not significantly different among the three routes at any of the posttreatment times studied except at 6 hr posttreatment. In mares given 0.25 mg, progestero...
Tischner M, Kosiniak K, Bielański W.The emission of stallion semen was studied with the aid of
an `open' Krak\l=o'\w-72Model artificial vagina. The pattern of mating
behaviour was constant in all copulations observed : a mean number of
seven intravaginal thrusts was required to elicit ejaculation. The
pressure within the vestibule of the artificial vagina averaged 66 mmHg
at the beginning of copulation, 142 mmHg just before ejaculation, and
70 mmHg during the emission of semen. Emission appeared to be a more
variable process. Five to ten jets were observed; the mean number was
eight. The early jets occurred under high pr...
The Journal of physiologyNovember 1, 1974
Volume 242, Issue 3 805-826 doi: 10.1113/jphysiol.1974.sp010735
Comline RS, Silver M.1. Blood gas tensions, pH, PCV, O(2) affinity and red cell 2,3-diphosphoglycerate (DPG) levels have been measured in uterine and umbilical blood in conscious cows and mares with indwelling vascular catheters and in sows under sodium pentobarbitone anaesthesia.2. Large P(O2) gradients (20-24 mmHg) were observed between the uterine and umbilical venous blood in the cow and pig, while in the mare the corresponding P(O2) difference was only 2.7 +/- 1.7 mmHg. Alterations in maternal arterial P(O2) did not affect the large vein-to-vein P(O2) difference in either ruminant or pig.3. In the cow the pre...
Irvine CH, Turner JE, Alexander SL, Shand N, van Noordt S.In mares, dioestrous FSH profiles based on once-a-day sampling are variable; however, the pulsatility of plasma FSH, which has been suggested by limited windows of intensive sampling, may contribute to this variability. Jugular blood from six mares was sampled at 4 h intervals throughout an ovulatory cycle to determine cyclic FSH and LH patterns more accurately and to measure gonadotrophin pulse frequency during dioestrus. Synchronous pulses of FSH and LH occurred regularly in all mares between day 4 and day 12 (ovulation = day 0) with a mean (+/- SEM) frequency of 1.9 +/- 0.1 (FSH) or 1.6 +/-...
Turna Yilmaz O, Gunduz MC, Evkuran Dal G, Kurban I, Erzengin OM, Ucmak M.Doppler ultrasonography is a noninvasive technique which enables us to follow the physiologic and physiopathologic changes in blood flow in tissues. It is becoming an essential tool in veterinary medicine, especially in theriogenology. Twenty-seven Arabian mares were grouped by age ('young', 3-10 y, n=15; 'old', 19-23 y, n=12). The uterine arteries of the mares were examined using Doppler ultrasonography when an ovarian follicle ≥35mm was visible (Day -1). After these measurements, human chorionic gonadotropin (hCG; 2500IU) was administered to 14 mares selected randomly. One day later (Day 0...
Haider W, Brehm W, Keller H.An apparently unilateral cryptorchid stallion was referred to the clinic with a history of colic. In the course of laparotomy an ileus caused by strangulation of the small intestine was found and the horse was euthanized because of poor prognosis. During autopsy strictures and ectasia of the jejunum were found as well as hermaphroditism along with male phenotype. The frequency of cryptorchidism in the case of intersexuality is discussed.
Scherbarth R, Pózvári M, Heilkenbrinker T, Mumme J.From 1972 to 1991, presecretion on an average of 183 stallions per year had been examined. Facultatively pathogenic germs were ascertained in 13.5% of the samples. However, the portion showed considerable annual fluctuation, as did the percentage of the different kinds of germs. In most of the cases, only minimal growth had been observed in culture. Except for the total percentage, these results are contradictory to those we found during the examination of cervical swabs of mares. In order to ascertain the importance of the respective results and to render possible a correct interpretation, th...
Stock KF, Distl O, Hoeschele I.Simulated data were used to determine the properties of multivariate prediction of breeding values for categorical and continuous traits using phenotypic, molecular genetic and pedigree information by mixed linear-threshold animal models via Gibbs sampling. Simulation parameters were chosen such that the data resembled situations encountered in Warmblood horse populations. Genetic evaluation was performed in the context of the radiographic findings in the equine limbs. The simulated pedigree comprised seven generations and 40 000 animals per generation. The simulated data included additive gen...
