Effect of oxytocin, prostaglandin F2 alpha, and clenbuterol on uterine dynamics in mares

The effects of oxytocin, prostaglandin F2 alpha (PGF2 alpha), and clenbuterol on uterine contractility and tone during anestrus and diestrus, and during mobility and postfixation of the embryonic vesicle were studied in 51 pony mares. Contractility was assessed by scoring real-time ultrasound images, and tone was assessed by transrectal digital compression. Scoring was done by an operator who had no knowledge of treatment assignments. In anovulatory mares primed with progesterone for 16 d, oxytocin did not significantly alter contractility but did stimulate an increase in tone, whereas clenbuterol depressed both contractility and tone. The PGF2 alpha given on Days 12, 15, and 18 did not significantly alter uterine contractility in pregnant mares, but it increased contractility on all days in nonpregnant mares. Clenbuterol decreased both tone and contractility when given to pregnant mares on the day of embryonic-vesicle fixation, while it decreased tone but not contractility when given on Day 19. Clenbuterol treatment was associated with dislodgment of the fixed embryo in only 1 of 5 mares. However, on Day 19, clenbuterol treatment was associated with a change in shape of the conceptus when viewed in a cross section of the uterine horn. The conceptus shape became more circular rather than irregular or triangular, as indicated by a significant decrease in the variation in the distances between adjacent walls measured in 4 different directions. Results indicated that: 1) oxytocin increased uterine tone but did not alter contractility in progesterone-primed anestrous mares; 2) on Days 12, 15 and 18, PGF2 alpha increased uterine contractility in nonpregnant mares but not in pregnant mares; 3) clenbuterol decreased both tone and contractility at all reproductive states except for a lack of a decrease in contractility on Day 19 of pregnancy; and 4) reduction in uterine tone from clenbuterol treatment on Day 19 was associated with a change in the two-dimensional shape of the in situ conceptus from irregular to a more circular form.     

Uterine clearance and resistance to persistent endometritis in the mare

The objective of this article is to review the role of uterine defense mechanisms in natural resistance to chronic or persistent endometritis. A breakdown of uterine physical clearance mechanisms is currently believed to play a major role in susceptibility to persistent endometritis. Mares with increased susceptibility to persistent endometritis have impaired myometrial contractility in response to an acute inflammation, resulting in an accumulation of fluid and inflammatory products within the uterine lumen. The origin of this defect remains unknown. Recent studies have demonstrated that spermatozoa trigger PMN chemotaxis into the uterine lumen. This observation suggests that a transient endometritis is a normal physiological response to breeding. However, in mares with impaired uterine defense mechanisms, the condition may develop into a persistent endometritis and subsequent subfertility. In contrast to spermatozoa, seminal plasma has a suppressive effect on complement activation and PMN chemotaxis (65). The exact role of seminal components in breeding-induced inflammation needs further investigation.     

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.     

Use of mesenchymal stem cells or autologous conditioned serum to modulate the inflammatory response to spermatozoa in mares

Current treatments for Persistent mating-induced endometritis such as uterine lavage and oxytocin therapy focus on aiding the uterus in removal of inflammatory products, but these treatments do not modulate the inciting inflammatory response. Biological treatments, such as autologous conditioned serum (ACS) and mesenchymal stem cells (MSCs), have been used in human and veterinary medicine for immunomodulation for over 10 years. The objectives of this project were to evaluate the ability of ACS or MSCs to modulate the inflammatory response to spermatozoa after breeding. Two experiments were performed with six normal mares in each study to evaluate the effects of intrauterine administration of ACS, dexamethasone, or a placebo (experiment 1), or allogeneic MSCs or a placebo (experiment 2) on the inflammatory response to spermatozoa using clinical and biochemical endpoints. Treatment with ACS and MSCs significantly (P < 0.05) reduced the number of neutrophils in the uterine lumen 6 hours after the sperm challenge. An increase (P < 0.05) in the anti-inflammatory cytokine IL-1Ra was observed after treatment with MSCs before exposure to spermatozoa. There was no difference in IL-1Ra concentration in mares treated with ACS, dexamethasone, or a placebo. Mesenchymal stem cells and ACS were able to modulate the immune response to spermatozoa in normal mares. The effect may be due to an increase in IL-1Ra in MSCs-treated mares, but other bioactive molecules may be responsible for the decrease in neutrophils in ACS-treated mares. Autologous conditioned serum and bone-derived culture expanded MSCs were able to modulate the uterine inflammatory response to spermatozoa in normal mares. Treatment with allogeneic stem cells may be beneficial if a similar modulation in inflammatory cytokines occurs in mares affected by persistent mating–induced endometritis.     

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).     

