Omneity® Pellets
All-In-One Vitamin & Mineral Pellet
Topic:Mares
Mares and horses are integral components of equine studies, focusing on the reproductive and behavioral aspects of equine biology. Mares, or adult female horses, play a significant role in breeding programs and are often studied for their reproductive physiology, gestation, and maternal behaviors. Horses, as a broader category, encompass both sexes and all age groups, providing a comprehensive view of equine anatomy, physiology, and behavior. Research in this area often investigates the differences and similarities between mares and other horses in terms of hormonal cycles, reproductive health, and social interactions. This page compiles peer-reviewed studies and scholarly articles that explore the biological and behavioral characteristics of mares and horses, offering insights into their roles in equine science and management.
Embryonic loss in mares. Incidence, possible causes, and diagnostic considerations. Fertilization rates were similar for normal and subfertile mares, and much of the difference in fertility between normal and subfertile mares was due to embryonic loss. Fertilization rate estimates for mares ranged from 71 to 96 per cent. The incidence of embryonic loss detected by ultrasonography between Days 11 and 50 was approximately 9 per cent for normal mares, and the estimated incidence of embryonic loss before Day 14 was also 9 per cent. Therefore, the estimated incidence of embryonic loss in normal mares between fertilization and Day 50 is approximately 18 per cent (Fig. 1). In subfer...
Control of the estrous cycle in the mare. All current approaches to manipulating the reproductive biology of the nonpregnant mare are discussed.
Ultrasonic imaging of equine ovarian follicles and corpora lutea. One of the most profound theriogenology applications of transrectal diagnostic ultrasonography in mares involves the imaging of ovarian follicles and corpora lutea. The resolving capabilities (frequency) and quality of the scanner directly affect the minimal size of a structure that can be imaged and the quality of the image. High-frequency scanners (5 or 7.5 MHz) of good quality can image a 2-mm follicle and the corpus luteum throughout its functional life. A low-frequency scanner (3 or 3.5 MHz) can image a 6-mm follicle and the corpus luteum for several days after ovulation. Equine follicles...
Nonsurgical treatment of uterine torsion in seven mares. Nonsurgical correction of uterine torsion was performed in 7 mares, and 6 foals were subsequently born alive. Uterine rupture necessitated euthanasia in 1 mare. Correction was achieved by rolling of the mares after general anesthesia had been induced. Previously, this technique was believed to be associated with a high prevalence of fetal and maternal mortality. Nonsurgical correction may be a satisfactory alternative to abdominal surgery in treating uterine torsion in mares.
Endometrial biopsy of the mare. A review and update. The endometrial biopsy is a safe and effective means of predicting a mare's prognosis for foaling. A thorough understanding of the normal cyclic and seasonal pattern displayed by the normal endometrium is necessary before interpreting pathologic changes. Several systems for prognostic classification have been proposed, including a recent one that combines many of the criteria used in the other systems.
Hydramnios causing uterine rupture in a mare. An 18-year-old mare, 285 days pregnant, was evaluated for apparent abdominal pain of 8 hours' duration. A large volume of sanguinous fluid was obtained on abdominocentesis, and digital vaginal examination revealed a dilated cervix and blood in the uterus. Abdominal palpation per rectum revealed the uterus to be large and distended with fluid. Ultrasonography revealed a dead fetus on the floor of the cranial portion of the abdomen. The mare was euthanatized, and necropsy confirmed that the uterus had ruptured, and that the fetus, within its chorioallantois, was in the abdomen. The amniotic sac ...
Diagnosis and correction of twin pregnancy in the mare. Reproductive Physiology 1. Twin pregnancies result in high rates of abortion, stillbirth, and neonatal mortality. 2. Twins develop subsequent to multiple ovulations. Multiple ovulations are related to breed, parity, and mare history. Multiple ovulations are most frequently seen in Thoroughbred and Draft mares. Multiple ovulations are more common in barren and perhaps maiden mares than in lactating mares, and they are more common in certain individual mares. 3. Equine embryos are motile in the uterus from the time of first detection (Days 9 to 10) until fixation (Day 16). They are frequently lo...
Equine neonatal isoerythrolysis: evidence for prevention by maternal antibodies to the Ca blood group antigen. Foals with the Ca blood group antigen on their RBC were given colostrum with anti-Ca antibodies (6 foals) or colostrum without anti-Ca antibodies (6 foals). The PCV were determined at birth and 2, 4, and 6 days after birth for the foals in each group. Significant differences were not observed for the PCV between the 2 groups, indicating that foals were not adversely affected by ingesting colostrum with the anti-Ca antibody. Standardbred mares without the Aa blood group antigen were evaluated to determine whether production of anti-Ca antibodies influenced production of anti-Aa antibodies. Of 2...
