Fertility in horses encompasses the physiological processes and factors influencing reproductive success in equine species. It involves the study of reproductive anatomy, endocrinology, and behavior, as well as the management practices that affect breeding outcomes. Key aspects include the estrous cycle, conception rates, and factors impacting stallion and mare fertility. Reproductive technologies such as artificial insemination, embryo transfer, and hormonal therapies are also explored to enhance breeding efficiency. This page compiles peer-reviewed research studies and scholarly articles that examine the biological mechanisms, management strategies, and technological advancements related to equine fertility.
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.
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...
Swierstra EE, Gebauer MR, Pickett BW.The cycle of the seminiferous epithelium of the stallion was
divided into eight stages, using as criteria the presence of meiotic divi-
sions, shape of the spermatid nuclei and location of spermatids with
elongated nuclei in the tubule. The mean frequencies ofstages 1 to 8 were
16\m=.\9, 14\m=.\9, 3\m=.\2, 15\m=.\8, 7\m=.\4, 13\m=.\5, 12\m=.\6 and 15\m=.\7%, respectively. The
duration of one cycle of the seminiferous epithelium was 12\m=.\2 days
(S.E.\m=+-\0\m=.\1) as determined by injecting a single dose of 700 \g=m\Ciof
[3H]thymidine into each spermatic artery of six stallions and rem...
Millar R, Francis J.Day (1939) recorded 95% fertility in wild
ponies, but in heavy horses it was only 52%
and in thoroughbreds 68%. Variation of fertility was stated by Anderson (1922) was not due
to disease or physiological malfunction, but to
highly artificial methods of mating. In New
Zealand, Bain (1948) recorded the fertility of
mares in 1944 as 61%. MahaiIey (1950) made
a survey in Western Australia and found fertility
rates which varied from 17% to 50% before
veterinary assistance was obtained.
An article in the British Racehorse (Anon
1949) revealed no evidence of any progress in
the control o...
Ginther OJ, Bergfelt DR.Seasonally anovulatory mares were injected, i.m., twice daily with a GnRH analogue (GnRH-A), and hCG was given when the largest follicle reached 35 mm in diameter. In Exp. 1, treatment was initiated on 23 December when the largest follicle per mare was less than or equal to 17 mm. An ovulatory response (ovulation within 21 days) occurred in 17 of 30 (57%) GnRH-A-treated mares on a mean of 15.8 days. The shortest interval to ovulation in control mares (N = 10) was 57 days. The diameter of the largest follicle first increased significantly 6 days after start of treatment. In Exp. 2, treatment wa...
Rigby S, Love C, Carpenter K, Varner D, Blanchard T.Eleven light-breed pregnant mares (335 to 347 d gestaton) were used to evaluate the use of prostaglandin E2 as a cervical ripening agent prior to induction of parturition during the months of April and May. Six hours prior to induction, each mare's cervix was examined per vagina for softness and dilation. Each mare was then assigned to 1 of 2 treatment groups: Group PGE mares (n = 7) received 2.0 to 2.5 mg prostaglandin E2 deposited intracervically; Group SAL mares (n = 4) received 0.5 mL of sterile NaCl deposited intracervically. Six hours later, the mares were readied for parturition by wrap...
Varadin M.Infertility, resulting from failure to conceive during the preceding breeding season, was caused by various forms of endometritis in forty-four mares of Highland and Arabian breeds in Yugoslavia. Chronic mucopurulent and latent catarrhal endometritis occurred most frequently. Douching of the uterus on alternate days for 9 days with warm and cold sterile salt solutions (ranging from 7% to 1% w/v) in the early autumn resulted in conception in 47-7% of mares at an average of 15-2 days after the onset of treatment, and another 36-7% becoming pregnant in the following spring. Mating at the wrong st...
