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.
Lowe JE, Baldwin BH, Foote RH, Hillman RB, Kallfelz FA.Surgical thyroidectomies (Thx) were per-formed in 6 yearling grade horse colts, (3 males, 3 females). Five control colts (3 males, 2 females) were included and comparative studies were carried out for 67 weeks. The comparative measurements included rectal temperature, heart rate, feed consumption, packed cell volume, serum cholesterol, serum calcium, serum phosphorus, serum TO height, heart girth, body weight, epiphyseal plate closure and tooth eruption times. A thyroprotein supplement was fed to the Thx males during weeks 46 to 53. The Thx animals failed to grow in height, were sensi-tive to ...
Stabenfeldt GH, Hughes JP, Wheat JD, Evans JW, Kennedy PC, Cupps PT.The effect of hysterectomy on ovarian activity was studied
in four mares. The cyclic secretion pattern of plasma progestins normally
observed in the intact mare was interrupted by hysterectomy. Follicular
activity was observed in all four hysterectomized mares, in spite of pro-
longed luteal activity, with a large number of follicles attaining ovulatory
size without the occurrence of ovulation. Some ovulations were observed
at irregular intervals in two out of four hysterectomized mares in spite
of plasma progestin levels which ranged from 2 to 6 ng/ml. While all
ovulations which occur...
Allen WR, Stewart F, Cooper MJ, Crowhurst RC, Simpson DJ, McEnery RJ, Greenwood RE, Rossdale PD, Ricketts SW.This research investigates the use of synthetic prostaglandin analogues, specifically ICI-81008 and ICI-79939, in mares for inducing luteolysis, the regression of the corpus luteum, to manage infertility issues. The study […]
Smith ID.Progesterone concentration was measured by a protein-binding assay in peripheral plasma samples taken from 8 thoroughbred mares throughout pregnancy and for 2 days after parturition. There were considerable differences between individuals at any one time in gestation but, on average, levels rose during the first 60 days of gestation, fell to a minimum at about 180 days when the accessory corpora lutea regress and finally reached their highest mean value of 11.5 mg/ml±1.2 (S.E.M.) during the period 270 days to term, significantly higher than the mean, 7.6 ng/ml±0.5 (S.E.M) for the whole of ge...
van Niekerk CH, Morgenthal JC, Sanders CP, Malan JE.Progesterone concentrations were assayed by a competitive protein-binding technique
in peripheral plasma samples collected twice
daily during four oestrous cycles of three
mares, and once a day during the first seven
weeks of pregnancy in four mares. Large
variations were found in progesterone levels
between morning and evening samples on the
same day in the same mare.
The lowest progesterone concentration
was found about the time of ovulation. Within 24 hours after ovulation the progesterone
concentration increased and two peaks, one
at 5 days and another at 8 days, were found.
Be...
Klingeborn B.Twelve mares were vaccinated with attenuated equine abortion virus (EAV) strain RAC-H. Two nonvaccinated mares served as controls. In at least three mares the vaccination appeared to coincide with a natural infection. This was indicated by characterization of the EAV isolated from nasal secretions of six vaccinated mares, a nonvaccinated control, and also from the lung, spleen, and liver of a fetus aborted by a vaccinated mare. The relative sensitivity of the isolated EAV to dithiothreitol was used to distinguish the RAC-H strain and wild-type virus. Of the 10 EAV isolates, four were recognize...
Buff PR, Messer NT, Cogswell AM, Wilson DA, Johnson PJ, Keisler DH, Ganjam VK.Endocrine characteristics of Quarter Horse-type mares were determined during a 68 h feed deprivation and again in the same mares following surgical thyroidectomy (THX). A crossover experimental design was implemented, in which mares received brome hay available ad libitum (FED) or were food deprived (RES) for 68 h. Blood samples were collected every 20 min for 48 h, beginning 20 h after the onset of food deprivation. Concentrations of triiodothyronine and thyroxine were undetectable post-THX. Plasma concentrations of thyrotropin were greater post-THX versus pre-THX (P<0 x 001). Plasma conce...
Pascoe DR, Stabenfeldt GH, Hughes JP, Kindahl H.Thirty mares with normal estrous cycles were allotted equally to 5 groups and infused with 250 ml of saline (NaCl) solution in utero on the seventh day after ovulation to test the effects of temperature, osmolarity, or pH of the saline solution on prostaglandin F2 alpha (PGF2 alpha) release and luteolysis. Intrauterine infusion of phosphate-buffered saline solution failed to alter the duration of the luteal phase, compared with the control group. Similarly, increasing the temperature of phosphate-buffered saline solution to 42 C or increasing (600 mosm) or decreasing osmolarity (less than 10 m...
