Mesenteric tears of the descending (small) colon as a postpartum complication in two mares.

Segmental ischemic necrosis of the descending colon associated with discrete tears of the mesocolon were diagnosed in 2 mares following foaling. After foaling, both mares had a slow onset of signs of abdominal pain and gradual deterioration of clinical status. Increases in peritoneal fluid total protein concentration and WBC count and a palpable impaction of the descending colon on examination per rectum were useful diagnostic aids. Surgical intervention was successful in one mare, but not in the other.     

Ventrocaudal cystorrhaphy without urethral sphincterotomy in two broodmares

Two broodmares were diagnosed with rupture of the urinary bladder. One mare revealed abnormalities post partum and the other associated with ante partum uterine torsion. The clinical symptoms included mild abdominal pain, anorexia, decreased urinary volume and increased peritoneal fluid. In one mare, based on the creatinine level of the peritoneal fluid and serum biochemical abnormalities, uroperitoneum was diagnosed. In the other mare, the bladder rupture was found during the celiotomy for surgical repair of uterine torsion that was diagnosed upon rectal examination. Surgery was performed without a urethral sphincterotomy. The vaginal floor was incised in a standing position and the bladder was diverted into the vagina in order to suture the tears located in the ventrocaudal aspect of the bladder. Both mares survived after treatment for uraemia. Bladder rupture, although uncommon, may affect peripartum mares. Approach to the ruptured bladder without urethral sphincterotomy in a standing position should be considered as a choice for surgical repair.     

Equine granulosa cell tumors.

Unilateral ovariectomy was performed on 3 mares affected with granulosa cell tumors. Tumor fluid in each mare was found to contain estrogen, testosterone, and progesterone. In 2 mares, preoperative blood plasma concentrations of these hormones were comparable to those of a series of clinically normal mares. The other mare, which had a history of aggressive, masculine behavior, had higher testosterone content in the tumor fluid and in the preoperative blood sample. After surgical removal of the tumors, each mare developed follicles and ovulated with the remaining ovary. Each was eventually bred and 2 conceived. The probability of metastasis of these tumors in mares appears uncertain. Data from other species suggests a guarded long-term prognosis may be justified.     

Ovariohysterectomy in Six Mares

Six mares had ovariohysterectomy performed for chronic pyometra associated with cervical abnormalities, uterine neoplasia, or removal of a macerated fetus. Ovariohysterectomy was performed through a ventral midline incision with access to the ovarian and uterine vessels aided by traction on the uterus and retraction of abdominal viscera. Abdominal pain, the most common complication after surgery, occurred in four mares but resolved within 36 hours. Peritonitis occurred in two mares; one mare was subsequently euthanatized. Other complications that resolved with treatment included infection of the uterine stump (two mares), abdominal hemorrhage (one mare), diarrhea (one mare), and incisional infection (one mare). Complications after surgery can be reduced by removing as much of the uterus as possible, minimizing peritoneal contamination with uterine contents, and providing a secure closure of the caudal reproductive tract.     

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 266 mares without the Aa antigen, 3 of 61 (5%) mares without the Ca blood group antigen produced anti-Aa antibodies and 43 of 205 (21%) with the Ca blood group antigen produced anti-Aa antibodies. These 2 groups of mares were significantly (P = 0.006) different; Ca-negative mares were less likely to produce antibodies to Aa than were mares with the Ca blood group antigen. This observation was consistent with a hypothesis of antibody-mediated immunosuppression of immune response to the Aa blood group antigen by antibodies to the Ca blood group antigen, ie, when a mare is exposed to her foal's RBC and already has antibodies to the Ca blood group antigen on the foal's RBC, then she is less likely to initiate an immune response to the Aa blood group antigen also on the foal's RBC.     

