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Topic:Veterinary Medicine
Veterinary medicine for horses encompasses the study and application of medical practices to diagnose, treat, and prevent diseases in equine species. This field involves a comprehensive understanding of equine anatomy, physiology, pathology, and pharmacology. Veterinary practitioners employ a range of diagnostic tools and therapeutic interventions to address health issues in horses, including lameness, gastrointestinal disorders, respiratory conditions, and infectious diseases. Preventative care, such as vaccination and deworming programs, is also a significant aspect of equine veterinary medicine. This page gathers peer-reviewed research studies and scholarly articles that explore various aspects of veterinary medicine as it pertains to horses, including advancements in diagnostic techniques, treatment protocols, and preventive health strategies.
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...
Oxytocin administration prolongs luteal function in cyclic mares. Recent evidence indicates that, in mares, as in the domestic ruminants, oxytocin and its endometrial receptor play important roles in stimulating the pulsatile releases of prostaglandin F2 alpha from the endometrium that effect luteolysis. In the present experiment, continuous administration of oxytocin by subcutaneous minipump to five mares during days 8-20 after ovulation abolished luteolysis in four of them, while all four of the control mares infused similarly with saline underwent luteolysis at the expected time. When oxytocin administration began on day 10, instead of on day 8, after ovu...
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...
Ultrastructure, protein phosphorylation and mRNA status of equine oocytes matured in vivo and in vitro. Equine oocytes were collected by follicle aspiration in vivo or by dissection of material obtained from an abattoir, and the ultrastructure, protein phosphorylation and mRNA status of the oocytes were evaluated. Electron microscopy studies indicated that the nucleus had a smooth membrane in oocytes with a compact cumulus, whereas the nuclear membrane was undulated in all other groups. Oocytes with compact cumuli had only a few microvilli, whereas those with expanded cumuli had more microvilli. There were only small numbers of cortical granules close to the oolemma in oocytes with compact cumul...
Apoptosis in equine granulosa cells and its relationship to cumulus expansion and oocyte chromatin configuration in ovarian follicles. During the oestrous cycle follicles grow and either ovulate or regress. Regressing follicles undergo atresia and in many species apoptosis has been identified as the underlying mechanism in this process. The aims of this study were to establish whether equine granulosa cells degenerate via an apoptotic mechanism and whether the presence of apoptotic cell death in granulosa cells is correlated with oocyte quality. Ovaries from mares at unknown stages of the oestrous cycle were obtained from an abattoir. In Expt 1, follicles (n=352) from 37 mares were processed. DNA was extracted from granulosa ...
Pregnancies produced from fertile and infertile stallions by intracytoplasmic sperm injection (ICSI) of single frozen-thawed spermatozoa into in vivo matured mare oocytes. The use of intracytoplasmic sperm injection (ICSI) for in vitro fertilization of equine oocytes and the developmental potential of these oocytes after transfer to the Fallopian tubes of synchronized mares were examined. Oocytes were aspirated from mature follicles 39 h after injection of a GnRH analogue and transported 190 km at 39 degrees C. Semen from a fertile and an infertile stallion was frozen and prepared for injection. Successfully injected oocytes were transferred surgically into the ampulla of the Fallopian tube either: (i) 4-8 h after semen injection; or (ii) after 24-48 h culture b...
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...
Indirect determination of stallion sperm capacitation based on esterase release from spermatozoa challenged with lysophosphatidylcholine. A spectrophotometric assay was developed to measure the amount of esterase released from stallion spermatozoa. This assay was used to determine the percentages of capacitated stallion spermatozoa, determined by the ability of spermatozoa to undergo an acrosome reaction and release esterase in response to a lysophosphatidylcholine challenge, for spermatozoa incubated under conditions to increase intracellular calcium and cAMP. Incubation with 100 nmol calcium ionophore A23187 l(-1) induced 66% of stallion spermatozoa to capacitate after 60 min of incubation at 37 degrees C. Subsequent experimen...
Identification of proteins in the equine embryonic capsule. An acellular embryonic capsule envelops equine conceptuses between day 6 and day 23 after ovulation. As all of the factors mediating embryo-mother signalling must pass through the capsule, it acts like a 'mailbox'. Therefore, we have started to map the proteins in this special extracellular matrix at the interface between mother and embryo. In the present study, one- and two-dimensional gel electrophoresis were used to examine a range of proteins. Use of western blotting identified three specific proteins in the capsules of equine conceptuses recovered on day 16 after ovulation: insulin-like g...
