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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.
Equine frozen semen: freezability and fertility field results. The freezability of stallion semen defined as the number of selected ejaculates/total number of ejaculates frozen from 161 different stallions was analyzed. Of the stallions, 19, 30, 27 and 24% had a freezability of 0%, 0 to 33%, 33 to 66%, over 66%, respectively In 85 different stallions, the correlation of freezability between first and second year was 0.60 (P < 0.001). The relationship between fertility with fresh and frozen semen and freezability was analyzed in 40 stallions whose freezability and fertility information was recorded during 5 years. There was a strong relationship between...
The effects of parturition and peripartum complications on the peritoneal fluid composition of mares. Abnormalities in peritoneal fluid are diagnostically useful for managing equine colic; however, their significance in post-dystocia mares is not known. This study was to determine what changes, if any, occurred following obstetrical manipulations. Peritoneal fluid samples were collected from 2 groups of foaling mares to establish control values, and from a third group that had developed clinical abnormalities (CAb,n = 14) or had made an uneventful recovery (CN,n = 36) following fetal extraction. In Group 1 mares, samples were collected before and after induced parturitions (n = 7), and althoug...
Puberty and growth rate in thoroughbred fillies. We measured progesterone and estradiol levels from birth to the beginning of adult life in 10 Thoroughbred fillies from the Equilia Stud Farm in Avaré SP, Brasil. The animals were measured and weighed monthly for the determination of body development and of a possible correlation between the rate of weight and height gain and the onset of detectable sex hormone levels. Jugular blood was collected twice a week and stored at -20 degrees C until assay of progesterone by a solid phase RIA with a sensitivity of 0.32 nmol L and of estradiol by liquid phase RIA adapted to low levels (3.67 pmol L ). ...
Effect of beta-carotene administration on reproductive function of horse and pony mares. The objective of this study was to determine whether supplemental beta-carotene would influence reproductive function in mares maintained on spring and summer pastures and to characterize plasma carotene concentrations during the estrous cycle. Carotene concentrations in plasma did not vary with day of estrous cycle (P = 0.7455). Mares receiving every other day injections of beta-carotene (400 mg; n = 4) or saline (10 ml; n = 4) during proestrus/estrus did not differ in plasma estradiol (E(2)) concentrations (P = 0.6313), follicle development (P = 0.8068), or plasma progesterone (P(4)) concent...
Luteal blood flow and progesterone production in mares. The temporal relationships between blood flow in the corpus luteum (CL) and circulating progesterone concentrations were studied in 20 mares. Retrospective inspection of plasma progesterone concentrations indicated that a precipitous decrease occurred during Days 15-17 (Day 0 = ovulation) and was defined as the luteolytic period. Mean percentage of CL with color-Doppler signals for blood flow was maximum on Day 10 (77.3%), and Days 10-14 (49.8%) were defined as the preluteolytic period. The cross-sectional area of the CL decreased progressively from Day 4 (9.0 cm2) to Day 19 (1.5 cm2). Progest...
Genetic and permanent environmental variability of twinning in Thoroughbred horses estimated via three threshold models. Twinning is a serious problem in Thoroughbred horses, as most of the multiple pregnancies are miscarried and live foals present lower performance values. The aim of this study was to estimate the heritability and repeatability of twinning in Thoroughbred horses. A total of 12648 pregnancies of 2033 Thoroughbred mares born between 1929 and 1994 in 11 studs were included. The analysis was performed by the use of AI-REML algorithm under three threshold animal models. The first model included effects of stud, mare's birth period and interaction between them as fixed. The second model included the ...
Social relationships in a herd of Sorraia horses Part I. Correlates of social dominance and contexts of aggression. Factors related to dominance rank and the functions of aggression were studied in a herd of Sorraia horses, Equus caballus, under extensive management. Subjects were 10 adult mares 5-18 years old and a stallion introduced into the group for breeding. Dominance relationships among mares were clear, irrespective of rank difference, and remained stable after introduction of the stallion. The dominance hierarchy was significantly linear and rank was positively correlated with age and total aggressiveness. Higher-ranking mares received lower frequency and intensity of agonistic interactions. Nevert...
Characterisation of lymphocyte subsets in the equine oviduct. The equine oviduct is the site of fertilisation and location of embryonic development during the first 5 or 6 days. It therefore has an important influence on mare fertility. Although histopathological changes have been described previously, there is limited information regarding lymphocyte subtypes present in the mucosa of the normal equine oviduct. Objective: To characterise the distribution of CD3+, CD4+, CD8+ and B lymphocytes in the equine oviduct from inseminated mares during oestrus and dioestrus, and from noninseminated mares during the immediate post ovulatory period. Methods: Oviduct...
