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Topic:Clinical Study
Clinical studies in equine research involve the systematic investigation of health and disease in horses through structured scientific methods. These studies aim to evaluate the safety and efficacy of treatments, understand disease mechanisms, and improve veterinary care practices. Clinical studies can include randomized controlled trials, observational studies, and case-control studies. They may focus on various aspects such as pharmacokinetics, therapeutic interventions, and diagnostic techniques. This page compiles peer-reviewed research studies and scholarly articles that explore the design, implementation, and findings of clinical studies in equine medicine, providing insights into their impact on horse health and veterinary practices.
Interactions of xylazine and acepromazine with oxytocin and the effects of these interactions on intrauterine pressure in normal mares and mares with delayed uterine clearance. The effects of the sedatives xylazine (predominantly alpha2 agonist) and acepromazine (predominantly alpha1 antagonist) and their influence on intrauterine pressure were measured in four reproductively normal mares and four mares with delayed uterine clearance. Intrauterine pressure was measured in each mare during oestrus for three 100 min periods using an 8-F catheter with three discrete pressure sensors. After 10 min of baseline recording, xylazine, acepromazine or saline was administered i.v. Oxytocin was administered i.v. after a further 30 min, and pressure recordings were continued for ...
Transport of spermatozoa in the reproductive tracts of mares. A scintigraphic method was developed to study sperm migration in the reproductive tracts of mares. Mares (n=5) and stallions (n=2) were used to test various steps of the procedure and three other mares and a stallion were used to study sperm transportation. A radiolabelling solution was prepared from 99mTc (Technetium-99m) and hexamethyl propylene amine oxime. The highest labelling of spermatozoa (57-72%) was obtained by incubation of the spermatozoa with the radiolabelling solution for 20 min at 20 degrees C. Radioactivity outside the spermatozoa was removed by centrifugation and by two subse...
Functional disturbances in the endometrium of barren mares: a histological and immunohistological study. Different types of endometrial maldifferentiation were investigated by histopathological (haematoxylin-eosin (HE), periodic acid Schiff-alcian blue and picro-sirius red staining) and immunohistological (oestrogen and progesterone receptors, Ki-67 antigen, intermediate filaments and laminin) analysis of endometrial biopsy specimens from mares (n=34), most of which had been barren for at least 1 year. Two major features were observed: (i) unequal differentiation, in which two functional stages are visible within a single biopsy sample: areas which are differentiated in accordance with the stage ...
Intra- and inter-stallion variation in sperm morphology and their relationship with fertility. Dismount semen samples were collected from Thoroughbred stallions during the breeding season to determine the magnitude and significance of the variation in sperm morphology within (intra-) and among (inter-) stallions. The degree of intra-stallion variation in sperm morphology during the breeding season was substantial (coefficient of variation: 20%; range 8-56%), but did not affect the day-to-day fertility of sperm samples taken from the same stallion (intra-stallion). This variability did not affect the pregnancy rate of the mares with which each stallion was mated. The degree of interstall...
Changes in PGF2alpha secretion during prolonged luteal phase in mares. The aim of this study was to characterize changes in PGF2alpha secretion in mares with persistent corpora lutea that were induced by administering altrenogest during oestrus. In Expt 1, PGF2alpha secretion was compared among mares undergoing normal oestrous cycles (n=7) and mares undergoing prolonged luteal phases (n=6), using the mean 15-ketodihydro-PGF2alpha (PGFM) plasma concentrations, peak PGFM concentrations and number of PGFM surges each day, from day 12 to day 16 of the luteal phase. In Expt 2, oxytocin-induced PGF2alpha secretion was characterized on days 13 and 16 of the luteal phase...
Effect of L-glutamine for freezing equine embryos: evaluation by DAPI staining and transfer of multiple embryos to recipient mares. Day 6.5 equine embryos (n=30) were frozen in a medium containing glycerol (2.5-10.0%) supplemented with 0, 20 or 100 mmol L-glutamine 1(-1). After thawing, the embryos were tested individually, using 4',6'-diamidino-2-phenylindole (DAPI) staining to evaluate cell death. Three embryos (one frozen at each L-glutamine concentration) were transferred together into individual recipient mares. Pregnancy diagnosis was performed at day 12 (age of embryo). Embryos were collected at day 14 (age of embryo) and were identified by PCR amplified microsatellite analysis. Nine of ten recipient mares that rece...
