Endometritis in the mare: A comparison between reproductive history and uterine biopsy as techniques for predicting susceptibility of mares to uterine infection

Thirty mares with no clinical signs of endometritis were categorized as being susceptible or resistant to uterine infection depending on whether or not they had a history of recurrent endometritis. The same mares were then independently classified as susceptible or resistant on the basis of their uterine biopsies; those with significant endometrial degeneration were considered to be susceptible to endometritis. The mares then received an intrauterine inoculation of pathogenic Streptococcus zooepidemicus . Those mares which eliminated bacteria by 10 d after inoculation were considered truly resistant to endometritis, whereas those still infected at 10 d were considered susceptible. The original classifications based on history or biopsy were compared to the inoculation results. A history of recurrent endometritis provided a more sensitive (0.90) and specific (0.95) indication of susceptibility to uterine infection than a uterine biopsy with significant endometrial degeneration (sensitivity 0.5, specificity 0.75).     

Use of a low-volume uterine flush for diagnosing endometritis in chronically infertile mares

Low-volume uterine flush (n=401) was performed in 308 infertile mares to diagnose endometritis. Mares evaluated were either barren after three or more breedings or had two or more unsuccessful embryo recovery attempts during consecutive cycles. Culture results were compared with cytological and histological findings, efflux clarity and pH to substantiate that the micro-organisms recovered were truly pathogens. Cytological specimens were evaluated for presence of epithelial and inflammatory cells, bacteria, yeast and debris. Endometrial biopsies (n=110) were examined for the presence of neutrophils in the stratum compactum. Micro-organisms were recovered in 282/401 (70%) of low-volume flushes; E. coli was most frequently isolated (42.2%), followed by beta hemolytic Streptococcus (37.6%). Efflux clarity of 318 flushes was clear (n=109), cloudy (n=149), or mucoid (n=60). Isolation of micro-organisms was highly associated with cloudy and mucoid effluxes (P<0.001), debris on cytological specimens (P<0.001), increased efflux pH (P<0.003), and neutrophils on endometrial biopsy (P<0.01). E. coli was associated with debris on cytological smear (P<0.002), whereas beta hemolytic Streptococcus was associated with increased efflux pH (P<0.002). Using the presence of neutrophils in a tissue specimen as the "best standard" for diagnosing endometritis, the sensitivity of flush culture was 0.71 and for flush cytology was 0.8, whereas the specificity was 0.86 and 0.67, respectively. Neutrophils in uterine flushes under-reported inflammation; only 86/282 positive cultures were positive on cytology. The clinical estimate of a contaminated (false positive) flush culture was 11%, if a false positive was defined as positive culture with clear efflux and no debris or neutrophils on cytology (26/228). In conclusion, a low-volume uterine flush was a rapid, accurate method for identifying mares with chronic endometritis. When micro-organisms were recovered, endometritis was confirmed by efflux clarity, pH and cytological findings of debris, bacteria, or neutrophils. E. coli was most commonly isolated and it appeared to differ in pathogenicity from beta hemolytic Streptococcus.     

Prostaglandin production by horse embryos and the effect of co-culture of embryos with endometrium from pregnant mares

Embryos, endometrial biopsies, and uterine lavage fluid were collected from pregnant and non-pregnant mares 14 days after ovulation. Embryos were cultured for 20.5 h with and without endometrial tissue from pregnant mares, and endometrial tissue was cultured alone. Endometrial content of PGF tended to be higher (P = 0.06) in non-pregnant than in pregnant mares, but the amount of PGF released from tissue during culture was similar for pregnant and non-pregnant mares. Lavage fluid from non-pregnant mares also tended (P = 0.08) to contain higher concentrations of PGF. Coincubation of embryos with endometrium from pregnant mares significantly (P = 0.01) lowered concentrations of PGF in medium. Tissue concentrations and release of PGE-2 and 6-keto-PGF-1 alpha were similar in endometrial samples from pregnant and non-pregnant mares and prostaglandin production was unaffected by the presence of an embryo during incubation. Horse embryos released all three prostaglandins during a 20.5-h incubation.     

