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.
Renaudin CD, Troedsson MH, Gillis CL, King VL, Bodena A.The objective of this study was to determine normal variations in the utero placental thickness during mid- and late gestation in the mare. Normal, healthy pregnant mares (n = 9) were examined monthly from 4 mo of gestation until parturition by transrectal and transabdominal ultrasonography. At each examination, the combined thickness of the uterus and the placenta (CTUP) was measured at the placento-cervical junction (transrectally) and at the uterine body or the uterine horns (transabdominally). In addition, the echogenicity of the amniotic and allantoic fluids was evaluated by transrectal u...
Brück I, Anderson GA, Hyland JH.The influence of different maternal plasma progesterone concentrations on embryonic glucose metabolism was studied. Uterine flushes were obtained after treating ovariectomized mares (n = 3) with 0 (control), 100 or 200 mg progesterone daily for 7 d. A group of progesterone-induced proteins (PIP) of Mr approximately 20,000 were identified in flushes from progesterone treatments by SDS-PAGE but were not observed in control flushes. Progesterone-induced proteins were removed from half the pooled flush in each treatment group by Sepharose blue CL-6B. In a 3 x 2 factorial (progesterone treatments, ...
Giger R, Meier HP, Küpfer U.In a retrospective study the gestation lengths of two groups, each consisting of 193 "Freiberger" mares, were compared. The mares of the first group were bred by a donkey, those of the second group by a stallion of the "Freiberger" breed. On average, the gestation length of mares with "Freiberger" foals lasted 336.5 days, and that of mares with mule foals 343.1 days. The difference between both groups was significant (p < 0.001). The shortest and longest observed gestation length of mares with "Freiberger" foals was 307 and 361 days, and that of mares with mule foals 315 and 369 days, respecti...
Glaser AL, de Vries AA, Rottier PJ, Horzinek MC, Colenbrander B.Sero-epidemiological surveys have revealed that equine arteritis virus (EAV) is prevalent in most European countries. The virus causes sporadic cases of respiratory disease and abortion in horses, the incidence of which has increased in recent years. Mares and geldings eliminate virus after acute infection, but 30% to 60% of stallions become persistently infected. In these animals, EAV is maintained within the reproductive tract and is shed continuously in the semen. Persistent infection with EAV in stallions has no negative consequences for fertility but mares inseminated with virus-contamina...
Reilas T, Katila T, Mäkelä O, Huhtinen M, Koskinen E.Intrauterine fluid (IUF) was collected using a tampon from mid-oestrous mares (n = 57) with and without ultrasonically detectable accumulations of free intraluminal fluid. Bacteria were cultured and neutrophils counted from all samples (n = 57). Total protein concentration, trypsin-inhibitor capacity (TIC), and plasmin, beta-glucuronidase (B-Gase) and N-acetyl-beta-D-glucosaminidase (NAGase) activities were determined in 27 IUF samples. The motility of spermatozoa in the presence of IUF, IUF extended with Kenney's medium (1:1) and Kenney's medium alone was analysed in 9 samples using a Hamilto...
Welle MM, Audigé L, Belz JP.Endometrial biopsies of 44 broodmares were histologically examined on days 3, 6, and 9 postpartum. The mares were subdivided into three groups according to the course of the puerperal period. In 29 mares, parturition and expulsion of the placenta was normal, six mares showed dystocia, and in nine mares, the placenta was retained for > 2 hours. Tissue samples were evaluated histologically, and the average numbers of granulocytes, lymphocytes, macrophages, siderophages, and mast cells was determined. Protease content of mast cells was examined with a double-enzyme immunohistochemical staining te...
Meier HP, Gertsch U, Kohler S.Twin pregnancies are a serious problem in stud medicine as they terminate in most cases in abortion, stillbirth or the delivery of dead or weak and deformed foals. In recent years, the introduction of sonography has greatly improved the management of mares with twin conceptuses, in particular monitoring the phenomenon of spontaneous embryo reduction to a single vesicle. This allows supervision of pregnancy with relatively little expenditure and loss of time. We document the spontaneous reduction to single vesicles of unilateral twin pregnancies in a draught- and a warmblood-mare. In both mares...