Equine trophoblast as an immunological target. A cytotoxic T-lymphocyte assay was used to determine whether equine chorionic girdle cells are susceptible to lysis by CD8+ cytotoxic T cells primed in vitro against allogeneic lymphocytes. Classical cytotoxic T-lymphocyte activity against fresh or cultured trophoblast targets was demonstrated using peripheral blood lymphocytes from nonpregnant mares. Lysis of allogeneic (horse) and xenogeneic (donkey) lymphocyte targets was used as a control for trophoblast lysis. The major histocompatibility complex (MHC) class I specificity of the cytotoxic T-lymphocyte reactions was determined using panels...
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...
Effects of steroids on endometrial oxytocin mRNA production. In this study, the roles of oestrogen and progesterone in the regulation of oxytocin gene expression in equine endometrium were examined. Anoestrous mares (n=19) were assigned randomly to one of the following treatment groups: control (vehicle control for 1 day; n=3); progesterone (250 mg progesterone per day for 6 days; n=4); oestradiol (5 mg beta-oestradiol 17-valerate per day for 6 days; n=4); oestradiol plus short duration progesterone (5 mg beta-oestradiol 17-valerate per day for 6 days followed by 250 mg progesterone per day for 6 days; n=4); and oestradiol plus long duration progesteron...
The role of seminal plasma in post-breeding uterine inflammation. The effect of seminal plasma on polymorphonuclear neutrophil (PMN) chemotaxis, PMN phagocytosis and complement-induced cytolysis was determined using blood plasma pooled from four horses and seminal plasma pooled from two stallions. To investigate chemotaxis, complement in blood plasma was activated with E. coli lipopolysaccharide in the presence of 0-50% seminal plasma diluted with a standardized volume of McCoy's medium and placed in a chemotactic chamber. Chemotaxis of blood derived equine PMNs toward the chemoattractants was determined after incubation at 37 degrees C for 45 min. To invest...
Comparison of the cryoprotectant properties of glycerol and ethylene glycol for early (day 6) equine embryos. Early (day 6) equine embryos (n=23) were assigned to four treatment groups to assess the cryoprotectant properties of glycerol and ethylene glycol and the effect of adding sucrose during removal of the cryoprotectant: (i) group GG (n=5) embryos were frozen and thawed using 1.5 mol glycerol l(-1) as the cryoprotectant, which was added at 22 degrees C in four steps (0.375, 0.75, 1.125 and 1.5 mol glycerol l(-1)), and removed after thawing in five steps (1.5, 1.125, 0.75, 0.375 and 0.0 mol glycerol l(-1)); (ii) group GS (n=6) embryos were frozen and thawed using 1.5 mol glycerol l(-1) as for grou...
Effect of increased daylight during late pregnancy on the reproductive performance of mares after parturition. The aim of the present study was to determine the effect of prolonged photoperiod during late pregnancy on subsequent ovarian activity and fertility in mares. Pregnant mares (n=13) due to give birth in January and February were stimulated by a fixed photoperiod (16 h light: 8 h dark) from 15 November (during the last 2-3 months of gestation) until up to 1 month after parturition. A control group of mares (n=9) due to give birth at the same time were kept in the same stable and management regimen, but under natural light conditions. Light-treated mares ovulated during foal oestrus approximately...
The uterus as a source of oxytocin in cyclic mares. In a recent study, continuous administration of oxytocin by subcutaneous minipump to mares from day 8 to 20 after ovulation prevented luteolysis in most of the treated but none of the control mares, indicating a role for oxytocin in cyclical luteolysis in mares. In the present study, measurement of oxytocin concentrations in uterine flushings recovered from nine mares during days 14-18 after ovulation gave values that were many times higher than those measured concurrently in peripheral plasma. Furthermore, intrauterine administration of oxytocin to four mares on day 14 after ovulation stimula...
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 ...
Preservation of stallion sperm quality by native phosphocaseinate: a direct or indirect effect? Milk-based diluents are generally considered efficient for survival of stallion spermatozoa in vitro. However, milk is a complex and variable medium and native phosphocaseinate is a milk component that is more efficient for preservation of sperm motility and fertility, although the mechanisms involved in this protection have not yet been elucidated. The aim of the present study was to characterize the interactions between native phosphocaseinate and equine spermatozoa. No binding between sperm membranes and native phosphocaseinate was observed using indirect immunofluorescent staining or elect...