Effect of frozen semen on the uterus of mares with pathological uterine changes

Pregnancy rates after frozen semen inseminations (AI), particularly in older and problem mares, are lower than after fresh semen AI. Uterine contractility and the inflammatory reaction after frozen semen insemination were studied in two groups of mares: the abnormal group comprised of 6 old barren mares categorized in biopsy category IIB or III, and the control group including 6 reproductively normal young maiden mares in biopsy category I or IIA. All 12 mares were inseminated in the first cycle with 2 mL of phosphate-buffered saline (PBS) and in their second cycle with 2 mL of frozen semen containing 800 x 10(6) spermatozoa. Before and 1, 2, 4, 8, and 20 to 24 h after this treatment, all mares were examined by ultrasonography for intrauterine fluid accumulations (IUFA). The examinations were videotaped to count the number of uterine contractions later. Uterine fluid was obtained by tampon before treatment, and by the tampon method followed by uterine lavage after the last examination. Fluids were cultured bacteriologically, and polymorphonuclear leukocytes (PMN) were counted. Trypsin-inhibitor capacity (TIC), lysozyme concentration, and beta-glucuronidase (BGase) and N-acetyl-beta-D-glucosaminidase (NAGase) activities were determined in frozen-thawed tampon and lavage fluids. Both treatments induced significant neutrophilia in the uterine lumen. Although PMN concentrations were numerically higher after frozen semen AI than after PBS-treatment, the difference was not significant. There was not any difference between the mare groups either. The amount of IUFA differed only in the normal group between frozen semen AI and PBS treatment, and between 0- and 24-h samples for frozen semen AI. Although abnormal mares showed consistently more fluid than normal mares, this difference was not significant. Uterine contractions and enzyme concentrations between groups did not differ. None of the variables showed significant differences between the normal and abnormal mares in their reaction to frozen semen AI.     

Effect of oxytocin and flunixin meglumine on uterine response to insemination in mares

The most probable reason for persistent postbreeding endometritis in mares is weak myometrial contractility. The influence of oxytocin (OT; an ecbolic agent) and flunixin meglumine (FLU; a prostaglandin inhibitor serving as a model for mares with decreased uterine contractility) on uterine response to artificial insemination (AI) was studied in mares with no history of reproductive failure. The mares were treated intravenously with 10 mL saline (Group C, n = 10) or 0.01 IU/kg OT (Group OT, n = 10) 2, 4, 8, and 25 h after AI. Group FLU (n = 11) was treated with 1.1 mg/kg FLU 2 h after AI and with saline thereafter. The mares received the same treatments in the first and third cycles but were sampled either at 8 or 25 h. The amount of intrauterine fluid (IUF) and edema and the number of uterine contractions were recorded before AI and 10 min after the treatments using transrectal ultrasonography. At 8 h after AI, the mares were treated with human chorionic gonadotropin, and, after 8-h or 25-h scans, a 500-mL uterine lavage and a biopsy were performed. Ovulation was confirmed at 48 h and pregnancy 14 to 17 d after AI. No manipulations were done during the second estrus. At 8 h after AI, Group FLU had more polymorphonuclear leukocytes (PMNs) in the uterine lavage fluid than did Group OT (P < 0.05), but uterine contractions did not differ significantly. At 25 h, the PMN concentrations were low in all groups. Group OT rarely showed IUF. The uterine biopsy specimens of Group FLU showed less inflammation of the stroma but more PMNs in the uterine lumen 8 h after AI than that of the control group (P < 0.05). The pregnancy rates did not differ between the groups (63% C, 53% OT, and 50% FLU). Oxytocin rapidly and effectively removed IUF and PMNs after AI and thereby shortened the duration of postbreeding inflammation.     

The use of dexamethasone administered to mares at breeding time in the modulation of persistent mating induced endometritis

The present study describes the effect of a single dose of dexamethasone administered to mares at time of breeding. In an initial experiment, the authors investigated safety of treatment. In a second experiment the effect of treatment on the uterine environment, fetal development and pregnancy outcome was examined. In the final part of the study, mares susceptible to persistent mating induced endometritis were identified, by means of a risk factor score system and the effect of treatment evaluated. Results indicated that dexamethasone administered at breeding time did not negatively impact on mares medical and reproductive traits. A reduced inflammatory response was observed post-mating in treated versus control mares and mares with multiple risk factors for susceptibility to persistent mating induced endometritis showed improved pregnancy rates following treatment. The authors concluded that a single dose of dexamethasone administered at the time of breeding is safe and can be used to modulate the uterine inflammatory response to breeding in susceptible mares.     

