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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.
Expression and regulation of transcripts encoding two members of the NR5A nuclear receptor subfamily of orphan nuclear receptors, steroidogenic factor-1 and NR5A2, in equine ovarian cells during the ovulatory process. Steroidogenic factor-1 (SF-1, NR5A1a) is a member of the NR5A nuclear receptor subfamily and has been implicated as a key transcriptional regulator of all ovarian steroidogenic genes in vitro. To establish links between the expression of SF-1 and that of the steroidogenic genes in vivo, the objectives of this study were to clone equine SF-1 and examine the regulation of its messenger RNA (mRNA) in follicular cells during human CG (hCG)-induced ovulation. The equine SF-1 primary transcript was cloned by a combination of RT-PCR techniques. Results showed that the transcript was composed of a 5'-...
Fertility of mares after unilateral laparoscopic tubal ligation. To develop a technique for laparoscopic tubal (oviductal) ligation and to evaluate pregnancy rates for mares that ovulated ipsilateral or contralateral to the ligated oviduct. Methods: Randomized prospective clinical trial comparing pregnancy rates after unilateral laparoscopic tubal ligation. Methods: Twelve mares of light horse breeds. Methods: One oviduct in each of 6 mares was surgically ligated with a laparoscopic technique; 6 other mares served as nonligated controls. Mares with unilateral tubal ligations (UTL) were inseminated with 500 million progressively motile sperm during 1 cycle w...
Comparison of culture and insemination techniques for equine oocyte transfer. This study was designed to test 3 approaches for insemination and transfer of oocytes to recipient mares. Oocytes were recovered transvaginally from naturally cycling donor mares 24 to 26 h after an intravenous injection of 2500 IU of hCG when follicles reached 35 mm in diameter. Multiple oocytes (1 to 4) were transferred surgically into the oviducts of 4 or 5 recipient mares per group. Three groups of transfers were compared: 1) transfer of oocytes cultured in vitro for 12 to 14 h postcollection with insemination of the recipient 2 h postsurgery; 2) transfer of oocytes into the oviduct within...
Centrifugation and addition of glycerol at 22 degres C instead of 4 degrees C improve post-thaw motility and fertility of stallion spermatozoa. The aims of this study were to evaluate the effects of cooling rate to 4 degrees C and temperature at the time of centrifugation/glycerol-addition (freezing extender: INRA82 + 2% egg yolk + 2.5% glycerol) on postcentrifugation recovery rate, post-thaw motility and per-cycle fertility. When centrifugation/glycerol-addition was performed at 4 degrees C (14 ejaculates), a moderate cooling rate (37 degrees C to 4 degrees C in I h) resulted in higher post-thaw motility (45%) than when using a slow cooling rate (37 degrees C to 4 degrees C in 4 h) (39%; P<0.05). When centrifugation/glycerol-addit...
T-cell distribution in two different segments of the equine endometrium 6 and 48 hours after insemination. The T-cell response after the introduction of semen into the uterine cavity in the mare was studied by examining, immunohistochemically, the distribution of helper T-cells (CD4+) and cytotoxic T-cells (CD8+) in endometrial biopsy specimens. Endometrial tissue samples were obtained from twenty-five gynecologically healthy mares during estrus before and 6 or 48 h after deposition of a single dose of stallion semen. An increase (P=0.04) in the number of helper T-cells (CD4+) compared to pre-insemination values was observed in the uterine body in both groups, 6 and 48 h, after insemination. No sig...
Effects of maternally administered depot ACTH(1-24) on fetal maturation and the timing of parturition in the mare. The aims of this study were to ascertain 1) whether fetal maturation could be induced precociously by maternal administration with adrenocorticotrophic hormone (ACTH) and 2) whether maturation could be achieved without significant risk to mare or fetus. Twenty-two mares received either 1 mg (low dose, LD, n = 6) or 4 or 5 mg (higher dose, HD, n = 16) synthetic Depot ACTH(1-24) at 300, 301 and 302 days gestation. Because, during the course of the study, ACTH appeared to have a greater influence on mares mated during the later part of the breeding season, the HD group were divided retrospectivel...
