Surgical Removal of One Conceptus from Fifteen Mares with Twin Concepti

A surgical technique for removal of one conceptus from mares with twin concepti more than 35 days of gestational age was evaluated. One conceptus was removed surgically from each of 15 mares carrying twin concepti that were 41 to 65 days of gestational age. As determined by ultrasonography, eight mares had bicornuate and seven mares had unicornuate twin concepti. For maintenance of pregnancy if surgical trauma should cause prostaglandin release and luteolysis, progesterone was administered prophylactically. Flunixin meglumine was administered perioperatively to minimize prostaglandin release. Five mares with bicornuate twin concepti delivered a single viable foal; in one mare the fetus was alive 4 days after surgery when the mare was euthanatized because of a fractured femur. None of the remaining feti in the seven mares with unicornuate twin concepti survived. The poor survival rate of unicornuate twin concepti was attributed to disruption of the remaining chorioallantois during surgery. Thirteen mares have been rebred successfully.     

Videoendoscopic evaluation of the mare's uterus: III. Findings in the pregnant mare.

During a 5-year period 65 Pony and 20 Thoroughbred pregnant mares were subjected to videoendoscopic hysteroscopy from 10 to 266 days of gestation. The aims of these examinations were to 1) observe foetal and placental development in vivo (60 Pony and 10 Thoroughbred mares); 2) eliminate one of unicornuate twin conceptuses (9 Thoroughbred mares); 3) recover embryonic foetal and placental tissues non-surgically for experimental purposes (47 Pony mares); 4) induce focal separation of the placenta in late gestation as an experimental model of placentitis (5 pony mares and 1 Thoroughbred mare). It was possible to view the embryo and all constituent extra-embryonic membranes of the conceptus between Days 10 and 87 of gestation without having to perforate the allantochorion. This allowed study of physiological processes such as the coordinated uterine contractions responsible for conceptus motility between Days 7 and 17, active foetal movements, which began as early as Day 34, and invasion of chorionic girdle cells into the endometrium, which occurred between Days 34 and 38. From Day 90, vision of the foetus was reduced or prevented by the increased thickness of the allantochorion. Transendoscopic recovery of the conceptus was successful in all of 10 mares under 30 days of gestation, whereas only 10 of 18 attempts between Days 30 and 45 produced the conceptus without resorting to uterine lavage after initial rupture of the allantochorion. All 9 attempts to eliminate one of unilateral twin conceptuses were unsuccessful and the technique was abandoned as clinically unsuitable. Nevertheless, 9 of 22 (41%) single conceptuses remained viable after one or more hysteroscopic examinations.(ABSTRACT TRUNCATED AT 250 WORDS)     

Chronic flunixin meglumine therapy in foals

Effects of a therapeutic dose of flunixin meglumine on gastric mucosa of horse foals were determined by endoscopy, double-contrast radiography, and gross and histologic examinations. Foals were administered 1.1 mg of flunixin meglumine/kg of body weight, PO/day for 30 days in an encapsulated form that was divided into 2 doses/day (group 1; n = 3) or by IM injection once a day (group 2; n = 7). Three control foals (group 3; n = 3) were administered capsules (n = 1) containing dextrose powder or IM injections (n = 2) of vehicle solution without flunixin meglumine. All 3 groups-1 foals given flunixin meglumine PO developed oral ulcers. Group-2 foals given flunixin meglumine IM did not develop oral ulcers. One control foal (group 3) developed 1 oral ulcer that healed during the study. Endoscopic examination revealed linear crease-like mucosal lesions in the glandular portion of the stomach in 2 group-2 foals. Radiographic evidence of gastric ulcers was observed in only 1 gastrogram of a group-1 foal. Foals were euthanatized, and necropsy revealed erosions and/or ulcers of the glandular portion of the stomach. Oral ulcers were observed in all 3 group-1 foals. Erosions of the glandular portion of the stomach developed in all 10 foals given flunixin meglumine, but did not develop in group-3 foals. Ulceration of the glandular portion of the stomach was present in 1 group-2 foal.     

