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Topic:Reproduction
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.
Factors affecting the composition of mare uterine fluid. The influx of protein and polymorphonuclear leucocytes (PMN) into the uterine lumen was examined at different intervals after intrauterine infusion of fluids. The intrauterine infusion of both phosphate buffered saline (PBS) and a solution of lipopolysaccharide (LPS) derived from Escherichia coli resulted in a biphasic influx of protein in the uterine flushings peaking three and six hours after infusion. LPS infusion caused an additional influx of protein at 24 hours. The initial influx of protein preceded a biphasic influx of PMN which peaked six and 24 hours after both infusions. Uterine flu...
Clinical significance of aerobic bacterial flora of the uterus, vagina, vestibule, and clitoral fossa of clinically normal mares. Swab specimens for bacterial culture were obtained from the uterus, vagina, vestibule, and clitoral fossa of 48 mares that had normal reproductive tracts, no history of reproductive problems, and no inflammation on evaluation of endometrial biopsy. The mares were predominantly Thoroughbred and Standardbred. Swab specimens of the vagina were obtained through a sterile speculum; swab specimens of the uterus were obtained by use of a double-guarded, occluded culture instrument. Fifteen (31%) of the uterine swab specimens and 20 (42%) of the vaginal swab specimens yielded growth on aerobic culture...
Effects of hormone implants on estrus and ovulation in feral mares. Five groups of 30 captive feral mares each were implanted with silastic rods containing estradiol (E) and/or progesterone (P): E only with 8 g, P only with 24 g, P+HE with 8 g P + 8 g E, HP+E with 12 g P + 4 g E, HP+LE with 12 g P + 2 g E. Arbitrary group designations were differentiated by relative high (H) and low (L) amounts of steroid. Thirty mares received silastic rods containing no hormone (CI). Five mares from each group were bled every 2 wk for 4 mo and monthly for another 5 mo. All mares were tested for estrus by allowing them to stand in an alley between two pens of stallions and vi...
Effects of gonadotrophin-releasing hormone and prostaglandin F-2 alpha on corpus luteum function and timing of the subsequent ovulation in the mare. Standard bred mares that were cycling normally were treated beginning on Days 9 or 10 of the oestrous cycle with repeated pulses of GnRH (20 micrograms/h) and/or a single injection of prostaglandin (PG)F-2 alpha (alfaprostol, 3 mg), and were subsequently bled and palpated daily until the next ovulation. GnRH treatment increased serum concentrations of LH and progesterone at 4 days after the start of treatment compared to controls. The combination of PGF-2 alpha + GnRH treatment resulted in an immediate decline in serum progesterone values, and subsequently decreased the interval to next ovulat...
Concentrations of immunoreactive leukotriene B4 in uterine lavage fluid from mares with experimentally induced and naturally occurring endometritis. Acute endometritis was induced in ovariectomized pony mares by infusion of a 1% solution of oyster glycogen. Maximum concentrations of immunoreactive leukotriene B4 in uterine washings coincided with the greatest rate of infiltration of neutrophils into the uterine lumen. Concentrations of immunoreactive leukotriene B4 decreased to basal levels 6 h after infusion and were unaffected by administration of ovarian steroids to ovariectomized mares. Uterine washings from mares with persistent endometritis did not contain significantly different concentrations of leukotriene B4 from genitally normal...
Studies of stallion sperm survival: preservation of progressive motility of stallion spermatozoa by low ionic strength media. Preservation of stallion sperm forward motility was studied using a video recording system in semen diluted with media of different ionic strength and sodium content. After 8 hr of incubation at room temperature, semen diluted in a low ionic strength media containing sucrose displayed 65 +/- 9% motility with 68 +/- 3% of the motile sperm showing forward motility (diameter of head trajectory greater than or equal to 80 microns). In contrast, sperm populations diluted and incubated with a normal ionic strength media containing sodium had 56 +/- 7% motile sperm of which only 36 +/- 7% displayed f...
Evaluation of the post-partum mare in relation to foal heat breeding. II. Uterine swabbing and biopsies. Fifty-three post-partum (p. p.) periods were studied in 38 mares. Uterine samples were taken on
the 2nd and 5th days p.p. and thereafter every other day until ovulation. Uterine swabs were
examined for bacteria and neutrophils and uterine biopsy specimens for neutrophils and lymphocytes.
