Omneity® Pellets
All-In-One Vitamin & Mineral Pellet
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.
The variety of sterility and gradual progression to fertility in hybrids of the horse and donkey. Generally speaking, the majority of F1 hybrids between the horse and donkey are sterile and do conform to the hypothesis of gametogenic breakdown. The results of our own research, nevertheless, lead us to conclude that there is variability in degree of sterility and fertility for both F1 and B1 individuals, with a gradual advance from sterility to fertility being seen. This is the subject we will discuss from the point of view of oestrus, ovulation, mating, pregnancy, spermatogenesis, endocrine activity, isozymes and karyotypic analysis in this paper.
Uterine clearance mechanisms during the early postovulatory period in mares. Uterine response to inoculation with Streptococcus zooepidemicus organisms, 51Cr-labeled 15-microns microspheres, and charcoal was evaluated in 9 mares (4 resistant and 5 susceptible to endometritis) to determine mechanical and cellular clearance rates during the early postovulatory period. Mares were inoculated at estrus prior to ovulation during estrous cycles 1, 3, and 5. Uterine swab specimens for aerobic and anaerobic bacteriologic culture and serum for progesterone determination were obtained on postovulation day 3 during estrous cycle 1, on the day of ovulation during estrous cycle 3, a...
The role of the Flehmen response in the behavioral repertoire of the stallion. The role of the Flehmen response in equine behavior was investigated under field and laboratory conditions. In Experiment 1, a field study made of five stallions on pasture with between three and eighteen mares each during the season indicated the following: 1) The Flehmen response was most frequently preceded by nasal, rather than oral, investigation of substances; 2) The stallions' rate of Flehmen varied with the estrous cycles of the mares; 3) The rate of Flehmen response did not show a variation with time of day; and 4) The Flehmen response was most frequently followed by marking behaviors...
Androgen synthesis and aromatization by equine corpus luteum microsomes. Whereas mare corpus luteum does not produce androgens or estrogens in vivo, the incubation of mare corpus luteum microsomes with progesterone and NADPH resulted in 17 alpha-hydroxyprogesterone and estrogen production with a small yield of androstenedione. In the presence of an aromatase inhibitor (4-hydroxyandrostenedione), 17 alpha-hydroxyprogesterone and androstenedione were accumulated. Aromatization of testosterone and androstenedione occurred via stereospecific loss of the 1 beta, 2 beta hydrogen atoms and was inhibited by MgCl2, KCl, and EDTA. The Km of estrogen synthetase from equine co...
Leiomyoma of the tunica albuginea in a horse. A leiomyoma of the left testicle was found in a 7-year-old Arabian stallion at routine castration. The neoplasm consisted of interlacing bundles of well-differentiated, haphazardly arranged, smooth muscle cells attached superficially to the tunica albuginea.
Hastened transport of equine embryos through the oviduct of the mare. The purposes of this experiment were 1) to test the hypothesis that placing rabbit embryos into the mare's uterus would hasten oviduct transport and 2) to determine if placing fluid into the uterus of bred mares on Day 4 and/or Day 5 would subsequently disrupt the mare's pregnancy. The hypothesis that placing rabbit embryos into the mare's uterus would hasten oviduct transport was not supported, since the uterine recovery rate of equine embryos on Day 5 was not significantly higher (P>0.05) for mares receiving rabbit embryos on Day 4 than for mares receiving no uterine infusion on Day 4 (1 10 ...
Twin embryos in mares. II: Post fixation embryo reduction. Recent findings on the development and natural outcome of twins from Day 17 (immediately after fixation) to Day 40 are reviewed. Incidence of embryo reduction was increased significantly when the vesicles became fixed unilaterally, rather than bilaterally, and when the vesicles were unequal in diameter. Of 68 mares with twins on the day of fixation, post fixation embryo reduction occurred in 41 (60 per cent). The incidence of reduction was 41 of 48 (85 per cent) following unilateral fixation; reduction occurred in all of 22 mares with vesicles of dissimilar size (4 mm or more difference in dia...
Equine body temperature and progesterone fluctuations during estrus and near parturition. Body temperature and serum progesterone concentrations were measured in mares to determine if a change in either could be useful in predicting estrus, ovulation or parturition. There was no significant correlation (P > 0.1) between rectal temperature and the environmental temperature or progesterone concentration. Progesterone concentration did correlate with stage of estrous cycle and the stage of pregnancy. Significant differences (P < 0.05) in temperature were noted at different times throughout the day. No change in temperature occurred that could be utilized to predict estrus, ovula...
Temporal appearance of seasonal changes in numbers of Sertoli cells, Leydig cells, and germ cells in stallions. The temporal appearance of seasonal changes in numbers of Leydig, Sertoli, and germ cells was evaluated to determine if seasonally increased daily spermatozoan production might be preceded by changes in numbers of either of two somatic testicular cells. A significant increase in numbers of spermatogonia and Sertoli cells preceded the significant increase in number of Leydig cells in the approaching breeding season. Seasonal changes in parenchymal weight and in numbers of Sertoli cells, Leydig cells, and germ cells were maximal in May and June. Numbers of A or B spermatogonia in June were 2.4 t...