Continuous monitoring of penicillin G and gentamicin in allantoic fluid of pregnant pony mares by in vivo microdialysis

REASONS FOR PERFORMING STUDY: Most current treatments for placentitis in mares are empirical with few control studies to evaluate their effectiveness. OBJECTIVE: To monitor drug concentrations in allantoic fluid of pregnant pony mares using in vivo microdialysis and establish if this method would be useful for determining allantoic concentrations of drugs in normal mares and those with placentitis. METHODS: Five late gestational pony mares had microdialysis probes inserted into the allantoic fluid using transabdominal ultrasound-guided allantocentesis. Single injections of penicillin G (22,000 u/kg), gentamicin (6.6 mg/kg bwt) and flunixin meglumine (1 mg/kg bwt) were administered i.v. and dialysate samples collected continuously for 24 h. In a separate study, drug concentrations were monitored in allantoic fluid of 2 mares with experimental placentitis induced by intracervical inoculation with Streptococcus equi ssp. zooepidemicus. Drug concentrations were measured by high performance liquid chromatography (penicillin G, flunixin meglumine) or enzyme-linked immunosorbent assay (gentamicin). RESULTS: Penicillin G and gentamicin achieved average peak concentrations of 9.8+/-2.2 and 8.5+/-3.1 microg/ml, respectively, in allantoic fluid of noninfected mares. Pharmacokinetic comparisons indicate that penicillin G persists much longer in allantoic fluid than blood, whereas gentamicin exhibited similar profiles in the 2 compartments. Flunixin meglumine was not detected in allantoic fluid. In infected mares, penicillin G achieved a similar peak concentration in allantoic fluid (11.2 microg/ml) whereas peak gentamicin concentration (3.9 microg/ml) appeared to be reduced relative to drug concentrations in noninfected mares. CONCLUSIONS: Microdialysis is a useful technique for continuous in vivo monitoring of drugs in equine allantoic fluid. Our results indicate that penicillin G and gentamicin undergo effective placental transfer in pregnant mares and in 2 mares that transplacental drug transfer may be altered selectively if active placental infection is present. POTENTIAL RELEVANCE: Further studies are needed to evaluate the feasibility of using increased dose intervals for penicillin G and an increased dose rate of gentamicin to effectively combat placental infections in mares.     

Diagnosis and management of abnormal embryonic development characterized by formation of an embryonic vesicle without an embryo in mares

OBJECTIVE: To determine the incidence, ultrasonographic characteristics, and risk factors associated with embryonic development characterized by formation of an embryonic vesicle without an embryo in mares. DESIGN: Prevalence survey. ANIMALS: 159 pregnant mares. PROCEDURES: From 1994 to 1998, mares between 11 and 40 days after ovulation with normal and abnormal embryonic development were examined ultrasonographically, and characteristics of each conceptus were recorded. RESULTS: The incidence of abnormal embryonic development in mares characterized by formation of an embryonic vesicle without an embryo was 7/159 (4.4%) during the 5 breeding seasons. Age and breed of mare or type of semen used did not differ for mares with normal and abnormal embryonic development. The percentage of mares in which the conceptus was undersized during > or = 1 examination was significantly higher for mares with abnormal conceptuses (5/7), compared with mares with normal conceptuses (2/147; 1.4%). The percentage of examinations during which the conceptus was undersized was significantly higher for abnormal conceptuses (12/27; 44.4%), compared with normal conceptuses (4/448; 0.9%). CONCLUSIONS AND CLINICAL RELEVANCE: To diagnose an embryonic vesicle without an embryo, mares should be examined by use of transrectal ultrasonography on day 25 after ovulation. When an embryo cannot be identified at that time, mares should be reexamined at intervals of 1 to 3 days until day 30. Because undersized conceptuses are more likely to be abnormal, development of undersized conceptuses should be monitored closely.     