Uncoupling of the equine reproductive axes during transition into anoestrus. The reproductive activity of light horse mares (n=12) was monitored each day from 3 September until 29 January, or until the mares entered anoestrus, by behaviour evaluation, ultrasonography and blood sampling. Follicles, corpora lutea and ovulation, as well as oestradiol, progesterone, and LH and FSH concentrations, were analysed to determine a reproductive profile for the transition into anoestrus. The results of the present study indicate that light horse mares progress through four phases during the autumn transition into anoestrus: (i) normal cycles; (ii) aberrant cycles; (iii) anovulatio...
Influence of the dopamine antagonist domperidone on the vernal transition in seasonally anoestrous mares. The aim of the present study was to determine the effect of prolonged administration of the dopamine antagonist domperidone on follicular development, ovulation and endocrine profiles in anoestrous mares. Anoestrous mares (n=16) were maintained under natural photoperiod and ambient temperature. Eight of the mares were treated with domperidone each day from 15 January until the first ovulation of the year. The mean number and size of follicles > or =20 mm in diameter were significantly greater in domperidone-treated mares than in control mares by day 14 of treatment. The day of first ovulati...
Ovulation synchrony after follicle ablation in mares. Two experiments were performed to determine the efficacy of ultrasound-guided transvaginal follicle ablation for synchronizing ovarian function in mares. The experiments were initiated at random stages of the oestrous cycle in control (nonablated) and follicle-ablated mares. On day 0, all follicles > or =10 mm in diameter were punctured, aspirated and curettaged in ablated mares, and, on day 4, two doses of PGF2alpha were administered with a 12 h interval between the doses to both ablated and nonablated (control) mares. In Expt 1, hCG was administered to the ablated mares on the first or se...
Exposure of progesterone receptors on the plasma membranes of stallion spermatozoa as a parameter for prediction of fertility. Subfertility in stallions is attributed to the inability of spermatozoa to undergo the acrosome reaction in response to progesterone. In the present study, it was assessed whether there is a correlation between stallion fertility, defined on the basis of first cycle foaling rate and first cycle 'non-return rate', and the proportion of spermatozoa with exposed progesterone receptors on their plasma membranes. Semen from Dutch Warmblood (n=10) and Friesian (n=4) stallions was analysed. Progesterone 3-(o-carboxymethyl) oxime-BSA coupled with fluorescein isothiocyanate was used as a progesterone r...
Repeated follicle aspiration in mares: consequences for follicle growth and oocyte quality. Cumulus-oocyte complexes (COCs) recovered from ovaries of mares killed at abattoirs or after in vivo collection have heterogeneous morphologies and meiotic competence as follicles of variable quality are used. It is thought that it should be possible to recover more uniform COCs, with respect to morphology and nuclear maturation, by repeated follicle aspiration. Therefore, the influence of repeated follicle aspiration on the number and diameter of follicles > or =5 mm in diameter, the morphology and recovery rate of COCs, and the chromatin configuration in oocytes was investigated. Repeated...
Hydrocoele of the vaginal cavity of stallions. The aim of the present study was to analyse the effect of hydrocoele of the vaginal cavity of stallions on semen characteristics, libido and fertility, and to contribute to the understanding of the aetiopathology of this condition in stallions. Hydrocoele did not substantially affect either the libido or semen characteristics of affected stallions compared with a control group, and had no effect on fertility. However, the protein content of hydrocoelic fluid was significantly higher than that of peritoneal fluid and was lower than the protein content of blood serum. Electrophoretic profiles of...
Motility, morphology and triple stain analysis of fresh, cooled and frozen-thawed stallion spermatozoa. The aim of the present study was to determine whether there are characteristics of fresh, cooled and frozen-thawed semen samples that can be used to predict the suitability of stallion semen for preservation by cooling or freezing. Each of three ejaculates obtained from 12 stallions was divided into aliquots to be analysed for sperm motility, morphology and membrane integrity as fresh, cooled and frozen-thawed samples. The percentage of morphologically normal spermatozoa was similar in fresh and cooled samples and both were greater than in the frozen samples. There were no strong linear relati...
Testicular and hormonal changes in stallions with thermally induced testicular degeneration. The scrota of three Pony stallions and one miniature horse were insulated for 36 h. Plasma testosterone concentrations decreased gradually and were significantly (P < 0.05) lower than pretreatment values at 16, 24, 30, 38 and 44 h after onset of scrotal insulation. Plasma LH and oestradiol concentrations were significantly (P < 0.05) decreased 18 h, and 24 and 26 h, after onset of scrotal insulation, respectively. Plasma FSH concentrations were significantly (P < 0.05) decreased 4 days after the insulation was removed. Decreases in the potential daily sperm output per Pony for early p...
