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.
Shortridge EH.Extract
Recent reviews of brucellosis in horses (Stableforth and Galloway, Citation1959; Mascaro and Hoffman, Citation1963: Ritscher, Citation1963) refer to Brucella abortus associated with fistulous withers, arthritis and debility and emphasize the rarity of abortion caused by this organism. One case of abortion in a mare caused by Br. abortus was reported as having occurred in Iowa, U.S.A. (McNutt and Murray, Citation1924).
Bornstein S.Two intersex horses were characterized externally by vulva and “enlarged clitoris-hypoplastic penis” and internally by uterus and testicles. Both had a normal female karyotype 64/XX. One of the horses whose body measurements were in accordance with mares of the same breed, showed a distinct stallion behaviour.
Loy RG, Swan SM.Progesterone in oil solution injected into mares intramuscularly in midcycle blocked estrus and ovulation at levels of 100 mg. per day or higher. Fifty milligrams per day prevented estrus but not ovulation. The interval from end of treatment to estrus appeared to depend upon dosage, and the effects on subsequent cyclic patterns were confounded by season of the year. Neither 50 nor 100 mg. per day stopped estrus or blocked ovulation when treatment was started on day 1 of estrus. Injection of 100 mg. per day of progesterone in oil delayed postpartum estrus and ovulation, but 50 mg. per day did n...
Parrilla Hernández S, Franck T, Munaut C, Feyereisen É, Piret J, Farnir F, Reigner F, Barrière P, Deleuze S.Myeloperoxidase (MPO), as a marker of neutrophil activation, has been associated with equine endometritis. However, in absence of inflammation, MPO is constantly detected in the uterine lumen of estrous mares. The aim of this study was to characterize MPO in the uterus of mares under physiological conditions as a first step to better understand the role of this enzyme in equine reproduction. Total and active MPO concentrations were determined, by ELISA and SIEFED assay, respectively, in low-volume lavages from mares in estrus ( = 26), diestrus ( = 18) and anestrus ( = 8) in absence of endometr...
McCue PM, Matthews PM, Prell MJ, Bellone RR, Allen H.Genetic testing is required for the registration of foals of most equine breeds. Objective: To describe two clinical cases of marked delayed embryonic development or delayed fertilisation in pregnancies generated by embryo transfer. Methods: Case report. Methods: Donor mares were inseminated with semen from one stallion during one oestrous cycle and semen from a different stallion on the subsequent oestrous cycle. Embryo(s) were collected 8 days after ovulation during the second oestrous cycle and transferred into synchronised recipient mares. Genetic testing was performed to determine paren...
Squires EL, McKinnon AO, Carnevale EM, Morris R, Nett TM.For embryos collected from mares 7 days after ovulation, embryo recovery for single-ovulating mares was 53% compared to 106% for double-ovulating mares. Pregnancy rates 50 days after surgical transfer were 68 and 129%, respectively. Concentrations of LH were similar during the periovulatory period for cycles which included single or double ovulations. Horse pituitary extract given for 5.5 days resulted in greater than or equal to 2 ovulations (mean 3.8) in 26 of 28 mares and 2.0 embryos were recovered per donor compared to 0.65 for controls. Non-surgical pregnancy rates for embryos collected f...
Meintjes M, Graff KJ, Paccamonti D, Eilts BE, Paul JB, Thompson DL, Kearney MT, Godke RA.When aspirating ovarian follicles in pregnant mares to obtain oocytes for in vitro fertilisation (IVF), the effect of the manipulation on circulating concentrations of progesterone may be an important consideration in terms of the maintenance of pregnancy. The object of this study was to compare the effects of 3 different forms of transvaginal ultrasound-guided follicle aspiration (Treatment 1, no aspiration, n = 4; Treatment 2, aspirate only follicles > or =20 mm in diameter, n = 7; Treatment 3, aspirate all visible follicles, n = 7) on peripheral plasma progesterone concentrations between Da...