Sharp DC, Thatcher MJ, Salute ME, Fuchs AR.The effect of transcervical endometrial biopsy on the concentrations of plasma immunoreactive oxytocin and 15-keto-13,14-dihydro-prostaglandin F2 alpha (PGFM) was studied in 18 pony mares on days 8, 12 and 14 after ovulation, days 12 and 14 of early pregnancy and at oestrus. Five biopsy specimens were taken within 15 min and consecutive specimens from each mare were pooled two (A) and three (B) together for measurement of the number of oxytocin receptors. Blood samples were collected at intervals of 5 min for 15 min beginning just before the initial biopsy. Biopsy procedure elicited prompt oxy...
van den Berg IS.An apparatus for collection of free-flow urine from female horses is described. This apparatus is a modification of a similar device described previously. It allows the collection of voided urine from adult female horses without confining them to metabolic stables or resorting to invasive procedures like bladder catheterisation. It is relatively easy to use after a short adaptation period.
Crossett B, Allen WR, Stewart F.Large quantities of an unusual 19 kDa protein (p19) are secreted into the lumen of the uterus of the mare (Equus caballus) during the oestrous cycle and early pregnancy. p19 associates strongly with the acellular capsule that surrounds the young horse conceptus and is believed to be important in maintaining pregnancy. Here we report the complete cDNA sequence encoding p19, its expression patterns in horse tissues and a Southern blot analysis of the gene in horse DNA. The predicted amino acid sequence of the p19 cDNA demonstrated a signal peptide of 18 residues and a mature protein of 162 resid...
Ball BA.There are considerable differences between mammalian species in the distribution and activity of ciliated cells within the oviduct, and limited information is available concerning either the distribution or activity of cilia within the equine oviduct. Patterns of ciliary activity were characterized in the ampulla and isthmus of oviducts recovered at 2 d after ovulation from 10 mares, and scanning electron microscopy was used to examine regional differences in the distribution of cilia in oviducts from 3 of these mares. Based upon the motility of 15 microm latex microspheres, ciliary activity w...
Dobrinski I, Ignotz GG, Thomas PG, Ball BA.To test the hypotheses that the attachment of equine spermatozoa to uterine tubal (oviductal) epithelial cells (OEC) in vitro is mediated by glycoproteins, and that proteins with carbohydrate-binding properties are present in the periacrosomal plasma membrane of equine spermatozoa. Methods: 4 reproductively sound stallions, and 1 mare in estrus. Methods: In experiment 1a, fluorescent-labeled spermatozoa were cocultured with monolayers of OEC in the presence of 50 mM glucose, fructose, galactose, mannose, N-acetyl glucosamine, N-acetyl galactosamine, or N-acetyl neuraminic acid, or 10 mg of fet...
Merritt AM, Burrow JA, Horbal MJ, Madison JB, Tran T.To better characterize the source of the large nonparietal secretory response to pentagastrin (PG) expressed in gastric contents of cannulated horses. Methods: Adult cross-bred horses: 4 geldings and 1 mare. Methods: Horses were prepared by surgical insertion of a silastic gastric cannula from which gastric contents after feed was withheld could be continuously collected by gravity drainage. During experiments, the horses were lightly restrained in stocks, the gastric cannula was opened, and a catheter was inserted into a jugular vein. Over the next 5 hours, gastric contents were collected in ...
Watson ED, Thomson SR.Aromatase P-450 (P-450arom) is a crucial regulatory enzyme that is necessary for conversion of androgens to oestrogens. Corpora lutea and follicles were obtained from the ovaries of cyclic mares and from mares at day 20 and days 40-70 of pregnancy. The presence of P-450arom within specific cell types was investigated by immunostaining to determine potential sites of oestrogen synthesis. Immunoreactivity for P-450arom was confined to the granulosa layer of non-atretic follicles > 5 mm in diameter and to corpora lutea at all stages of the oestrous cycle and during pregnancy. These findings co...
Rasch K, Schoon HA, Sieme H, Klug E.The aim of this field study was to examine the influence of the uterotonic substance oxytocin in 2 different therapeutic dosages of 15 and 25 i.u., respectively on the uterine drainage of oestrous mares and on their fertility. In addition endometrial biopsies of mares with and without intrauterine fluid accumulations around the time of ovulation were evaluated histomorphologically regarding the aetiology of susceptibility to uterine infection. A population of 59 Hanoverian Warmblood mares was used in this study. The mares were divided into Group A (mares with intrauterine fluid accumulations [...
