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.
WIDE M, WIDE L.THE use of a hæmagglutination inhibition reaction for the diagnosis of pregnancy in women was reported by Wide and Gemzell1 and Wide2. In this reaction human chorionic gonadotrophin (HCG) inhibited the agglutination of stable HCG-coated blood cells. The same immunological technique was applied for the assay of pregnant mare serum gonadotrophin (PMS) and was used as a pregnancy diagnosis test in mares. Sera from pregnant mares containing elevated levels of gonadotrophin inhibited an agglutination reaction of PMS-coated formalinized erythrocytes in the presence of PMS anti-serum, while sera fro...
DARLINGTON RW, RANDALL CC.Equine abortion virus was purified from the plasma of infected golden Syrian hamsters by differential centrifugation and nuclease treatment. The preparations were essentially free of nonviral elements on electron microscopic examination, and sedimentation in sucrose and potassium tartrate density gradients resulted in a single visible band. Electron microscopy of this band showed it to be composed of viral particles, and injection into hamsters resulted in infection and death of the animals. The viral particles had a sedimentation coefficient of approximately 2200 S and a hydrated density of 1...
SAVARD K.The urinary ketonic estrogens were studied at monthly intervals in five pregnant mares. Estrone and equilin appear to be the principal components and equilenin a minor constituent of the mares’ estrogens. The levels of equilin rise from the 4–5th months to equal and in some instances exceed those of estrone in the late months of pregnancy. A partition chromatographic method for the separation of the ketonic phenolic steroids of pregnant mares’ urine is described.
SHORT RV.Progesterone levels have been measured in the peripheral blood of pregnant and non-pregnant
mares, and in umbilical cord blood collected during foaling. It was found that progesterone was
readily detectable in the blood of pregnant and non-pregnant animals provided that there was a
fully developed corpus luteum present in the ovaries. During the second half of gestation, when
the ovaries have become fibrotic, progesterone was no longer detectable in the peripheral blood,
even though it was present in high concentrations in umbilical cord blood.
The reasons for this apparent disappearance...
Nett TM, Pickett BW.Two studies were conducted to determine the relationship between LH and progesterone and between PMSG and progesterone during pregnancy in mares. In the first, samples of jugular blood were collected daily from 7 mares from the first day of oestrus until Day 28 of pregnancy, and in the second, samples were collected weekly from 14 mares from Day 35 of gestation until parturition. In an attempt to prolong secretion of progesterone from accessory corpora lutea, 7 of these 14 mares were injected with increasing doses (2--10 mg) of diethylstilboestrol (DES) between Days 84 and 142 of gestation. Th...
Enders AC, Jones CJ, Lantz KC, Schlafke S, Liu IK.Invasion of trophoblast cells of the chorionic girdle into the endometrium and their subsequent dependence as endometrial cup cells on the maternal vascular system are unique features of equine gestation. This study of exocrine secretion by the endometrial glands and endocrine secretion by the cup cells was initiated to examine the relationships between and the effects of two disparate epithelial cell types sharing the endometrium. Endometrial cups were examined from day 36 to day 83 of gestation by light and electron microscopy, and immunohistochemical and lectin analysis. As the cup cells in...
Hülskötter K, Aurich C, Köhne M, Baumgärtner W, Wohlsein P.Adenomatous hyperplasia of the equine allantoic epithelium (EAAH) is an infrequently observed nodular or plaque-like change in the placenta of the mare which is presented as a case description. EAAH is most frequently diagnosed in cases of aborted fetuses and is associated with inflammatory changes of the placenta. Histologically, different degrees of EAAH may be distinguished; however, these are not associated with specific clinical signs, degree of inflammation, a particular pathogen, or the frequency of abortions. It is assumed that EAAH represents a secondary, reactive change and has per s...
Conforti VA, Vanderwall DK, Woods GL.The in vitro maturation (IVM) of equine oocytes is typically performed using various synthetic media; however, an optimal IVM system for equine oocytes has not been developed. The aim of the present study was to evaluate the effects of two types of follicular fluid (FF) obtained from cyclic mares and two incubation intervals for the IVM of equine cumulus-oocyte complexes (COCs). Follicular fluid was collected from medium-sized (20-29 mm diameter) and large (e30 mm; post-human chorionic gonadotrophin administration) follicles using transvaginal ultrasound-guided follicle aspiration. Compact (n ...
Ellington JE, Ball BA, Blue BJ, Wilker CE.Reliable capacitation of equine spermatozoa has been a major obstacle in the development of equine in vitro fertilization. Experiments were done to compare in vitro capacitation of equine spermatozoa by use of heparin/caffeine, calcium ionophore, uterine tube epithelial cell (UTEC)-conditioned medium, and direct culturing of spermatozoa with UTEC (coculturing). Capacitation-like changes, as determined by chlortetracycline membrane staining patterns, developed with UTEC-conditioned medium and coculturing, equivalent to that with calcium ionophore. Both of these treatments induced more (P < 0.05...