Allen WR, Pashen RL.The blastomeres of 192- to 8-cell embryos recovered surgically 1-3 days after ovulation from 23 Pony mares were mechanically separated and inserted, in various combinations, into evacuated pig zonae pellucidae to make 27 'half' and 17 'quarter' micromanipulated embryos. These were embedded in agar and cultured in vivo in the ligated oviducts of ewes for 3.5-5 days to allow development to the late morula/early blastocyst stage. Subsequent surgical or non-surgical transfer of 13 'half' and 17 'quarter' embryos to mares resulted in 10 established pregnancies, including 2 monozygotic pairs. Surgic...
Liu S, Lian S, Yang Y, Fu C, Ma H, Xiong Z, Ling Y, Zhao C.An experiment was conducted to study the association between the single nucleotide polymorphisms (SNPs) in 5'-untranslated regions (5'-UTR) of equine chorionic gonadotropin (eCG) genes and the serum eCG levels. Methods: SNPs in 5'-UTR of eCG genes were screened across 10 horse breeds, including 7 Chinese indigenous breeds and 3 imported breeds using iPLEX chemistry, and the association between the serum eCG levels of 174 pregnant Da'an mares and their serum eCG levels (determined with ELISA) was analyzed. Results: Four SNPs were identified in the 5'-UTR of the eCGα gene, and one of them was u...
Cebulj-Kadunc N, Bozic M, Kosec M, Cestnik V.Haematological parameters [red blood cell count (RBC), white blood cell count (WBC), packed cell volume (PCV), haemoglobin concentration, mean cell volume (MCV), mean cell haemoglobin (MCH) and mean cell haemoglobin concentration (MCHC)] in resting Lipizzan horses were determined for 143 stallions, 104 mares and 25 foals. The mean RBC and WBC values in Lipizzans were in the lower part of the normal range for warm-blooded horses. The mean PCV, MCV and MCH values were higher, but the mean haemoglobin concentration and MCHC values were lower than reported for other warm-blooded horses. In foals, ...
Von Dollen KA, Jones M, Beachler T, Harris TL, Papich MG, Lyle SK, Bailey CS.The use of antimicrobials for the management of equine uterine disease is commonplace, with antibiotic selection generally based on empirical evidence or in vitro sensitivity results. However, the potential disconnect between these laboratory results and clinical efficacy in the mare raises concern for antibiotic failure and subsequent development of resistant organisms. In this work, we attempt to bridge this gap by using an ex vivo model of the equine postpartum uterus to quantitatively evaluate the antimicrobial activity of two commonly used antibiotic treatments in the mare (ceftiofur an...
Solti L, Eulenberger K, Kurth D, Schöne L.Anoestrous mares were treated with prostaglandin (n = 43) and those that did not respond to prostaglandin (n = 29) with a synthetic progestagen, allyloestrenol, at a dose of 0.05 mg/kg body mass for 12 days. After the cessation of the long-term per os gestagen blockade the animals were checked for heat and, if a preovulatory follicle could be palpated, 2000 IU hCG was administered to induce ovulation. In some animals the plasma 17 beta-oestradiol (E2) and progesterone (P4) levels were also followed up throughout the gestagen treatment and for 10-14 days thereafter. As the favourable oestrus ra...
Hüthwohl H, Weiss R, Schmeer N, Schliesser T.Classification based on biochemical characteristics of 389 strains of plasma-coagulase-negative (plc-) staphylococci isolated from the genital tract of mares and stallions resulted in the following distribution of species: St. sciuri 130 (33.4%), St. equorum 42 (10.8%), St. xylosus 16 (4.1%), St. epidermidis 35 (9.0%), St. simulans 24 (6.2%), St. haemolyticus 33 (8.5%), St. warneri 18 (4.6%), St. lentus 12 (3.1%), St. hyicus 11 (2.8%). Strains of St. cohnii, St. capitis, St. gallinarum, St. saprophyticus and St. hominis have only been found sporadically (a. 1%). 48 (12.3%) strains could not be...