Monorchidism in the horse. Six horses with monorchidism, identified at surgery for cryptorchidectomy, are reported. All six presented with a single scrotal testis. Following surgical removal of one testis, they were either hormonally, anatomically or behaviourally determined to be geldings. Three other horses reported in the literature are reviewed. Of these nine cases of monorchidism, eight were thought to be caused by testicular degeneration and one by testicular agenesis. The vaginal process was present in all of the former and absent in the latter. The left side was involved in five of these eight horses. In seven, ...
Twin embryos in mares. I: From ovulation to fixation. Recent findings on the origin and development of twins from ovulation (Day 0) to fixation (mean: Day 16) are reviewed. Available data show that almost all twins originate from multiple ovulations. Results of recent ultrasound studies indicate that the number of days between double ovulations does not affect the conception rate per ovum or embryo survival during the first 16 days after each ovulation. Embryo reduction is the natural elimination of excess embryos so that only one embryo enters the foetal stage. In two studies, embryo reduction before or on the day of fixation was not considered ...
Reproductive traits, lactation and foal growth in mares fed altrenogest. Lactating mares were assigned as controls or fed altrenogest (.044 mg.kg body wt-1.d-1) for 15 d after foaling. Mares (n = 6) fed altrenogest were inseminated during the first estrus after treatment and mares (n = 6) in the control group were inseminated during the second postpartum estrus. Ovulation during the estrus in which mares were inseminated occurred 26 +/- 1 d postpartum for treated mares and 36 +/- 1 d postpartum for control mares. The percentage of mares conceiving was not different for control (67%) and alternogest-treated (100%) mares. No differences were observed in tone and size...
Changes in serum concentrations of luteinizing hormone and follicle-stimulating hormone following injection of gonadotropin-releasing hormone during pregnancy and after parturition in mares. High concentrations of estrogens in the peripheral circulation during late gestation inhibit synthesis of LH and markedly reduce pituitary content of LH at the end of pregnancy in most domestic species. Because blood concentrations of estrogen peak shortly before mid-gestation in the mare and then gradually decrease until parturition, we hypothesized that pituitary content of LH may increase during late gestation. To test this hypothesis 10 horse mares were challenged with a maximally stimulatory dose (2 micrograms/kg) of GnRH on d 240 and 320 of gestation and d 3 after parturition. A separate...
Evaluation of three strip tests for measuring electrolytes in mares’ pre-partum mammary secretions and for predicting parturition. Three strip test kits which measure calcium and/or magnesium in mares' mammary secretions were compared and assessed for their accuracy in:- 1) measuring these electrolytes compared to standard laboratory measurements, and 2) predicting the time of parturition. Daily samples of mammary secretions were obtained pre-partum from 35 Thoroughbred mares and allocated a score. Measurement of mammary secretion calcium and/or magnesium by the strip tests and laboratory methods correlated significantly (P less than 0.001). The results obtained for prediction of parturition were analysed by two methods. ...
A spectrophotometric procedure for the determination of objective measurements of equine spermatozoan motility. A spectrophotometric procedure was developed and evaluated for the objective measurement of equine spermatozoan motility. A 100 mul sample of a sperm suspension, prepared by the removal of seminal plasma, was layered under a column of optically clear medium in a specially designed spectrophotometric cuvette maintained at 37 degrees C. Changes in light transmittance above the interface of the sperm suspension and medium were recorded on chart paper. As sperm cells swam into the medium, a decrease in light transmittance was recorded as a deflection on the chart paper. Chart recordings were analy...
[The occurrence and significance of plasma coagulase negative staphylococci from the genital tract of horses]. Classification based on biochemical characteristics of 389 strains of plasma-coagulase-negative (plc-) staphylococci isolated from the genital tract of mares and stallions resulted in the following distribution of species: St. sciuri 130 (33.4%), St. equorum 42 (10.8%), St. xylosus 16 (4.1%), St. epidermidis 35 (9.0%), St. simulans 24 (6.2%), St. haemolyticus 33 (8.5%), St. warneri 18 (4.6%), St. lentus 12 (3.1%), St. hyicus 11 (2.8%). Strains of St. cohnii, St. capitis, St. gallinarum, St. saprophyticus and St. hominis have only been found sporadically (a. 1%). 48 (12.3%) strains could not be...
[Preservation capability of horse semen by the use of two diluents and preservation temperatures]. 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...
Occipitoatlantoaxial malformation with duplication of the atlas and axis in a half Arabian foal. An unusual occipitoatlantoaxial malformation is described in a 2-week-old male part Arabian foal that was unable to stand at birth and showed signs of spastic tetraparesis due to a cervical spinal cord compression. There were 2 atlases present. One was fused to the occipital bones. The other articulated with the first atlas and an axis which had a long dens that projected into the vertebral canal. Examination of the ossification centers of the axis indicated partial duplication of that bone.