Whitcomb RW, Schneyer AL, Roser JF, Hughes JP.Using a LH radioligand receptor assay (RRA) previously validated for use in serum and an equine monoclonal RIA, we have distinguished a subset of subfertile stallions with an elevated RRA/RIA ratio. After purification of the active moiety by anion exchange chromatography and immunoprecipitation with the equine LH (eLH) monoclonal antibody, RRA activity remained in the supernatant. This activity was also recognized by a polyclonal LH antibody (GDN 15) with wide cross-species recognition. This active fraction was further purified by gel filtration chromatography and shown to displace labeled eLH...
Janett F, Aebi L, Burger D, Imboden I, Hässig M, Kindahl H, Thun R.The objective of this study was to evaluate the effect of the non-steroidal anti-inflammatory drug (NSAID) vedaprofen (Quadrisol) on quality and freezability of stallion semen. Experiments were performed using 22 Franches Montagnes stallions from the National Stud in Avenches (Switzerland) randomly divided into a control and test group. Vedaprofen was given orally to all stallions of the test group at the recommended therapeutic dose (initial dose of 2mg/kg followed by 1mg/kg body weight every 12h) for 14 days. Control animals received the same amount of carrier substance. During treatment, bl...
Allen WR, Bracher V.During a 5-year period 65 Pony and 20 Thoroughbred pregnant mares were subjected to videoendoscopic hysteroscopy from 10 to 266 days of gestation. The aims of these examinations were to 1) observe foetal and placental development in vivo (60 Pony and 10 Thoroughbred mares); 2) eliminate one of unicornuate twin conceptuses (9 Thoroughbred mares); 3) recover embryonic foetal and placental tissues non-surgically for experimental purposes (47 Pony mares); 4) induce focal separation of the placenta in late gestation as an experimental model of placentitis (5 pony mares and 1 Thoroughbred mare). It ...
A 1.8-year-old maiden Thoroughbred filly, without previous history of mating or reproductive management, was referred for clinical inspection due to the presence of sanguineous vaginal discharge and severe abdominal pain. Transrectal palpation indicated uterine asymmetry, and transrectal ultrasonography revealed a mass near the cervix measuring 8.3 cm in diameter, with heterogeneous echogenicity, a trabeculated center, and a well-defined hyperechoic border. Smaller masses surrounded the larger uterine mass. During the examination, the mare expelled a uterine mass through the vulva. Histologica...
Yu FH, Yun YW, Yuen BH, Moon YS.Immature female rats treated with superovulatory doses of pregnant mare serum gonadotropin (PMSG) were used to study the effects of the antiandrogen hydroxyflutamide on steroid production, particularly the biologically active androgens, in two experiments. In the first experiment, animals were given either 5 mg hydroxyflutamide or vehicle alone at 30 and 36 h following 40 IU PMSG. Compared with the vehicle group, hydroxyflutamide treatment significantly reduced the percentage of degenerate oocytes recovered from oviducts (p less than 0.05). Serum levels of testosterone and androstenedione, and...
Sertich PL, Watson ED.Twelve mares were allowed to foal naturally, after which they were monitored to study uterine involution. Starting on day 3 after parturition, the internal genital tract was examined per rectum manually and ultrasonographically every other day for changes in uterine characteristics and ovarian activity. By day 5, gravid and nongravid uterine horns were similar in size, and by day 7, uterine fluid was absent. On day 7 after parturition, endometrial biopsy samples were obtained for histologic evaluation, and uterine swab specimens were obtained for microbiologic culture. Uterine swab specimens f...
Vogelsang MM, Kraemer DC, Potter GD, Stott GG.Oocytes recovered by follicular aspiration were evaluated by light and transmission electron microscopy. Of the 22 oocytes, 4 exhibited characteristics of degeneration, and the remaining 18 were in various stages of meiotic development. Of the non-degenerate oocytes, 14 were in the germinal vesicle stage, 2 had undergone nuclear membrane disintegration, 1 displayed chromosomes in late metaphase I-early anaphase I, and 1 oocyte was in the process of extrusion of the first polar body. Although some oocytes retained complete cumulus cell investments, oocytes were predominantly enclosed only by th...
Watson ED, Stokes CR.The rate of clearance of 125I-labelled polyvinyl pyrrolidone (PVP) from blood was measured in mares as an indicator of macrophage function. In three out of four cycling mares, PVP clearance was slower during oestrus than dioestrus. Similarly, administration of oestrogen to four ovariectomised mares tended to depress PVP clearance compared with clearance from the same mares before they received oestrogen. However, the effect of oestrogen was not statistically significant. Mares susceptible to persistent endometritis had rates of PVP clearance which were similar to those of genitally normal mare...