Dynamics of follicle populations and gonadotropin concentrations in fillies age two to ten months. Follicle populations and concentrations of circulating gonadotropins were studied during age 2-10 months in 10 spring-born pony fillies. Blood sampling and ultrasound scanning were done every 4 days and daily for four 30 day periods. During 5-12 weeks, FSH concentrations were lower in 6 fillies with follicles > or = 6 mm (mean +/- s.e. 1.4 +/- 0.1 ng/ml) than in 4 fillies with follicles 10 mm and gonadotropin concentrations increased. Waves of follicular growth were identified during the 30 day periods by significant increases in the diameter of the 10 largest follicles. The waves did not ...
Acrosomal ultrastructure of stallion spermatozoa cryopreserved with ethylene glycol using two packaging systems. The present experiments aimed to examine the substitution of glycerol (G) by ethylene glycol (E) as a cryoprotective agent for stallion spermatozoa. Two different ethylene glycol concentrations (5% and 10%) and also the association of glycerol (2%) and ethylene glycol (3%) (E/G) were studied (Experiment 1). In Experiment 2, two packing systems (0.5 x 4.0 ml) were evaluated using both cryoprotectors. In both experiments, the sperm membrane integrity after freezing was evaluated using transmission electron microscopy. The mean post-thaw motility was 34.25, 36.5, 29.25 and 34.75% for G5%, E5%, E1...
Changes in the plasma membrane proteins of stallion spermatozoa during maturation in the epididymis. The present paper reports modifications in the electrophoretic and cytochemical characteristics of mature and immature stallion spermatozoa. Some sperm surface glycoproteins (36, 32, 29, 21, 20, 18 kDa) detected in cauda epididymidis spermatozoa, were either absent or present in a very low relative concentration in immature sperm cells. A major 14 kDa protein band, observed in sperm extracts obtained from ductus efferentes, progressively decreased along the epididymal ductus. The nature and distribution of carbohydrate residues on the sperm membrane, during epididymal maturation, was also stud...
Relationship between embryo recovery rate and uterine lavage fluid composition in postpartum mares. The aim of the study was to determine whether neutrophil numbers (PMN), trypsin-inhibitor capacity (TIC), lysozyme, N-acetyl-beta-D-glucosaminidase (NAGase), beta-glucuronidase (B-Gase), total protein, and plasmin in uterine lavage fluid of postpartum (p.p.) mares, either at the time of foal heat insemination or around the time of arrival of the embryo in the uterus, could be used in predicting conception. Fifteen mares were inseminated within 13 h after the first p.p. ovulation. Uterine lavage fluids were successfully collected from 9 out of 12 mares before insemination and from all 15 mares ...
A survey of the fertility of Icelandic stallions. Very limited information is available on the breeding performance of Icelandic stallions, let alone the effect that management practices may have had on such performance. As an extensively kept, largely genetically isolated breed of horse it provides a good model for the study of factors that affect reproductive performance without the additional complication of selective breeding, infectious infertility and breed effect. A survey was conducted using 27 Icelandic stallions covering 1590 mares within the normal Icelandic breeding system (May to September). During the season, stallions cover mar...
A novel uterine lipocalin supporting pregnancy in equids. Horses, donkeys, and therefore, probably all equids, secrete a nonglycosylated, progesterone-dependent, 19-kDa protein (P19) into the uterine lumen during early pregnancy, and significant quantities of it are taken up by the developing conceptus. Sequence analysis and structural modelling have identified P19 as a lipocalin with greatest similarity to the murine major urinary protein lipocalins. However, lack of strong identity with any particular group of lipocalins and several unusual structural features, including a unique amino acid triplet within one of the invariant domains and an unusual...
Sex determination by simultaneous amplification of equine SRY and amelogenin genes. A quick method for sex determination of horses was developed. Simultaneous amplification of the equine sex-determining region of the Y chromosome gene (SRY) and amelogenin gene (AMEL) accomplished the determination of the presence of both the Y chromosome and SRY gene. In agarose gel electrophoresis, a normal stallion showed 1 SRY band and 3 AMEL (AMELX, AMELY, and AMELX/AMELY heteroduplex) bands, and a normal mare showed a single AMELX band. In XY-mares, 3 AMEL bands were detected as in a normal stallion, but no SRY band. The present method enables a quick diagnosis for XY-mare prior to cytog...