Predicting ovulation in the mare on the basis of follicular growth and serum oestrone sulphate and progesterone levels. Follicular growth and hormone determinations were used to predict ovulation in the mare. Thirty Finnhorse mares were used for the investigation and 38 oestrous cycles were studied. The mares were examined by rectal palpation and ultrasonography every 6 hours during late oestrus. Daily blood samples were obtained for progesterone and oestrone sulphate determination. The preovulatory follicle grew 3 mm a day up to 2 days before ovulation. The size then remained constant, before diminishing by 2-3 mm during the last 12 hours. The maximal diameter of the follicle was 43 +/- 4 mm. In 89% of the fol...
Semen selenium content and sperm mitochondrial volume in human and some animal species. Selenium (Se) and glutathione peroxidase (GSH-Px) were determined from the seminal plasma samples and spermatozoa of human and four different animal species. The human sperm Se concentration was 1.8 +/- 0.8 micrograms/g dry weight, which was about half of that in the bull. Abnormal sperm morphology and motility correlated with low sperm Se content. The volume of sperm mitochondrial sheath in human, bull and stallion was measured using transmission electron microscopy. In these species the sperm Se content was highly correlated with the volume of mitochondria. Among the five species studied, th...
Synthesis and aromatization of 19-norandrogens in the stallion testis. The results of the measurement of 19-nortestosterone in the testiscular artery and vein of the stallion, the very low levels of this steroid in the peripheral blood of geldings and the similar patterns of increase in the peripheral levels of 19-nortestosterone and testosterone after hCG stimulation, show that 19-nortestosterone, like testosterone, is essentially synthesized in the testis. This testicular origin was confirmed by the ability of testicular tissue to synthesize 19-norandrogens from [4-14C]androgens in vitro. 19-Nortestosterone was 50% conjugated in the peripheral blood and almost ...
Plasma prolactin concentrations in mares and their neonates after oxytocin induction of parturition. Studies were undertaken to investigate the effects of oxytocin induction on prolactin release in term (Group II) and preterm (Group III) mares and to compare these effects to spontaneously foaling mares (Group I). Since physiological concentrations of prolactin in blood have not been measured in the neonatal foal, experiments were designed to monitor prolactin in the cord artery and jugular blood of the foals from all groups of mares. Although prolactin levels varied in term mares (Group I and II) during the last 11 days of pregnancy, an increase was observed between Day -6 and Day 0 (2.7 and ...
Colostral volume and immunoglobulin G and M determinations in mares. Colostral volume and IgG and IgM concentrations were determined in 6 multiparous mares at foaling and them every 2 hours from 16 to 20 hours after parturition. Serum IgG and IgM concentrations at foaling also were determined in each mare. The rate of mammary secretion was 292 +/- 26 ml/h (range, 202 to 389 ml/h), and the colostral volume was 5.1 +/- 0.5 L (range, 3.2 to 7.0 L). The colostral IgG and IgM contents were 440 +/- 106 g (range, 199 to 855 g) and 3.1 +/- 0.9 g (range, 0.7 g to 7.1 g), respectively. There was no significant correlation between serum and initial colostral IgG and IgM c...
Distribution of histological lesions in the equine endometrium. The distribution of histopathological lesions in the equine endometrium was examined to investigate the representativeness of a single biopsy specimen in terms of the whole endometrium. Five sections from each of 110 uteri obtained from slaughtered mares were evaluated microscopically and classified according to a four-category grading system used for endometrial biopsies. Depending on the extent of agreement between the categories of the homologous sections, the uteri were considered to show either good agreement (81 uteri; 73.6 per cent), moderate agreement (26 uteri; 23.6 per cent) or poor ...
Influences of season and artificial photoperiod on stallions: pituitary and testicular responses to exogenous GnRH. Effects of season and photoperiod on the anterior pituitary gland and testes were studied by responses to exogenous GnRH. Stallions were assigned to one of three treatments: 1) control, exposed to natural day length; 2) S-L, 8 h of 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; or 3) S-S, 8:16 from July 16, 1982 until March 5, 1984. Approximately every 8 wk, stallions were administered GnRH (2 micrograms/kg BW) and blood was sampled at 20-min intervals for 2 h before and 8 h after GnRH administration. Concentrations of LH, FSH ...
Predictive utility of pre-partum temperature changes in the mare. Rectal temperature was recorded from 22 mares at 0700, 1500 and 2300 h daily for seven days pre-partum and one day post partum. A circadian variation in rectal temperature was present with the lowest temperature recorded at 0700 h. Because of this, the mares were divided into three groups based on time of parturition; those foaling between 0700 and 1500 h (n = 2); between 1500 and 2300 h (n = 13); and between 2300 and 0700 h (n = 7). On the day prior to delivery (Day -1) the circadian pattern was absent because the nocturnal increase did not occur. A significant decrease in temperature was rec...
Gamete intrafallopian transfer (GIFT). Gamete intrafallopian transfer (GIFT), developed in 1984, was the result of further studies on in vitro fertilization (IVF). Since that time many nurses have worked in settings near in vitro fertilization centers and, therefore, have a basic understanding of the technology. An overview is given of the GIFT procedure to prepare nurses to advise and refer couples who may qualify for GIFT and to highlight the shift in the fertility program nurse coordinator's functions toward the positions of administrator and consultant.