Rossini JB, Rodriguez J, Bresnahan DR, Stokes JE, Carnevale EM.The clinical use of intracytoplasmic sperm injection (ICSI) in horses usually involves the transfer of embryos into recipient mares, resulting in substantial cost increases. This is essential when subfertile mares are oocyte donors; but some donors are fertile, with ICSI compensating for limited or poor-quality spermatozoa. Fertile oocyte donors could carry pregnancies, eliminating the need for a recipient. We assessed the potential of using oocyte donors as recipients for their own ICSI-produced embryos during the same cycle. Donors in oestrus and with large dominant follicles were administer...
Ginther OJ, Beg MA, Neves AP, Mattos RC, Petrucci BP, Gastal MO, Gastal EL.Plasma concentrations of FSH, LH, oestradiol and progesterone were studied daily during 12 interovulatory intervals and 21 periovulatory periods in nine Miniature ponies. The peak of the FSH surge that was temporally associated with emergence of the future ovulatory follicle occurred when the follicle was approximately 9 mm, compared with a reported diameter of 13 mm in larger breeds. The ovulatory LH surge involved a slow increase between Days 13 and 18 (ovulation=Day 0; 0.6+/-0.1 ng day(-1)), a minimal increase or a plateau on Days 18 to 21 (0.04+/-0.1 ng day(-1)), and a rapid increase after...
Shivers CA, Liu IK.Sera and follicular fluid from mares previously determined as having antibodies to the zona pellucida were exposed to porcine ovarian oocytes before insemination with boar spermatozoa in vitro. There was a dramatic decline in the number of spermatozoa bound to zonae compared to treatments with sera and follicular fluid from mares negative for zona antibodies. These data suggest that antibodies reactive with the zona pellucida may be responsible for reduced or even complete infertility in some mares. In a group of 50 randomly selected mares tested for antizona antibodies, 2 pregnant mares were ...
Berndtson WE, Jones LS.Testes were obtained from 47 1-20-year-old stallions during the natural breeding season. Total testicular testosterone and testosterone/g testis increased with age (P less than 0.005), and total testicular testosterone was associated with larger testis size (P less than 0.05). Neither testosterone per gram nor per paired testes were related to total Sertoli cell number (P greater than 0.05), but greater testosterone per paired testes was associated with fewer Sertoli cells per unit of seminiferous tubule length (P less than 0.005) or basement membrane area (P less than 0.02) and with a higher ...
Pipers FS, Zent W, Holder R, Asbury A.Ultrasonographic detection of pregnancy was performed in 952 Thoroughbred mares. Characteristic images were obtained between 12 and 55 days after breeding. Twins in the same uterine horn as well as twins in opposite horns were imaged, and for the first few months of gestation appeared similar to single pregnancies. Growth curves as a function of time were developed, utilizing horizontal diameters of the blastocysts versus breeding dates. Comparisons between horizontal and vertical diameters demonstrated no appreciable differences when observed as a group. Growth curves derived from twins did n...
Merkies K, Buhr MM.Spermatozoal function is affected by the ability to regulate intracellular calcium concentrations ([Ca2+]i), and may be influenced by epididymal maturation as well as environmental components. Regulation of [Ca2+]i in ejaculated and epididymal stallion spermatozoa was monitored over time in various media. Spermatozoa from each of 5 pony stallions (3 ejaculate samples and 1 caput and cauda sample) were labeled with the fluorescent calcium indicator probe Indo-1 in a calcium-free modified Tyrode's buffer. Fluorescent emissions were monitored by a dual wavelength spectrofluorometer over 5 h. Calc...
Bresnahan DR, Lupole RE, Stilz CR, Carnevale EM.Zona pellucida (ZP) proteins are important for fertilization and sperm binding and are closely associated with cumulus cells. Communication between cumulus and oocytes is facilitated by intracellular membrane channels composed of connexins. The extent aging impacts potential differences in fertilization and reductions in fertility is not well understood. This study characterized age-related differences in transcript abundance of ZP proteins and connexins in cells from ovarian follicles. Additionally, differences in sperm binding to oocytes from old and young mares was evaluated. For experiment...
