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Topic:Mares
Mares and horses are integral components of equine studies, focusing on the reproductive and behavioral aspects of equine biology. Mares, or adult female horses, play a significant role in breeding programs and are often studied for their reproductive physiology, gestation, and maternal behaviors. Horses, as a broader category, encompass both sexes and all age groups, providing a comprehensive view of equine anatomy, physiology, and behavior. Research in this area often investigates the differences and similarities between mares and other horses in terms of hormonal cycles, reproductive health, and social interactions. This page compiles peer-reviewed studies and scholarly articles that explore the biological and behavioral characteristics of mares and horses, offering insights into their roles in equine science and management.
15-Ketodihydro-PGF2alpha and cortisol plasma concentrations in newborn foals after spontaneous or oxytocin-induced parturition. Hormonal changes during early neonatal life play a major role in the physiological processes underlying the maturation of several organs. Since prostaglandins and cortisol are associated with fetal organ system maturation, the aim of this study was to evaluate 15-ketodihydro-PGF(2alpha) (PGM) and cortisol plasma concentrations during the first 21 days after birth in foals born by either spontaneous (24 foals) or low-dose oxytocin (OT)-induced parturition performed after at least 320 gestational days (25 foals) since induction is often considered to be a cause of prematurity. After spontaneous ...
Early effects of equine FSH (eFSH) treatment on hormonal and reproductive parameters in mares intended to carry their own pregnancy. Superovulatory treatment may potentially increase the embryo recovery rate and the per-cycle pregnancy rate in normal or subfertile mares that are managed properly. However, some studies suggest a possible negative effect of superovulatory treatment on ovarian follicular maturation and embryo viability. Objectives of the present study were to investigate the early effects of eFSH treatment in reproductively normal mares in terms of: folliculogenesis, pregnancy rate, early embryonic development, reproductive tract parameters (tone and edema), and serum estradiol-17beta and progesterone concentr...
Age-related dynamics of follicles and hormones during an induced ovulatory follicular wave in mares. An ovulatory follicular wave was induced by ablation of follicles > or =6mm and treatment with prostaglandin F2alpha (PGF) on Day 10 (ovulation=Day 0). Follicle and hormone dynamics of the induced waves were compared among three age groups: young (5-6 y, n=14 waves), intermediate (10-14 y, n=16), and old (> or =18, n=15). During the common-growth phase of the induced wave (Days 12-17), diameter of the future ovulatory follicle was not different among ages, but the young group had more (P or =10mm. The number was correlated (r=+0.7; P<0.0001) within mares between consecutive interovula...
Abortion in a horse following Neorickettsia risticii infection. A pregnant 18-year-old Quarterhorse mare presented with fever, anorexia, tachycardia, tachypnea, and gastrointestinal hypermotility at day 68 of gestation. Potomac horse fever was diagnosed based on polymerase chain reaction (PCR) analysis of whole blood and a high antibody titer to Neorickettsia risticii. The mare made a rapid clinical recovery following antibiotic therapy, but aborted 98 days later. Necropsy on the aborted fetus revealed lymphohistiocytic colitis, lymphadenitis, myocarditis, and hepatitis. The placenta was grossly and histologically normal. Formalin-fixed lymph node, thymus,...
Gross anatomy of the female genital organs of the domestic donkey (Equus asinus Linné, 1758). Although donkeys play an important role as companion or pack and draught animals, theriogenological studies and anatomical data on the genital organs of the jenny are sparse. To provide anatomical descriptions and morphometric data, the organa genitalia feminina, their arteries and the ligamentum latum uteri of 10 adult but maiden jennies were examined by means of gross anatomical and morphometric techniques. In comparison with anatomical data of horses obtained from literature the genital organs of jennies appear to be more voluminous in relation to the body mass and the position of the ovari...
Uterine involution and endometrial function in postpartum pony mares. To determine endometrial regeneration in postpartum mares by analysis of histologic features, apoptosis and cell proliferation markers, lectin binding, cytokines, and progesterone and estrogen receptors in endometrial biopsy specimens. Methods: 9 postpartum mares. Methods: Mares were examined on postpartum days 1, 9, and 16, and uterine biopsy specimens were obtained for histologic examination. Lectin binding was analyzed histochemically, and expressions of Ki-67 antigen (proliferation marker), lysozyme, and caspase 3 (apoptosis marker) were studied immunohistochemically. Gene expressions for ...
Factors affecting foal birth weight in Thoroughbred horses. Foaling data from 348 Thoroughbred foals born on a commercial stud were analysed to investigate interrelationships among mare age, parity, gestation length, foal sex, placental weight, and foal birth weight. Placental weight was positively correlated with foal birth weight up to a threshold of 6.5 kg; above this, placental weight was not significantly associated with foal birth weight. Placental weight was assessed, including the amniotic membranes and umbilical cord as well as the allantochorion. Using path analysis, parity was positively associated with foal birth weight both directly and th...