Oxytocin and PGF2alpha release in mares resistant and susceptible to persistent mating-induced endometritis. Mares resistant (n=7) and susceptible (n=9) to persistent mating-induced endometritis were artificially inseminated (AI) during oestrus with chilled extended semen. Blood samples were collected from 30 min before AI, for 2 h after AI and again between 16 and 18 h after AI. Samples were assayed for oxytocin and the PGF2alpha metabolite 13,14-dihydro-15-keto PGF2alpha (PGFM). AI caused a significant increase in oxytocin concentrations in both the resistant and susceptible mares and there was no significant difference in oxytocin release between the two groups of mares. Mean PGFM concentrations w...
Evaluation of equine fetal growth from day 100 of gestation to parturition by ultrasonography. Transrectal and transabdominal ultrasonography were performed on normal pregnant mares (n=10) at 2 week intervals from day 100 of gestation to parturition to evaluate fetal growth. Several fetal anatomical regions (head, eye, aorta, abdomen, rib, gonad, kidney and femur) were imaged and measured using standardized scan plans. The results of these analyses indicate that all of the biometric parameters correlate strongly with the day of gestation. Growth charts were developed, which demonstrate that the following variables have linear relationships with the day of gestation on which they were me...
Biophysical and 1H magnetic resonance spectroscopy characteristics of fractionated stallion ejaculates. The composition of seminal plasma must be determined to assess the possible roles of sex gland secretions in survival of stallion spermatozoa. In the present study, an automated semen collection device and 1H magnetic resonance spectroscopy were used to analyse and compare the composition of seminal plasma from fractionated and nonfractionated stallion ejaculates. The contribution of each semen component to the ejaculate (sequence of production of component and concentration) was evaluated and its relationship to biophysical parameters was determined. 1H magnetic resonance spectroscopy was use...
Quantitative histological analysis of equine embryos at exactly 156 and 168 h after ovulation. Equine embryos were collected at exactly 156 +/- 0.5 (n=8) and 168 +/- 0.5 h (n=11) after ovulation. The embryos were fixed in glutaraldehyde, sectioned serially and observed using light microscopy. In the 156 h group, all embryos were early blastocysts except for one, which was a morula. The morula and one early blastocyst had no capsule. The capsules of the other embryos were thin. The mean +/- SD total number of cells was 275 +/- 105 (range 117-417). The mean +/- SD proportions of mitotic and pycnotic cells were 2.5 +/- 1.2 and 1.1 +/- 1.8%, respectively, and there were no differences betwe...
Freezing of stallion semen: interactions among cooling treatments, semen extenders and stallions. In the present study, the interactions among stallions, semen extenders and cooling treatments before stallion semen samples were frozen were studied. In Expt 1, the effects of four cooling treatments and three semen extenders were investigated (11 stallions x four split ejaculates), whereas in Expt 2, the effects of two semen extenders, two egg yolk concentrations and two glycerol concentrations were investigated (six stallions x five split ejaculates). Sperm motility after thawing was evaluated. In Expt 1, the extender x cooling treatment interaction was significant. Centrifugation and addit...
Immunolocalization of a novel protein (P19) in the endometrium of fertile and subfertile mares. One of the major progesterone-dependent endometrial proteins in the mare is a novel 19 kDa lipocalin (P19). This protein is secreted by the endometrial glands and is readily detectable in uterine secretions during the luteal phase of the oestrous cycle and early pregnancy. The function of P19 is unknown, but since most lipocalins act as carriers of small hydrophobic molecules, it probably transports a maternal factor to the conceptus during pregnancy. In this study, a high titre antiserum raised against recombinant-derived P19 was used to detect by immunohistochemistry the protein in endometri...
Testicular biopsy in stallions: diagnostic potential and effects on prospective fertility. Testicular biopsy was performed as a standing procedure on fertile, mature stallions (n=7) under sedation and local anaesthesia. The 'Biopty' instrument was used to collect three samples from the left testis of each stallion. The oestradiol, testosterone and inhibin content in each testis were assessed by validated radioimmunoassay (RIA); protein concentrations were determined and the testes were prepared histologically for haematoxylin and eosin staining. The fertility status of each stallion was assessed before and after testicular biopsy by semen evaluation, changes in total scrotal width, ...
Immunization with stallion lymphocytes for treatment of recurrent spontaneous abortion in thoroughbred mares. The incidence of recurrent spontaneous abortion within the human population in the Western world is low (2-5%) but significant, and a proportion of these pregnancy losses are thought to have an underlying immunological cause. Immunization of women who have a history of recurrent spontaneous abortion with lymphocytes isolated from their husband or a third party donor is one of several forms of immunotherapy used to treat the problem. Early pregnancy loss in Thoroughbred mares is also significant and, as in women, a small number of mares undergo repeated pregnancy losses. Two trials have been pe...
