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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.
Developmental capacity of equine oocytes matured and cultured in equine trophoblast-conditioned media. The objective was to compare culture media for in vitro maturation of equine oocytes and for in vitro culture of zygotes produced from IVF of partially zona-removed oocytes. Cumulus-oocyte complexes from slaughterhouse-derived ovaries were washed in m-Dulbecco's PBS and cultured in TCM-199, F10-DMEM or c-F10-DMEM (50% F10-DMEM + 50% F10-DMEM conditioned medium from culture of an equine trophoblast monolayer for 3 or 4 days). All media included FSH, LH, E2, and 10% FCS. After 28 to 30 h maturation, cumulus expansion was scored from 0 (no expansion) to 4 (fully expanded). Oocytes with a 1st pola...
Pharmacokinetics of orbifloxacin and its concentration in body fluids and in endometrial tissues of mares. Pharmacokinetics and distribution of orbifloxacin into body fluids and endometrium was studied in 6 mares after intragastric (IG) administration at a single dose rate of 7.5 mg/kg body weight. Orbifloxacin concentrations were serially measured in serum, synovial fluid, peritoneal fluid, urine, cerebrospinal fluid, and endometrial tissues over 24 hours. Minimum inhibitory concentrations of orbifloxacin were determined for 120 equine pathogens over an 11-month period. The mean peak serum concentration (Cmax) was 2.41+/-0.30 microg/mL at 1.5 hours after administration and decreased to 0.17+/-0.01...
Effect of insemination time of frozen semen on incidence of uterine fluid in mares. Ninety five mares were inseminated with frozen semen either within 12 h before ovulation or within 8 h after ovulation. The effect of preovulatory versus postovulatory insemination (AI) on the subsequent detection of uterine fluid was studied. The overall pregnancy rate was 43% and this was not significantly influenced by preovulatory or postovulatory insemination. When mares were first examined 12 h after AI, 18 of 52 mares (35%) had accumulated uterine fluid. However, when mares were first examined 18 to 24 h after AI, only 6 of 43 mares (14%) had uterine fluid. Presence of intrauterine flui...
Immunohistochemical study of the distribution of adrenergic and peptidergic innervation in the equine uterus and the cervix. Little is known about neurogenic regulation of uterine contractility in mares. The present study investigated the distribution of adrenergic and peptidergic nerves in the mare uterus. Samples from the uterine horn, body and cervix were collected from 18 cyclic mares for immunohistochemistry. The uterus was well supplied with adrenergic nerves. A large number of tyrosine hydroxylase- and dopamine beta-hydroxylase-immunoreactive nerve bundles and fibres were present in the myometrium and endometrium in all regions of the uterus and cervix. These adrenergic nerve bundles and fibres travelled para...
Response of estradiol and inhibin to experimentally reduced luteinizing hormone during follicle deviation in mares. The increase in LH concentrations at the time of the decrease in FSH concentrations during follicle deviation in mares was studied to determine the role of LH in the production of estradiol and immunoreactive inhibin (ir-inhibin). Ten days after ovulation, all follicles > or =6 mm were ablated, prostaglandin F(2 alpha) was given, and either 0 mg (control group, n = 15) or 100 mg of progesterone in safflower oil (treated group, n = 16) was given daily for 14 days, encompassing the day of diameter deviation. The follicular and hormonal data were normalized to the expected day of the beginning...
Clinical and virological evaluation of the efficacy of an inactivated EHV1 and EHV4 whole virus vaccine (Duvaxyn EHV1,4). Vaccination/challenge experiments in foals and pregnant mares. Pregnant mares and young foals were vaccinated with Duvaxyn EHV1,4, an inactivated and adjuvanted vaccine containing both the EHV-1 and 4 antigens. SN and CF antibody titres were induced two weeks after first vaccination. Antibody levels were boosted after second vaccination, however they never reached the levels induced after virus challenge. Young foals were challenged with virulent EHV-1 and EHV-4 field viruses. Pregnant mares were challenged with the highly abortigenic EHV-1 strain Ab4. Vaccinated animals showed a clear reduction in clinical signs and virus excretion compared to unvaccinat...