Peltier MM, Peltier MR, Sharp DC, Ott EA.The objective of this study was to determine whether supplemental beta-carotene would influence reproductive function in mares maintained on spring and summer pastures and to characterize plasma carotene concentrations during the estrous cycle. Carotene concentrations in plasma did not vary with day of estrous cycle (P = 0.7455). Mares receiving every other day injections of beta-carotene (400 mg; n = 4) or saline (10 ml; n = 4) during proestrus/estrus did not differ in plasma estradiol (E(2)) concentrations (P = 0.6313), follicle development (P = 0.8068), or plasma progesterone (P(4)) concent...
Douglas RH, Ginther OJ.Nine groups of pony mares (3/group) were used in a 3 times 3 factorial experiment. The factors were dose of PGF-2 alpha (0, 0.25 of 1.25 mg and route of administration (im, iu or il). Mares were laparotomized and treated on day 7 postovulation. Jugular blood was collected for progesterone RIA at 0 (pretreatment) and 1,6,12,24,48, and 72 hr posttreatment. In mares given either 0.25 mg or 1.25 mg PGF-2alpha, progesterone concentrations were not significantly different among the three routes at any of the posttreatment times studied except at 6 hr posttreatment. In mares given 0.25 mg, progestero...
López ML, Fuentes P, Retamal C, De Souza W.The occurrence, localization and ultrastructural characteristics of a blood-tissue barrier throughout the stallion proximal seminal excurrent duct system were studied by the exclusion of electron-dense tracers and freeze-fracture techniques. Striking differences were observed in the distribution of lanthanum tracer and in the geometrical organization of the zonulae occludentes along the ductus efferentes, epididymides and vas deferens. The zonulae occludentes domain, the principal structural component of the blood-epididymis barrier, differed in permeability, width and strand numbers along the...
Spier SJ, Meagher DM.Rational perioperative management improves the success rate of abdominal surgery. Important aspects of management are discussed, including principles of fluid therapy, nutrition, intravenous catheterization, antimicrobial prophylaxis, and the use of nonsteroidal anti-inflammatory medication. Current advances in the area of immunotherapy are mentioned.
Allen WE.The ovaries of twenty pregnant mares were examined daily, per rectum, for the first 4 months of gestation and note was made of their estimated size and follicular content. Serial blood samples from sixteen of the mares were assayed for PMSG. A marked seasonal effect was noted on ovarian size, follicular content and ovulation rate during pregnancy but there was no such effect on PMSG production. It is concluded that PMSG is synergistic with gonadotrophins of pituitary origin and that the latter hormone are the primary stimulus on the ovary of the pregnant horse.
Scarlet D, Budik S, Aurich C.A new device for storage and shipping of cell cultures--the Petaka G3 cell management device--was tested for its applicability for cooled-storage of equine semen. Semen from three stallions was processed with EquiPro extender either without antibiotics (three ejaculates per stallion) or with gentamicin (250 mg/l; three ejaculates per stallion). Semen was either stored at five (anaerobic conditions) or 15 °C (aerobic conditions) in syringes or cell culture devices. Total and progressive motility, as well as membrane integrity of spermatozoa, were evaluated from days 1 to 7 after collection wit...
Alves BG, Alves KA, Hyde KA, Aguiar FLN, Souza SS, Brandão FAS, Garcia EC, Pinto Y, Gastal MO, Figueiredo JR, Teixeira DIA, Gastal EL.Ovarian tissue transplantation (OTT) is a technique well established and successfully applied in humans using mainly orthotopic or heterotopic transplantation sites. In livestock, OTT is still in its infancy and, therefore, different aspects of the technique, including the efficiency of different heterotopic OTT sites as well as the potential effect of age (i.e., young vs. old mares) in the ovarian graft quality, need to be investigated. The present study investigated the efficacy of the intramuscular (IM) or the novel subvulvar mucosa (SV) heterotopic autotransplantation sites to maintain the...
Park CA, Hines HC, Threlfall WR.Equine lymphocyte antigen (ELA) gene frequencies were estimated for pacing and trotting Standardbred mares residing on a breeding farm in central Ohio. The ELA gene frequencies for Ohio Standardbreds did not differ significantly from the ELA gene frequencies of Kentucky Standardbreds, determined by Bailey (1983). No significant differences were found in the distribution of ELA class I antigens in horses with lower overall fertility or a history of abortion on the investigated breeding farm. Likewise, no significant association was observed when the ELA types of both the mare and the stallion t...
Steiner N, Lindner A.By means of a survey, the reproductive rate of mares and the foal losses in ten Thoroughbred, Saddlebred and Pony studs in Germany, mainly from North-Rhine-Westfalia, were collected and evaluated. Data for the survey were recorded for 1985-1990. The study also examined the hygienic management in the surveyed studs, and the morbidity rate of suckling foals was obtained for 1990. In addition to the survey questionnaire each stud was visited once. Two studs of each horse group were visited several times every week from March to August in order to evaluate as exactly as possible the husbandry and ...