Cyathostomes in horses in Canada resistant to pyrantel salts and effectively removed by moxidectin. Clinical trials using fecal egg count reduction tests and coproculture were conducted with yearlings and mares on a farm in 1997. Fecal samples were taken from each horse to estimate the number of strongyle eggs/g feces with Cornell-Wisconsin centrifugal flotation and Cornell-McMaster dilution techniques. Eleven of 15 yearlings, which had been on a daily feeding of grain with pyrantel tartrate for 66 d were found with strongyle eggs in feces. This was the first time the in-feed medication had been used on the farm. Nine yearlings were randomised into three groups; continuation of daily pyrante...
Gonadotropin secretion and pituitary responsiveness to GnRH in mares with granulosa-theca cell tumor. Granulosa-theca cell tumors (GTCTs) are able to secrete variable amounts of sex steroids and immunoreactive inhibin (ir-INH). Although the pituitary appears to be affected by the presence of a GTCT, pituitary responsiveness to exogenous GnRH has not been examined. The aims of the present study were to: (i) assess the plasma hormone concentrations of ir-INH, gonadotropins and sex steroids in eight mares with GTCT and (ii) assess the responsiveness of pituitary gonadotroph cells to exogenous GnRH stimulus both before and after tumor removal. In seven mares, the contralateral ovary was firm, smal...
Effect of prostaglandin F2alpha on ovarian, adrenal, and pituitary hormones and on luteal blood flow in mares. The effect of a single injection of prostaglandin F2alpha (PGF) during mid-diestrus on systemic concentrations of progesterone, LH, FSH, estradiol, and cortisol and on blood flow to the corpus luteum was studied in 10 controls and 10 PGF-treated mares. Blood flow was assessed by estimating the percentage of corpus luteum with color-Doppler signals of blood flow during real-time scanning of the entire structure and by the diameter of the vascular pedicle near its attachment to the ovary. Treatment was done 8 days after ovulation and 0 h was immediately before the treatment. Examinations and col...
Morphine administration in horses anaesthetized for upper respiratory tract surgery. To determine the effect of morphine administration on commonly monitored cardio-respiratory variables and recovery quality in horses undergoing anaesthesia and surgery. Methods: Prospective, randomized clinical study. Methods: Thirty-eight thoroughbred horses, 32 geldings and six mares, 3-13 years old, weighing 411-600 kg. Methods: A standard anaesthetic technique was used. Twenty minutes after induction of anaesthesia horses received 0.1 mg kg(-1) (0.1 m) or 0.2 mg kg(-1) (0.2 m) morphine by intravenous injection. A control group did not receive morphine. Heart rate, respiratory rate (fr), me...
Endometrial nitric oxide production and nitric oxide synthases in the equine endometrium: Relationship with microvascular density during the estrous cycle. Nitric oxide (NO) plays an important role in angiogenesis and in the regulation of the blood flow. This study was carried out to investigate (i) the effects of endogenous estrogens and progestins and exogenous progesterone (P(4)) (5 ng/ml or 1 microg/ml) or estradiol 17beta (E(2)beta) (50 pg/ml or 1 microg/ml) on in vitro endometrial NO synthesis; (ii) the presence of different isoforms of NO synthase; (iii) and their relationship to microvascular density in the equine endometrium during the estrous cycle. NOS expression was also evaluated in the myometrium. Expression of endothelial and induc...
Nocardioform placentitis with isolation of Amycolatopsis spp in a Florida-bred mare. A 4-year-old Thoroughbred mare was evaluated because of placental abnormalities and a retained placental remnant. Results: Microbial culture of the placenta yielded pure growth of Amycolatopsis spp. Histologic examination of the placenta revealed a focally expanding chorionitis with intralesional gram-positive filamentous bacilli and multifocal allantoic adenomatous hyperplasia on the apposing allantoic surface. Results: Treatment with lavage and oxytocin resulted in expulsion of the placental remnant within hours of parturition. The mare did not become pregnant again despite multiple breeding...
Management of hydrops amnion in a mare resulting in birth of a live foal. A 19-year-old Thoroughbred mare was evaluated at 265 days of gestation with a markedly distended abdomen and edema of the ventral portion of the abdomen. Results: The uterus was distended over the pelvic rim, making transrectal palpation of the fetus impossible. Transabdominal ultrasonography revealed excessive amounts of fetal fluid. Results of analysis of fluid obtained via amnio- and allantocentesis confirmed that the amniotic cavity was large. Results: The mare was monitored for signs of weakness of the prepubic tendon and abdominal wall. The fetus and placenta were monitored for signs of ...