Seidel GE.Principles for selecting future research projects include interests of investigators, fundability, potential applications, ethical considerations, being able to formulate testable hypotheses and choosing the best models, including selection of the most appropriate species. The following 10 areas of assisted reproduction seem especially appropriate for further research: efficacious capacitation of bovine spermatozoa in vitro; improved in vitro bovine oocyte maturation; decreasing variability and increasing efficacy of bovine superovulation; improved fertility of sexed semen; improving equine IV...
Hinrichs K, Riera FL.Ten mares were used to investigate the effect of administration of prostaglandin F2 alpha on uterine tubal motility, as reflected by embryo recovery from the uterus 5 days after ovulation (day 0). Mares were assigned to 3 groups: group A, uterine flush for embryo recovery on day 7; group B, uterine flush for embryo recovery on day 5; and group C, uterine flush for embryo recovery on day 5, after treatment with prostaglandin F2 alpha (10 mg, IM) on day 3. Each mare was assigned to each group once. Embryo recovery rates for the 3 groups were: A, 6 of 10; B, 2 of 8; and C, 0 of 10. The embryo rec...
Azuma T, Choi YH, Hochi S, Oguri N.The development of in-vitro matured and microfertilized horse oocytes was examined in vitro. Fertilized oocytes were produced by 20-h insemination of in-vitro matured and partially zona-removed oocytes with frozen spermatozoa that had been treated with caffeine/calcium ionophore A23187 (fertilization rate 34.2%, monospermy rate 76.9%). Embryonic development was assessed by the number of nuclei stained with Giemsa solution. In Experiment 1, a continuous 8-day culture of the microfertilized oocytes in TCM199 or modified synthetic oviduct fluid (m-SOF) supplemented with 10% fetal bovine serum or ...
Tekin N, Wöckener A, Klug E.The effect of a skim milk extender and a glycine-containing extender on sperm motility and acrosome morphology of stallion semen was examined. There was no difference concerning acrosome morphology. After 24 hours of preservation motility of the ejaculates diluted with glycine extender was significantly superior to those handled with skim milk extender. Storage at 5 degrees C in all cases gave better results than storage at room temperature. Skim milk extender is an appropriate diluent when the semen is used for al on the day of its collection, whereas the glycine-containing extender offers th...
Chavatte-Palmer P, Duchamp G, Palmer E, Ousey JC, Rossdale PD, Lombès M.Progesterone, oestrogen and glucocorticoid receptor concentrations in the uterus and mammary glands of pregnant mares during mid- to late gestation (from day 150 of gestation to term) were measured by binding assays to investigate the hormonal mechanisms involved in pregnancy maintenance and lactation. Uterine progesterone receptor concentrations did not increase significantly with increasing gestational age (from 67.8 +/- 13.7 to 126.1 +/- 48.7fmol mg(-1) protein), whereas oestrogen receptor concentrations were significantly higher in pregnant mares (271.7 +/- 28.9 fmol mg(-1) protein) than i...
Perdomo-González DI, Id-Lahoucine S, Molina A, Cánovas A, Laseca N, Azor PJ, Valera M.Transmission Ratio Distortion (TRD) is a genetic phenomenon widely demonstrated in several livestock species, but barely in equine species. The TRD occurs when certain genotypes are over- or under-represented in the offspring of a particular mating and can be caused by a variety of factors during gamete formation or during embryonic development. For this study, 126 394 trios consisting of a stallion, mare, and offspring were genotyped using a panel of 17 neutral microsatellite markers recommended by the International Society for Animal Genetics for paternity tests and individual identification...
Uhlmannsiek L, Shen H, Eylers H, Martinsson G, Sieme H, Wolkers WF, Oldenhof H.Cryopreserved semen is routinely shipped in liquid nitrogen. Dry ice could serve as an alternative coolant, however, frozen storage above liquid nitrogen temperatures (LN2, -196 °C) may negatively affect shelf-life and cryosurvival. In this study, we determined critical temperatures for storage of cryopreserved stallion sperm. We evaluated: (i) effects of cooling samples to different subzero temperatures (-10 °C to -80 °C) prior to storing in LN2, (ii) stability at different storage temperatures (i.e., in LN2, dry ice, -80 °C and -20 °C freezers, 5 °C refrigerator), and (iii) sperm...