Lima AG, Costa LC, Alvarenga MA, Martins CB.The presence of anovulatory haemorrhagic follicles during the oestrous cycle of mares causes financial impacts, slowing conception and increasing the number of services per pregnancy. Non-steroidal anti-inflammatory drugs (NSAIDs) such as meloxicam and phenylbutazone are used in the treatment of several disorders in mares, and these drugs can impair the formation of prostaglandins (PGs) and consequently interfere with reproductive activity. This study aimed to evaluate the effects of treatment with NSAIDs on the development of pre-ovulatory follicles in mares. In total, 11 mares were studied o...
Sobiraj A, Bostedt H.This review article deals with a critical comparison between the direct clinical diagnosis for the pregnancy of the mare (rectal and in some cases also vaginal exploration) and indirect methods. Both methods are discussed whether they can be seen as a mutual completion or are suitable for their own. The indirect methods for the pregnancy diagnosis include the hormone-analytic tests as progesterone concentration in serum or milk, the biological and immunological measurements for PMSG in the serum, finally the biological and chemical methods for estrogen contents in the urine of the mare. Furthe...
Roser JF, Dudan F, Little TV, Livesay-Wilkins P, Hillman RB.Studies were undertaken to investigate the effects of oxytocin induction on prolactin release in term (Group II) and preterm (Group III) mares and to compare these effects to spontaneously foaling mares (Group I). Since physiological concentrations of prolactin in blood have not been measured in the neonatal foal, experiments were designed to monitor prolactin in the cord artery and jugular blood of the foals from all groups of mares. Although prolactin levels varied in term mares (Group I and II) during the last 11 days of pregnancy, an increase was observed between Day -6 and Day 0 (2.7 and ...
Weitkamp LR, Kenney RM, Bailey E, MacCluer JW, Brown JS, Blanchard TL, Sertich PL, Love CC, Hunt PR.Histological features of the endometrium, as assessed in biopsy samples, were related to Standardbred mare genotypes for transferrin, esterase (as a control) and equine leucocyte antigens (ELA). Pathological changes were found more frequently in each successively older age group of mares. Among mares aged 6-19 years, there were significant pathologic changes on first examination following an infertile breeding season for 46 of 90 (51%) of transferrin homozygotes and 50 of 146 (34%) of transferrin heterozygotes. The difference between the two groups was significant for the total data (chi 1(2) ...
Lebedev SG, Lebedeva LF.A medium containing egg yolk, mare's milk and/or modified PBS was used to culture Day-8 to 8.5 equine blastocysts. Twenty-one variants of the medium containing different concentrations of the 3 components were prepared. Embryos were recovered nonsurgically and placed into the media at 37 degrees C for 24 h. A total of 45 embryos was cultured; of these 7 died in culture and 13 showed inadequate development at the onset, while 25 continued to grow in the media. It was established that embryos grew best in media containing 20 to 60% yolk, 20 to 60% mare's milk and/or 20 to 60% PBS. It was found e...
Sönmez C, Eroglu A.The present study was carried out to investigate the pregnancy rate after covering in the foal heat (Group I), in the subsequent spontaneous heat (Group II), and in the induced heat (Group III) after administration of 7.5 mg of the prostaglandin F2 alpha analogue Luprostiol (Reprodin, Bayer) between the 20th and 22nd day post partum. Breeding during foal heat resulted in a pregnancy rate of 43.9% compared to 48.6% in the subsequent spontaneous heat post partum. Of 18 mares in group III, 14 mares had a foal heat, whereas 4 others had not shown a foal heat. 1-8 days after treatment, 14 mares (77...
Urschel KL, Escobar J, McCutcheon LJ, Geor RJ.The objective of this study was to determine whether the rate of insulin infusion during isoglycemic hyperinsulinemic clamp procedures affected measures of insulin action, including glucose disposal and plasma non-esterified fatty acid, endothelin-1, and nitric oxide concentrations, in mature, healthy horses. Eight thoroughbred mares were studied during a 2-h hyperinsulinemic clamp procedure, conducted at each of 4 rates of insulin infusion: 0 (CON), 1.2 (LOWINS), 3 (MEDINS), and 6 (HIGHINS) mU · kg(-1) · min(-1). The infusion rate of a dextrose solution was adjusted throughout the clamp pro...