Gastal MO, Gastal EL, Kot K, Ginther OJ.The temporal relationships among day of conceptus fixation (cessation of mobility), conceptus diameter, uterine tone, uterine contractility, and myometrial and endometrial thickness of the middle and caudal segments of the uterine horns were assessed in 13 pony mares with fixation in the caudal segment of a uterine horn. The mean day of fixation (14.9 +/- 0.3) was established by 2-h mobility trials. Uterine tone increased (P < 0.0001) gradually over Days 11 to 21, whereas uterine contractility decreased (P < 0.0001) between Days 14 and 18. The diameter of the spherical embryonic vesicle ...
Hochi S, Maruyama K, Oguri N.The present study was designed to examine the suitability of ethylene glycol as a cryoprotectant for equine embryos. Blastocysts recovered nonsurgically from Day 6 donor mares were cryopreserved by conventional 2-step freezing in the presence of 10% ethylene glycol (EG), 10% glycerol (Gly), or 10% ethylene glycol + 0.1M sucrose (EG + Suc). After thawing, the EG and Gly were removed by a 6-step manner, and the EG + Suc was diluted to one fourth in the freezing straw. The postthaw blastocysts were transferred nonsurgically into the uteri of recipient mares on Days 4 to 7 after ovulation. Pregnan...
Murray MJ, Eichorn ES.To determine the effect of decreasing gastric acidity in a feed-deprivation protocol on induction of gastric ulcers, and to determine whether stall confinement may be a factor contributing to gastric ulceration in horses. Methods: 8 adult horses, 4 geldings and 4 mares, 3 to 8 years old, and 7 adult horses, 5 geldings and 2 mares, 4 to 11 years old. Methods: Gastric ulceration was induced in horses by alternating 24-hour periods of feed deprivation and ad libitum access to hay, for a total of 96 hours' feed deprivation. This protocol was repeated with the horses receiving the histamine type-2 ...
Van Hoogmoed L, Snyder JR, Christopher M, Vatistas N.To characterize, in mares, changes in peritoneal fluid that occurred within the first 7 days after routine foaling. Methods: Prospective observational trial. Methods: 15 mares. Methods: Abdominocentesis was performed within 10 days before foaling and again 12 hours, 3 days, and 7 days after each horse foaled. Data recorded for each sample included total nucleated cell count, differential cell count, specific gravity, fibrinogen concentration, and total protein concentration. Smears of each sample were examined by a single clinical pathologist. Results: There were not any significant difference...
Corveleyn S, Deprez P, Van der Weken G, Baeyens W, Remon JP.Six healthy mares ranging in age from 6 to 12 years and weighing from 415 to 540 kg were used to determine the rectal bioavailability of ketoprofen. For the rectal administration, three different formulations, each containing 1 g of ketoprofen, were administered in a fatty and a hydrophilic suppository base and as a liquid suspension. An average elimination half-life of 1.3 h (+/-1.2) was found. The average value for the total plasma clearance (ClT) was 131.9mL/ min.kg (range 95-183.5). The volume of distribution Vd(area) was 255 mL/kg and the mean residence time (MRT) value was 0.47 h. After ...
Csik-Salmon J, Blais D, Vaillancourt D, Garon O, Bisaillon A.Loss of rear motor control is the main limiting factor in the use of caudal epidural anesthesia in the horse. In man and laboratory animals, a small dose of an opiate combined with a local anesthetic enhances analgesia without impairing motor function. Thus, the amount of local anesthetic administered may be reduced. Butorphanol is an opiate widely used in horses. It has a good margin of safety and few cardiorespiratory effects. The effects of lidocaine (0.25 mg/kg) and lidocaine-butorphanol (0.25 mg/kg, and 0.04 mg/kg, respectively) were compared in 2 groups of 5 healthy unsedated mares. Hors...
Brinsko SP, Ignotz GG, Ball BA, Thomas PG, Currie WB, Ellington JE.To compare the electrophoretic patterns of proteins synthesized and secreted by oviductal epithelial cell (OEC) explants obtained from young, fertile and aged, subfertile mares. Methods: Young, fertile (n = 5; 2 to 7 years old) and aged, subfertile (n = 5; 17 to 24 years old) mares. Methods: 2-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and computerized densitometry. Results: Variation in the synthesis and secretion of polypeptides from young, fertile mare OEC (YOEC) and aged, subfertile mare OEC (AOEC) was evidenced by differences in the intensity of radiolabeled pol...