Analgesic, hemodynamic, and respiratory effects induced by caudal epidural administration of meperidine hydrochloride in mares. To determine the analgesic, hemodynamic, and respiratory effects induced by caudal epidural administration of meperidine hydrochloride in mares. Methods: 7 healthy mares. Methods: Each mare received meperidine (5%; 0.8 mg/kg of body weight) or saline (0.9% NaCl) solution via caudal epidural injection on 2 occasions. At least 2 weeks elapsed between treatments. Degree of analgesia in response to noxious electrical, thermal, and skin and muscle prick stimuli was determined before and for 5 hours after treatment. In addition, cardiovascular and respiratory variables were measured and degree of se...
Neonatal isoerythrolysis involving the Qc and Db antigens in a foal. In 1992, a multiparous 13-year-old Thoroughbred mare and her 48-hour-old colt were examined because of possible neonatal isoerythrolysis (NI). Supportive treatment was administered, and the foal recovered without requiring a transfusion. According to the owners, the mare had delivered foals without incident during 1987 and 1991. The mare was barren during 1993, but in 1994, delivered a filly that developed severe NI. The foal was given 3 transfusions and eventually recovered without complications. Blood typing analysis of the mare and its foals indicated that all 4 foals were positive for the ...
Role of prostaglandins in intrauterine migration of the equine conceptus. Between at least day 9 and day 16 after ovulation the spherical equine conceptus migrates continuously throughout the uterine lumen, propelled by peristaltic myometrial contractions. This unusually long period of intrauterine movement ensures that the conceptus delivers its anti-luteolytic signal to the entire endometrium to achieve luteostasis. The present experiment tested the hypothesis that prostaglandins stimulate the myometrial contractions that result in the migration of the conceptus. Serial ultrasonographic examinations of the uteri of eight mares performed during 2 h periods between ...
Effect of periovulatory prostaglandin F2alpha on pregnancy rates and luteal function in the mare. The objective of this study was to determine whether periovulatory treatments with PGF2alpha affects the development of the CL, and whether the treatment was detrimental to the establishment of pregnancy. Reproductively sound mares were assigned randomly to one of the following treatment groups during consecutive estrus cycles: 1. 3,000 IU hCG within 24 hours before artificial insemination and 500 microg cloprostenol (PGF2alpha analogue) on Days 0, 1, and 2 after ovulation (n=8), 2. 2 mL sterile water injection within 24 hours before artificial insemination and 500 microg cloprostenol on Days ...
The effect of different quantities and compositions of pelleted diets on immune response of mares during the production of anti-tetanus sera. Research was carried out into the effect that different quantities and compositions of concentrated portions of meal had on certain haematological properties and on the immune response of mares in the course of hyper-immune antitetanus sera production. The experiment involved 24 Nonius and Lipizzaner cross-bred mares divided into two groups of 12 animals each, a control group and a trial group. The experiment lasted 12 months, with haematological and immunological tests being carried out every 30 days. During the course of the experiment each mare was subjected to 11 immunisation cycles, and i...
Induction of luteolysis in mares by ultrasound-guided intraluteal treatment with PGF2alpha. To evaluate the technique of ultrasound-guided luteal injection in mares, PGF2alpha was administered under ultrasound guidance to horse mares (n = 7 to 9 per group) on Day 9 postovulation via either a systemic (i.m.; zero, 0.01, 0.1, or 5 mg/dose) route or a local intraluteal (i.l.; zero, 0.01 or 0.1 mg/dose) route. The luteolytic efficacy of each treatment was determined based on post-treatment decreases in progesterone concentration, interval to uterine edema (IE) and interovulatory interval (IOI). Local administration of PGF2alpha directly into the CL consistently induced luteolysis, at dos...
Effect of low-dose zearalenone exposure on luteal function, follicular activity and uterine oedema in cycling mares. The effect of 10-day zearalenone administration starting 10 days after ovulation was studied in 6 cycling trotter mares in the summer period. After an entire oestrous cycle (Cycle 1), mares were given 7 mg purified zearalenone per os daily (1 mg/ml in ethyl alcohol) beginning on Day 10 of Cycle 2. Toxin exposure was continued until the subsequent ovulation. Luteal function and follicular activity were monitored daily by rectal palpation, ultrasonography and blood sampling for progesterone. During toxin exposure, all animals were in good physical condition. The toxin had no effect on the length...