Relationships between uterine culture, cytology and pregnancy rates in a Thoroughbred practice

Endometrial cytology and culture specimens (n=2123) were collected concurrently with a guarded uterine culture instrument from 970 mares (738 barren, 1230 foaling and 155 maiden mares) during three breeding seasons (2001-2004). Results were compared to the 28-d pregnancy rate for the cycle from which the samples were taken. Cytological smears were evaluated for inflammation at x100 and graded as: not inflammatory (0-2 neutrophils/field), moderate inflammation (2-5 neutrophils/field), severe inflammation (>5 neutrophils/field), or hypocellular (scant epithelial cells and no neutrophils). Uterine culture swabs were plated within 6h, incubated for 72 h and results determined at 24, 48, and 72 h. Approximately, 20% (n=423) cytology samples were positive for inflammation (>2 neutrophils), whereas approximately 11% (n=231) of cultures had microorganisms recovered. A majority (64%) of the positive cultures (147/231) had inflammation on cytology smears. Streptococcus equi subsp. zooepidemicus was associated with more positive cytology results than coliforms (P<0.01). Mares with positive cytology or culture had lower pregnancy rates than mares with normal findings (P<0.01). Lowest pregnancy rates were recorded for mares with severe endometrial inflammation (21%, versus moderate inflammation 48%). Isolation of a microorganism from mares with endometrial inflammation was not associated with a further reduction in pregnancy rates. In barren, foaling and maiden mares, cytology was positive in 28, 17, and 5%, respectively, and culture was positive in 12.2, 11.1, and 3.2%. Foaling and maiden mares had higher pregnancy rates than barren mares (62, 69, and 44%, respectively, P<0.001). In conclusion, a positive cytology was twice as common as a positive culture, and isolation of microorganisms was associated with reduced pregnancy rates, even in the apparent absence of inflammation.     

The effects of EDTA-Tris infusion on the equine endometrium

Four groups of five pony mares each were used to determine if the intrauterine infusion of EDTA-Tris solution caused adverse effects on the endometrium. The uteri of mares were infused with either saline or EDTA-Tris solution or biopsied or sham-biopsied without infusion. Acute endometritis developed in one (20%) to three (60%) mares in each group during the seven days following treatment, but there were no differences (P > 0.05) in the incidence of endometritis among the groups. Endometrial fibrosis was not evident in biopsies taken on days 14, 30 and 60 following infusion of saline or EDTA-Tris. It was concluded that the endometrial response to saline and EDTA-Tris was not different and that EDTA-Tris may be a useful adjunct to treatment of uterine infections in the mare.     

The effect of transcervical uterine manipulations on establishment of uterine infection in mares under the influence of progesterone

Four pony mares were used in a cross-over study to investigate the effect of different treatments on experimentally-induced endometritis. The mares were treated with progesterone to facilitate establishment of uterine infections. They received an intrauterine infusion of Streptococcus zooepidemicus 5 days after the start of progesterone therapy. Five days later, they were treated by intrauterine infusions of 2 g ampicillin in 50 ml sterile water or by sterile water without antibiotic for 3 consecutive days. Prior to infusion of Strep. zooepidemicus , no bacteria were cultured from the uteri of the mares. However, 5 days after infusion of Strep. zooepidemicus and prior to antibiotic therapy, mixed bacterial growths were cultured from endometrial swabbings. After antibiotic therapy, ampicillin-resistant organisms were cultured from endometrial swabbings. Two other progesterone-treated mares received an intrauterine infusion of sterile phosphate buffered saline instead of bacteria. Mixed bacterial cultures were recovered 5 days later from the endometrial swabbings of these mares. It was concluded that the high circulating concentrations of progesterone were probably responsible for the treatment failure and that in clinical situations, therapy involving transcervical manipulations should not be administered when mares are in diestrus.     