Surfactant proteins A and D in the genital tract of mares. The presence of surface-active material in the lung alveolus has been known for several decades as being essential for normal lung function. Surfactant is essential for reducing the surface tension at the alveolar air-liquid interface. Pulmonary surfactant is composed of 90% lipids and 10% proteins. There are four non-serum proteins surfactant protein-A (SP-A), surfactant protein-B (SP-B), surfactant protein-C (SP-C) and surfactant protein-D (SP-D) named in chronologic order of discovery. Lung SP-A and SP-D belong to a family of collagen-containing C-type lectin family called collectins. The h...
Influence of reproductive stage at PRID insertion on synchronization of estrus and ovulation in mares. In the present study, we investigated the effects of reproductive status, size of follicles and plasma progesterone concentrations of mares at PRID insertion on the efficacy of the treatment, estrous cycle patterns, plasma concentrations of progesterone and LH. The progesterone-releasing device (PRID) was administered intravaginally to 28 Haflinger mares for 11 days at different reproductive stages: anestrus (n=6), estrus (n=11) and diestrus (n=11). Plasma concentrations of progesterone at insertion (Day 1) of PRID differed among treatment groups (anestrus: 0.2-0.6 ng mL(-1), estrus: 0.2-0.5 a...
Measurement of redox potential and steroid concentrations in the follicular fluid of growing and regressing follicles of mares. The aim of this study was to prove if oxidation-reduction levels in the follicular fluid were new functional indices of follicular health and whether there was a high level of accordance with endocrinological parameters and with the growth stage as detected by ultrasound monitoring of individual follicles during the oestrous cycle in mares. Follicles were classified as growing and regressing follicles using ultrasonography. Altogether 48 follicles with a diameter from 20 to 56 mm were aspirated by transvaginal ultrasound guided follicular aspiration. Follicular concentration of oestradiol and ...
Relationships of changes in B-mode echotexture and colour-Doppler signals in the wall of the preovulatory follicle to changes in systemic oestradiol concentrations and the effects of human chorionic gonadotrophin in mares. A duplex grey-scale and colour-Doppler ultrasound instrument was used to study the changes in the wall of the preovulatory follicle in mares. When the follicle reached > or =35 mm (hour 0), mares were randomized into control (n = 16) and human chorionic gonadotropin (hCG)-treated (n = 16) groups. The hCG treatment was given at hour 0. Scanning was done every 12 h until hour 36, every hour between hours 36 and 48, and every 12 h thereafter until ovulation. Blood was sampled every 12 h for oestradiol assay. During the period 0-24 h post-treatment, oestradiol concentrations decreased in the hC...
Holding immature equine oocytes in the absence of meiotic inhibitors: effect on germinal vesicle chromatin and blastocyst development after intracytoplasmic sperm injection. Holding immature oocytes before the onset of maturation simplifies oocyte transport and aids in scheduling later manipulations. We report here a method for holding equine oocytes in the absence of meiotic inhibitors. In Experiment 1, immature oocytes with expanded cumuli were cultured at 38.2 degrees C in medium containing cycloheximide, or were held at room-temperature in M199 with Hanks' salts, for 16-18 h before maturation. Control oocytes were matured immediately after recovery. Oocytes were fertilized by intracytoplasmic sperm injection and cultured for 4d. Embryo development was not diff...
Reproduction in high body condition mares with high versus low leptin concentrations. Previous results from our laboratory indicated that a majority of mares with high body condition scores (BCS) displayed estrous cycles or had considerable follicular activity during the winter. Among these high BCS mares, about 35% of them exhibited a persistent hyperleptinemia and hyperinsulinemia. The current experiment was designed to compare the reproductive characteristics of high BCS mares with hyperleptinemia to those with normal (low) plasma concentrations of leptin during the winter and the first estrous cycle (or the first full cycle encountered for those already cycling). Light hors...
Leptin concentration in plasma and in milk during the interpartum period in the mare. The aim of this work is to investigate on plasma profiles of leptin and estradiol 17beta during the interpartum period and leptin concentrations in the milk and in the colostrum during the period from parturition to the successive delivery in mare. Leptin plasma concentration varied from 5.1+/-2.3 ng/ml after the first parturition (week 0) to 3.0+/-0.7 at week 21 (p<0.05), then it increased to maximal level at week 49 (6.9+/-1.0 ng/ml, p<0.05). Leptin concentration in the colostrum and in the milk has been significantly (p<0.05) higher than that in plasma samples at week 1 (milk 8.8+/...