Shivers CA, Liu IK.Sera and follicular fluid from mares previously determined as having antibodies to the zona pellucida were exposed to porcine ovarian oocytes before insemination with boar spermatozoa in vitro. There was a dramatic decline in the number of spermatozoa bound to zonae compared to treatments with sera and follicular fluid from mares negative for zona antibodies. These data suggest that antibodies reactive with the zona pellucida may be responsible for reduced or even complete infertility in some mares. In a group of 50 randomly selected mares tested for antizona antibodies, 2 pregnant mares were ...
Driancourt MA, Palmer E.An experiment was carried out on pony mares to establish the time of the oestrous cycle at which ovarian follicles are recruited for ovulation. In one group (n=7), the cycle was interrupted at the preovulatory stage by removing the preovulatory follicle; in another group (n=13) the cycle was interrupted at day 6 of the luteal phase by inducing luteolysis with a prostaglandin injection (PG). In a subgroup (n=7) of those given PG, the ovary not bearing the corpus luteum was removed at the time of injection. A further group (n=6) served as surgical controls. The interval to the next ovulation and...
Knott LE, Fonseca-Martinez BA, O'Connor AM, Goodrich LR, McIlwraith CW, Colbath AC.To evaluate the use of mesenchymal stem cells (MSCs), autologous conditioned serum (ACS), platelet-rich plasma (PRP), and autologous protein solution (APS) for the treatment of equine musculoskeletal disease by diplomates of the American College of Veterinary Surgery (ACVS), and American College of Veterinary Sports Medicine and Rehabilitation (ACVSMR). Methods: Cross-sectional study. Methods: Diplomates (n = 423). Methods: An email link was sent to ACVS and ACVMR diplomates. A survey contained 59 questions regarding demographics, as well as indications, frequency, adverse effects, and limit...
Smith KC, Whitwell KE, Mumford JA, Hannant D, Blunden AS, Tearle JP.The V592 strain of equid herpesvirus-1 (EHV-1), which was originally isolated from a fetus during an abortion epizootic, has proved to be of low virulence in infection studies. Five Welsh Mountain pony mares and one foal were challenged intranasally or by aerosol with this isolate, and monitored clinically and virologically. All six animals shed virus in nasopharyngeal mucus, and viraemia was recorded from day 7 post-infection (PI). Pathological investigations revealed mild rhinitis and bronchiolitis in the mares, with viral antigen expression in degenerating epithelial cells of the nasal muco...
Güvenc K, Reilas T, Katila T.It is unclear whether AI of mares deep into the uterine horn causes more or less inflammation of the endometrium than conventional AI. Thus, we compared uterine inflammatory reactions of mares inseminated with two different doses of frozen-thawed semen into the tip of the uterine horn (UH) ipsilateral to the preovulatory follicle with those of mares inseminated into the uterine body (UB). Thirty-two mares were assigned to one of four groups (eight mares/group): UB20=AI into UB, 20 x 10(6)sperm/0.5 mL; UB200=AI into UB, 200 x 10(6)sperm/0.5 mL; UH20=AI into UH, 20 x 10(6)sperm/0.5 mL; UH200=AI ...
Pyörälä S, Taponen J, Katila T.Use of antimicrobials for veterinary indications related to reproduction in cattle and horses is reviewed. Antimicrobial compounds are widely used to treat and prevent infections of reproductive organs. Total amounts of antimicrobials for such purposes, estimated by weight, are low compared with major uses in food animals. The most common reproduction-related indication in cattle is mastitis. The number of intramammary products available for treatment of mastitis in the European Union is high. Metritis and endometritis also require antimicrobial treatment of cattle and specific products for in...
Sahmi F, Nicola E, Price CA.The objective was to establish a cell line-based bioassay for FSH in horse serum for screening samples with high eCG bioactivity. A cell line (HEK293) was transiently cotransfected with an FSH reporter expression plasmid and a cAMP-responsive β-galactosidase reporter plasmid. Cells were bulk frozen, and thawed for assay purposes. This assay was specific for FSH, with no cross-reaction with LH or insulin-like growth factor-1. Standard curves (eCG) and serum samples from pregnant mares passed parallel line bioassay validity tests (linearity and parallelism). Estimates of bioactivity with this b...
Gronwall R.Endogenous creatinine clearance and renal excretion of phenylbutazone, osmotically active material, and compounds contributing to the urinary refractive index were studied in 12 Thoroughbred mares after no treatment, after water administration, or after furosemide administration. Urine was quantitatively collected, using urinary bladder catheters. On average, urine flow of the mares was 9 microliters/min/kg without treatment and increased to about 50 microliters/min/kg after water administration and to about 70 microliters/min/kg after furosemide administration. Water administration increased ...