Flisińska-Bojanowska A, Gill J, Komosa M.1. The diurnal changes in the levels of lactic (LA) and pyruvic (PA) acids and in values of pH, pO2 and pCO2 were studied in the blood of barren and later on in pregnant and lactating mares, throughout three subsequent years. 2. Blood samples were taken every 4 hr, for one day, each month, throughout 3 years. 3. The mares were kept and fed in the same conditions, lighting was natural. 4. In barren mares, diurnal rhythm in LA, PA, pO2 and pCO2 was found. 5. The pregnancy as well as lactation masked diurnal rhythms in parameters studied, except the LA level during lactation but then the acrophas...
Ginther OJ, Williams D, Curran S.Transrectal ultrasonic examinations were made in 31 pregnant pony mares once a week during Months 6 to 11. Each uterine horn was divided into 3 approximately equal segments (caudal, middle, cranial). The percentage of examinations with cranial fetal presentation increased (P<0.05) progressively from 58% at Month 6 to 99% at Month 9 and was followed in all mares by entry of the fetal hind limbs into one uterine horn. The mean number of uterinehorn segments with limb parts increased (P<0.05) between each set of consecutive months from Month 6 to Month 10. Initially (Months 7 and 8), retrac...
Manning HS, Runcan EE, Dias de Moraes CR, Coutinho da Silva MA.The objective of this study was to use estrous behavior alone to determine the appropriate time for beginning an oxytocin treatment protocol for estrus suppression. We hypothesized that administration of oxytocin beginning 8 days after the onset of estrus will prolong the luteal phase in mares. Twenty-three light breed mares (aged 4-20 years) were exposed to a stallion and observed for signs of sexual receptivity. Mares not displaying signs received 250 μg of cloprostenol intramuscularly (IM) and were teased again 3-4 days later. On the day that estrous behavior was observed (Day 0), mare...
Wilke K, Weimann M, Jung M, Geldermann H.10 different oligonucleotide probes were evaluated for DNA fingerprinting in horses. Five probes were able to detect polymorphic bands. The probes (GT)(8) , (GTG)(5) and (GGAT)(4) are most informative for individual identification and were used to analyze a population of Hannoveranian horses. The probability that two individuals have the same DNA fingerprint pattern is 1.2 × 10(-8) , 5.2 × 10(-10) and 1.5 × 10(-7) respectively. Using a combination of the three probes, paternity tests were performed with exclusion probabilities between 0.08% and 4%. ZUSAMMENFASSUNG: Oligonukleotide-Sonden fÃ...
Najjar A, Ben Said S, Benaoun B, Chetoui C, Ezzaouia M, Ben Mrad M.The study was undertaken in order to evaluate sperm morphology features of post-thawed semen of Tunisian Arab stallions. Forty two ejaculates was collected and frozen, during years 2009 and 2010, from 9 stallions aged between 9 to 24 years. After thawing, sperm morphology was studied after eosin-nigrosin stain. The percentages of abnormal head, mid piece, flagella, sperm with droplets and the total abnormal sperm were determined. Analysis of variance was carried out using SAS software. The results showed that all sperm morphology features varied among ejaculates within stallion and among stall...
Inoue S.Maternal aging has negative influences on the development and racing performance of their offspring in racehorses. However, the mechanism by which pregnancy at old age reduces the race performance of the offspring is unknown. Here, two hypotheses were posited: 1) Foals born to older mares are more likely to have muscular, skeletal, and cognitive disadvantages (direct effects). 2) Foals born to older mares are more likely to be affected by non-physiological factors correlating with the mare's age, such as the quality of sires (e.g. low-quality sires are likely to be chosen as partners of older ...
Linford RL, McCue PM, Montavon S, Lasley BL.A cannulation technique was developed to collect blood samples from the ovarian vein of mares over an extended period. Ovarian venous cannulae placed in 4 mares remained patent for a mean (+/- SEM) duration of 36.8 (+/- 6.2) days. During mid-diestrus, concentrations of progesterone in the ovarian vein ipsilateral to the corpus luteum (1,663.8 +/- 238.8 ng/ml) were significantly (P less than 0.001) higher than concentrations measured in paired samples from the jugular vein (6.1 +/- 0.3 ng/ml). Concentration of estradiol in the ovarian vein ranged from a mean of 1,053.2 +/- 303.1 pg/ml during di...