Production of live foals from sperm-injected oocytes harvested from pregnant mares. In vitro fertilization in horses has been less successful than anticipated owing to: (i) the inability to collect large numbers of good quality oocytes; (ii) alterations in the zona pellucida that occur during in vitro maturation of equine oocytes; and (iii) inadequate preparation of equine sperm cells. In addition, studies in humans, mice and cattle have indicated that high concentrations of glucose in culture media may inhibit embryonic development in vitro and this may also be a problem for development of equine embryos in vitro. The aims of the present study were: (i) to achieve fertilizat...
The structural morphology and epithelial association of spermatozoa at the uterotubal junction: a descriptive study of equine spermatozoa in situ using scanning electron microscopy. Uterotubal junction tissues (n=12) recovered from young nulliparous mares 4 h after insemination were examined for spermatozoa in situ using scanning electron microscopy. Mares were inseminated before ovulation with semen containing 66-85% morphologically abnormal spermatozoa and approximately 1 x 10(9) progressively motile spermatozoa. Spermatozoa were found in all the tissues and displayed a variety of relationships to the epithelium, depending on regional location, spatial constraints and epithelial surface characteristics. Spermatozoa were most abundant in the epithelial folds on the uteri...
Estimation of sodium and potassium concentrations in the uterine fluid of mares by microdialysis and ion chromatography. Equine blastocyst fluid has a lower [Na+], a higher [K+] and a lower osmolality than does normal blood serum. Based on the assumptions that the sodium pump is primarily responsible for fluid accumulation and that ions transported actively into the blastocyst increase blastocyst osmolality above that of the external medium, we hypothesized that the [Na+] and the osmolality of mare uterine fluid are lower than those of blastocyst fluid. Microdialysis and ion chromatography were used to estimate [Na+] and [K+] of uterine fluid. Mares (n=10) were used for in vivo measurements at different stages o...
Mucus production by endometrium of reproductively healthy mares and mares with delayed uterine clearance. The aims of this study were to compare various staining and fixation techniques for endometrial biopsy samples and, thus, to investigate the mucociliary apparatus in endometrium from reproductively healthy mares and mares with delayed uterine clearance. Endometrial samples were collected from the left and right uterine horns of reproductively healthy mares (n=5) and mares with delayed uterine clearance (n=4) during anoestrus, transition, oestrus and dioestrus. Each sample of endometrium was fixed in either Bouin's fixative or formalin, and stained with alcian blue (pH 1.0 or 2.5), periodic aci...
Possible role of autoimmunity to spermatozoa in idiopathic infertility of stallions. Testicular degeneration is a major cause of subfertility in stallions, although an aetiological diagnosis cannot be made in most cases. In the present study, autoimmune testicular degeneration was induced and evaluated in stallions by immunizing stallions with their own spermatozoa mixed with an adjuvant. The factors evaluated included changes in semen quality and testicular histology. A large decrease in sperm number and quality was observed in response to sperm autoantigens. An ELISA test specific for antisperm antibodies was developed which enabled antibody titres in serum, seminal plasma a...
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 exocrine and endocrine secretion: trophoblast and glands of the endometrial cups. Invasion of trophoblast cells of the chorionic girdle into the endometrium and their subsequent dependence as endometrial cup cells on the maternal vascular system are unique features of equine gestation. This study of exocrine secretion by the endometrial glands and endocrine secretion by the cup cells was initiated to examine the relationships between and the effects of two disparate epithelial cell types sharing the endometrium. Endometrial cups were examined from day 36 to day 83 of gestation by light and electron microscopy, and immunohistochemical and lectin analysis. As the cup cells in...
A comparative gene map of the horse (Equus caballus). A comparative gene map of the horse genome composed of 127 loci was assembled based on the new assignment of 68 equine type I loci and on data published previously. PCR primers based on consensus gene sequences conserved across mammalian species were used to amplify markers for assigning 68 equine type I loci to 27 horse synteny groups established previously with a horse-mouse somatic cell hybrid panel (SCHP, UC Davis). This increased the number of coding genes mapped to the horse genome by over 2-fold and allowed refinements of the comparative mapping data available for this species. In conju...
Rabies surveillance in the United States during 1998. During 1998, 49 states, the District of Columbia, and Puerto Rico reported 7,961 cases of rabies in nonhuman animals and 1 case in a human being to the Centers for Disease Control and Prevention, a decrease of 6.5% from 8,509 cases in nonhuman animals and 4 cases in human beings reported in 1997. More than 92% (7,358 cases) were in wild animals, whereas > 7.5% (603 cases) were in domestic species (compared with 93% in wild animals and 7% in domestic species in 1997). Decreases were evident in all of the major contributing species groups, with the exception of skunks and bats. The relative cont...