Intestinal carcinoid in a mare: an etiologic consideration for chronic colic in horses. Intestinal carcinoid, or argentaffinoma, should be an etiologic consideration for horses with chronic colic. A mare was referred with a history of chronic colic. Previously, the signs of colic had subsided in response to impiric treatment, but recent episodes of colic did not. Clinical signs and results of physical examination supported the finding of strangulating obstruction of the small intestine. Exploratory celiotomy revealed internal herniation with simultaneous volvulus of the jejunum and accompanying carcinoid.
Embryo reduction before day 11 in mares with twin conceptuses. Incidence of embryo reduction (natural elimination of one member of a twin set) before d 11 was studied by comparing the number of ultrasonically detected conceptuses per ovulation between single and double ovulators. Effect of unilateral (n = 24) vs bilateral (n = 26) double ovulations on the incidence of embryo reduction also was considered. Each of 50 double-ovulating mares was matched with two single ovulators yielding 100 ovulations, or potential embryos, per group. Frequency with which an ovulation resulted in a conceptus was greater for single ovulators (85%, P less than .01) and for bi...
Factors affecting the composition of mare uterine fluid. The influx of protein and polymorphonuclear leucocytes (PMN) into the uterine lumen was examined at different intervals after intrauterine infusion of fluids. The intrauterine infusion of both phosphate buffered saline (PBS) and a solution of lipopolysaccharide (LPS) derived from Escherichia coli resulted in a biphasic influx of protein in the uterine flushings peaking three and six hours after infusion. LPS infusion caused an additional influx of protein at 24 hours. The initial influx of protein preceded a biphasic influx of PMN which peaked six and 24 hours after both infusions. Uterine flu...
Piperazine resistance in population-B equine strongyles: a study of selection in Thoroughbreds in Kentucky from 1966 through 1983. Observations were completed over an 18-year period (1966 through 1983) in Thoroughbred mares (15/year) and yearlings (11 to 24/year) on a farm where benzimidazole-resistant small strongyles had emerged previously (1962 to 1965). This farm was operated as a closed, nonboarding type, which included a racing stable for its home-bred foals. At 2-week intervals, counts of worm eggs per gram of feces (EPG) and larvae per gram of feces were done to monitor strongyle infections and efficacies of bimonthly (every 8 weeks) antiparasitic treatments that were administered by stomach tube or were fed (dich...
Clinical significance of aerobic bacterial flora of the uterus, vagina, vestibule, and clitoral fossa of clinically normal mares. Swab specimens for bacterial culture were obtained from the uterus, vagina, vestibule, and clitoral fossa of 48 mares that had normal reproductive tracts, no history of reproductive problems, and no inflammation on evaluation of endometrial biopsy. The mares were predominantly Thoroughbred and Standardbred. Swab specimens of the vagina were obtained through a sterile speculum; swab specimens of the uterus were obtained by use of a double-guarded, occluded culture instrument. Fifteen (31%) of the uterine swab specimens and 20 (42%) of the vaginal swab specimens yielded growth on aerobic culture...
Effects of hormone implants on estrus and ovulation in feral mares. Five groups of 30 captive feral mares each were implanted with silastic rods containing estradiol (E) and/or progesterone (P): E only with 8 g, P only with 24 g, P+HE with 8 g P + 8 g E, HP+E with 12 g P + 4 g E, HP+LE with 12 g P + 2 g E. Arbitrary group designations were differentiated by relative high (H) and low (L) amounts of steroid. Thirty mares received silastic rods containing no hormone (CI). Five mares from each group were bled every 2 wk for 4 mo and monthly for another 5 mo. All mares were tested for estrus by allowing them to stand in an alley between two pens of stallions and vi...
Effects of gonadotrophin-releasing hormone and prostaglandin F-2 alpha on corpus luteum function and timing of the subsequent ovulation in the mare. Standard bred mares that were cycling normally were treated beginning on Days 9 or 10 of the oestrous cycle with repeated pulses of GnRH (20 micrograms/h) and/or a single injection of prostaglandin (PG)F-2 alpha (alfaprostol, 3 mg), and were subsequently bled and palpated daily until the next ovulation. GnRH treatment increased serum concentrations of LH and progesterone at 4 days after the start of treatment compared to controls. The combination of PGF-2 alpha + GnRH treatment resulted in an immediate decline in serum progesterone values, and subsequently decreased the interval to next ovulat...
Ureteropyelonephritis in a Friesian mare. A 14-year-old Friesian breeding mare had strangury, depression, inappetence, neutrophilia and uraemia. Its urine had a low specific gravity and contained protein, blood cells and bacteria. Rectal examination showed that both kidneys and ureters were enlarged. Post mortem examination confirmed the diagnosis of pyelonephritis and revealed that small tumours in the vulva were probably the cause of the uropathy.
Vitamin A, E and D nutrition in mares and foals during the winter season: effect of feeding two different vitamin-mineral concentrates. The effects of feeding two different vitamin-mineral concentrates on serum levels of vitamins A, E and D and some growth indicators were examined in 30 pregnant mares and 30 foals. One concentrate contained vitamins A and E and the other did not. Both contained vitamin D3. No differences (P greater than .05) in serum levels of retinol and alpha-tocopherol were observed between the feeding groups in the mares, whereas in the weanlings serum levels of dietary vitamins A and E increased (P less than .01) during late winter and early spring. However, the values did not increase to levels found in ...