Long MT, Goetz TE, Kakoma I, Whiteley HE, Lock TE, Holland CJ, Foreman JH, Baker GJ.Fetal infectivity of Ehrlichia risticii was investigated in 19 ponies that were E risticii negative on the basis of results of an indirect fluorescent antibody (IFA) test. Thirteen pregnant ponies were infected by IV administration of E risticii between 90 and 180 days of gestation. Six pregnant ponies served as noninfected controls. Each infected pony had clinical signs of equine monocytic ehrlichiosis, was confirmed to be ehrlichemic, and developed an IFA titer to E risticii. Two infected ponies became recumbent, were unresponsive to supportive care, and were euthanatized. After recovery fro...
Ginther OJ, Lara A, Leoni M, Bergfelt DR.Four herds of pony mares, each consisting of a stallion and six mares, were used to characterize the nature of herding by the stallion and the factors that induced the herding behavior. Herding behaviors were compared among four successive treatments (six mares alone, stallion added, two new mares added, and entire herd moved to a new pasture). A new treatment was initiated every 7 days and behavior was studied for 5 consecutive days (Days 1-5) for each treatment. Observations were made every 10 min during a 2-h period for each day. The extent of herding was quantitated by the mean distances b...
Fitzgerald BP, Reedy SE, Sessions DR, Powell DM, McManus CJ.The seasonal nature of reproductive activity in mares is widely accepted and considerable attention has focused on the mechanisms that lead to the initiation of the breeding season. In contrast, considerably less information is available about the termination of the breeding season. It is interesting to note that each winter a sub-population of mares continues to undergo oestrous cyclicity during the non-breeding season. Continuation of reproductive activity during the winter occurs most frequently in mares that maintain a non-pregnant condition in successive years. The maintenance of a non-pr...
Fernandes CB, Loux SC, Scoggin KE, Squires EL, Troedsson MH, Esteller-Vico A, Ball BA.The cervix is a dynamic structure that undergoes dramatic changes during the estrous cycle, pregnancy and parturition. It is well established that hormonal changes, including estrogens, progestogens and prostaglandins, regulate the expression of key proteins involved in cervical function. The arachidonic acid cascade is important in the remodeling and relaxation of the cervix in the days preceding parturition. Despite the complexity of this mechanism, regulation of cervical function has received little study in the mare. Therefore, the objective of this study was to compare the expression of e...
Newcombe JR, Paccamonti D, Cuervo-Arango J.Data were analysed retrospectively from fourteen breeding seasons at an Equine Fertility Clinic for the effect of interval between pre- and postovulatory examinations for immediate postovulatory insemination on pregnancy rate (PR) and embryo loss rate (ELR). Mares of various breeds and ages were examined at intervals which varied from 0.5 to 15h between the pre- and postovulatory period over 867 cycles. When ovulation was detected they were inseminated with a single dose of commercial frozen-thawed semen. All mares were treated in the post-insemination period with intrauterine antibiotics and ...
Siddiqui MA, Gastal EL, Gastal MO, Beg MA, Ginther OJ.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 progesterone (p ...
Morris LH, Allen WR.The need for relatively high numbers of spermatozoa for artificial insemination limits our application of recently available technologies such as sex-sorted semen. The fertility of two different methods of low dose insemination using fresh, frozen and sex-sorted semen are compared in this overview. Satisfactory conception rates are described using very low doses of spermatozoa inseminated by either hysteroscopic or deep uterine insemination methods, proving the stallion is fully fertile. The hysteroscopic method appears to give higher conception rates when inseminating fewer than 5 x 10(6) spe...
Stewart DR, Stabenfeldt GH, Hughes JP.Plasma relaxin concentrations were measured hourly by radio immunoassay in 4 pregnant mares from 11 days before until 4 days after natural foaling. Pre-partum levels ranged from 4 to 7 ng/ml without any surge until the second stage of labour when they increased rapidly to about 11 ng/ml. In 3 of these mares, relaxin activity declined immediately after the expulsion of the placenta and was below detectable levels within 36 h. In the other mare relaxin activity did not fall until after the mechanical removal of the placenta 7 h after foaling. Eight mares were induced to foal by the administratio...
Brocca G, Centelleghe C, Padoan E, Stoppini R, Giudice C, Castagnaro M, Zappulli V.A 24-year-old Irish Cob mare was presented with a peripheral iris mass, which was surgically resected and diagnosed as an undifferentiated neuroepithelial tumor. A few months later, a relapse occurred with histological features characterized by a more solid appearance and squamous differentiation. Subsequently, the mare was presented with rapidly spreading multiple subcutaneous masses and, at the onset of neurological signs, was humanely euthanized and subjected to a complete post mortem examination. The necropsy confirmed the presence of numerous widespread masses in the subcutaneous tissue, ...