Use of leukocytes as treatment for endometritis in mares experimentally infected with Streptococcus equi subsp. zooepidemicus

This study compared four treatments for bacterial endometritis in mares experimentally infected with Streptococcus zooepidemicus. Twenty-five mares were used, 20 resistant and five susceptible to endometritis. Mares would be in estrus when infected. Twenty-four hours after inoculation, clinical, bacteriological and cytological examinations were performed and repeated until the first occurrence: negative cytology and no Streptococcus growth or the seventh day post-infection. All mares showed clinical signs of endometritis and were assigned to one of the following treatments: (1) intrauterine infusion of fresh leukocytes; (2) intrauterine infusion of frozen-thawed leukocytes; (3) intrauterine infusion of lysed leukocytes; (4) intrauterine infusion of recombinant human interleukin-8 (rhIL-8); (5) control. Mares were submitted to all treatments, with at least a 14-day interval between treatments in a Latin square design. Treatment did not affect (P=0.121) time needed for resistant mares to eliminate bacteria. Time needed for elimination of bacteria was similar in susceptible mares treated with fresh and frozen leukocytes (P=0.333). Susceptible mares treated with frozen leukocytes also did not differ from those treated with lysed leukocytes (P=0.227) for time to eliminate bacteria, but were significantly different (P>0.02) from those treated with rhIL-8 and control. In resistant mares, physical clearance ability was probably the responsible for bacterial elimination. Intrauterine infusions in susceptible mares with viable or lysed leukocytes associated or not to opsonizing factors, reduced the time to elimination of bacteria. Infusions with bactericidal effect (functional neutrophils and granules) was likely effective and responsible for the more rapid elimination of bacteria in susceptible mares.     

Embryonic loss in pony mares induced by intrauterine infusion of Candida parapsilosis

Pony mares which were detected pregnant by transrectal ultrasonography received a single intrauterine infusion of either sterile saline (control, n = 12 mares) or 10(6)Candida parapsilosis (treated, n = 12 mares) between Days 11 to 14 postovulation. Subsequent embryonic loss was studied by daily ultrasonography of the mare's uterus, by serum progesterone levels, by endometrial swabs for cytologic and microbiologic examination and by endometrial biopsies that were taken after embryonic loss was detected. Significantly fewer (P<0.01) embryonic losses occurred in control than in treated mares (4 12 vs 12 12 ). The mean interval from intrauterine infusion until embryonic loss was 5.8 +/- 2.8 d for control mares (n = 4) and 2.1 +/- 0.2 d for treated mares (n = 12). Prior to embryonic loss, moderate to marked edema of the endometrial folds in 12 of 12 treated mares and free fluid in the uterine lumen of 5 of 12 treated mares were detected by ultrasonography. After embryonic loss, Candida parapsilosis was cultured from the uteri of 8 of 12 treated mares, and E . coli was cultured from the uteri of 2 of 4 control mares. Postloss endometrial smears had cytologic evidence of inflammation in 10 of 12 treated mares and 3 of 4 control mares. Intrauterine inoculation of C. parapsilosis consistently induced embryonic loss and may provide a basis to further study the relationship between endometritis and embryonic loss in mares.     

Biodegradable estradiol microspheres do not affect uterine involution or characteristics of postpartum estrus in mares

Quarterhorse mares were used to investigate effects of estradiol-17beta on uterine involution, duration of estrus, interval to ovulation, and fertility achieved by breeding on the first postpartum estrus. On the day of foaling, mares were injected with biodegradable poly (DL-lactide) microspheres containing either 100 mg estradiol-17beta (25 mares) or no drug (27 mares). The treatment period was considered to last for 12 to 15 d. Estrus was determined by teasing mares (n=16) with a stallion. Ovulation was detected by transrectal ultrasonographic examination of ovaries (n=48). On Days 6, 11 and 16 post partum, transrectal ultrasonography was used to measure cross-sectional diameters of the uterine body, uterine horns, and fluid within the uterine lumen (n=28). Uteri were swabbed for bacteriologic culture, and uterine biopsies were obtained from the previously gravid uterine horn on Days 11 and 16 post partum, for assessment of endometritis and morphometric analysis of endometrial histioarchitecture (n=19). Twenty-two mares were bred on foal-heat, and pregnancy was determined by transrectal ultrasonography on 14 to 16 and 30 to 35 d after breeding. With only one exception (diameter of previously gravid uterine horn on Day 11), mean values for all measures of uterine involution did not differ between treatment groups (P > 0.05). No differences were detected between treatment group means for length of estrus or interval to ovulation (P > 0.05). No differences were detected between treatment group liklihoods for recovery of potential bacterial pathogens, presence of endometritis, or presence of intrauterine fluid at 11 or 16 d post partum (P > 0.05). Pregnancy rate of mares treated with estradiol (5 11 ; 45%) was not different from that of control mares (9 11 ; 82%; P > 0.05). Estradiol treatment did not hasten uterine involution, increase duration of estrus, delay ovulation, or increase fertility in these postpartum mares.     