Lectin binding patterns of uterine glands in mares with chronic endometrial degeneration. To evaluate changes of glycoconjugate in uterine glands of endometrial tissues obtained from mares. Methods: adult mares. Methods: Uterine biopsy samples were collected during the breeding season and analyzed histologically for signs of chronic endometrial degeneration. Stage of the estrous cycle was established, using clinical examination and determination of hormonal status. Uterine tissue samples were analyzed, using lectin histochemical and immunohistochemical techniques (estrogen and progesterone receptors). Connective tissues were stained to determine alterations of ground substance in p...
Use of buserelin to induce ovulation in the cyclic mare. Inducing ovulation in a cyclic mare is often necessary. For this purpose, hCG has been used commonly, but the response can be reduced after successive administrations. The aims of this study were to test the effectiveness of buserelin in hastening ovulation in estrus mares, and its influence on fertility; and to investigate the effect of treatment on LH secretion. Five crossover trials were designed to compare the effect of two treatments: buserelin (40 microg in 4 doses i.v. at 12 h intervals) vs placebo (Experiments 1 and 2); buserelin 40 microg (in 4 doses i.v.) vs 20 microg (Experiment 3);...
The effect of the gonadotropin-releasing hormone analog, buserelin, on pregnancy rates in horse and pony mares. We conducted a series of trials over a four-year period on a total of 2,346 mares, to determine the effect of a single dose of the GnRH analog buserelin (20 to 40 microg i.m. or s.c.) on pregnancy rates when given between 8 and 12 days after service. Although there were some statistically significant improvements in pregnancy rates in individual trials, meta-analysis of the data overall showed significant improvements at all times examined, i.e. 13 to 16, 19 to 23, 28 to 31 and 38 to 42 days after service. These results indicate that treatment of mares with 20 to 40 microg buserelin between Da...
Opioidergic inhibition of luteinising hormone and prolactin release changes during pregnancy in pony mares. In equine species, luteinising hormone (LH) and prolactin (PRL) release are reduced throughout pregnancy but increase at foaling. The present experiments were designed to study a possible opioidergic regulation of LH and PRL release in pregnant Shetland mares (n=6). At various stages of pregnancy (days 26.4+/-0.6, 75.4+/-5.4, 171.8+/-2.4, 226.2+/-4.8, 282.7+/-3.4 and 319.8+/-2.1), mares were injected with the opioid antagonist naloxone (0.5 mg/kg body weight) and saline. The two treatments were always separated by 2 days, and mares served as their own controls. Two hours after being given nalo...
Effect of number and diameter of follicles on plasma concentrations of inhibin and FSH in mares. The role of the number of follicles and circulating immunoreactive inhibin in the decrease in plasma FSH concentrations that occurs during development of a follicular wave was studied in mares. All follicles > or = 6 mm in diameter were ablated by ultrasound-guided transvaginal aspiration of follicular fluid on day 10 after ovulation. During the subsequent wave, all follicles, the three largest follicles (three follicle group), the largest follicle (single follicle group) or no follicles were retained and the remaining follicles were ablated before they reached > 10 mm in diameter (n = 1...
Confocal microscopy of germinal vesicle-stage equine oocytes. The objectives were to compare cumulus type with nucleus form in equine cumulus oocyte complexes (COCs), to define the percentage of germinal vesicle (GV)-stage oocytes within a population of mares, and to further define GV nucleus shapes of equine oocytes. Cumulus types were as follows: 1) compact (56/208, 26.9%), 2) slightly expanded (37/208, 17.8%), 3) moderately expanded (27/208, 13.0%), 4) greatly expanded (15/208, 7.2%), or 5) denuded (73/208, 35.1%). One hundred thirty of 208 COCs (62.5%) were GV-stage, 21/208 (10.1%) were condensed chromatin-stage, 8/208 (3.8%) were polar body-stage, 4...
Ovulation rate and distribution in the thoroughbred mare, as determined by ultrasonic scanning: the effect of age. Ovarian activity was monitored in 2181 oestrous cycles from 1136 thoroughbred brood mares to accurately determine overall ovulation rate, the relative distribution of ovulations between left and right ovary, whether mare age had an effect on these parameters and whether ovulation pattern in one cycle affected the pattern within the next. Ultrasonic scanning was used in preference to rectal palpation and slaughterhouse material due to its greater accuracy. Mare's ages ranged from 3 to 22 years. The results obtained indicated a similar incidence of ovulation occurring on the right (49.5% of all ...