McCue PM, Fleury JJ, Denniston DJ, Graham JK, Squires EL.A technique was developed for oviductal insemination of mares, in which a small number of motile spermatozoa are deposited directly into the oviduct. Pregnancy rates in mares inseminated by traditional intrauterine artificial insemination were compared with rates in mares inseminated by oviductal insemination. Fifteen mares were inseminated with 5 x 10(8) progressively motile spermatozoa by intrauterine artificial insemination, and 14 mares were inseminated with 5 x 10(4) progressively motile spermatozoa by oviductal insemination. Pregnancy rates in mares inseminated by intrauterine artificial...
Neves AP, Keller A, Trein CR, Möller G, Jobim MI, Castilho LF, Cardoso MR, Leibold W, Zerbe H, Klug E, Gregory RM, Mattos RC.This study compared four treatments for bacterial endometritis in mares experimentally infected with Streptococcus zooepidemicus. Twenty-five mares were used, 20 resistant and five susceptible to endometritis. Mares would be in estrus when infected. Twenty-four hours after inoculation, clinical, bacteriological and cytological examinations were performed and repeated until the first occurrence: negative cytology and no Streptococcus growth or the seventh day post-infection. All mares showed clinical signs of endometritis and were assigned to one of the following treatments: (1) intrauterine in...
Townsend J, Westcott K, Tortonese DJ.In the horse, pronounced changes in fertility occur annually in response to photoperiod. However, the mechanisms regulating gonadotrophin synthesis and release in this species remain unclear. Here, we investigated the expression of gonadotrophin subunits and GnRH receptor (GnRH-R) mRNA in the pituitary glands of Thoroughbred horses during the breeding (BS) and non-breeding (NBS) season. Seasonal effects on the prevalence of gonadotrophs in the pars distalis were also examined. GnRH-R and common alpha-, LHbeta- and FSHbeta-subunit mRNA contents were determined by Northern analysis and the preva...
Aurich C, Schlote S, Hoppen HO, Klug E, Hoppe H, Aurich JE.To investigate an involvement of endogenous opioids in the regulation of circannual changes in reproductive activity, effects of the opioid antagonist naloxone on the concentration of immunoreactive and bioactive luteinizing hormone (LH) in plasma were measured in mares during the anovulatory season. Naloxone (0.5 mg/kg i.v.) caused a significant increase (P < 0.05) in immunoreactive as well as bioactive LH concentration in plasma. The amplitude of the increase in LH concentrations measured with an in vitro bioassay was more pronounced than the amplitude of the increase in LH secretion dete...
Glaser AL, de Vries AA, Rottier PJ, Horzinek MC, Colenbrander B.Sero-epidemiological surveys have revealed that equine arteritis virus (EAV) is prevalent in most European countries. The virus causes sporadic cases of respiratory disease and abortion in horses, the incidence of which has increased in recent years. Mares and geldings eliminate virus after acute infection, but 30% to 60% of stallions become persistently infected. In these animals, EAV is maintained within the reproductive tract and is shed continuously in the semen. Persistent infection with EAV in stallions has no negative consequences for fertility but mares inseminated with virus-contamina...
Viafara JAS, Portilho RV, Maculan R, Souza Júnior JF, Silva CM, Rodrigues PG, El Azzi MS, Souza JC.This study evaluated the presence of polyunsaturated fatty acids in circulating blood and in the ovarian follicular fluid of mares, after supplementation of the diet with linseed oil. Six Mangalarga Marchador mares, weighing 397.00±31.89 kg, were kept on native pasture, and assigned to the current study. In a switch over design, mares were randomly allocated to receive 150 ml of vegetable oil daily, containing polyunsaturated fatty acids n3 (62.23 g ALA, 20.34 g LA, 2.27 g EPA, 2.32 g DHA), (n=3) or no supplementation (n=3) in two replicates. Blood and follicular fluid samples were taken on t...