Nielsen MK, Littman BA, Orzech SW, Ripley NE.Equine cyathostomins are ubiquitous in grazing horses around the world and a main target in parasite control programs. Anthelmintic resistance has been reported with increasing frequency in these parasites over the past decades, and recent findings of fulminant resistance to the macrocyclic lactone class have raised severe concerns. This study aimed to evaluate ivermectin efficacy in cohorts of yearlings and mares present on four different farms in Central Kentucky. Strongylid egg counts were determined with an automated egg counting system, and the percent fecal egg count reduction (FECR) was...
Timoney PJ, Dillon PB, Geraghty VP, McArdle JF.Aspects of experimental transmission of the causal bacterium of contagious equine metritis (CEM) to albino Swiss mice were investigated. Whereas infection was established in the majority of female mice, the organism was recovered from only a limited number of male mice after challenge. No clinical evidence of infection was observed in the experimental mice. There was only one instance of presumptive venereal transmission of the CEM bacterium. One third of infected females conceived and had normal litters.
Shand N, Irvine CH, Turner JE, Alexander SL.Jugular blood samples were collected at 4 h intervals from six mares during an oestrous cycle to study the hormonal events that occur around the time of luteolysis. Blood samples from day 10 (day 0 = ovulation) until day 3 of oestrus were assayed for prostaglandin metabolite 13,14-dihydro-15-keto PGF2alpha (PGFM), oxytocin, prolactin, progesterone and oestrogen conjugates. PGF2alpha (0.5 or 1.5 mg) was administered to six mid-dioestrous mares and the oxytocin and prolactin responses were measured. One to five large (peak > or =2 x nadir) pulses of PGFM, oxytocin and prolactin were detected ...
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 ...
Westendorf J, Wobeser B, Epp T.Inter- and intra-rater variability negatively affects the reliability of various histopathology grading scales used as prognostic aids in human and veterinary medicine. The Kenney-Doig categorization (grading) scale, which is used to associate equine endometrial histologic lesions with prognostic estimation of a broodmare's reproductive potential, has not been evaluated for inter- or intra-rater variability, to our knowledge. To assess whether the Kenney-Doig system produces reliable results among observers, 8 pathologists, all with American College of Veterinary Pathologists certification, we...
Woods GL, Steiner JV.The objective of this project was to produce multiple pregnant recipient mares during one year from each of four mares which were in athletic training and competition. Twenty-six embryos were recovered from the four mares in 38 collection attempts. Each embryo was surgically transferred to one of 20 recipient mares. Nine of 10 recipient mares which were transferred to on one occasion were detected pregnant at the one week post transfer pregnancy examination and six of eight mares which were transferred to on two occasions were detected pregnant at one of the one-week post transfer pregnancy ex...
Cremonesi F, Anderson K, Lange-Consiglio A.TWO METHODS HAVE BEEN DESCRIBED TO RECOVER OOCYTES FROM EQUINE FOLLICLES IN EXCISED OVARIES: aspiration and scraping. Aim of this work was to develop an effective method for collecting equine oocytes using Tuohy needle and comparing this technique to aspiration and scraping, with or without tunica albuginea removal. This hollow hypodermic needle, usually employed for inserting epidural catheters, is designed with a slightly curved tip, shaped similar to a small curette. In unpeeled ovaries, the recovery rates of Tuohy needle group was higher (P < .05) than in the 16 g needle aspiration and ...
Gobato MLM, Segabinazzi LGTM, Scheeren VFC, Bandeira RS, Freitas-Dell'Aqua CP, Dell'Aqua JA, Papa FO.Artificial insemination using cooled-transported semen has marked importance in equine breeding programs around the world, and the high value of mules has generated avid interest in donkey semen biotechnology. However, donkey semen cools poorly in commercially available equine extenders. Therefore, this study aimed to develop approaches to improve the ability of donkey semen to tolerate cooling. Ejaculates of seven donkeys (n = 21) were cooled at 5°C for 48 h in three different extenders (milk-based, SM; sodium caseinate-based, SC; or egg yolk-based, EY) in the presence or absence of seminal ...
Nagel C, Aurich C, Aurich J.This review summarizes current knowledge on stress-like responses in parturient animals and their role for the onset and fine-tuning of parturition. The antepartum maternal cortisol increase is part of the endocrine changes that initiate parturition but a further increase in cortisol release during labor indicates a stress response. During the last minutes of delivery, sinus arrhythmias occur in 80% of foaling mares and 60% of calving cows. Expulsion of the neonate is thus characterized by parasympathetic dominance. In late-pregnant cows transported by road, cortisol concentrations increased b...