Effect of surgical manipulation, placental fluid, and flunixin meglumine on fetal viability and prostaglandin F2 alpha release in the gravid uterus of mares

Twenty-one pregnant mares with single or twin conceptuses between 41 and 65 days of gestational age were allotted to 5 treatment groups. A ventral median celiotomy was performed in all mares. In group-1 mares (3 mares, single conceptus), the uterus and fetus were palpated for 5 minutes. In group-2 mares (3 mares, single conceptus, flunixin meglumine), 250 ml of sterile placental fluid was injected into the nongravid uterine horn. In group-3 mares (4 mares, unicornuate twin conceptuses), group-4 mares (3 mares, unicornuate twin conceptuses, flunixin meglumine), and group-5 mares (8 mares, bicornuate twin conceptuses, flunixin meglumine), 1 conceptus was removed from the uterus via hysterotomy. All mares received progesterone prophylactically until day 100 of gestation or until the fetus died. The 3 mares in group 1 delivered clinically normal, live foals. The mean prostaglandin F2 alpha metabolite (PGFM) plasma concentration peaked at 180 +/- 5.2 pg/ml during uterine manipulation and fetal palpation, then declined to baseline by 1 hour. Free placental fluid (group 2) undermined the chorioallantois ventrally and resulted in fetal death within 3 hours after surgery. The mean PGFM plasma concentration peaked at 39 +/- 4 pg/ml following injection of placental fluid. None of the remaining fetuses in the 7 mares with unicornuate twin conceptuses (groups 3 and 4) survived. Five mares with unicornuate twin conceptuses (group 5) delivered single viable foals. In another mare in group 5, the fetus was alive 4 days after surgery, when the mare was euthanatized for a fractured femur.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hydrallantois in the Mare – A Report of Five Cases

Hydrallantois in the mare is a very rare condition, and clinical reports help to gather information to elucidate its pathogenesis, treatment options and prognosis. Five different cases of hydrallantois in the mare are reported in this article, all with the involvement of placentitis. The five mares were presented because of acute distention of the abdomen, dyspnoea, stiff gait and a lack of appetite. After a gradual release of the excessive amount of allantoic fluid, an abortion was induced in all five mares. The foals were either born dead or euthanized. The mares recovered quickly. One mare conceived within the same season, one remained barren despite several cycles of natural breeding, and no data were available on the other three mares. In this series, the condition is reported for the first time in two Shetland ponies, both pregnant with foals sharing a close genetic background. In both cases, the condition led to hyperlipidemia. The condition as it occurs in nulliparous mares is also discussed. Finally, the possible involvement of placentitis in the pathogenesis is emphasized.     

Persistent breeding-induced endometritis after hysteroscopic insemination in the mare

Low-dose insemination has been proposed to reduce persistent breeding-induced endometritis (PBIE) in mares with delayed uterine clearance (DUC). Others proposed that hysteroscopic insemination induces an exaggerated inflammatory response and should be avoided in DUC mares. The objectives here were to evaluate presence and severity of PBIE in normal and DUC mares after hysteroscopic insemination with fresh semen, and to determine if hysteroscopy could be used in DUC mares without inducing excessive inflammation. Reproductively normal (n = 4) and DUC (n = 5) mares received four treatments in random order: uterine body insemination (UB, 1 × 10(9) spermatozoa, 20 ml), hysteroscopic insemination (HYST, 5 × 10(6) spermatozoa, 0.5 ml), sham hysteroscopic insemination (SHAM, semen extender, 0.5 ml) and hysteroscopic infusion of seminal plasma (SP, 0.5 ml). Significantly more DUC (50%) mares than normal (14%) mares accumulated intrauterine fluid 24 h post-treatment. The difference in fluid accumulation between DUC (40%) mares and normal (7%) mares was also significant 48 h post-treatment. Fluid scores were not significantly different between treatments in normal mares. However, treatments HYST and SHAM resulted in significantly higher fluid scores 24 h but not 48 h post-treatment in DUC mares. There was no effect of treatment or mare group on the percentage and total number of neutrophils in uterine fluid 48 h post-treatment. Percentage of neutrophils was correlated with duration of hysteroscopy in normal mares, with procedures lasting ≥ 9 min associated with PBIE. There was no effect of mare group, treatment or duration of hysteroscopy on pregnancy rate. Hysteroscopy induces a transient inflammation that is not more severe than that after conventional artificial insemination, suggesting no contraindication to its use in DUC mares.     