Sarnecky BA, Vanderwall DK, Mason HM, Kirschner SM, Ambrose B, Parker TL.Prolonging function of the corpus luteum (CL) is a method of suppressing estrus that relies on continued secretion of endogenous progesterone to keep mares out of heat naturally. The use of oxytocin treatment to prolong CL function is gaining increasing use, and the most common treatment protocol involves administration of 60 units of oxytocin intramuscularly (IM) once daily on days 7-14 after ovulation (eight daily treatments). Although that protocol induces prolonged CL function in ≥70% of treated mares, the need for daily administration is a drawback to its use. Therefore, the objective o...
Tsunoda RH, Serrano-Recalde EC, Arruda RP, Oliveira BMM, Pinto SCC, Celeghini ECC.The aim was to evaluate effects of addition of pentoxifylline to skimmed milk semen extender on uterine inflammatory response. Thirty-six estrous cycles of 15 mares were randomly divided into five groups for artificial insemination (AI): Control: mimicking the AI procedure (n = 7); Extender: deposition of skimmed milk based extender (n = 7); Extender + PTX: skimmed milk based extender plus pentoxifylline (7.18 mM; n = 8); Semen: semen diluted with extender without pentoxifylline (n = 7), and Semen + PTX: semen diluted with extender containing pentoxifylline (n = 7). M...
Watson ED.Corpora lutea were recovered from mares either 4 to 5 days or 12 to 13 days after ovulation. Mixed populations of luteal cells were prepared by collagenase digestion and were incubated for 24 h in the presence or absence of prostaglandin (PG) F-2 alpha (250 ng/ml). PGF-2 alpha significantly (P = 0.03) reduced progesterone secretion by cells from late diestrous corpora lutea and tended (P = 0.06) to reduce secretion by early diestrous cells. PGF-2 alpha had no significant effect on leukotriene B-4 (LTB-4) production by cells from early diestrous corpora lutea, but significantly (P = 0.03) incre...
Fanelli D, Tesi M, Rota A, Panzani D, Camillo F.In a veterinary medicine curriculum, students' hands-on practice is essential but is still considered one of the major deficiencies in veterinary schools in Europe. After theoretical and basic practical training, students, under the control of experienced veterinarians (supervisors), monitored the reproductive cycle of embryo recipients by transrectal palpation and ultrasound. To evaluate the skills of students, the question "Has she ovulated?" was posed when a dominant follicle ≥ 35 mm was recorded in the previous day's examination and a score of 1 or 0 was assigned in the case of a correct...
Meinecke B, Gips H.The aim of the present investigations was to characterize the endocrine changes in the peripheral plasma during the periparturient phase of mares with a known history of obstetrical disorders. Blood plasma samples from 9 mares (8 mares during parturition, 1 mare during abortion) were collected and the following steroid hormones were radioimmunologically determined: progesterone (P4), dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEA-S), estrone (E1), estrone sulfate (E1-S), estradiol-17 beta (E2), estriol (E3), cortisol and transcortin. In general, with the exception of corti...
Hawkes M, Richard A, Oldfield C, Toothaker A, Stokes M, Causey R.Postbreeding bacterial uterine infections inflict major losses on the equine industry. Microcurrents propelled by ciliated cells between the folds of the uterus and cervix have been proposed as a means by which contaminants are expelled. Previous data have shown possible ciliary microcurrents propelling carbon particles, occasionally rotating, through cervical folds. However, adherence to the epithelium may have interfered with movement of carbon in these studies. Therefore, we tested potentially nonadherent substances to reveal ciliary microcurrents on the equine cervix under high magnificati...
Benamou AE, Harris RC.The changes in carnitine in plasma and milk during the first 3 months of lactation were studied in 14 broodmares and their foals. Six of the mares (Group S) were given a supplement of 10 g carnitine split between the morning and evening feeds, starting 2 weeks before birth. At birth the plasma carnitine concentration in Group S mares was about twice that in Group NS mares (no supplement). In both groups the concentration initially declined in the days after birth. Whilst this trend was reversed in Group S mares, the concentration in Group NS mares remained at a reduced level for the remainder ...