Artificial insemination with cooled-shipped semen is the primary method used in the equine breeding industry; yet, sperm quality and fertility can be suboptimal for some stallions when standard techniques are used. Therefore, there is a critical need to develop alternative approaches for these stallions. Objective: To assess sperm quality parameters and fertility of cooled-stored stallion semen processed by SpermFilter® or centrifugation and resuspended in three extenders. Methods: Controlled and field study. Methods: In Experiment 1, semen was collected from 21 stallions classified as having...
Shakeel M, Choi Y, Yoon M.Cryptorchidism affects spermatogenesis and testis development, often resulting in stallion subfertility/infertility. This study aims to identify the specific germ cells impacted by cryptorchism in stallions. In a previous study, we found that PGP9.5 and VASA are molecular markers expressed in different germ cells within stallions. Herein, we assessed the heat stress-induced response of spermatogonial stem cells (SSCs) in the seminiferous tubules (ST) of cryptorchid stallion testes (CST) and normal stallion testes (NST). This goal was accomplished by comparing PGP9.5 and VASA expression pattern...
Morris L, Harteveld R, Gibb Z.Insemination of mares with frozen-thawed spermatozoa requires intensive management and results in 40%-60% per cycle pregnancy rates. Objective: To determine if satisfactory fertility is possible for frozen-thawed semen after processing it through a microfluidic device, followed by storage at 17°C for up to 24 h before fixed-time insemination. Methods: Uncontrolled field trials. Methods: A pilot study evaluated the motility of frozen-thawed spermatozoa after centrifugation and storage (17°C) in two different media for up to 48 h. Subsequently, the motility of frozen-thawed semen processed...
Sala-Ayala L, Martínez-Boví R, Querol-Paajanen A, Cuervo-Arango J.The aims of this study were to determine the effect of the embryo flushing technique and the number of flushing attempts performed by operators of different experience on embryo recovery (ER). Ten non-lactating mares were inseminated with the same stallion in six cycles each (n = 60). Embryo flushing (EF) was performed 7-9 days after ovulation by three operators (OP; 20 EF cycles each): OP1 had performed >500 EF before the study, while OP2 and 3 had performed 0 EF. Each EF was performed with 2 flushing attempts (FA) using 1L of ringer's lactate "in-and-out" using two EF techniques: 1) ...
Arroyo-Salvo C, Río S, Bogetti ME, Plaza J, Miragaya M, Yaneff A, Davio C, Fissore R, Gervasi MG, Gambini A, Perez-Martinez S.Factors contributing to the limited success of in vitro fertilization in horses remain to be studied. In this work, we elucidated the effect of different essential capacitation media components, bicarbonate, and bovine serum albumin or polyvinyl-alcohol, and the incubation microenvironment on sperm parameters associated with capacitation, acrosome reaction, and their ability to activate oocytes via heterologous intracytoplasmic spermatozoa injection in equine cryopreserved spermatozoa. Methods: Frozen-thawed spermatozoa underwent incubation at different time intervals in either Tyrode's albumi...
Aguila L, Cabrera P, Arias ME, Silva M, Felmer R.Intracytoplasmic sperm injection (ICSI) in horses is currently employed for clinical and commercial uses, but the protocol could be optimized to improve its efficiency. We have hypothesized that destabilization of plasma and acrosomal membranes prior to injection would positively impact the developmental potential of equine zygotes generated by ICSI. This study evaluated effects of the sperm treatment with lysolecithin on plasma and acrosomal membranes and on oocyte activation ability, initially following heterologous ICSI on bovine oocytes and subsequently employing equine oocytes. The effect...