Relationship between peripartal plasma oxytocin and prostaglandin F(2alpha) metabolite and placental expulsion time in heavy draft mares

The aim of this study was to clarify the relationship between circulating oxytocin (OT) and PGF(2alpha) metabolite (PGFM) in mares at the third stage of labor and placental expulsion time in order to investigate a cause of retained placenta of which the incidence increase in a heavy draft mare. Blood was sampled every 5 min from foaling to expulsion of the placenta in 18 heavy draft mares to evaluate circulating OT and PGFM. The relationships between OT and PGFM concentration and recorded placental expulsion times were investigated. The results were as follows (1) The highest level of OT concentration was observed close to foaling in 15 mares. (2) The OT concentrations close to foaling were variable with a large difference from the lowest concentration, 22.1 pg/ml, to the highest concentration, 209.3 pg/ml. (3) The highest level of PGFM was observed close to foaling in 17 mares. (4) During the 60 min following foaling, the OT concentrations of the mares (n=11) that had a shorter placental expulsion time (i.e., <1 h), were significantly higher than those of the mares (n=7) that had a longer placental expulsion time (i.e., >1 h; P<0.05). Collectively, the OT concentration immediately after foaling is negatively related to the placental expulsion time. Deficiency of OT secretion at foaling have should be considered as one of the causes of retained placenta in heavy draft mares.     

Reduction of Twin Pregnancy in the Mare by Transvaginal Ultrasound-Guided Aspiration

Diagnosis and management of twin pregnancies in the mare are an ongoing challenge in equine reproduction. Early detection of twin and manual crush of one vesicle are the main steps in the management of twins. Few studies were carried out about the use of transvaginal ultrasound-guided aspiration (TUGA) for reduction of twins in the mare. In this study, the efficiency of TUGA for management of twin pregnancies was investigated. Reduction of unicornuate twins between 16 and 25 days of gestation gave a success rate of 70.0% (14 viable foals/20 twin pregnancies); when reduction was performed after day 40 of gestation, all mares (one unicornuate; three bicornuate) lost both. For those cases in which the window for early crush of a twin vesicle has been missed, TUGA can be successfully used to reduce twin pregnancy between 16 and 25 days of gestation.     

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 bilateral double ovulators (77%, P less than .05) than for unilateral double ovulators (60%). The difference between single and bilateral ovulators was not significant. Expected frequencies for none, one or two conceptuses per mare for double ovulators were calculated using the d-11 pregnancy rate for the single ovulators (85%). For unilateral ovulators, but not for bilateral ovulators, observed frequencies of none, one or two conceptuses were different (P less than .05) from expected (observed and expected, respectively, for no conceptuses, 29% and 2%; one conceptus, 21% and 26%; two conceptuses, 50% and 72%). Results did not indicate the existence of an embryo reduction phenomenon before d 11 in bilateral ovulators; each ovum had the same chance (no significant difference) of developing into a d-11 conceptus as an ovum in single ovulators. In unilateral double ovulators, the lower d-11 pregnancy rate per ovum, compared with bilateral ovulators and single ovulators, was attributable to a greater frequency of mares with no embryonic vesicles rather than to a greater frequency of mares with one vesicle.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of flunixin meglumine on endotoxin-induced prostaglandin F2 alpha secretion during early pregnancy in mares

The role of prostaglandin F2 alpha (PGF2 alpha) in embryonic loss following induced endotoxemia was studied in mares that were 21 to 44 days pregnant. Thirteen pregnant mares were treated with a nonsteroidal anti-inflammatory drug, flunixin meglumine, to inhibit the synthesis of PGF2 alpha caused by Salmonella typhimurium endotoxin given IV. Flunixin meglumine was administered either before injection of the endotoxin (group 1, -10 min; n = 7), or after endotoxin injection into the mares (group 2, 1 hour, n = 3; group 3, 2 hours, n = 3); 12 pregnant mares (group 4) were given only S typhimurium endotoxin. In group 4, the secretion of PGF2 alpha, as determined by plasma 15-keto-13,14-dihydro-PGF2 alpha concentrations, was biphasic, initially peaking at 30 minutes followed by a second, larger peak approximately 105 minutes after the endotoxin was given IV. When flunixin meglumine was administered at -10 minutes, synthesis of PGF2 alpha was inhibited for several hours, after administration of flunixin meglumine at 1 hour, the second secretory surge of PGF2 alpha was blocked, and administration of the drug at 2 hours did not substantially modify the secretion of PGF2 alpha. Plasma progesterone concentrations were unchanged after endotoxin injections were given in group 1. In group 2, progesterone values decreased less than 2 ng/ml and remained low for several days. In group 3 and group 4, progesterone concentrations decreased to values less than 0.5 ng/ml by 48 hours after endotoxin injections were given.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of flunixin and flunixin plus prednisone on the gastrointestinal tract of dogs