Spermatozoa morphology during the breeding season in Thoroughbred stallions in Japan. The morphology of spermatozoa of modern Thoroughbred stallions in Japan was investigated during the breeding season. A total of 299 semen samples were collected from the penises of 16 stallions immediately after service. The rate of abnormalities in sperm heads and tails, spermatozoa with cytoplasmic droplets and slides with medusa cells to total observed slides in each stallion were 3.9 +/- 2.1%, 11.5 +/- 5.9%, 2.4 +/- 2.6% and 20.1%, respectively. The values for the area, length, width and aspect ratio of the stallion sperm head were 12.54 +/- 1.34 microm(2), 5.93 +/- 0.40 microm, 2.69 +/- 0...
Cefquinome concentrations in endometrium after intrauterine treatment of cobactan 4.5% in mares and inflammatory response of the endometrium to this treatment. This study was conducted to measure the concentration of cefquinome in the endometrium of mares after intrauterine treatment and to evaluate associated inflammation. Mares (n = 14) were randomly assigned to one of the following groups: (i) control (n = 4) were either not treated (n = 2) or received (n = 2) lactated Ringer's intrauterine for 1 or 3 days; (ii) treated mares (n = 10) received intrauterine cefquinome for 1 or 3 days. After at least 10 days had passed following the last treatment and ovulation, mares were given Prostaglandin F2alpha (PGF2alpha) and were randomly assigned to an alte...
Primary unilateral fibroleiomyoma of the ovary in a pregnant mare: a case report. Fibroleiomyomas of the ovary are rare. This smooth muscle tumour may develop and increase in size during pregnancy. Diagnosis is based on histological and immunohistochemical analyses. Histologically, the ovarian fibroleiomyoma consists of non-invasive bundles of smooth muscle cells that synthesize collagen-like extracellular matrix. This case report describes an ovarian fibroleiomyoma in a pregnant multiparous broodmare with a history of intermittent signs of colic.
Development of one vs multiple ovulatory follicles and associated systemic hormone concentrations in mares. Ablation of follicles > or = 6 mm in diameter and treatment with PGF2alpha 10 days after ovulation were used to induce the development of ovulatory waves. Comparisons were made between induced waves with one (33 waves, 72%) and multiple (13 waves, 28%) ovulatory follicles. Diameter deviation was defined as the separation of follicles into dominant and subordinate categories. Multiple ovulatory follicles were preceded by more (p or = 20 mm at the beginning of deviation, higher LH preceding deviation (approached significance, p < 0.08), lower (p < 0.05) concentrations of FSH on the day...
Effect of HCG in the presence of HCG antibodies on the follicle, hormone concentrations, and oocyte in mares. Follicle blood flow, follicular-fluid and plasma hormone concentrations, and oocyte quality were studied 30 h after an ovulation-inducing hCG treatment when the pre-ovulatory follicle was 32 mm. Mares were grouped as positive (n = 16) and negative (n = 44) for hCG antibodies before the experimental hCG treatment. Percentage of the follicle wall with blood flow signals was less (p < 0.05) in the antibody positive group than in the negative group. The concentrations of follicular-fluid oestradiol and free IGF1, and plasma oestradiol were greater (p < 0.001), and follicular-fluid progestero...
Maternal transfer of IgE and subsequent development of IgE responses in the horse (Equus callabus). Immunoglobulin E (IgE) mediates the immune response to parasites, but can also cause allergies. In humans maternal IgE is not transferred to cord blood and high levels of cord blood IgE are associated with subsequent allergy. In horses, both maternal IgG and IgE are transferred via colostrum; the IgE levels in the mare's serum, the colostrum and the foal's serum are correlated but the consequences of IgE transfer to foals are not known. By about 6 weeks of age the levels of IgE in foal serum have dropped to a nadir, at 6 months of age the level of IgE has risen only very slightly and is no lon...
Follicle deviation in ovulatory follicular waves with one or two dominant follicles in mares. The follicle and hormone aspects of diameter deviation and development of one dominant (>/=28 mm) follicle (1DF) vs two dominant follicles (2DF) were studied in 32 ovulatory follicular waves in mares. Follicles were ranked each day as F1 (largest) to F3. The beginning of deviation was designated day 0 and preceded the first increase in the differences in diameter between F1 and F2 in the 1DF group and between a combination of F1 and F2 vs F3 in the 2DF group. One dominant follicle and 2DF developed in 21 (66%) and 11 (34%) waves, respectively. Double ovulations occurred in only one of the w...