Fuentes F, Contreras MJ, Arroyo-Salvo C, Cabrera P P, Silva M, Merino O, Arias ME, Felmer R.Although under appropriate laboratory conditions, sperm from different mammalian species can be capacitated in vitro, the optimal conditions for sperm capacitation in the stallion have been elusive. This study evaluated the effect of different capacitating inducers in Whitten and Tyrode media and assessed their impact on capacitation-related factors. Stallion sperm were incubated with different combinations of capacitating inducers at 38.5 °C in an air atmosphere. Sperm quality variables such as motility, mitochondrial membrane potential, and lipid peroxidation were assessed. Membrane fluidi...
Martínez-Boví R, Gaber JTH, Sala-Ayala L, Plaza-Dávila M, Cuervo-Arango J.The effect of embryo reinsertion immediately after embryo flushing was studied. In Experiment 1, eight mares were used during 32 cycles (8 cycles in each group). For the first two groups, inseminated mares were flushed 8 days after ovulation and prostaglandin F2α was not administered: in group EF-ET (embryo flushing and embryo transfer) the embryo was reinserted in the same donor mare, while in the EF group, no further procedure was performed. In the third group (ET), non-inseminated mares (recipients) received a Day 8 embryo. Progesterone concentration was measured before EF/ET and 72 h afte...
Khan Y, El-Shalofy A, Kaps M, Gautier C, Aurich C.We aimed to determine associations between experimentally impaired uterine clearance or treatment with ecbolic drugs on luteal development in estrous mares after insemination. In a crossover design, eight mares were treated with saline (CON), clenbuterol (CLEN), oxytocin (OXY) and carbetocin (CARB) from the day of first insemination until 2 days after ovulation. Between treatments, the mares rested for one cycle. Estrous mares were examined for the presence of free intrauterine fluid by transrectal ultrasound. Endometrial swabs for cytology and bacteriology were collected on days 1 and 14. Blo...
Goudet G, Beauclercq S, Douet C, Reigner F, Deleuze S, Nadal-Desbarats L.Successful reproductive management of domestic mammals depends primarily upon timely identification of oestrous cycle stages. There is a need to develop an alternative non-invasive, welfare-friendly, accurate and reliable method to identify reproductive cycle stages. This is of particular interest for horse breeders, because horses are high-value farm animals that require careful management and individual monitoring. Saliva sampling is non-invasive, painless and welfare-friendly. Thus, we performed a metabolomic analysis of equine saliva during different reproductive stages to identify changes...
Ricard RM, Wobeser B. is a reported cause of infertility and endometritis in sheep, cattle, and pigs; however, the association between uterine disease and is poorly understood in horses. Recently, a high prevalence of in equine aborted chorioallantoises was reported in horses in western Canada. Based on this high prevalence, investigation into the effects of on infertility and endometritis in western Canadian mares is prudent. We examined 98 formalin-fixed, paraffin-embedded endometrial biopsies from western Canada submitted between 2014 and 2022 using a -specific 16S rRNA PCR test; 40 samples tested positive f...
Jung H, Yoon M.Spermatogonial stem cells originate from gonocytes and undergo self-renewal and differentiation to generate mature spermatozoa via spermatogenesis in the seminiferous tubules of the testis in male mammals. Owing to the unique capacity of these cells, the spermatogonial stem cell transplantation technique, which enables the restoration of male fertility by transfer of germlines between donor and recipient males, has been developed. Thus, spermatogonial stem cell transplantation can be used as an important next-generation reproductive and breeding tool in livestock production. However, in large ...
Flores JG, Bueno VC, Bastos HBA, Rechsteiner SMDEF.Reproductive biotechniques in the equine species have advanced in the last decade and horse breeders have started to question the possibilities of interfering in the determination of foal sex. The aim of the present study was to verify whether the variables mares and stallion's age, side of the ovary containing the preovulatory follicle, preovulatory follicle diameter, time between breeding and ovulation, and ovulation inducing hormones influence the sex of the foal. A total of 259 reproductive cycles of 160 mares and 22 Thoroughbred stallions were used. Statistical analysis was performed usin...