The occurrence of bacteria and leukocytes was most common on day 5 p. p. The dominant organism
on day 2 was E. coli and on day 5 P-haemolytic streptococci. Thirty-four mares were inseminated
during the first p. p. oestrus. Only the occurrence of neutrophils in day 5 biopsy specimens correlated
with foal ...
Body temperature and behaviour of mares during the last two weeks of pregnancy. Average daily core body temperature and behavioural patterns of pregnant mares were studied, in search of definitive signs of parturition within 24 h of the event. Nineteen pony mares were sampled twice daily for core body temperature. A significant temperature drop, averaging 0.1 degrees C (0.2 degrees F) was observed during the day prior to parturition. Between 18.00 h and 06.00 h, during the two weeks before parturition, Thoroughbred and Standardbred mares (n = 52) spent an average 66.8 per cent of their time standing, 27.0 per cent eating, 4.9 per cent lying in sternal recumbency, 1.0 per ...
Effect of exogenous ovarian steroids on the uterine luminal prostaglandins in ovariectomised mares with experimental endometritis. 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...
Loss of polar trophoblast during differentiation of the blastocyst of the horse. Twelve blastocysts, collected 7-12 days after ovulation (Day 0), were examined by light and electron microscopy to investigate the nature of the relationship of the polar trophoblast (Rauber's layer) to the inner cell mass. On Day 7, the polar trophoblast was intact and formed a flattened layer overlying the epiblast cells of the inner cell mass. As blastocysts enlarged to greater than 1 mm in diameter, small discontinuities appeared in the polar trophoblast, where epiblast cells intruded onto the surface. At this time, trophoblast cells adhered closely to adjacent and underlying epiblast cell...
Influences of season and artificial photoperiod on stallions: luteinizing hormone follicle-stimulating hormone and testosterone. Influence of day length on seasonal endocrine responses were studied using stallions (seven per group). Treatments included 1) control, with natural day length; 2) 8 h light and 16 h dark (8:16) for 20 wk beginning July 16, 1982 then 16:8 from December 2, 1982 until March 5, 1984 (S-L); or 3) 8:16 from July 16, 1982 until March 5, 1984 (S-S). Blood was sampled hourly for 5 h every 4 wk; sera were pooled within horse, and luteinizing hormone (LH), follicle-stimulating hormone (FSH) and testosterone were quantified. Blood was collected every 20 min for 24 h every 8 wk and 2 wk before and after t...
Secretion rates and short-term patterns of gonadotrophin-releasing hormone, FSH and LH in the normal stallion in the breeding season. Pituitary venous blood was collected by a painless nonsurgical cannulation method from five ambulatory stallions at 5-min intervals for 5-6 h during the breeding season. In four adult stallions, statistical analysis showed that pulses of gonadotrophin-releasing hormone (GnRH) and LH were coincident (P less than 0.01), as were pulses of FSH and LH (P less than 0.05). Furthermore, the patterns of changes in concentration of FSH and LH were highly correlated in each of the four stallions. However, seemingly ineffective pulses of GnRH were also observed, with 28% of GnRH pulses failing to induce a...
Testis size and onset of spermatogenesis in Cape mountain zebras (Equus zebra zebra). Testis mass of adult Cape mountain zebra stallions (mean 70.0 g) was appreciably less than that of other zebra species and domestic horses. The histological appearance of the testes of 11-, 24- and 29-month-old colts was typically prepubertal. Spermatogenic activity of a 4-year-old stallion obtained at the end of summer was at a very low level, while a 4.5-year-old stallion obtained 6 weeks after the winter solstice showed a marked increase in spermatogenesis compared with the 4-year-old. Stallions 6.5-19 years of age collected in different seasons all showed active spermatogenesis.
Gonadotropin secretion in ovariectomized pony mares treated with dexamethasone or progesterone and subsequently with dihydrotestosterone. Twelve long-term ovariectomized (OVX) pony mares were used to determine the effects of dexamethasone (DEX) or progesterone (PR) on concentrations of follicle stimulating hormone (FSH) and luteinizing hormone (LH) in daily blood samples and after administration of gonadotropin releasing hormone (GnRH). All mares were subsequently administered dihydrotestosterone (DHT) to determine if DEX or PR treatment altered the FSH or LH response to this androgen. Daily blood sampling was started on day 1. After a pretreatment injection of GnRH on day 5, four mares were administered DEX at 125 micrograms/kg...