Control of follicular development and luteal function in the mare: effects of a GnRH antagonist. Control of the equine estrous cycle was studied by suppressing gonadotropin secretion by administration of a GnRH antagonist to cyclic pony mares. Four mares received vehicle (control cycle) or a GnRH antagonist, Antarelix (100 microg/kg) on Day 8 of diestrus, and blood samples were collected at 15-min intervals from 0 to 16 h, 24 to 36 h, and daily until the next ovulation. Ovarian activity was monitored by transrectal ultrasonography, and measurement of plasma concentrations of progesterone and estradiol. Antagonist treatment eliminated large diestrous pulses of LH. Progesterone concentratio...
Effect of dose and day of treatment on uterine response to oxytocin in mares. To determine the effect of dose and day of oxytocin treatment on intrauterine pressure, 6 normal mares were treated with 10 or 25 IU oxytocin 2 days before ovulation, on the day of ovulation and 2 days after ovulation. Intrauterine pressure (IUP) was measured using micro-tip-catheters (one placed intrauterine, a second and third serving as reference sensors in the vagina and external to the mare) and transmitted by telemetry for 30 min to establish a baseline before saline was administered, iv, and for an additional 30 min after saline administration. Oxytocin was then given, iv, and IUP was r...
Equine uteroplacental metabolism at mid- and late gestation. Uptakes of oxygen, glucose and lactate by the gravid uterus, fetus and uteroplacental tissues were measured in chronically catheterized pregnant ponies and their fetuses at mid- and late gestation (term 335 days). Rates of O2 uptake by the gravid uterus, fetus and uteroplacental tissues were significant at both gestational ages and were 2- to 3-fold higher in late gestation than the mid-gestation values of 3338+/-794, 1352+/-258 and 2035 +/- 602 micromol min(-1), respectively (n = 4). Similarly, there were significant uptakes of glucose by the gravid uterus, fetus and uteroplacental tissues at...
Cytological identification and quantification of testicular cell types using fine needle aspiration in horses. Fifteen stallions of different breeds, age 3-11 years, had their right testicles evaluated by fine needle aspiration cytology (FNAC). Cytological analysis showed the following spermatogenic cell types: spermatogonia (1.6% +/- 1.1); spermatocyte I (3.4% +/- 2.2); spermatocyte II (0.8% +/- 0.7); early spermatids (25.5% +/- 9.5); late spermatids (37.0% +/- 9.3). Spermatozoal numbers were expressed as the spermatic index (SI = 31.5% +/- 8.5) and Sertoli cells were expressed as the Sertoli cell index (SEI = 20.9% +/- 17.0) (means +/- s.d). Identification of cell types was relatively easy and no imm...
Localization of the lectin reactive sites in adult and prepubertal horse testes. The testes of prepubertal and adult horses were investigated using 10 horseradish peroxidase conjugated lectins combined with sialidase digestion and potassium hydroxide treatment, to localise the oligosaccharide sequences of glycoconjugates during spermatid maturation. In adult animals, the lectins showed a variable affinity for spermatids and Sertoli cell apical extensions. Soybean agglutinin (SBA), peanut agglutinin (PNA), Ricinus communis agglutinin (RCA-I) and wheat germ agglutinin (WGA) bound to the acrosomal structures of spermatids, whereas Griffonia simplicifolia agglutinin (GSA-II) l...
Clinical experiences of treating septic arthritis in the equine by repeated joint lavage: a series of 39 cases. The condition of septic arthritis was treated in 12 foals with 21 affected joints (Group I) and in 27 adult horses. The adult horses were divided into three groups, based on aetiology of the condition: haematogenous (Group II, n = 6), iatrogenic (Group III, n = 6), and perforating trauma (Group IV, n = 15). The treatment consisted of an initial systemic antibiotic that anticipated the microbial agents that were considered most likely per group, repeated through-and-through joint lavages every other day and non-steroidal anti-inflammatory drugs. The antibiotics were adjusted to the results of b...
Individual mares bias investment in sons and daughters in relation to their condition. The Trivers-Willard hypothesis (TWH) predicts that a mother will treat a son or daughter differently depending on her ability to invest and the impact of her investment on offspring reproductive success. Although many studies have investigated the hypothesis, few have definitively supported or refuted it because of confounding factors or an inappropriate level of analysis. We studied maternal investment in sons and daughters in feral horses, Equus caballus, which meet the assumptions of the TWH with a minimum of confounding variables. Population level analyses revealed no differences in matern...