Effects of oral treatment with N-acetylcysteine on the viscosity of intrauterine mucus and endometrial function in estrous mares

Persistent breeding-induced endometritis is ranked as the third most common medical problem in the adult mare and leads to enormous economic loss in horse breeding. In mares suffering from persistent breeding-induced endometritis, increased amounts of intrauterine (i.u.) fluid or viscous mucus in estrus or after breeding may act as a barrier for sperm and can contribute to low fertility. Current therapies of these mares aim to eliminate i.u. fluid and mucus by uterine lavage and/or administration of ecbolic drugs. Recently, i.u. administration of N-acetylcysteine (NAC) has been shown to support therapy in mares with endometritis. It was the objective of the present study to investigate effects of an oral administration of NAC on the viscosity of i.u. fluid in estrous mares. It was hypothesized that oral treatment with NAC reduces the viscosity of i.u. fluid and has a positive effect on the inflammatory response of the endometrium. Mares (n = 12) were included in the study as soon as estrus was detected (ovarian follicle >3.0 cm and endometrial edema), which was defined as Day 1. They were randomly assigned to a treatment (10 mg/kg NAC on Days 1-4) or a control group (no treatment). On days 1 and 5 i.u. mucus was collected and its rheologic properties were accessed. On Day 5, endometrial biopsies were obtained and evaluated for integrity of the luminal epithelium, number of polymorphonuclear neutrophils (PMN), staining for cyclooxygenase 2 (COX2), staining with Kiel 67 antigen (Ki-67), lectins and periodic acid Schiff (PAS). In the treatment group, viscosity of i.u. mucus increased significantly between Days 1 and 5 (P < 0.05), while no differences were found in control mares (n.s.). At no time were significant differences between treated and control mares seen. Integrity of epithelium was not affected. After NAC treatment the mean number of PMN in endometrial biopsies was significantly lower compared to mares of the control group (1.9 ± 0.3 vs. 4.8 ± 0.4; P < 0.05). Nuclear immunostaining for COX2 was significantly lower after NAC treatment compared to control mares (P < 0.05). Score for PAS and Alcain staining of mucus in deep uterine glands differed significantly between groups (both P < 0.05). We conclude that oral NAC treatment does not reduce viscosity of uterine mucus but has an antiinflammatory effect on the equine endometrium.     

Effects of ecbolic agents on measurements of uterine involution in the mare

Thirteen postparturient mares were used to investigate the effects of ecbolic agents on the rate of uterine involution. Mares were randomly assigned to one of three treatment groups: Group S = intravenous injection of 2 ml saline twice daily for 10 days post partum (n=4); Group O = intravenous injection of 20 units oxytocin twice daily for 10 days post partum (n=4); and Group P = intramuscular injection of 500 mcg fluprostenol twice daily for 10 days post partum (n=5). Ovulation was determined by daily transrectal ultrasonographic examination of the ovaries. On Days 6, 11 and 16 post partum, transrectal ultrasonography was used to measure cross-sectional diameters of the uterine body, uterine horns and fluid within the uterine lumen. Uteri were swabbed for aerobic bacteriologic culture on Days 11 and 16 post partum. Uterine biopsies were obtained from the base of the previously gravid uterine horn on Days 11 and 16 post partum for subjective assessment of endometritis and morphometric analysis of endometrial histoarchitecture. Mean values for all measurements of uterine involution did not differ among groups (P>0.05). For all mares, the diameter of luminal fluid was not correlated to diameter of the uterine body or uterine horns, or to morphometric measurements of endometrial histoarchitecture of the previously gravid uterine horn (P>0.05). Likewise, accumulation of fluid within the uterine lumen was not associated with endometritis or recovery of potential bacterial pathogens (P>0.05). Mean diameter of the previously gravid uterine horn was negatively correlated with morphometric measures of endometrial histoarchitecture of the previously gravid uterine horn (P<0.01).     