Effect on fertility of human chorionic gonadotrophin and uterine lavage with oxytocin performed after mating in Arabian barren mares

The objective of the present study was to evaluate the beneficial effect of hCG injected immediately after mating in Arabian barren mares treated with uterine lavage and oxytocin. Arabian barren mares (n = 36) with PMIE were subjected to detailed clinical examinations including palpation per rectum, vaginoscopy, and cytological examination. After mating the 36 mares were randomly divided into four groups. The mares in group 1 (n = 10) were immediately after breeding injected with hCG 3000 IU IM. Uterine lavage with 1 L of N-saline containing 4 million IU of crystalline penicillin and 4 g of streptomycin sulphate was performed 4 h after breeding. Then mares received two injections of oxytocin 40 IU IM 2 h apart after 6 h of mating. Mares in group 2 (n = 10) treated with uterine lavage and oxytocin as group 1. While mares in group 3 (n = 10) received uterine lavage only. A control group (n = 6) as group 4 did not received any treatment. The results of clinical examination indicated that 69.4% of PMIE mares were harboring severe endometritis and 30.6% with a moderate form of endometritis. Significant (P < 0.01) increase in lymphocytes were founded in barren mares included in this study. Higher pregnancy rate (P < 0.01) was founded in Arabian barren mares 80% injected with hCG immediately after breeding and uterine lavage and oxytocin. No significant difference was found in mares received uterine lavage and oxytocin and uterine lavage only. In a conclusion, administration of hCG immediately after mating and intrauterine lavage containing antibiotics performed 4 h and two injections of oxytocin 40 IU IM 2 h apart after 6 h of mating had improved fertility of Arabian barren mares.     

Mares with delayed uterine clearance have an intrinsic defect in myometrial function

Persistent, postmating endometritis affects approximately 15% of mares and results in reduced fertility and sizable economic losses to the horse-breeding industry. Mares that are susceptible to postmating endometritis have delayed uterine clearance associated with reduced uterine contractility. Unfortunately, the mechanism for reduced uterine contractility remains an enigma. The present study examined the hypothesis that mares with delayed uterine clearance have an intrinsic contractile defect of the myometrium. Myometrial contractility was evaluated in vitro by measuring isometric tension generated by longitudinal and circular uterine muscle strips in response to KCl, oxytocin, and prostaglandin F(2alpha) (PGF(2alpha)) for young nulliparous mares, older reproductively normal mares, and older mares with delayed uterine clearance. In addition, intracellular Ca(2+) regulation was evaluated using laser cytometry to measure oxytocin-stimulated intracellular Ca(2+) transients of myometrial cells loaded with a Ca(2+)-sensitive fluorescent dye, fluo-4. For all contractile agonists, myometrium from mares with delayed uterine clearance failed to generate as much tension as myometrium from older normal mares. Oxytocin-stimulated intracellular Ca(2+) transients were similar for myometrial cells from mares with delayed uterine clearance and from older normal mares, suggesting that the contractile defect did not result from altered regulation of intracellular Ca(2+) concentration. Furthermore, no apparent age-dependent decline was observed in myometrial contractility; KCl-depolarized and oxytocin-stimulated longitudinal myometrium from young normal mares and older normal mares generated similar responses. However, circular myometrium from young normal mares failed to generate as much tension as myometrium from older normal mares when stimulated with oxytocin or PGF(2alpha), suggesting possible age-related alterations in receptor-second messenger signaling mechanisms downstream of intracellular Ca(2+) release. In summary, for mares with delayed uterine clearance, an intrinsic contractile defect of the myometrium may contribute to reduced uterine contractility following breeding.     

Effects of postparturient uterine lavage on uterine involution in the mare

Eighteen postparturient mares were used to evaluate effects of uterine lavage on uterine involution. Mares were randomly assigned to one of three treatment groups: Group 1 (seven mares), no lavage; Group 2 (five mares), lavage on Day 3 post partum; and Group 3 (six mares), lavage on Days 3, 4, and 5 post partum. Five liters sterile physiologic saline, prewarmed to 42 degrees C, were used for each lavage. Transrectal ultrasound examination of the reproductive tract was performed on Day 11 post partum to detect the presence of free fluid in the uterine lumen, to estimate the cross-sectional diameter of the uterine horns and body, and to determine if ovulation had occurred. Endometrial biopsies were also taken on Day 11 post partum to evaluate endometrial histologic characteristics. Lavage had no effect (P>0.05) on diameter of the uterine body or previously gravid uterine horn, presence of fluid in the uterine lumen, or number of mares which had ovulated by Day 11 post partum. Histologic characteristics of the endometrium (height of luminal epithelium, gland depth, relative gland vclume, and inflammatory-cell score) were not affected by treatment (P>0.05). Postpartum uterine lavage did not significantly affect uterine involution by the parameters measured in normal-foaling mares at Day 11 post partum.     