Melengestrol acetate as a tool for inducing early ovulation in transitional mares

The efficacy of melengestrol acetate (MGA) to shorten the vernal transition of mares by synchronising and accelerating the first ovulation of the year after 60 days of phototherapy was determined by ultrasonographic monitoring. Sixteen mares in late transition were fed two doses of MGA (150 mg/mare/day and 100 mg/mare/day, respectively) for 10 days. A luteolytic dose of prostaglandin was administered to each mare one day after the end of MGA treatment. The presence and duration of oestrus, follicular growth, uterine oedema and presence of ovulation were monitored by ultrasonography and the cervical tone was evaluated by rectal palpation. Ovulation was detected in 87.5% of the mares treated with 150 mg MGA/mare/day for 10 days, and in 62.5% of the mares receiving 100 mg MGA/mare/day for 10 days. This was statistically different (P = 0.03) from the untreated control mares having an ovulation rate of 20%. Mares that received 150 mg MGA/day for 10 days had a mean treatment to ovulation interval of 13.1 +/- 5.97 days after the end of treatment, while mares that received 100 mg MGA/day for 10 days had a mean of 25.6 +/- 10.50 days (P = 0.01) to ovulation. These results suggest that MGA can be used for synchronising and hastening the first ovulation of the year in mares.     

Hydrallantois in two mares

This report describes two mares with hydrallantois. One mare spontaneously entered labor, while the other had labor induced. Uterine inertia necessitated that delivery be assisted in both mares. After delivery, each mare went into hypovolemic shock. One mare survived and the other had to be euthanatized due to rupture of the ventral abdominal musculature with inguinal herniation. The occurrence, diagnosis, treatment and outcome of hydrallantois in the mare are discussed.     

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.     

Body fluid and endometrial concentrations of ketoconazole in mares after intravenous injection or repeated gavage

After single oral administration of ketoconazole (30 mg/kg bodyweight [bwt]) in 50 ml of corn syrup to a healthy mare, the drug was not detected in serum. Ketoconazole in 0.2 N HC1 was administered intragastrically to six healthy adult horses in five consecutive doses of 30 mg/kg bwt at 12 h intervals. Ketoconazole concentrations were measured in serum, synovial fluid, peritoneal fluid, cerebrospinal fluid (CSF), urine and endometrium. Mean peak serum ketoconazole concentration was 3.76 micrograms/ml at 1.5 to 2 h after intragastric administration. Mean peak synovial concentration was 0.87 micrograms/ml 3 h after the fifth dose. Similarly, mean peritoneal concentration peaked 3 h after the fifth dose at 1.62 micrograms/ml. Mean endometrial concentrations peaked at 2.73 micrograms/ml 2 h after the fifth dose. Ketoconazole was detected in the CSF of only one of the six mares at a concentration of 0.28 micrograms/ml 3 h after the fifth dose. The highest measured concentration of ketoconazole in urine was 6.15 micrograms/ml 2 h after the fifth dose. A single intravenous injection of ketoconazole (10 mg/kg bwt) was given to one of the six mares; the overall elimination rate constant was estimated at 0.22/h and bioavailability after oral administration was 23 per cent.     

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.     

Pharmacokinetics and body fluid and endometrial concentrations of cefoxitin in mares

Four healthy adult mares were each given a single injection of sodium cefoxitin (20 mg/kg of body weight, IV), and serum cefoxitin concentrations were measured serially during a 6-hour period. The mean elimination rate constant was 1.08/hour and the elimination half-life was 0.82 hour. The apparent volume of distribution (at steady state) and the clearance of the drug were estimated at 0.12 L/kg and 259 ml/hr/kg, respectively. Each mare and 2 additional mares were then given 4 consecutive IM injections of sodium cefoxitin (400 mg/ml) at a dosage of 20 mg/kg. Cefoxitin concentrations in serum, synovial fluid, peritoneal fluid, CSF, urine, and endometrium were measured serially. After IM administration, the highest mean serum concentration was 23.1 micrograms/ml 30 minutes after the 2nd injection. The highest mean synovial concentration was 11.4 micrograms/ml 1 hour after the 4th injection. The highest mean peritoneal concentration was 10.4 micrograms/ml 2 hours after the 4th injection. The highest mean endometrial concentration was 4.5 micrograms/g 4 hours after the 4th injection. Mean urine concentrations reached 11,645 micrograms/ml. Cefoxitin did not readily penetrate the CSF. Bioavailability of cefoxitin given IM was 65% to 89% (mean +/- SEM = 77% +/- 5.9%). One of the 6 mares developed acute laminitis during the IM experiment.     