Flunixin meglumine has been reported to induce gastrointestinal lesions in dogs when administered at therapeutic dosages. We administered flunixin meglumine to dogs daily for 10 days to assess the effect of this drug on the gastrointestinal tract. We also evaluated the possibility of corticosteroid potentiation of gastrointestinal toxicosis by concurrent administration of prednisone to 1 group of dogs. Dogs were monitored for gastrointestinal toxicosis by means of serial endoscopic evaluation, measurement of fecal occult blood, PCV, and total solid concentration, and by physical examination. There were 3 treatment groups of 5 dogs each. Group-1 dogs were given 2.2 mg of flunixin meglumine/kg daily, in 2 divided doses IM; group-2 dogs were given 4.4 mg of flunixin meglumine/kg daily, in 2 divided doses IM; and group-3 dogs were given 2.2 mg of flunixin meglumine/kg daily, in 2 divided doses IM plus 1.1 mg of prednisone/kg/d orally, in 2 divided doses. A fourth group of 5 dogs served as a control group. Endoscopically visible gastric mucosal lesions developed in all treated dogs within 4 days of initiating treatment. Lesions first developed in the gastric pylorus and antrum and lesions at these sites were more severe than those observed elsewhere. Dogs treated with flunixin meglumine plus prednisone developed the earliest and most severe lesions; lesion scores in group-2 dogs were higher than those in group-1 dogs. All dogs treated had occult blood in their feces by day 5 and its presence appeared to correlate more closely with endoscopic findings than did physical examination findings or changes in values for PCV or total solids.(ABSTRACT TRUNCATED AT 250 WORDS)     

Maternal dexamethasone treatment in late gestation induces precocious fetal maturation and delivery in healthy Thoroughbred mares

Reasons for performing study: The foal requires an active hypothalamo‐pituitary‐adrenal (HPA) axis for organ maturation and post natal survival. Prenatal administration of synthetic glucocorticoids may provide an effective method for inducing fetal maturation safely in the mare. Objectives: To determine whether dexamethasone administered to late pregnant mares: 1) will induce fetal maturation and precocious delivery; 2) is safe to use and 3) to identify endocrine responses in the mare and foal. Methods: Pregnant Thoroughbred mares received either 100 mg dexamethasone i.m. (treated n = 5) or 50 ml saline i.m. (control n = 5) at 315, 316 and 317 days of gestation. Plasma progestagens, cortisol and prostaglandin F_2α metabolite (PGFM) concentrations were measured before and after treatment. The foals were weighed, the crown‐rump length (CRL) measured and an adrenal stimulation test performed on Day 1. Results: Dexamethasone significantly (P<0.01) reduced gestation length in treated mares without apparent adverse effects. Plasma progestagens increased (P<0.05), and cortisol and PGFM (P<0.05) decreased, following dexamethasone treatment compared with control mares. Foals were clinically mature but those from dexamethasone treated mares had reduced (P<0.05) CRL, but not bodyweights, compared with controls. Their cortisol concentrations increased following exogenous adrenocorticotrophic hormone stimulation but 2 foals from dexamethasone treated mares showed evidence of adrenal suppression. Conclusions: Dexamethasone stimulates precocious fetal maturation and delivery in healthy late pregnant mares. However, fetal HPA activity may be suppressed. Potential relevance: Dexamethasone treatment could be used to improve foal viability in mares at risk of preterm delivery. The endocrine effects of such a therapy must be evaluated before clinical intervention with glucocorticoids can be recommended.     