Shikichi M, Iwata K, Ito K, Miyakoshi D, Murase H, Sato F, Korosue K, Nagata S, Nambo Y.Measurement of progestines and estrogens in maternal plasma has been advocated as an indicator of foeto-placental function. The goals of the present study were as follows: to determine progestin and estrogen concentrations in mares with normal and abnormal pregnancies during late gestation, evaluate the diagnostic value of hormone concentrations, and investigate the relationship between hormone concentrations after treatment and the survival of foals. Blood samples were collected monthly from 459 pregnant mares between Day 201 of gestation and foaling. Progestin and estrogen concentrations wer...
Evans TJ, Ganjam VK, Miller MA, Niswender KD, Krause WJ, Youngquist RS.Endometrial periglandular fibrosis (EPF) has been proposed as a possible aetiology for equine embryonic and fetal loss. However, the pathophysiology of EPF is not well understood. Angiotensin-converting enzyme (ACE) is found in macrophages, endothelium (during angiogenesis) and myofibroblasts at sites of fibrosis in the heart, kidneys, liver and skin in several species. An increase in local tissue ACE-binding activity appears to be a critical event in the initiation and progression of fibrosis in these tissues. The aim of this study was to investigate the correlation between ACE activity in th...
Hosteller DE, Sprecher DJ, Yamini B, Ames NK.Transrectal palpation of an 18-mo-old, anestrous Holstein nulligravida revealed an enlarged left ovary. Ultrasonographically, the mass resembled known equine granulosa cell tumor (GCT) images. Slowly, virilism developed. Fifty-five days after initial diagnosis, unilateral ovariectomy was performed The presurgical serum concentration of testosterone was equal to that of a mature bull. During the 3 mo period following surgery, estrus expression resumed, the serum testosterone concentration returned to baseline, and the heifer was diagnosed pregnant following AI. A low grade, malignant GCT was th...
Roth TL, White KL, Thompson DL, Barry BE, Capehart JS, Colborn DR, Rabb MH.In this experiment we have identified and partially characterized the immunosuppressive activity of preimplantation horse conceptus-conditioned medium (HCCM). Horse conceptuses were nonsurgically flushed from mares at Days 9-10 (n = 6), 15-16 (n = 3), and 25-26 (n = 3). After incubating the conceptuses for 24 h in RPMI-1640 supplemented with 15% fetal calf serum (FCS) and 1% penicillin/streptomycin, HCCM was obtained from cultures and tested for immunosuppressive activity in lymphocyte proliferation assays. Peripheral blood lymphocytes obtained from randomly selected mares were stimulated with...
Boye JK, Bulkeley EA, Dujovne GA.To describe uterine prolapse, predispositions, and outcomes in mares treated between 1988 and 2019. 24 mares with uterine prolapse. Clinical records were retrospectively reviewed, and follow-up information was gathered. The Mann-Whitney U test and Fisher exact test were used to analyze results for history and outcome variables for potential association with mare survival to hospital discharge. The χ2 test was used to compare breed distribution. Age was known in 23 mares (median, 11.1 years). For 15 mares with exact known parity, the median parity was 3 births (range, 1 to 13 births). For 22 m...
Bailey CJ, Reid SW, Hodgson DR, Rose RJ.To determine whether sex or foaling period were associated with time to first race start and whether sex, age at time of first race start, or inter-race period were associated with career duration for Thoroughbred racehorses in Australia. Methods: 553 Thoroughbred racehorses. Methods: Race records through to the end of the 6-year-old racing season were obtained for each horse. Product-limit survival analysis was used to determine whether sex or foaling period was associated with time to first race start and whether sex or age at first race was associated with career duration. A Cox proportiona...
Smits K, Willems S, Van Steendam K, Van De Velde M, De Lange V, Ververs C, Roels K, Govaere J, Van Nieuwerburgh F, Peelman L, Deforce D, Van Soom A.During maternal recognition of pregnancy (MRP), a conceptus-derived signal leads to the persistence of the corpus luteum and the maintenance of gestation. In the horse, the nature of this signal remains to be elucidated. Several studies have focused on the changes in gene expression during MRP, but little information exists at the protein level. The aim of this study was to identify the proteins at the embryo-maternal interface around signalling of MRP in the horse (day 13) by means of mass spectrometry. A distinct influence of pregnancy was established, with 119 proteins differentially expres...