Endometritis in the mare caused by a Coryneform organism--a case report and experimental studies

Persistent purulent endometritis in a mare was attributed to an unclassified species of Corynebacterium. Following intrauterine infusions of 20% betadine for 5 days the purulent vulval discharge ceased and the mare appeared clinically normal. Based on histological examination of endometrial biopsy samples, the severe acute inflammatory reaction had largely resolved 2 days after therapy. Three maiden mares considered resistant to bacterial endometritis received single intrauterine inoculations of 1.8 X 10(9) colony-forming units of the Corynebacterium species. The uterine response was followed by vaginal speculum examinations, uterine cultures and cytology, and endometrial histology. After an acute inflammatory reaction, each mare had recovered completely within 2 weeks. Most rapid recovery occurred in the mare in estrus at the time of inoculation. Subsequent secondary infections were detected in two mares. The uncertainty of correlations between results obtained by various diagnostic techniques emphasized the problems associated with each. This report illustrates the concept that endometritis in individual mares may relate more to as yet unidentified "mare factors" controlling uterine defense than to primary invasion by bacteria.     

Retrospective study on the incidence of postinsemination uterine fluid in mares inseminated with frozen/thawed semen

Uterine fluid accumulation has been reported after insemination or natural breeding of mares. This retrospective study examined the factors affecting the incidence of uterine fluid after insemination of frozen semen. Specifically, this study determined the association between mare age, reproductive status, fluid accumulation, and pregnancy rates in mares. Records were available from 283 warmblood mares throughout 496 cycles. Mares were divided into maiden, foaling, and barren and age groups of 3 to 9, 10 to 16, and more than 16 years. Mares were inseminated only once with frozen semen within 4 to 8 hours before or after ovulation. Ultrasound examinations were performed 12 to 18 hours after insemination. A depth of at least 20 mm of fluid was considered significant. Mares with less than 20 mm were treated with oxytocin, and those with more than 20mm of fluid were given oxytocin and uterine lavage. Pregnancy determination was performed at 14 to 16 and 30 to 50 days after ovulation. Fluid level of more than 20 mm was recorded in 25% of the cycles. Barren mares and aged mares (10-16 and > 16 years) had a higher incidence of uterine fluid accumulations. Per-cycle pregnancy rate was lower (45%) in mares with uterine fluid than in mares without uterine fluid (51%). This difference was primarily due to the reduction in fertility of mares who were older than 16 years and retained fluid after insemination. Apparently, oxytocin and lavage treatments provided acceptable fertility in the other groups of mares that had uterine fluid.

Introduction

Use of equine frozen semen is accepted by the majority of horse registries. According to several field studies,[1, 2, 3, 4 and 5] insemination of frozen semen has resulted in acceptable pregnancy rates. Postbreeding fluid accumulation is a physiologic inflammation that clears the uterus of foreign material such as excess spermatozoa, seminal plasma, bacteria, and extenders. [6, 7, 8, 9 and 10] Uterine fluid can be easily diagnosed with ultrasonography. [10, 11 and 12] Persistent postbreeding uterine fluid has been associated with a decrease in fertility after natural mating or artificial insemination (AI) of fresh semen. [11, 12 and 13] Predisposing factors to persistent fluid accumulations are reduced myometrial contractions, poor lymphatic drainage, large overstretched uterus, and cervical incompetence. [7, 14 and 15] Normal mares are able to expel uterine fluid quickly after inseminations, whereas susceptible mares accumulate fluid in their uterine lumen for more than 12 hours after breeding or insemination. [10]It is commonly stated that insemination with frozen semen leads to greater post-AI fluid accumulation than insemination with fresh or cooled semen or after natural mating. Apparently, there is only 1 controlled study on this comparison.[7] The authors reported that infusion of frozen semen resulted in a greater inflammatory response than natural breeding. In a field study, [16] 16% of mares naturally mated had persistent postbreeding fluid accumulations compared with a 30% rate reported for mares inseminated with frozen semen. [1 and 2] More recently, Watson et al. [17] reported a postbreeding fluid accumulation rate of 16%, which is identical to that reported for natural mating. [16] It is difficult to compare studies because details of mare selection and insemination or breeding frequencies are not always reported. Obviously, a higher proportion of barren and aged mares in a study would increase the incidence of postbreeding fluid accumulation. [1 and 2]The study presented herein was a retrospective study designed to determine the incidence of postbreeding fluid accumulation in a large number of mares inseminated with frozen semen. Associations were determined between mare age, reproductive status and fluid accumulation, and pregnancy rate in mares with and without uterine fluid accumulation.