Embryo transfer induces a subclinical endometritis in recipient mares which can be prevented by treatment with non-steroid anti-inflammatory drugs

We tested the hypothesis that subclinical endometritis occurs after embryo transfer (ET) in the horse. Recipient mares were treated with meclofenamic acid (M) or flunixin meglumin (F) after ET or were left untreated (n=9 per group). Embryos were re-collected 4 days after transfer. Endometrial biopsies were taken for histology and analysis of cyclooxygenase-2 (COX-2) by immunohistochemistry and for PCR. Bacteriological swabs were collected from the uterus and lavage fluid of donor and recipient mares. Progesterone and prostaglandin F(2alpha) release was analysed in recipient mares after ET. Four days after ET, four embryos were recovered from group M and three from group F and untreated mares, each. The number of polymorph nuclear neutrophils was reduced in treated mares (p<0.05). Expression of mRNA for inflammatory cytokines did not differ between groups. In group M, expression of endometrial prostaglandin-E-synthase was higher than in group F (p<0.05). Three out of nine control mares unterwent preterm luteolysis (p<0.05 vs. treatment groups), prostaglandin release (p<0.05) and the number of COX-2 positive cells (p<0.01) were significantly higher than in treated mares. Only few bacteriological swabs were positive. In conclusion, treatment of embryo recipient mares with non-steroid anti-inflammatory drugs inhibits the inflammatory response of the endometrium after ET. Meclofenamic acid may have advantages in comparison to flunixin meglumin due to a different influence on prostaglandin synthesis that may not result in inhibition of embryonic mobility.     

Susceptibility to persistent breeding-induced endometritis in the mare: relationship to endometrial biopsy score and age, and variations between seasons

The objectives were to: (1) investigate the associations of age and endometrial biopsy score with uterine fluid retention after insemination; and (2) determine if a strict classification of susceptibility to persistent breeding-induced endometritis (PBIE) based on biopsy score, endometrial cytology, and fluid retention after inseminations, is consistent over subsequent breeding seasons. In Experiment 1, 57 mares were inseminated with 10⁹ freeze-killed sperm during estrus and evaluated for uterine fluid retention 48 h and 96 h after insemination. Comparisons were made between fluid retention and biopsy score or age. In Experiment 2, a subset of 14 mares was classified for susceptibility to persistent breeding-induced endometritis in two subsequent breeding seasons. Biopsy score and age were associated with fluid retention (P < 0.001). In addition, age was related to biopsy score (P < 0.001). Of the mares examined for susceptibility, 36% (5 of 14) changed status during subsequent seasons. Three mares changed to a more severe classification (intermediate to susceptible, or resistant to intermediate), whereas two mares changed to a less severe classification (susceptible to intermediate).     

Endometritis in the mare: a diagnostic study comparing cultures from swab and biopsy

The objective of this study was to compare results from endometrial culture swabs with results from culturing of endometrial biopsies. The culture results were related to cytological findings (polymorphonuclear; PMN-cells) and histological observations (PMN-cells). Biopsy and swab samples were smeared on the surface of a blood agar petri dish, and examined for growth of bacteria. Cytology samples were obtained from endometrial biopsies, stained and examined under microscopy for the presence of PMN-cells. Endometrial biopsies were examined for the presence of PMN-infiltration of the endometrial luminal epithelium and the stratum compactum. Using the presence of PMNs in a tissue specimen as the "best standard" for diagnosing endometritis, the sensitivity of bacterial growth from an endometrial biopsy was 0.82. The sensitivity for cytology was 0.77, and the sensitivity of bacterial growth from an endometrial surface swab was 0.34. The specificity for biopsy cultures, swab cultures, and cytology to diagnose endometritis were 0.92, 1.0, and 1.0 respectively. The positive predictive value for biopsy cultures, swab cultures, and cytology were 0.97, 1.0, and 1.0 respectively. The negative predictive value for biopsy cultures, swab cultures, and cytology were 0.67, 0.44, and 0.62 respectively. In conclusion, bacteriological culture and cytology from an endometrial biopsy provide the practitioner with the most accurate results regarding both sensitivity and positive predictive value.     