Effects of angiotensin II on the acrosome reaction in equine spermatozoa. Angiotensin II is a hormone with a wide array of physiological effects that exerts its effect via interaction with two major subtypes of receptor. The results of this study show that angiotensin II (from 1 to 100 nmol l(-1)) initiates acrosomal exocytosis in equine spermatozoa that have undergone capacitation in vitro in a TALP-TEST (Tyrode's albumin lactate pyruvate; 188.7 mmol TES l(-1), 84.8 mmol Tris l(-1)) buffer with cAMP. The acrosome reaction and sperm viability were assessed with fluorescein isothiocyanate-Pisum sativum agglutinin (FITC-PSA) and Hoechst 33258, respectively. The initia...
Fetal maceration and retention of fetal bones in a mare. A 19-year-old Quarter Horse mare was evaluated because of bloody vaginal discharge that was apparent immediately following breeding. On transrectal ultrasonography, it was evident that the uterus was filled with fluid containing echogenic particles; linear hyperechoic structures were also visible. Endoscopy was performed, which revealed a number of bones adhered to the cranial wall and floor of the right uterine horn as well as purulent fluid in both uterine horns. Bacterial endometritis and fetal maceration were diagnosed. The mare was treated with antibiotics, and the fetal bones were manual...
[Environment and secular sperm trend. Stallion’s semen quality during the last two decades]. Several reports have suggested that human semen quality has declined throughout the world over the last few decades. Chemicals in the environment acting as endocrine disruptors have been implicated as a possible cause. If this is indeed the case, then similar effects may be observed in animals. We report data on secular trends in semen quality of stallions collected during the last two decades by French National Studs. Methods: We analyzed 1489 ejaculates collected from 390 Breton draught stallions between 1981 and 1996 and 341 ejaculates from 86 anglo-arab thoroughbred stallions from 1985 and...
Effect of centrifugation and partial removal of seminal plasma on equine spermatozoal motility after cooling and storage. The objective of this study was to determine if centrifugation and partial removal of seminal plasma would improve spermatozoal motility in semen from stallions whose whole ejaculates have poor tolerance to cooling and storage. Stallions were divided into two groups (n = 5/group) based on the ability of their extended semen to maintain spermatozoal motility after cooling and storage. Group 1 stallions ("good coolers") produced semen in which progressive spermatozoal motility after 24 h of cooling and storage was reduced by < or = 30% of progressive motility prior to storage. Group 2 stallions ...
Amounts of selected coagulation factors in pre- and post-mortem follicular fluid are similar and do not correlate with molecular mass. This study was designed to evaluate the amounts of coagulation factors and to determine whether the protein profile in pre-ovulatory ovarian follicular fluid aspirated from ovaries collected from mares at slaughter are representative of that in follicular fluid collected from live animals. The proteins evaluated included, (i) albumin, ceruloplasmin and fibronectin, (ii) the procoagulant plasma proteins, Factor V (FV), Factor VII (FVII), Factor X (FX) and prothrombin, and (iii) the anticoagulant plasma proteins, antithrombin and alpha2-macroglobulin. The amounts of the individual proteins were ...
Separate sites and mechanisms for placental transport of calcium, iron and glucose in the equine placenta. The placenta is the only channel for transport of nutrients to the conceptus and the fetal nutrient demands increase exponentially to term. The 9 kDa calcium binding protein (calbindin, 9CBP) and the iron binding protein uteroferrin (UF) are proving to be reliable markers for epithelia that mediate active transcellular calcium and iron transport and the glucose transporter proteins (GT1 and GT3) for glucose transport by facilitated diffusion. Light and electron microscope immunocytochemistry have been used on perfusion fixed resin embedded material to establish the distribution of 9CBP, UF, GT...
Catalase activity in equine semen. To characterize the activity of catalase in equine semen. Methods: 15 stallions of known and unknown reproductive history. Methods: Seminal plasma was collected from raw equine semen by centrifugation, and samples of seminal plasma were frozen prior to assay for catalase activity. Tissue samples (n = 3 stallions) from the bulbourethral gland, prostate gland, vesicular gland, and testis were homogenized, and cauda epididymal fluid was collected for determination of catalase activity. Catalase activity was determined as an enzyme kinetic assay by the disappearance of H2O2 as measured by ultravio...