Materials and methods

Mares

Records were available from 283 warmblood mares inseminated with frozen semen at the Cristella Veterinary Clinic in Italy during 1998 to 2001. Mares ranging in age from 3 to 20 years were inseminated with semen that was frozen in 10 centers and was from 34 stallions. The broodmare population was subdivided into 3 reproductive groups: 89 maiden mares (mean age, 7.2 years), 106 foaling mares (mean age, 9.4 years), and 87 barren mares (mean age, 11.9 years). Maiden mares older than 7 years were selected with biopsy scores of 1 or 2 only. Barren mares were open for no more than 2 consecutive seasons and had negative cytology and bacteriology scores. Age groups were divided as follows: 3 to 9 years (n = 132), 10 to 16 years (n = 137) and older than 16 years (n = 14). Data from 496 cycles were used. Distribution of the estrous cycles was 172, 157, and 167 in the maiden, foaling, and barren groups, respectively; and 224, 244, and 28 in the youngest, intermediate, and oldest groups, respectively.

Mare reproductive management and artificial insemination protocol

During estrus, all mares underwent a daily ultrasound examination with a 5-mHz transrectal probe (SA 600 Vet; Medison Inc., Seoul, South Korea) until 1 or more 35-mm ovarian follicles were detected. Ovulation was then induced by the intravenous administration of 2000 IU of human chorionic gonadotropin (hCG). Ultrasound examination was performed 12 hours after hCG treatment and then every 4 to 8 hours until ovulation occurred. Mares were inseminated only once within a period of 4 to 8 hours before or after ovulation. The semen used was thawed according to the distribution center's instructions and had the following minimum post-thaw quality requirements: not less than 200 × 10⁶ progressively motile spermatozoa per dose and a minimum of 30% progressive spermatozoal motility. Foaling mares were not inseminated at their first postpartum (“foal heat”) estrous period, because pregnancy rates are recognized to be lower than during the subsequent estrous periods.[18] During the first postpartum estrus, ovarian ultrasound scan examinations were performed every 2 to 3 days until an ovulation was detected. A prostaglandin F₂α injection was given 5 days later to short-cycle the mare.

Postinsemination monitoring

An ultrasound examination of the reproductive tract was performed 12 to 18 hours after insemination to detect any intrauterine fluid accumulation. The presence and depth of intrauterine fluid was recorded. Twenty millimeters or more of grade II or III intrauterine fluid[19] was recorded as a significant amount of fluid. Mares with less than 20 mm of fluid were treated with an intravenous injection of 20 IU oxytocin. For mares with more than 20 mm of fluid, oxytocin was administered, and the uterus was flushed daily with buffered saline solution: 1-L aliquots were infused and recovered until the recovered fluid was clear. In these mares, oxytocin treatment was repeated up to 3 times daily. Post insemination treatments were performed for no more than 4 days after ovulation had occurred.Pregnancy diagnosis was performed with ultrasound at 14 to 16 days after ovulation. Scans were then repeated at 30 and 50 days of gestation to confirm the presence in the uterus of an apparently healthy developing conceptus.

Statistical analysis

χ² Analysis was used to determine the effect of reproductive status and age on the incidence of fluid accumulation. In addition, the influence of persistent uterine fluid accumulation on pregnancy rates per cycle was determined for each reproductive class and age by using χ² analysis.