Watson ED, Sertich PL, Zanecosky HG.Ovulation has been likened to an inflammatory process. Inflammatory cells accumulate in the ovulating follicle, presumably because of chemotactic factors. Chemotactic activity was measured in fluid aspirated from follicles of estrous mares 0, 12, 24, and 36 hours after ultrasonographic detection of a 35-mm follicle and IV treatment with 2,500 IU of human chorionic gonadotropin. Chemotaxis was assessed by measuring directional migration of equine neutrophils under agarose. Follicular fluid acted as a chemoattractant for neutrophils, but there was no significant difference in chemotactic activit...
Pinzón-Osorio CA, Cortés-Beltrán D, Sanchez-Isaza CA, Jiménez-Robayo LM, Lozano-Márquez H, Zambrano-Varón J, Jiménez-Escobar C.A 4-year-old Colombian Creole mare was presented for diagnosis because the external orifice of her cervix was not detectable when a uterine lavage as therapy for uterine fluid accumulation was attempted. Clinical and ultrasonographic evaluation of the genital tract revealed that ovaries were of normal size and showed structures suggestive of regular ovarian activity. However, granular free-floating fluid material distending the uterus was detected by ultrasound. Upon vaginal examination, the normal external cervical morphology was not evident. The vagina ended in a blind bag with a small papil...
Huber MJ, Roser JF, Riebold TW, Schmotzer WB, Grubb TL, Crisman RO.Seven pregnant mares underwent general anaesthesia, laparotomy, hysterotomy and removal of a 50-day conceptus. Eversion of the uterine horn through the hysterotomy site allowed direct visualisation and electrosurgical removal of endometrial cup tissue from 5 randomly selected mares (Nos 1-5), while cup tissue in 2 mares (Nos 6 and 7) was left intact. Two pregnant mares served as unoperated controls (Nos 8 and 9). Efforts to re-establish pregnancy were initiated 20 days after surgery. Serum samples collected before surgery and during the post-operative period were analysed for concentration of ...
Coutinho da Silva MA, Carnevale EM, Maclellan LJ, Seidel GE, Squires EL.The objective of the study was to compare embryo development rates after transfer of oocytes collected 22 or 33 h after hCG injection into recipients inseminated within the uterus or the oviduct. Oocytes were collected at approximately 22 or 33 h after hCG injections and incubated for approximately 16 or 1.5 h, respectively, before transfer. Intrauterine inseminations using 1 x 10(9) progressively motile sperm were done approximately 12 h before and 2 h after transfer. For intraoviductal inseminations (gamete intrafallopian transfer [GIFT]), semen was centrifuged through a Percoll gradient, an...
Rau J, Tiedemann D, Sielhorst J, Tönissen A, Burger D, Martinsson G, Rohn K, Oldenhof H, Sieme H.Transvaginal ultrasound-guided aspiration (TUA) is a procedure which can be used for the reduction of twins post-fixation in the mare. The aim of this study was to evaluate the effect of the age of mares and the day of gestation on the outcome of TUA treatment. Methods: In 88 mares, diagnosed pregnant with twins, TUA of the yolk sac or allantoic fluid was performed between day 30 and 62 of gestation. Mares were aged 3-22 years. Ultrasonographic examination for a viable singleton pregnancy was performed by referring veterinarians 5-7 days and 4 weeks after TUA. Based on reported findings, effec...
Watson ED.The ability of equine endometrium to release prostaglandin (PG) F, PGE2, and leukotriene (LT) B4 was studied in vitro, using endometrial tissue from diestrous mares. Because of the high cross-reactivity of the PGF antiserum with PGF1 alpha and with PGF2 alpha, results were quoted as total immunoreactive PGF. Significant concentrations of these arachidonate metabolites were released into tissue culture medium between 1 and 24 hours of incubation. Significantly higher concentrations of PGE, but not of PGE2 or LTB4, were released from endometria of mares with chronic endometritis than from genita...
Plotka ED, Vevea DN, Eagle TC, Tester JR, Siniff DB.Homogeneous Silastic rods containing ethinylestradiol (EE) (1.5 or 4 g), estradiol-17 beta (E) (4 g) or progesterone (P) (6 g) were implanted into feral mares (Equus caballus) between 4- and 10-yr-old. Six treatment groups (greater than or equal to 10 mares/group) of non-pregnant mares received 36 g P and 12 g E (P+E), 36 g P and 8 g EE (P+HEE), 1.5 g EE (LEE), 3 g EE (MEE, 8 g EE (HEE) or control-implanted mares (CI). CI received implants containing no steroid. Two groups of pregnant mares received P+HEE or HEE. Stallions were placed with the mares 15 to 26 mo after implanting. Blood was coll...