Comparison of three diagnostic methods to identify subclinical endometritis in mares

The objective of this study was to compare the accuracy of a uterine swab (US), a cytological brush (CB) and an endometrial biopsy (EB) to detect subclinical endometritis in mares. Cytological and bacteriological results of all three techniques were related to histological occurrence of polymorphonuclear neutrophils (PMNs) in the stratum compactum, commonly known as ‘best standard'; to diagnose endometritis.Samples were taken from 55 mares of different breeds without clinical signs of endometritis. Samples for US, CB and EB were collected, smeared on a microscopic slide and cultured for bacterial growth. Endometrial biopsy samples were additionally stored in 4% formaldehyde for histological analysis. Bacteriological cultures and cytological samples of all techniques were classified as negative (no uterine pathogens in monoculture; < 2% PMNs) or positive (uterine pathogens in > 90% of the grown colonies; > 2% PMNs) for endometritis. Uterine pathogens were diagnosed in 20.0% of the mares. Isolation of pathogens was not associated with positive cytological findings (r = −0.23; P = 0.87). None of the six mares with an Escherichia coli infection (10.9%) showed a positive cytological result. In contrast, two of five mares infected with Streptococcus zooepidemicus had a positive cytological result.Histologically, the presence of PMNs in the stratum compactum was regarded as positive for endometritis when the mare was in diestrus at time of sampling. Compared to the ‘best standard', sensitivity for cytology of CB, US and EB was 0.17, 0.00 and 0.25, respectively. Specificity for cytology of CB, US and EB was 0.83, 0.93 and 0.85, respectively. Sensitivity of uterine culture was 0.25, 0.33 and 0.25 for CB, US and EB, respectively. Specificity for culture of CB, US and EB was 0.80, 0.83 and 0.95, respectively. In conclusion, cytological or bacteriological examinations alone provide a high incidence of false negative results. Sensitivity of cytology combined with bacteriology of CB was 0.42. A combination of a bacteriological and a cytological examination of a CB sample improved the diagnostic performance in subfertile mares. Based on these results, we can recommend the CB to improve the diagnosis of subclinical endometritis in the mare compared to the US alone as currently used routine method.     

The functional competence of uterine-derived polymorphonuclear neutrophils (PMN) from mares resistant and susceptible to chronic uterine infection: a sequential migration analysis

The functional competence of uterine-derived polymorphonuclear neutrophils (PMNs) from 28 mares was measured for migration responsiveness by use of a chamber (filter) assay. Uterine infection was induced with Streptococcus zooepidemicus in mares considered resistant to chronic uterine infection (Grade I). In sequential analysis of uterine flushings obtained from these mares 5, 12, 15, 20, and 25 h after infection was induced, PMNs showed an initial rise at 12 h (from 5), then a general decline in migration response and in concentration of cells per ml from 12 through 25 h post-inoculation. In contrast, PMNs obtained from the uterine flushings from mares considered susceptible to chronic uterine infection (Grade III) demonstrated premature migration dysfunction 12 h after infection. Subsequent increases in functional competence of the PMNs were demonstrated at 15 and again at 25 h after induced infection. The concentration of uterine PMNs per ml from mares considered susceptible to chronic endometritis remained elevated from 12 through 25 h after inoculation, which suggests a possible continued recruitment of new PMNs from the peripheral circulation. The results of this study suggest that uterine-derived PMNs obtained from mares susceptible to chronic uterine infection have a compromised ability to migrate. This dysfunction may play an important role in rendering the endometrium (uterus) susceptible to chronic endometritis.     