Temporal detection of Lawsonia intracellularis using serology and real-time PCR in Thoroughbred horses residing on a farm endemic for equine proliferative enteropathy. The goals of this study were to evaluate titers of antibodies against Lawsonia intracellularis in 68 resident broodmares from a farm known to be endemic for equine proliferative enteropathy (EPE) and to evaluate maternal antibodies, occurrence of seroconversion and fecal shedding in their foals. Serum samples collected from mares at delivery and from foals pre- and post-colostrum ingestion and monthly thereafter were tested for the presence of L. intracellularis antibodies by immunoperoxidase monolayer assay (IPMA). Further, feces collected from mares at delivery and foals post-partum and mont...
Temporal relationships and repeatability of follicle diameters and hormone concentrations within individuals in mares. Data were collected daily from 23 mares during two consecutive interovulatory intervals (IOIs). Several significant (p < 0.05) new observations on temporal relationships were made. The FSH increase that begins before ovulation temporarily plateaued on the day of discharge of follicular fluid into the peritoneal cavity in association with ovulation. During the declining portion of the pre-ovulatory oestradiol surge, an abrupt reduction in the rate of decrease occurred in synchrony with the peak of the LH surge and is consistent with a negative effect of LH on oestradiol. Repeatability within...
Risk factors for the development of haemorrhagic anovulatory follicles in the mare. Haemorrhage into the dominant follicle during the reproductive season is a subtle but definitive cause of infertility in the mare population. This condition however can be of high relevance for an individual in which its incidence is abnormally high. Little is known about the nature and factors affecting the incidence of haemorrhagic anovulatory follicles (HAFs) in the mare. The objectives of the study were to define and characterize the ultrasonographic development and incidence of HAFs and to investigate possible risk factors influencing its occurrence. Detailed reproductive and ultrasound r...
Effect of suppression of FSH with a GnRH antagonist (acyline) before and during follicle deviation in the mare. A GnRH antagonist (Acyline) was used to study the role of FSH in early development of a follicular wave in 61 mares. In Experiment 1, a single dose of 3 mg per mare, compared with 0 and 1 mg, suppressed both the FSH and follicle responses to exogenous GnRH. In Experiment 2, high concentrations of FSH were induced by two successive ablations of all follicles >/= 6 mm on days 10 and 13 (day 0 = ovulation). A single treatment with Acyline resulted in significantly greater suppression of plasma concentrations of FSH than a single treatment with charcoal-extracted follicular fluid (source of inh...
Analysis of cartilage oligomeric matrix protein (COMP) in synovial fluid, serum and urine from 51 racehorses with carpal bone fracture. We investigated the relationship between cartilage oligomeric matrix protein (COMP) levels in synovial fluid (SF), serum and urine and the development of osteochondral damage and osteophyte (OP) formation following intraarticular fractures of the carpus in racehorses in order to assess the clinical usefulness of COMP as a diagnostic biomarker of developmental osteoarthritis (OA). Two monoclonal antibodies (mAb clones 2A11 and 3C8) raised against equine COMP were shown to be capable of detecting the molecule in serum and urine as well as SF. Fifty-one samples were obtained from 26 OP-positive (...
Heritability and repeatability of insect bite hypersensitivity in Dutch Shetland breeding mares. Insect bite hypersensitivity (IBH) is a seasonal recurrent allergic reaction of horses to the bites of certain Culicoides spp. and is found throughout the world. The aim of our study was to estimate the heritability and repeatability of IBH in the Dutch Shetland pony population. A total of 7,924 IBH scores on 6,073 mares were collected during foal inspections in 2003, 2005, and 2006. Mares were scored for clinical symptoms of IBH from June until February by 16 inspectors. Of all mares, 74.4% (n = 4,520) had a single observation, 20.7% (n = 1,255) had 2 observations, and 4.9% (n = 298) had 3 ob...
Aspiration of equine oocytes from immature follicles after treatment with equine pituitary extract (EPE) alone or in combination with hCG. This study examined the effect of treating mares with equine pituitary extract (EPE) alone or in combination with hCG on the recovery rate of immature follicles by transvaginal follicular aspiration (ovum pick-up; OPU). Ten normally cycling crossbred mares aged 3-15 years and weighing 350-400 kg were subjected to each of three treatments in a random sequence with each exposure to a new treatment separated by a rest cycle during which a spontaneous ovulation occurred. The treatments were (1) superovulated with 25mg EPE and treated with 2500 IU hCG, (2) superovulation with 25mg EPE, and (3) cont...