Nequin LG, King SS, Matt KS, Jurak RC.The transition from anoestrus to oestrus in mares is controlled by photoperiod. The present study examined whether additional daylength would accelerate the mares' response to gonadotrophin-releasing-hormone (GnRH). Nine anoestrous mares were placed under ambient or artificial long lighting on 7th January. The four month experimental period was divided into a three-day sequence which was repeated at 21 day intervals. Ovaries were palpated rectally on Day 1; saline was injected (1 ml intravenously [iv]) on Day 2; GnRH was administered (0.59 microgram/kg bodyweight iv) on Day 3. Blood was taken ...
Meinert C, Silva JF, Kroetz I, Klug E, Trigg TE, Hoppen HO, Jöchle W.A small, biocompatible and short-term implant releasing 1.5 mg or 2.25 mg of the GnRH analogue deslorelin was evaluated in 140 Hanoverian (warm blooded) mares during the 1990 breeding season (Study I). Mares in oestrus and with a follicle 40 +/- 2 mm in diameter were assigned alternately to treatment (70) or remained as untreated controls. Implants were administered subcutaneously, and intervals to ovulation determined by rectal examination and ultrasound at 12-h intervals. Since results with both doses of deslorelin were similar, data were pooled. Deslorelin implantation resulted in ovulation...
Choi YH, Hinrichs K.There is a clinical demand for cryopreservation of both in vivo-recovered and in vitro-produced (IVP) equine embryos. We previously reported successful vitrification of expanded equine blastocysts in fine-diameter microloader pipette tips (MPTs) after blastocoel collapse, in a research setting. Here, we report the results of clinical application of the MPT vitrification technique for both in vivo-recovered and IVP blastocysts. In vivo-recovered blastocysts were obtained by referring veterinarians on Days 6 to 8 after ovulation, and shipped 1 to 10 hours to the laboratory before vitrificat...
Carranza J, Yoong WA, Mateos C, Caño Vergara B, Gómez CL, Macías V.Horse reproduction tends to be seasonal. The main adjusting factor in their original temperate ranges is photoperiod variation, although it is absent in equatorial areas where horses were introduced by European colonizers. Hence, dates of reproduction in these areas may be influenced by factors affecting mares' conditions and the success of foaling. Here we study reproductive timing in Creole horses in Ecuador reared in an extensive production system. We found that foaling peaked in August. Mares' conditions showed one peak in June-July, before the start of the breeding season, and another in ...
Messer NT, Johnson PJ.Two adult Quarter Horse mares from the same farm developed signs of hepatic disease approximately 2 months after parturition. Both mares had received tetanus antitoxin at the time of foaling. One mare developed subcutaneous edema of the distal aspect of all 4 limbs, photodermatitis involving unpigmented areas of skin, and high serum activities of liver-specific enzymes. The other mare had signs of acute hepatic failure, including icterus, hepatic encephalopathy, and high serum activities of liver-specific enzymes, and died. The second mare had signs typical of serum hepatitis (Theiler's diseas...
Velineni S, Timoney JF, Artiushin SC, Donahue JM, Steinman M.Foals of mares infected with Leptospira interrogans serovar Pomona type kennewicki (Lk) may be aborted/stillborn or delivered as healthy foals. Is fetal survival explained in part by the immune response of the fetus to Leptospira antigens? Objective: To describe an outbreak of Leptospira abortion in which infected mares delivered dead/sick or normal foals and determine specificities of antibody in a collection of 54 fetuses from similar outbreaks. Methods: Outbreak investigation in combination with a case-control study of a larger set of samples from aborted fetuses. Methods: Serology and poly...
Pipers FS, Zent W, Holder R, Asbury A.Ultrasonographic detection of pregnancy was performed in 952 Thoroughbred mares. Characteristic images were obtained between 12 and 55 days after breeding. Twins in the same uterine horn as well as twins in opposite horns were imaged, and for the first few months of gestation appeared similar to single pregnancies. Growth curves as a function of time were developed, utilizing horizontal diameters of the blastocysts versus breeding dates. Comparisons between horizontal and vertical diameters demonstrated no appreciable differences when observed as a group. Growth curves derived from twins did n...
Saltiel A, Gutierrez A, de Buen-Llado N, Sosa C.After parturition, Thoroughbred mares were mated at the first post-partum oestrus (N = 24) or at a subsequent oestrus (N = 12). All mares were examined daily for: oestrous detection, palpation per rectum of the genital tract, vaginoscopic examination and cervico-endometrial cytology. Pregnancy diagnosis was carried out at Days 18, 35 and 45 after mating. An identical first service conception rate of 50% was found in both groups. The number of neutrophils followed a descending profile to only scattered cells at the first post-partum oestrus and in Group II mares remained at this very low level ...