Concentrations of immunoreactive leukotriene B4 in uterine lavage fluid from mares with experimentally induced and naturally occurring endometritis. Acute endometritis was induced in ovariectomized pony mares by infusion of a 1% solution of oyster glycogen. Maximum concentrations of immunoreactive leukotriene B4 in uterine washings coincided with the greatest rate of infiltration of neutrophils into the uterine lumen. Concentrations of immunoreactive leukotriene B4 decreased to basal levels 6 h after infusion and were unaffected by administration of ovarian steroids to ovariectomized mares. Uterine washings from mares with persistent endometritis did not contain significantly different concentrations of leukotriene B4 from genitally normal...
Serum profiles of vitamins A, E and D in mares and foals during different seasons. Twenty mares and 15 foals of the Finnhorse breed were used to determine serum levels of vitamins A, E and D during different seasons. Monthly serum samples were analyzed from mares for 22 mo and from foals for 13 mo after birth. The horses were kept on pasture from early June until early October and in stables during the winter months. Seasonal differences (P less than .001) were found in serum retinol, retinol to protein ratio, alpha-tocopherol and alpha-tocopherol to cholesterol ratio. Values were lowest from February through May and highest from June through August. Serum levels of retinol ...
Pharmacokinetics and body fluid and endometrial concentrations of trimethoprim-sulfamethoxazole in mares. Six healthy adult mares were each given a single IV injection of trimethoprim (TMP)-sulfamethoxazole (SMZ) at a dosage of 2.5 mg of TMP/kg of body weight and 12.5 mg of SMZ/kg. Serum concentrations of each drug were measured serially over a 24-hour period. For TMP, the mean overall elimination rate constant (K) was 0.43/hr and the elimination half-life (t1/2) was 1.9 hours. The apparent volume of distribution (at steady state) was 1.62 L/kg and TMP clearance was 886 ml/hr/kg. For SMZ, K was 0.22/hr and t1/2 was 3.53 hours. The apparent volume of distribution at steady state was 0.33 L/kg and S...
Evaluation of the post-partum mare in relation to foal heat breeding. II. Uterine swabbing and biopsies. Fifty-three post-partum (p. p.) periods were studied in 38 mares. Uterine samples were taken on
the 2nd and 5th days p.p. and thereafter every other day until ovulation. Uterine swabs were
examined for bacteria and neutrophils and uterine biopsy specimens for neutrophils and lymphocytes.
The occurrence of bacteria and leukocytes was most common on day 5 p. p. The dominant organism
on day 2 was E. coli and on day 5 P-haemolytic streptococci. Thirty-four mares were inseminated
during the first p. p. oestrus. Only the occurrence of neutrophils in day 5 biopsy specimens correlated
with foal ...
Body temperature and behaviour of mares during the last two weeks of pregnancy. Average daily core body temperature and behavioural patterns of pregnant mares were studied, in search of definitive signs of parturition within 24 h of the event. Nineteen pony mares were sampled twice daily for core body temperature. A significant temperature drop, averaging 0.1 degrees C (0.2 degrees F) was observed during the day prior to parturition. Between 18.00 h and 06.00 h, during the two weeks before parturition, Thoroughbred and Standardbred mares (n = 52) spent an average 66.8 per cent of their time standing, 27.0 per cent eating, 4.9 per cent lying in sternal recumbency, 1.0 per ...
Effect of exogenous ovarian steroids on the uterine luminal prostaglandins in ovariectomised mares with experimental endometritis. Prostaglandins (PGs) F and E2 were measured in lavage fluid from the uterus of ovariectomised mares after experimental induction of uterine inflammation. Treatment with progesterone alone, or progesterone followed by oestradiol, significantly increased the concentrations of these PGs in the lavage compared with mares treated with oestradiol or control mares. Ovarian steroids, therefore, influenced uterine PG synthesis in response to an inflammatory stimulus. To determine whether the uterine lavage procedure might contribute to the concentrations of prostaglandins in the lavage, the procedure w...
Consolidating pneumonia and pneumothorax in a horse. A 3-year-old Thoroughbred mare with signs of acute abdominal pain and chronic pneumonia was found to have pneumothorax. A single application of suction was successful in resolving the pneumothorax. The underlying pneumonia was treated with long-term antibiotic administration selected on the basis of results of bacteriologic culture and antimicrobial susceptibility testing of a transtracheal aspirate. The pneumonia resolved, and the mare returned to competition as a show hunter.
Generalised steatitis in an adult pony mare. Equine steatitis is a rare condition which is usually reported in foals. A case of generalised steatitis in an adult pony mare is described and compared with steatitis in other species. It is concluded that the condition resembled that recorded in foals but that its aetiopathogenesis remains obscure.