Embryonic loss in pony mares induced by intrauterine infusion of Candida parapsilosis. Pony mares which were detected pregnant by transrectal ultrasonography received a single intrauterine infusion of either sterile saline (control, n = 12 mares) or 10(6)Candida parapsilosis (treated, n = 12 mares) between Days 11 to 14 postovulation. Subsequent embryonic loss was studied by daily ultrasonography of the mare's uterus, by serum progesterone levels, by endometrial swabs for cytologic and microbiologic examination and by endometrial biopsies that were taken after embryonic loss was detected. Significantly fewer (P<0.01) embryonic losses occurred in control than in treated mares (4 ...
Comparison of early conceptus mobility between mares and jennies. The caracteristics of early intrauterine mobility of the conceptus were compared between ponies (n = 9) and donkeys (n = 9). The extensive mobility of the early conceptus, previously reported for ponies and horses, was found in donkeys as well. There were no significant differences between donkeys and ponies in the characteristics or patterns of mobility. However, the mean day of fixation was approximately one day later (P<0.05) in donkeys (Day 15.6 +/- 0.3) than in ponies (Day 14.7 +/- 0.2).
Age-related morphological and functional changes in the Leydig cells of the horse. Two ultrastructurally distinct types of Leydig cells were observed in the equine testis. Whereas the adult testis exhibited both postpubertal and adult Leydig cells, the testis of the pubertal horse contained only the postpubertal type, and that of the aged horse contained only the adult type. However, Percoll-purified testicular preparations from pubertal, adult, and aged horses all exhibited two distinct Leydig cell populations. The quantitative distribution and the functional characteristics of these Leydig cell populations (ability to bind human chorionic gonadotropin [hCG] and increase of...
[Karyotypes of cattle (Bos taurus) and horses (Equus caballus) on the basis of synaptonemal complexes]. The cytogenetic study performed has shown that karyotyping of meiotic cells can be based on the synaptonemal complexes (SC) of spreading pachytene spermatocytes of bull and of horse. The horse SC karyotype has not been previously described. A comparison of the relative length of SC with metaphase chromosomes of bull and horse somatic cells has revealed the correspondence of the chromosome length in pachytene of meiosis and metaphase, which is in agreement with the data on house mouse and Chinese hamster. The method of spreading pachytene cells may be of great practical importance in studies of...
Conformational restrictions of the sheep testicular receptor discriminates pituitary lutropin and placental gonadotropins. A membrane preparation from the testis of maturing Dorset-Leicester-Suffolk sheep, capable of discriminating pituitary LH (lutropin) from placental gonadotropins human choriogonadotropin (hCG) and equine choriogonadotropin is described. Maximum binding of 125I-oLH (ovine lutropin) to the testicular receptors occurred at 4 degrees C in a rapid manner, attaining equilibrium in 12-16 h. Under such optimal conditions, only unlabeled ovine LH or the structurally identical bovine LH effectively competed for receptor occupation. Other highly purified pituitary LH preparations from rat and human pitui...
A 64XX/65XXX mosaic mare (Equus caballus) and associated infertility. IT is well known that chromosomal abnormalities are
frequently associated with infertility in the mare (Table 1). The
most commonly reported abnormality is 6 3 x 0 which can
occur in a mosaic or non-mosaic form. Various other
aneuploidies of the sex chromosomes have been reported but
the 6SXXX genotype appears to be rare. Chandley et a1 (1975)
and Chandley (1984) have reported two 65XXX animals and
Walker (1979) a 64XW6SXXW6SXXY one.
This paper reports a mosaic 64XXh5XXX animal and
emphasises the need for more cytogenetic analysis in the
horse.
Chromosome anomalies and infertility in the mare. Nine reproductively normal mares, 25 infertile mares and one set of heterosexual twins were examined cytogenetically using conventional giemsa staining, C-banding and G-banding. It was concluded that G-banding was necessary to identify even gross anomalies. Three (12 per cent) of the infertile mares, but none of the controls, had a chromosomal anomaly. One was 63,XO, one a 63,XO/64,XX mixoploid and one a 64,XY sex reversed male. It is argued that a cytogenetic examination is a useful diagnostic technique but that routine screening of the whole population would be uneconomic.
A urethral extension technique to correct urine pooling (vesicovaginal reflux) in mares. A surgical technique involving reconstruction of the caudal vaginal vault was used to correct vesicovaginal reflux in 32 of 34 mares. After surgery, 22 of 24 mares became pregnant, and embryos were harvested for transfer from 6 of the other 10 mares. It was concluded that the procedure was safe and efficacious.