Pituitary response to steroid replacement therapy in fertile, subfertile and infertile stallions after castration. Recent studies in our laboratory investigating plasma gonadotrophin concentrations before and after castration indicate that the hypothalamic-pituitary axis is not the original site of dysfunction in stallions with idiopathic infertility. In the present study, fertile, subfertile and infertile stallions were subjected to replacement therapy with oestradiol and testosterone 1 year after castration to investigate hypothalamic-pituitary axis function further. Fertile (n=5), subfertile (n=3) and infertile (n=2) castrated stallions of Light horse breeds, aged 11-23 years, were given either oestradi...
Dopamine antagonist-induced reproductive function in anoestrous mares: gonadotrophin secretion and the effects of environmental cues. The effect of the dopamine antagonist sulpiride on FSH secretion and onset of reproductive activity in anoestrous mares under different environmental conditions was investigated. In Expt 1, sulpiride (0.5 mg (-)-sulpiride kg(-1) twice a day) had no affect on FSH pulse frequency, mean FSH concentration, basal FSH concentration or FSH pulse amplitude in anoestrous mares. These data do not support the hypothesis that dopamine inhibits reproductive activity by suppressing GnRH secretion, as it does in other species. In Expt 2, the interval to first ovulation (14.8 +/- 1.9 days; range 12-22 days) i...
Relationship between thyroid function and seasonal reproductive activity in mares. The relationship between thyroid function and seasonal reproductive activity in mares was investigated by comparing plasma triiodothyronine and thyroxine concentrations in anoestrous mares and in mares with cyclic ovarian activity during the anovulatory season. In study 1, the diurnal changes in plasma triiodothyronine and thyroxine concentrations on a single day were compared in anoestrous and cyclic mares. The mean thyroxine concentrations were significantly higher (P < 0.001) in the cyclic mares than in the anoestrous mares, whereas mean triiodothyronine concentrations were similar in bo...
Response of newborn foals with thyroid musculoskeletal disease to adrenocorticotrophic hormone (ACTH). Fetal maturation and equine parturition are not understood fully, although the adrenal and thyroid glands are thought to have regulatory roles. Thyroidectomized equine fetuses undergo prolonged gestation, and spontaneous diseases such as thyroid musculoskeletal disease and gestational fescue endophyte exposure are also associated with delayed parturition. Thyroid musculoskeletal disease is characterized by: histologically hyperplastic thyroid glands, chondro-osseous dysplasia and dysgenesis, angular limb deformity, low resting thyroxine and triiodothyronine concentrations, and lack of response...
Relationship between the degree of endometrial periglandular fibrosis and the presence of angiotensin-converting enzyme in the equine endometrium. Endometrial periglandular fibrosis (EPF) has been proposed as a possible aetiology for equine embryonic and fetal loss. However, the pathophysiology of EPF is not well understood. Angiotensin-converting enzyme (ACE) is found in macrophages, endothelium (during angiogenesis) and myofibroblasts at sites of fibrosis in the heart, kidneys, liver and skin in several species. An increase in local tissue ACE-binding activity appears to be a critical event in the initiation and progression of fibrosis in these tissues. The aim of this study was to investigate the correlation between ACE activity in th...
Effects of follicular fluid or progesterone on in vitro maturation of equine oocytes before intracytoplasmic sperm injection with non-sorted and sex-sorted spermatozoa. In Expt 1, compact cumulus oocyte complexes (COCs) were matured in: (i) control medium (Hepes-buffered TCM-199 with 10% oestrous cow serum (OCS) + oestradiol, LH and FSH); (ii) Hepes-buffered TCM-199 with 20% follicular fluid; or (iii) control medium containing 250 ng progesterone ml(-1). Mature oocytes were collected by transvaginal aspiration as a positive control for the in vitro maturation (IVM) treatments. Oocytes were fertilized by ICSI and cultured in Menezo's B2 + 5% fetal calf serum (FCS). There were no significant differences among IVM treatments. In Expt 2, oocytes with expanded COC...
Simultaneous recording of pituitary oxytocin secretion and myometrial activity in oestrous mares exposed to various breeding stimuli. The aim of this study was to investigate the effect of different breeding stimuli on uterine contractility and pituitary oxytocin release in five oestrous mares, in order to design better treatments for mares with defective physical uterine clearance mechanisms. Electrodes and strain gauges were implanted surgically on the uterine myometrium and myometrial activity was monitored with a Grass polygraph. A catheter was placed non-surgically in the intercavernous sinus of each oestrous mare to sample pituitary venous blood and a second catheter was placed in the jugular vein. Continuous sampling ...