Effect of flunixin meglumine on Escherichia coli heat-stable enterotoxin-induced diarrhea in calves

In a study to evaluate the effect of flunixin meglumine on secretory diarrhea, 11 calves were assigned to 3 groups: group 1 (n = 3) served as controls, group-2 calves (n = 4) were given 2.2 mg of flunixin meglumine/kg, IM at 7 AM and 3 PM, and group-3 calves (n = 4) were given 2.2 mg of flunixin meglumine/kg, IM at 7 AM, 11 AM, and 3 PM. All calves were given approximately 200 micrograms of heat-stable Escherichia coli enterotoxin (STa) orally at 8 AM. Mean cumulative fecal output for groups 1, 2, and 3 was 1,331.0 +/- 317.2 g, 1,544.3 +/- 154.4 g, and 785.5 +/- 276.5 g, respectively. There was a significant (P less than 0.05) reduction in mean fecal output in group-3 calves, compared with that in groups 1 and 2. Calves in group 2 tended to have a delay, but not a reduction, in their fecal output. At 12 hours, hemoconcentration was significantly (P less than 0.05) greater in group-1 calves than in group-2 or group-3 calves.     

Pharmacokinetics of metronidazole and its concentration in body fluids and endometrial tissues of mares.

Serum concentrations of metronidazole were determined in 6 healthy adult mares after a single IV injection of metronidazole (15 mg/kg of body weight). The mean elimination rate (K) was 0.23 h-1, and the mean elimination half-life (t1/2) was 3.1 hours. The apparent volume of distribution at steady state was 0.69 L/kg, and the clearance was 168 ml/h/kg. Each mare was then given a loading dose (15 mg/kg) of metronidazole at time 0, followed by 4 maintenance doses (7.5 mg/kg, q 6 h) by nasogastric tube. Metronidazole concentrations were measured in serial samples of serum, synovia, peritoneal fluid, and urine. Metronidazole concentrations in CSF and endometrial tissues were measured after the fourth maintenance dose. The highest mean concentration in serum was 13.9 +/- 2.18 micrograms/ml at 40 minutes after the loading dose (time 0). The highest mean synovial and peritoneal fluid concentrations were 8.9 +/- 1.31 micrograms/ml and 12.8 +/- 3.21 micrograms/ml, respectively, 2 hours after the loading dose. The lowest mean trough concentration in urine was 32 micrograms/ml. Mean concentration of metronidazole in CSF was 4.3 +/- 2.51 micrograms/ml and the mean concentration in endometrial tissues was 0.9 +/- 0.48 micrograms/g at 3 hours after the fourth maintenance dose. Two mares hospitalized for treatment of bacterial pleuropneumonia were given metronidazole (15.0 mg/kg, PO, initially then 7.5 mg/kg, PO, q 6 h), while concurrently receiving gentamicin, potassium penicillin, and flunixin meglumine IV. Metronidazole pharmacokinetics and serum concentrations in the sick mares were similar to those obtained in the healthy mares.     

Clinical and pathological effects of flunixin meglumine administration to neonatal foals.

The effects of daily intravenous administration of flunixin meglumine at dosages of 0.55, 1.1, 2.2 and 6.6 mg/kg for five days were examined in neonatal foals. Six two day old foals were used to evaluate the effect of each dosage. Foals were examined every day and blood samples collected on days 1, 3 and 6. All foals were euthanized after six days, necropsied and examined for lesions. The major clinical abnormality was diarrhea, but the incidence was not related to the dosage of flunixin meglumine administered. The foals receiving 6.6 mg/kg of flunixin meglumine had significantly more gastrointestinal ulceration and greater cecal pathology and cecal petechiation scores than those foals treated with saline. The foals in the 6.6 mg/kg treatment group had a greater loss of total protein during the study, but the difference was not significant. There were no statistically significant blood cellular or biochemical alterations associated with the administration of flunixin meglumine. There were no significant clinicopathological differences between healthy foals treated with the recommended dosage of flunixin meglumine and those treated with physiological saline.     

Effects of adrenocorticotropic hormone and flunixin meglumine on pregnancy retention in beef cows