Microvascular development and growth of uterine tissue during the estrous cycle in mares. To document uterine growth and microvascular development in the endometrium of uteri with differing degrees of fibrosis as well as uterine growth throughout the estrous cycle of mares. Methods: 30 mares. Methods: Uterine tissue was obtained during the breeding season from a slaughter facility. Stage of estrous cycle of the mares was assessed on the basis of ovarian structures and plasma progesterone concentrations. Endometrium was characterized by use of light microscopy, and blood vessel walls were marked by histochemical techniques. Microvascular development was evaluated by a computerized i...
Effects of estradiol-17beta administration on steady-state messenger ribonucleic acid (MRNA) encoding equine alpha and LH/CGbeta subunits in pituitaries of ovariectomized pony mares. The process of sexual recrudescence in the springtime in mares is characterized by renewal of follicular growth and acquisition of steroidogenic competence. Concomitant with renewal of follicular steroidogenesis is re-establishment of LH biosynthesis and secretion. Research results from our laboratory indicate that increased estradiol and LH secretion occur in close temporal association before the first ovulation of the year. Therefore, the hypothesis tested in this experiment was that estrogen administration to ovariectomized pony mares during the equivalent time of early vernal transition wo...
Effects of ovarian input on GnRH and LH secretion immediately postovulation in pony mares. The potential involvement of ovarian factors in regulating GnRH and LH postovulation was studied in ovarian intact (Group 1; n=3) and ovariectomized (OVX; Group 2; n=3) mares (OVX within 12 hr of ovulation). Blood samples were collected every 10 min for 6 hr from jugular vein (JV) and intercavernous sinus (ICS) during estrus and on Day 8 postovulation for LH and GnRH analysis. Additionally, JV samples were collected twice daily (12-hr intervals) for 30 days for LH and progesterone (P4) analysis. A significant treatment x day effect (P<0.0001) describes declining plasma LH concentrations in ...
A dipstick immunoassay to rapidly measure serum oestrone sulfate concentrations in horses. A dipstick, competitive immunoassay for rapidly measuring serum oestrone sulfate (OS) concentrations in horses was developed to distinguish mares 100 or more days pregnant from non-pregnant animals. 6-Ketoestrone 6-carboxymethyloxime conjugated to bovine serum albumin (oestrone CMO-BSA) was 'dotted' 25 mm from the bottom edge of 45 x 5 mm strips of polyester-film-supported cellulose nitrate membrane, pore size 3 microm. The strips were blocked, dried and a 15 x 5-mm cellulose absorbent sink attached 10 mm from the top of each strip. The manufactured dipsticks were stored with desiccant at room...
Studies on the supply of immunoglobulin G to newborn camel calves (Camelus dromedarius). A major problem in camel productivity is the high mortality rate of camel calves in the first 3 months. The causes for mortality are mainly poor management practice and infectious diseases. The purpose of this research, carried out on a ranch in Kenya, was to determine the immunoglobulin G (IgG) concentration in camel colostrum as well as the extent of the calves' passive immunization by maternal antibodies. IgG concentration in colostrum and in the serum of the calf were measured during the first 3 d of life. Evaluation was carried out by comparing the respective values with those for horses ...
Septicemia and peritonitis due to Actinobacillus equuli infection in an adult horse. Actinobacillus equuli is a rare cause of peritonitis in adult horses. Septicemia and peritonitis due to A. equuli were diagnosed at necropsy in an 8-year-old Saddlebred mare. The origin of the infection was not known; however, small necrotic colonic mucosal lesions presumed to have been caused by phenylbutazone treatment may have allowed bacterial invasion. A good response to antimicrobial treatment has been documented in the small numbers of previously reported acute cases of peritonitis. Because it is potentially treatable, it is important for pathologists and clinicians to identify horses w...
Effect of deslorelin acetate on gonadotropin secretion and ovarian follicle development in cycling mares. To evaluate gonadotropin secretion and ovarian function after administration of deslorelin acetate to induce ovulation in mares. Methods: Randomized controlled trial. Methods: 16 healthy mares with normal estrous cycles. Methods: 8 control mares were allowed to ovulate spontaneously, whereas 8 study mares received deslorelin to induce ovulation when an ovarian follicle > 35 mm in diameter was detected. Follicle development and serum concentrations of gonadotropins were monitored daily during 1 estrous cycle. Pituitary responsiveness to administration of gonadotropin-releasing hormone (GnRH)...