Results

The per-cycle pregnancy rate at 14-16 days after ovulation was 49.3% (245/496 cycles). By the end of the season, 245 of 283 mares (86.5%) were confirmed pregnant. Fluid level of at least 20 mm (grade II or III) was recorded in 126 of the 496 cycles (25.4%). Barren mares had a higher (P < .05) incidence of postbreeding fluid accumulation (64/167; 38.3%) than maiden (34/172; 19.7%) and foaling (28/157, 17.8%; Table 1) mares. The incidence of fluid accumulation was also higher in mares older than 16 years (19/28; 67.8%) than those aged 10 to 16 years (69/244; 28.2%) and 3 to 9 years (38/224; 17%). The incidence of uterine fluid was also higher (P < .05) for mares aged 10 to 16 years than those aged 3 to 9 years (Table 2). Overall, the per-cycle pregnancy rate was lower (P < .05) for mares with post-AI fluid accumulations than for those with no uterine fluid or only a small quantity of fluid (57/126, 41.9% vs 188/360, 56.2%). Pregnancy rates were similar (P > .05) for mares with or without uterine fluid when comparisons were made within maiden and barren mare groups. However, more foaling mares became pregnant when no fluid was detected after insemination. Pregnancy rate for this group (68.1%) was higher than that for maiden (44.2%) and barren (44.6%) mares (Table 3). Older mares with uterine fluid accumulations had a lower per-cycle pregnancy rate (36.8%) than mares in the same group but without fluid. Surprisingly, if no fluid was detected, the highest pregnancy rates were in mares older than 16 years ( Table 4).     

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.     

Pathology of maternal genital tract, placenta, and fetus in equine viral arteritis

Six pregnant mares were given equine viral arteritis virus intravenously. Tissues from genital tracts, placentae, and fetuses were examined by light and electron microscopy to study the mechanism of abortion. Four mares which died with acute disease had diffuse vacuolation of endometrial epithelium and systemic necrotizing vasculitis. Two of these mares had dead fetuses and two had live fetuses; virus was isolated from tissues of one live fetus. Placentae of mares dying from acute disease did not have lesions attributable to infection; virus was isolated from two of these placentae. One of the two mares which recovered from clinical disease aborted a dead fetus eight days after inoculation. The mare had severe necrotizing myometritis and virus was isolated from maternal ovaries and from fetal tissues. The fetus did not have lesions attributable to arteritis virus. These results suggest that although fetal death may occur in utero during acute equine viral arteritis, abortion probably is due to lesions in the uterus of the mare.     

Vaginal evisceration of the small intestine in three mares

Three mares were treated for vaginal evisceration of a portion of the small intestine. Evisceration occurred in 2 mares shortly after breeding accidents in which the stallion's penis penetrated the vaginal fornix dorsal to the cervix. The affected bowel was replaced through the laceration, and the vaginal defects were sutured with the mares standing, utilizing epidural anesthesia. One mare recovered without complications, was subsequently bred, and delivered a foal with no difficulty. The other mare developed signs of a strangulating small intestinal obstruction 24 hours after the injury, necessitating exploratory celiotomy. Two meters of small intestine had become devitalized secondary to avulsion of the mesentery and adjacent vascular supply during the evisceration. The affected portion was resected and a jejunocecostomy was performed. Recovery was uncomplicated and 21 months later the mare was 9 months in foal. A third mare was treated unsuccessfully for evisceration of several meters of small intestine through the external urethral orifice after rupture of the urinary bladder.     

Pleural effusion secondary to thoracic metastatic mammary adenocarcinoma in a mare

A 17-year-old Quarter Horse mare was examined nearly 3 years after excision and cryotherapy of a papillary mammary gland adenocarcinoma. The mare had been used for pleasure riding since surgery, but had recently developed progressive dyspnea. The mare had clinical evidence of pleural effusion, but died before further clinical examination and treatment were instituted. Necropsy revealed deep mammary masses with similar nodules in the deep inguinal, renal, and mediastinal lymph nodes and in the lungs, pericardium, visceral and parietal pleurae, and left ovary. The masses were identified as papillary mammary gland adenocarcinoma. Large volumes of free pleural and peritoneal fluid were detected. The pleural fluid contained similar neoplastic cells that could have been readily detected by exfoliative cytologic examination had the mare survived.