Boyd EH, Allen WE.Plasma drug concentrations were measured after two commercially available potentiated sulphonamides, trimethoprim and sulfadoxine and trimethoprim and sulphadiazine, were infused daily for 2 and 3 days, respectively, into the uteri of pony mares which had been mated before ovulation. Intravenous administration of trimethoprim and sulfadoxine allowed uterine absorption of trimethoprim (23-43%) and sulfadoxine (29-34%) to be calculated. After intra-uterine administration trimethoprim and sulphadiazine were detected in the milk of a lactating mare. In order to maintain plasma concentrations likel...
Mariella J, Castagnetti C, Prosperi A, Scagliarini A, Peli A.The purpose of this study is to investigate the presence of IL-4, IL-8, IL-13 and IFN-γ in equine colostrum and in foals' serum. Samples were obtained from 14 mares and their healthy foals. Soon after parturition, 10ml of colostrum was collected, filtered, centrifuged and frozen until assayed. Blood samples were obtained from each foal at birth (TO) and again after 24h (T24), after which they were frozen until assayed. Serum IgG was measured at 24h of age with an immunoturbidimetric quantitative method. Cytokine concentration was determined using commercially available ELISA tests. Statistica...
Bergfelt DR, Meira C, Fleury JJ, Fleury PD, Dell'Aqua JA, Adams GP.A regimen of progesterone plus estradiol (P&E) was used as a standard for ovarian synchronization to test the efficacy and evaluate the commercial application of ultrasound-guided follicle ablation as a non-steroidal alternative for ovulation synchronization in mares. Recipient mares at a private embryo transfer facility were at unknown stages of the estrous cycle at the start of the experiment on Day 1 when they were randomly assigned to an ablation group (n=18-21 mares) or to a P&E group (n=20-21 mares). In the ablation group, mares were lightly sedated and all follicles > or = 10...
Klein V, Müller K, Schoon HA, Reilas T, Rivera del Alamo MM, Katila T.Oestrous suppression by intrauterine devices (IUDs) is caused by prolongation of luteal function, but the biological mechanism is unknown. The aim of the study was to investigate mechanisms which could explain the action of IUDs. Thirty mares were age-matched and either inseminated (AI, n = 15) or fitted with an IUD (IUD, n = 15) and subsequently divided into four groups: AI-P, pregnant (n = 8); AI-N, non-pregnant (n = 7); IUD-P, prolonged luteal phase (n = 7); and IUD-N, normal luteal phase (n = 8). The median ages were 5.5 and 7 years in AI-P and IUD-P groups and 14 and 11 years in AI-N and ...
Blue HB, Blue MG, Kenney RM, Merritt TL.Forty uterine fluid samples were obtained from 4 mares classified as resistant to uterine bacterial infection. The uterus of each mare was flushed with 50 ml of saline solution during estrus and diestrus of successive estrous cycles. Bacteria or fungi were isolated from 4 samples, and 7 additional samples were obtained from a mare with active intrauterine infection. Fluid volumes obtained during estrus (means = 40.3 +/- 11 ml) tended to be greater than those recovered during diestrus (means = 36.8 +/- 7.9 ml), but the difference was not significant. Concentrations and yields of protein in reco...
Gee EK, Gillespie L, Bolwell CF.To compare the efficacy of oxytocin given once daily, either I/V or I/M, on Days 7-14 post-ovulation, on the expression of oestrus in mares through to 65 days post-ovulation. Methods: Eighteen mares of various breeds that were displaying normal oestrous cycles were randomly assigned to one of three treatment groups on the day of ovulation (Day 0), detected using transrectal ultrasonography. Mares in the control group (n = 6) were given 1 mL saline I/V; mares in the I/V and I/M groups (n = 6 per group) were injected with 10 IU oxytocin I/V and I/M, respectively. All treatments were given once d...