Relationships of age to uterine function and reproductive efficiency in mares

The uterine function and reproductive efficiency of 31 nonlactating pony mares were compared for two age groups: young (5 to 7 years, n=9) and old (>/=15 years, n=22). For pregnant mares, differences between age groups were not significant for the diameter of the largest follicle, cross-sectional area of the corpus luteum, growth profile of the embryonic vesicle or embryo mobility characteristics. Uterine contractility scores were lower (P<0.05), day of fixation of the embryonic vesicle was later (P<0.05), and uterine tone tended (P<0.10) to be lower in the old than the young mares. Endometrial biopsies in old mares had more (P<0.05) inflammatory cell infiltrations, more (P<0.05) fibrotic changes, and less dense (P<0.05) endometrial glands than in young mares. Ultrasonically detected intrauterine fluid collections were more extensive (P<0.05) in the old than the young mares. The pregnancy rate on Day 12 (Day 0=ovulation) was lower (P<0.05) and embryo-loss rate (Days 12 to 39) was greater (P<0.05) in old (32 and 62%, respectively) than in young (100 and 11%, respectively) mares. The results confirmed previous reports that old age was associated with increased endometrial inflammation, reduced pregnancy rate and increased embryo-loss rate. The results also indicated that uterine contractility and uterine tone were reduced and the fixation of the embryonic vesicle occurred later in old than in young mares.     

Changes in vascular perfusion of the endometrium in association with changes in location of the embryonic vesicle in mares

The equine embryonic vesicle is mobile on Days 12-14 (Day 0 = ovulation), when it is approximately 9-15 mm in diameter. Movement from one uterine horn to another occurs, on average, approximately 0.5 times per hour. Mobility ceases (fixation) on Days 15-17. Transrectal color Doppler ultrasonography was used to study the relationship of embryo mobility (experiment 1) and fixation (experiment 2) to endometrial vascular perfusion. In experiment 1, mares were bred and examined daily from Day 1 to Day 16 and were assigned, retrospectively, to a group in which an embryo was detected (pregnant mares; n = 16) or not detected (n = 8) by Day 12. Endometrial vascularity (scored 1-4, for none to maximal, respectively) did not differ on Days 1-8 between groups or between the sides with and without the corpus luteum. Endometrial vascularity scores were higher (P < 0.05) on Days 12-16 in both horns of pregnant mares compared to mares with no embryo. In pregnant mares, the scores increased (P < 0.05) between Day 10 and Day 12 in the horn with the embryo and were higher (P < 0.05) than scores in the opposite horn on Days 12-15. In experiment 2, 14 pregnant mares were examined from Day 13 to 6 days after fixation. Endometrial vascularity scores and number of colored pixels per cross-section of endometrium were greater (P < 0.05) in the endometrium surrounding the fixed vesicle than in the middle portion of the horn of fixation. Results supported the hypothesis that transient changes in endometrial vascular perfusion accompany the embryonic vesicle as the vesicle changes location during embryo mobility.     

Endometrial biopsy findings in mares with contagious equine metritis.

Endometrial biopsy samples before and after treatment were obtained from 10 mares naturally infected and one Pony mare experimentally infected with Contagious Equine Metritis in 1977. The histopathological features were a short-lived polymorphonuclear cell infiltration of the luminal epithelium and stroma followed by a very early and marked mononuclear cell infiltration of the stroma, including many plasma cells. The luminal epithelium responded with cellular proliferation which may have reflected a regenerative response. Following the initial acute response, intercellular basal vacuoles containing amorphous and granular material and degenerate leucocytes, were seen in association with the basement membrane for several weeks following infection and apparent recovery. Specimens taken from 9 mares after treatment suggested a varied response. Endometrial biopsy was useful in demonstrating an endometrial response to infection in individual mares prior to the isolation of the causal organism. Its usefullness as a screening test was limited by the ability of mares to harbour the organism in the lower genital tract whilst showing little or no evidence of acute endometritis.