Pregnancy loss in beef cattle after d 28 of gestation is variable, but it has been reported to be as great as 14% and has been related to transportation or handling stress. The primary objective of this study was to determine whether activation of the hypophyseal-adrenal axis with ACTH would mimic a stressful response and cause pregnancy loss in beef cattle. A secondary objective was to determine if a single injection of the PG synthesis inhibitor flunixin meglumine would attenuate the stress response and suppress serum PGF(2α) concentrations to prevent pregnancy loss. Forty nonlactating beef cows that were 34 ± 0.33 d pregnant were used for this study. In a 2 × 3 factorial arrangement, cows were randomly assigned to receive ACTH [0 or 0.5 IU/kg of BW, intramuscularly (i.m.)] at 0 and 2 h of the study and flunixin meglumine (0, 1.1, or 2.2 mg/kg of BW, i.m.) at 0 h. Blood samples were collected from all cows at 0 h and every 30 min for 4 h to measure serum cortisol and PGF(2α) metabolite (PGFM) concentrations. Rectal temperature was collected for each cow at 0, 120, and 240 min. Pregnancy exams were conducted 31 and 58 d after treatment by transrectal ultrasonography, and the presence of a fetal heartbeat was used as an indicator of fetal viability. Serum cortisol concentration was affected (P < 0.01) by ACTH, time, and the interaction of ACTH × time, but not by flunixin meglumine (P ≥ 0.14) or any other interactions. Cortisol concentrations increased (P < 0.01) in the serum of ACTH-treated cows immediately after ACTH treatment and remained increased (P < 0.01) throughout the 4-h sampling period. Serum PGFM concentration was not affected by ACTH (P = 0.97) or by any interactions (P > 0.35) with ACTH, but was affected (P < 0.01) by flunixin meglumine, time, and the interaction of flunixin meglumine × time. Regardless of dosage (1.1 or 2.2 mg/kg of BW), flunixin meglumine decreased (P < 0.01) serum PGFM concentrations in both ACTH-treated and control cows for the duration of the study. Although ACTH treatment induced a prolonged increase in serum cortisol concentration, none of the cows used in this study lost a pregnancy. In conclusion, the activation of the hypophyseal-adrenal axis with ACTH increased serum cortisol concentrations but did not increase serum concentrations of PGFM or cause pregnancy loss during early gestation in cows. Flunixin meglumine treatment suppressed serum PGFM concentrations in control and ACTH-treated cows.     

Relationship between estrous behavior in pregnant mares and the presence of a female conceptus

Unsolicited reports of estrous behavior in mares thought to be pregnant were received from owners or caretakers of Arabian mares. Estrous behavior was confirmed and mares were examined for pregnancy. Gender of the conceptus was determined at foaling in 11 mares in which estrous behavior was confirmed while an apparently viable, ultrasonically normal-appearing conceptus was present. In 9 mares in which the day of ovulation was known (Day 0), the estrous behavior occurred on Day 12, 13 or 14 (5 mares), Day 18 or 20 (2 mares), Day 40 (1 mare) and Day 60 (1 mare). In another study, 55 pony mares were observed for estrous behavior every 3 days for 20 minutes during Days 11 to 40. Estrous behavior was observed in 1 mare (2%) on Day 24. Combined for the 2 studies, the incidence of a female conceptus (12/12) was greater (P<0.01) than the incidence of a male conceptus (0/12) in mares that exhibited estrous behavior.     

Hydrocephalus in an American Miniature Horse Foal: A Case Report and Review

A 6-year-old multiparous American Miniature Horse mare was presented at 324 days of gestation for evaluation of vaginal bleeding. A manual obstetrical examination was performed and the cervix was found to be open with the fetus in transverse position. The mare was sedated and placed under general anesthesia. Attempts made to mutate the fetus were unsuccessful. A cesarean section was performed and the foal was noted to be in transverse position with marked enlargement of the cranium. The abdominal incision was closed in a routine manner, and the mare recovered from anesthesia without incident. Postoperative treatment consisted of flunixin meglumine, gentamicin sulfate, potassium penicillin, oxytocin, and intravenous fluid therapy. The mare was discharged to the owners 4 days after surgery. A lateral radiograph of the fetus was obtained and confirmed hydrocephalus. On necropsy, it was found that the calvarium measured 59 cm in circumference and was dome-shaped, the neuropil and leptomininges measured only 1 to 2 mm in thickness, the brainstem and cerebellum were reduced in size, and there was moderate distension of the third ventricle with stenosis of the mesencephalic aqueduct. Inflammatory and neoplastic causes of mesencephalic aqueductal obstruction were ruled out by histopatholgy. This represents a classic case of hydrocephalus because of stenosis of the mesencephalic aqueduct, which to our knowledge has not been previously reported in a miniature foal. Further investigation is warranted into the pathogenesis of mesencephalic aqueduct stenosis in foals, which has now been reported in several equine breeds.     