Vanderwall DK, Betschart RW, Squires EL.The objective of this study was to determine if the primary circulating metabolite of PGF2alpha, 13,14-dihydro-15-keto-PGF2alpha (PGFM), is biologically active and would induce luteolysis in nonpregnant mares. On Day 9 after ovulation, mares (n = 7/group) were randomly assigned to receive: 1) saline control, 2) 10 mg PGF2alpha or 3) 10 mg PGFM in 5 mL 0.9% sterile saline i.m. On Days 0 through 16, blood was collected for progesterone analysis. In addition, blood was collected immediately prior to treatment, hourly for 6 h, and then at 12 and 24 h after treatment for progesterone and PGFM analy...
Ellerbrock RE, Curcio BR, Zhong L, Honoroto J, Wilkins P, Lima FS, Giguere S, Canisso IF.Enrofloxacin may be an alternative antimicrobial for unresponsive cases of severe bacterial infections in pregnant mares. As pregnancy may affect drug bioavailability, distribution, metabolism and excretion, dose adjustment might be necessary. Objective: To determine the disposition of orally and intravenously administered enrofloxacin in pregnant and non-pregnant mares. Methods: Randomised cross-over experiment. Methods: Six light-breed, healthy pregnant mares (260 days gestation) were given a single dose of either intravenous (5 mg/kg bwt) or oral compounded (7.5 mg/kg bwt) enrofloxacin, ...
Taylor TB, Pemstein R, Loy RG.Two trials were conducted to (1) determine the degree of control of ovulation achieved by treating mares in late winter with progesterone and oestradiol-17 beta combined after prior exposure to an artificially increased photoperiod, and (2) to examine the effectiveness of such a procedure incorporated into equine breeding farm management systems. Following a 15-day treatment of 150 mg progesterone and 10 mg oestradiol-17 beta daily with 10 mg PGF-2 alpha on the last day of steroid treatment, 27 of 31 mares ovulated on Days 8-14 after the last injection in one trial. Conception rate for mares m...
Piccione G, Rizzo M, Arfuso F, Giannetto C, Di Pietro S, Bazzano M, Quartuccio M.During early post-partum period both neonatal foals and peripartum mares are most susceptible to diseases. The aim of this study was to establish physiologic modifications of leukogram during the first month after foaling in mares and their newborn foals. To this end blood samples were collected from nine mares and nine foals (T0-T10), every three days from the 1st day until the 30th day after foaling. Samples were analysed for white blood cell (WBC) count and differential leucocyte counts. Two-way repeated measure analysis of variance (ANOVA) showed, in postpartum mares WBC showed significant...
Willmann C, Budik S, Walter I, Aurich C.A positive influence of altrenogest treatment on a retarded development of the conceptus around the beginning of placentation in mares older than 8 years could be recently demonstrated. In the present study, effects of altrenogest treatment in early-pregnant mares on conceptus development and expression of endometrial and embryonic genes were investigated. Genes were chosen according to a possible involvement in embryo-maternal interaction and embryonic development in the equine species. Mares were treated with altrenogest (0.044 mg/kg bodyweight) or sunflower oil (placebo) from day 5 to 11 af...
Brown-Douglas CG, Perkins NR, Stafford KJ, Hedderley DI.To test published models for predicting time of foaling using data derived from prepartum mammary secretions and to develop a new model based on concentrations of mammary secretion constituents that accurately predicts time of foaling in Thoroughbred mares. Methods: Concentrations of sodium, potassium, calcium, citrate and lactose were measured in prepartum mammary secretions of 20 Thoroughbred mares in the 2 weeks before expected date of foaling. Models to predict time of foaling were fitted to data based on absolute concentration, change in concentration, and percentage change in concentrati...
Dhakal P, Tsunoda N, Nambo Y, Taniyama H, Nagaoka K, Watanabe G, Taya K.Although equine gestation is unique from the standpoint of fetal gonadal enlargement and regression, the activator of this process is still unknown. The present study aimed to show a possible role of activin during equine gestation. In the first experiment, weekly plasma samples from six pregnant mares were used to measure activin A. In the second experiment, eight pregnant mares carrying female (gestational days 110, 140, 180, and 270) and male fetuses (gestational days 120, 180, 225, and 314) were used for immunohistochemistry of activin receptors (IA, IB, IIA, IIB), and their intracellular ...