Yuyama T, Yusa S, Yoshizumi K, Yamano S, Murata S, Hirose T, Osanai R, Onishi Y, Osato S, Sasaki C, Sasaki Y, Kakuda T, Tsubaki S, Takai S.The prevalence of virulent R. equi having 15- to 17-kDa antigens (VapA) in fecal isolates from 13 thoroughbred foals and their dams on 5 farms in Kagoshima, Japan, and the plasmid profiles of VapA-positive isolates by restriction fragment digestion patterns were investigated to compare the genotypic variation among virulence plasmids of R. equi isolates from Japan. In total, 218 (24.6%) of 886 isolates from the feces of the 13 foals and 13 (12.5%) of 104 isolates from the feces of their dams demonstrated VapA-positive R. equi. Plasmid DNA preparations of 231 virulent isolates from foals and da...
De Lille AJ, Silvers ML, Cadario ME, Tran TQ, Cage CL, LeBlanc MM.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 ...
Lea RG, Stewart F, Allen WR, Ohno I, Clark DA.Endometrial tissue from the gravid uterine horn of pregnant mares was examined by northern analysis and in situ hybridization for mRNA that hybridized to cDNA and RNA probes generated from a mouse TGF-beta 2 1.2 kb cDNA clone. The mouse cDNA probe hybridized to characteristic TGF-beta 2 mRNA transcripts on a northern blot of total RNA isolated from horse endometrium collected at day 45 of gestation. Two major 4.0 and 3.5 kb transcripts and possibly a minor 1.6 kb transcript were observed, consistent with specific hybridization to equine TGF-beta 2 mRNA. By in situ hybridization, riboprobes tra...
Hansen PJ, Asbury AC.The release of opsonins into the uterine lumen of mares susceptible or resistant to endometritis was examined after intrauterine inoculation of a filtrate of Streptococcus culture fluid or vehicle. Uterine flushings were collected at 0.5 hour before and 2, 4, 6, 8, and 24 hours after inoculation on day 2 or 3 of estrus and on day 7 or 8 after ovulation. Amounts of opsonins in flushings were quantified as the H2O2 produced by leukocytes incubated with flushings-opsonized bacteria, compared with H2O2 produced by leukocytes incubated with nonopsonized bacteria. Opsonin values in flushings increas...
Turner DD, Garcia MC, Miller KF, Holtan DW, Ginther OJ.The influence of the ovaries and presence of a foal on periparturient concentrations of FSH and LH were studied in 19 Pony mares. In intact and ovariectomized mares, mean concentrations of FSH fluctuated between 1.1and 9.9 ng/ml on Days -14 to-1 before parturition (Day 0). A surge of FSH occurred in all mares in association with parturition. From Days 1 to 10, the high levels of FSH gradually decreased in the intact group to the minimal concentrations that occur during oestrus, but remained elevated in the ovariectomized mares. There were no significant pre-partum changes in LH in either type ...
Sinnemaa L, Järvimaa T, Lehmonen N, Mäkelä O, Reilas T, Sankari S, Katila T.The effect of artificial insemination (AI) volume on uterine contractility and inflammation and on elimination of semen in the reproductive tract of mares was examined for 4 h after AI using two methods, scintigraphy and ultrasonography. The same doses were used in both methods: 2 and 100 ml of skim milk-extended frozen semen. In the scintigraphic study, the number of reproductively normal mares was four per group and in the ultrasonographic study five per group. For scintigraphy, the semen was radiolabelled with technetium-99m. The static scintigrams were acquired immediately before and 30, 6...
Goudet G, Leclercq L, Bézard J, Duchamp G, Guillaume D, Palmer E.This study reports the follicular growth and oocyte competence for in vitro maturation and fertilization under the influence of circulating eCG. Three to 7 successive ultrasound-guided follicular punctures were performed on 4 pregnant mares from Day 23 until Day 75 of pregnancy and on 5 control mares whose embryonic vesicle was crushed on Day 22. All follicles larger than 5 mm were punctured 24 h after the largest follicle reached 18 mm. Expanded cumulus oocyte complexes (COCs) were stained at recovery to analyze the nuclear stage. Compact COCs were cultured in vitro for 46 h and either staine...
Huhtinen M, Reilas T, Katila T.The pregnancy rate is lower in mares inseminated at the first post-partum (p.p.) oestrus (40-50%) compared with pregnancy rates in subsequent oestrous cycles (55-65%). The causes of the lowered pregnancy rate are not fully understood. The aim of the present study was to examine if embryonic defects could be one of the reasons for lowered pregnancy rate. A total of 23 p.p. and 14 non-lactating control mares were flushed 7 days after detection of ovulation. Embryo recovery rate was 48% and 71% in p.p. and control mares, respectively (p = 0.16). Embryos were photographed, measured, graded and sta...