Immunohistochemical localization of oestrogen receptors alpha and beta, progesterone receptor and aromatase in the equine placenta. The functions of placental oestrogens during equine pregnancy are still unclear. Yet, they may act predominantly as local regulators of growth and differentiation in the microplacentomes. Thus, expression patterns of oestrogen receptors (ERs) alpha and beta were investigated in the microcotyledonary placenta from pregnant mares at 110, 121, 179, 199 and 309 days of gestation by immunohistochemistry. In microplacentomes, both the ER isoforms were detected in trophoblast (T) cells, chorionic villous stroma (FS), microcaruncular epithelium (ME) and microcaruncular stroma (MS). Proportions of posi...
Isolation of Arcanobacterium hippocoleae from a case of placentitis and stillbirth in a mare. Based on the scarcity of reports in veterinary medicine literature, it appears that Arcanobacterium spp. are rarely isolated from horses. Recently, a single isolate from vaginal discharge in a mare was characterized as a new species, Arcanobacterium hippocoleae. The present report describes a case of necrosuppurative placentitis and stillbirth in an American Quarterhorse mare. Numerous colonies of irregular, Gram-positive, rod-shaped bacteria were observed by histological examination within fibrin lattice associated with placental lesions. Arcanobacterium hippocoleae was isolated in large numb...
Unilateral and bilateral laparoscopic ovariectomy of mares by electrocautery. Twelve horses underwent standing laparoscopic ovariectomy using electrocoagulation and fine dissection as the only means of achieving haemostasis of the severed ovarian pedicle. Four mares had bilateral ovariectomy performed as a treatment for aggressive behaviour thought to be associated with the oestrous cycle. Eight mares had unilateral ovariectomy performed for removal of a granulosa thecal cell tumour (GCT). Electrocoagulation provided an effective means of haemostasis in both normal and pathological ovaries. Only one case (removal of a GCT) had mild haemorrhage following electrocoagulati...
Treatment with human chorionic gonadotropin (hCG) for ovulation induction is associated with an immediate 17beta-estradiol decrease and a more rapid LH increase in mares. The effect of treatment with an ovulation-inducing dose of human chorionic gonadotropin (hCG) on 17beta-estradiol (estradiol) and LH concentrations was studied in mares. In Experiment 1, treatment with hCG resulted in ovulation in approximately 48 h. The LH surge centralized to ovulation and the preovulatory decline in estradiol were not different between hCG-treated (n=15) and control (n=13) groups. In Experiment 2, concentrations of hCG decreased 92% between 1 and 48 h after hCG treatment, estradiol decreased (P<0.003) within 6h, and LH increased at a greater (P<0.02) rate after 12h (n...
[Quantitative prevalence of Anoplocephala sp. and egg shedding consistency in horses]. The objective of this work was to determine the quantitative prevalence of Anoplocephala sp. in thoroughbred horses raised in São José dos Pinhais, PR using the modified centrifugal-flotation technique. Repeatability values for the eggs per gram (EPG) were evaluated at 28-day intervals. The coproparasitological tests were made in 28 one-year old animals, 25 two-year old animals and 28 mares during the 2007 period of January 31st and June 15th. In the comparison of EPG, all mares presented low values than the foals (P = 0.04). The prevalence results indicated 50, 18 and 40% Anoplocephala sp. ...
Immunohistochemical and histochemical identification of proteins and carbohydrates in the equine endometrium Expression patterns for mares suffering from endometrosis. Although alterations in patterns of protein secretion revealed in uterine flushings from mares suffering from endometrosis have been described, little is known about alterations at the cellular level. Hence, the aim of this study was to characterize deviations in patterns of uterine gland secretion patterns using endometrial biopsies, histochemical and newly established immunohistochemical methods. Forty-eight endometrial biopsies were obtained from mares suffering from various types of endometrosis (active and inactive, destructive and non-destructive) and degree (mild to severe) were analyze...
Equine placenta expresses glutamine synthetase. In most mammalian species the developing fetus utilizes large amounts of glutamine derived both from the maternal circulation and synthesized de novo in the placenta. The present study was designed to determine the role of the placenta in glutamine synthesis in the horse. The placentae from eight Standardbred mares were sampled immediately after parturition together with additional tissues obtained at necropsy from three Standbred mares during diestrous. Glutamine synthetase protein was detectable in the non-pregnant horn of the placenta in amounts similar to those seen in gluteus muscle, but ...
The Endocrinology of equine parturition. Delivery of viable young requires co-ordination of fetal maturation with the onset of labour at term. In turn, this depends on a cascade of fetal and maternal endocrine events. The sequence of these events is broadly similar in most mammals but there are differences in placental hormone synthesis and in the timing and magnitude of key prepartum endocrine changes between species. In most farm animals, maternal progesterone (P4) levels decline and oestrogen levels increase in the last 5 - 10 days before delivery in response to activation of the fetal hypothalamicpituitary-adrenal (HPA) axis and ...