The effect of uterine torsion on mare and foal survival: a retrospective study, 1985--2005

REASONS FOR PERFORMING STUDY: Anecdotal speculation suggests that prognosis for survival of mares and foals following correction of uterine torsion has improved over the past 30 years. OBJECTIVES: To determine statistically the outcome of uterine torsion according to duration of clinical signs, stage of gestation, parity, physical examination findings, method of correction, prognosis for survival and reproductive health of the mare, and prospects for the foal within the neonatal period. METHODS: This retrospective study combined cases from 4 equine referral hospitals. RESULTS: The stage of gestation at which uterine torsion occurred was a risk factor for survival of mare and foal. Overall mare survival was 53/63 (84%); when uterine torsion occurred at < 320 days gestation, 36/37 (97%) of mares survived compared to 17/26 (65%) survival rate when uterine torsion occurred at > or = 320 days gestation. Overall foal survival was 54% (29/54). When uterine torsion occurred at < 320 days gestation, 21/29 (72%) foals survived compared to 8/25 (32%) when uterine torsion occurred at > or = 320 days gestation. Thirty mares were discharged from the hospital carrying a viable fetus following uterine torsion correction and 25/30 (83%) of these mares delivered live foals that survived beyond the neonatal period. CONCLUSIONS: Prognosis for survival for mares and foals following uterine torsion is good and improves if torsion occurs < 320 days compared to > or = 320 days gestation. CLINICAL RELEVANCE: Gestational timing of uterine torsion should be considered when advising clients about the prognosis for survival of the mare and foal. The prognosis for a mare delivering a live foal is good if the mare is discharged from the hospital following uterine torsion correction with a viable fetus.     

Elective cesarean section in mares: eight cases (1980-1989)

From 1980 to 1989, 8 cesarean sections were performed on an elective basis in 5 mares. Four mares had partially obstructed pelvic canals; 2 of these mares had previously lost foals because of dystocia. Cervical adhesions that might obstruct passage of the fetus through the pelvic canal was suspected in the fifth mare. Cesarean section was performed prior to mares entering the first stage of labor. Readiness for birth was estimated by development of the mare's mammary gland and the presence of colostrum in the udder. A ventral midline celiotomy provided excellent exposure and healed without complications in all instances. Eight viable foals were produced. One foal developed bacterial pneumonia and septicemia after surgery and died. Follow-up evaluation of the 7 foals discharged from the hospital failed to reveal complications associated with elective cesarean section. All mares survived the procedure. Fetal membranes were retained for up to 72 hours following surgery; however, systemic complications secondary to retained placenta did not develop. Three mares were bred subsequent to elective cesarean sections, with each mare conceiving the year following surgery. Three foals were produced by 1 mare and 2 foals have been produced by another mare by elective cesarean sections.     

Reproductive performance of Thoroughbred mares on six commercial stud farms

The records of 1630 mare years from 6 Thoroughbred stud farms in south eastern Australia were analysed for the years 1981 to 1986. Overall pregnancy and foaling rates were 83.9% and 69.3%, respectively. When calculated per served oestrous cycle, pregnancy and foaling rates were 54.7% and 43.1%, respectively. Pregnancy and foaling rates were higher (P < 0.001) for mares 3 to 10 years of age than for older mares. There was no difference in the pregnancy rates of maiden, barren and foaling mares. The foaling rate was significantly higher (P < 0.001) in mares that became pregnant during the first served oestrous cycle (77.8%) than in mares that needed two served oestrous cycles to become pregnant (65.4%). Of all diagnosed pregnancies, 19.5% were not completed. Pregnancy loss was lower (P < 0.05) in maiden (12.4%) than in barren (19.7%) or foaling (20.9%) mares. Twins were diagnosed in 7.8% of all pregnancies. If one conceptus was lost without external interference, 84.1% of pregnancies went to term. If one conceptus was manually crushed, 55.9% of pregnancies were maintained. If prostaglandin was used to terminate twin pregnancies, 60% of mares so treated produced foals the following year.