Thompson DL, Godke RA, Nett TM.Two hormonal treatments, chosen for their effectiveness in other seasonally breeding species, were tested in mares during the nonbreeding season to determine if they could induce ovarian activity and estrus during the winter. Of 15 functionally anestrous (anovulatory) mares, five received intravaginal, polyurethane sponges containing .75 g of melatonin on December 16; fresh sponges containing melatonin were inserted weekly until February 3. These mares also received daily injections of saline. Five other mares received daily im injections of 100 micrograms of thyrotropin-releasing hormone (TRH...
Watson ED, Pedersen HG, Thomson SR, Fraser HM.Control of the equine estrous cycle was studied by suppressing gonadotropin secretion by administration of a GnRH antagonist to cyclic pony mares. Four mares received vehicle (control cycle) or a GnRH antagonist, Antarelix (100 microg/kg) on Day 8 of diestrus, and blood samples were collected at 15-min intervals from 0 to 16 h, 24 to 36 h, and daily until the next ovulation. Ovarian activity was monitored by transrectal ultrasonography, and measurement of plasma concentrations of progesterone and estradiol. Antagonist treatment eliminated large diestrous pulses of LH. Progesterone concentratio...
Gibb Z, Grupen CG, Maxwell WM, Morris LH.The fertility of sex-sorted, cryopreserved stallion sperm must be improved for the sex-sorting technology to be applied commercially. Objective: To optimise the conditions used to liquid store stallion sperm prior to sex-sorting and assess the fertility of sperm following sex-sorting and cryopreservation. Methods: Both in vitro experiment and randomised controlled trial in healthy, client-owned mares. Methods: Stallion ejaculates (n = 9) were diluted in either a skimmed milk (KMT) or BSA (I-BSA) based media to 25 × 106 sperm/ml directly (+SP25) or washed to remove seminal plasma and diluted t...
Urwin VE, Allen WR.The concentrations of follicle stimulating hormone, luteinising hormone and progesterone were measured in serial blood samples taken throughout one or more oestrous cycles from 12 Thoroughbred mares, some of which exhibited single and others twin ovulations. The resulting profiles clearly demonstrated that no simple relationship exists between circulating gonadotrophin levels and subsequent ovulation rate in the mare. However, plasma progesterone concentrations during dioestrus are, as expected, higher following twin than single ovulations. The findings suggest that the underlying cause of twi...
Wilson DA, Foreman JH, Boero MJ, Didier PJ, Lerner DJ.A large granulosa cell tumor was believed to be responsible for causing obstruction and subsequent rupture of the small colon in a 10-year-old Quarter Horse mare. Two months earlier, a mass, tentatively diagnosed as granulosa cell tumor of the left ovary, had been identified by means of rectal palpation and ultrasonography. The mare was evaluated for clinical signs of acute, severe, abdominal pain, increased heart rate, cyanotic mucous membranes, clinical dehydration, with high PCV, leukopenia, and extreme abdominal distension. A large soft tissue mass and taut band that constricted the lumen ...
López-Bayghen C, Zozaya H, Ocampo L, Brumbaugh GW, Sumano H.The efficacy of melengestrol acetate (MGA) to shorten the vernal transition of mares by synchronising and accelerating the first ovulation of the year after 60 days of phototherapy was determined by ultrasonographic monitoring. Sixteen mares in late transition were fed two doses of MGA (150 mg/mare/day and 100 mg/mare/day, respectively) for 10 days. A luteolytic dose of prostaglandin was administered to each mare one day after the end of MGA treatment. The presence and duration of oestrus, follicular growth, uterine oedema and presence of ovulation were monitored by ultrasonography and the cer...
Okólski A, Babusik P, Tischner M, Lietz W.Comparisons were made between 2 methods of oocyte recovery from the ovarian follicles of slaughtered mares: 500 oocytes (3 per mare) were obtained by aspiration of follicular fluid from ovaries of 162 mares, and 120 oocytes (8 per mare) by isolation and rupture of follicles from ovaries of 14 mares. In the oocytes recovered after rupture of follicles, 89.2% were morphologically unchanged, in comparison to 29.3% obtained by aspiration of follicular fluid. Stallion spermatozoa capacitated in vitro were tested on zona-free hamster oocytes. The stallion spermatozoa were washed in TCM-199 and prein...