Raz T, Carley S, Card C.The objective was to compare the effects of eFSH and deslorelin treatment regimes on ovarian stimulation and embryo production of donor mares in early spring transition. Starting January 30th, mares kept under ambient light were examined by transrectal ultrasonography. When a follicle > or =25 mm was detected, mares were assigned to one of two treatment groups, using a sequential alternating treatment design. In the eFSH group, mares (n=18) were treated twice daily with eFSH (12.5mg im) until they achieved a follicle > or =35 mm; hCG was given 36 h later. In the deslorelin group, mares (n=18) ...
Miragaya MH, Woods GL, Losinno L.The occurrence of uterine and oviductal inflammation, and fertilisation rates, were measured on Day 3 post ovulation in inseminated mares that had either exhibited intrauterine lumenal fluid during a previous dioestrus (Experiment 1) or had acute endometritis induced by intrauterine infusion of 1% glycogen (Experiment 2). Endometritis was assessed by uterine cytology and histology whereas oviductal inflammation was measured histologically. Fertilisation rates were calculated from the percentage of cleaved ova recovered by retrograde flushing of the oviducts. Mares with or without pre-existing ...
Merlo B, Del Prete C, Mari G, Iacono E.The demand for equine in vitro produced embryos has increased over the last decade. The aim of this study was to compare the effects of an extended IVM or a prolonged period before fertilization, including holding time, on equine immature oocyte developmental competence. Oocytes, collected from abattoir-derived ovaries, were divided into 4 groups: H0/24 (n = 165) 0 h holding + standard 24-26 h IVM; H8/36 (n = 160) 8 h holding + 36 h IVM; H20/24 (n = 187) 20 h holding + 24 h IVM; H0/44 (n = 164) 0 h holding + 44 h IVM. Oocytes matured to MII were fertilized by intracytoplasm...
Pope NS, Sargent GF, Wiseman BS, Kesler DJ.Frequent blood samples were collected from 8 pony mares before, during and after labour, parturition and placental expulsion and assayed for progesterone, oestradiol, androstenedione and LH concentrations by radioimmunoassay. A significant (P less than 0.05) decrease in progesterone, oestradiol and in the progesterone:oestradiol ratio was not detected until 0.5 h after foaling. Androstenedione concentrations rose before and peaked at parturition and then declined. A significant (P less than 0.05) rise in LH was detected 0.5 h after parturition. This LH peak was not detected in one mare and she...
Griffin PG, Ginther OJ.Fetal activity and mobility and changes in diameter of the allantoic fluid compartment in the uterine horns were studied in mares between days 69 and 81 of pregnancy by use of transrectal ultrasonography (n = 12) and transcervical videoendoscopy (n = 8). The insertion tube of the videoendoscope was positioned within the allantoic sac to permit viewing of the fetus and entrance to each uterine horn. Each uterine horn was divided ultrasonographically into 3 segments of equal length, and the horns were designated on the basis of side of umbilical attachment (cord vs noncord horns). The diameter o...
Ball BA, Brinsko SP, Thomas PG, Miller PG, Ellington JE.Development of 1- to 2-cell in vivo fertilized equine embryos cultured with or without uterine tubal epithelial cells (UTEC) was studied. One- to 2-cell embryos (n = 26) were collected surgically from the uterine tubes of pony mares 1 day after ovulation. Four- to 8-cell embryos (n = 9) were collected 2 days after ovulation. Presumptive zygotes and 2-cell embryos were cultured with (n = 17) or without (n = 9) UTEC, and all 4- to 8-cell embryos were cocultured with UTEC as positive controls. Uterine tubal epithelial cells were used as cell suspensions within 2 weeks after initiation of cultures...
Withrow JM, Sargent GF, Scheffrahn NS, Kesler DJ.Two pony mares were administered 150 mg of testosterone propionate every other day for 20 days (ten injections) and every ten days there-after. An additional two mares and one stallion were not treated and served as controls. Testosterone propionate was dissolved in absolute ethanol and administered subcutaneously. Sex behavior tests were conducted 26 and 40 days after the first injection. Control mares exhibited very little male sex behavior. Both testosterone propionatetreated mares, however, exhibited mounting, sniffing, flehmen, biting and vocalization behavior in the presence of an estrou...