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 cervical dilation and intrauterine infusions on the timing of oviductal transport of equine embryos

Equine embryos spend 5 to 6 d in the oviduct before entering the uterus as expanded blastocysts, and cannot be consistently collected nonsurgically until Day 7. Technologies such as cryopreservation and embryo splitting, which are most successful with embryos at the morula or early blastocyst stage, have not been used in mares because equine morulae and early blastocysts are located in the oviduct and cannot be recovered nonsurgically. These experiments test the hypothesis that transport of equine embryos through the oviduct can be hastened by cervical dilation or by acute, sterile endometritis induced by intrauterine oyster glycogen treatment. Cervical dilation with or without intrauterine infusion of 0.5 ml PBS on Day 4 did not appear to hasten the transport of embryos into the uterus since Day 5 uterine embryo recovery rates were not higher (P > 0.1) for mares with cervical dilation or cervical dilation plus PBS infusion vs mares receiving no treatments (0 of 5 and 0 of 5 vs 0 of 10, respectively). Intrauterine infusions of 40 ml of 1% oyster glycogen or 40 ml of PBS on Day 3 did not appear to hasten the transport of embryos into the uterus since Day 5 uterine embryo recovery rates were not higher (P > 0.1) for oyster glycogen- or PBS-treated vs untreated mares (2 of 12 and 3 of 11 vs 0 of 10, respectively). Cervical and uterine treatments on Day 3 or Day 4 and uterine lavages on Day 5 decreased (P < 0.05) Days 11 to Day 15 pregnancy rates compared with that of untreated mares. Day 11 to Day 15 pregnancy rates were 1 of 5 for mares with Day 4 cervical dilation and Day 5 uterine lavage, 1 of 5 for mares with Day 4 PBS infusion and Day 5 uterine lavage, 2 of 12 for mares with Day 3 oyster glycogen infusion and Day 5 uterine lavage, and 3 of 11 for mares with Day 3 PBS infusion and Day 5 uterine lavage vs 7 of 10 for mares that received no treatment or lavage. Cervical and uterine manipulations on Day 3 or 4 and uterine lavage on Day 5 appeared to decrease pregnancy rates by Days 11 to 15. The results of these experiments do not support the hypothesis that cervical dilation or uterine infusion hasten oviductal transport, since neither cervical manipulation nor transcervical infusion of oyster glycogen or PBS into the uterus significantly hastened the rate of embryo transport into the uterus.     

Effect of ovarian hormones on promotion of bactericidal activity by uterine secretions of ovariectomized mares

The bactericidal and phagocytic activities of blood neutrophils suspended in uterine washings and the mobilization of neutrophils into the uterine lumen were studied in ovariectomized mares receiving oestradiol benzoate (N = 4), progesterone (N = 4) or oily vehicle (N = 4). Uterine lavage was performed sequentially up to 144 h after induction of endometritis by intrauterine infusion of glycogen (1%). There was no significant difference between the 3 groups in speed of mobilization of neutrophils into the uterus in the first 6 h after infusion but there were significantly more uterine luminal neutrophils in progesterone-treated than in oestradiol-treated mares by 24 h after infusion (P less than 0.01). Uterine washings collected from progesterone-treated mares at 0, 24 and 144 h were significantly worse at promoting bactericidal activity by neutrophils than washings from oestradiol-treated and control mares (P less than 0.001). In oestrogen-treated and control mares bactericidal activity had increased by 144 h but in progesterone-treated mares bactericidal activity remained low. Neither treatment nor time affected the ability of washings to opsonize yeast blastospores. Elevated concentrations of progesterone in plasma were therefore associated with decreased bactericidal activity of neutrophils suspended in uterine washings but the generation of C3b in washings did not appear to be affected by hormone treatment.     

Effects of day of estrous cycle, time of day, luteolysis, and embryo on uterine contractility in mares

One-minute continuous ultrasonic scans of longitudinal sections of the uterine body were videotaped, and contractility scores (1 to 5, minimal to maximal contractility) were assigned without knowledge of mare identity, day of the estrous cycle or pregnancy status. Contractility was assessed, and plasma progesterone concentrations were determined for each of 3 daily examinations (at 0800, 1600 and 2400 hours) from Day 9 to Day 19 (Day 0 = day of ovulation). For both the nonbred (n=11) and pregnant (n=11) mares, there was no effect of hour of scan on the extent of uterine contractility. When data for the nonbred mares were normalized to the onset of luteolysis (defined for each mare as the first >/=25% decrease in plasma progesterone concentrations between successive samples), there was an abrupt increase (P<0.05) in contractility 24 hours prior to the onset of luteolysis. Contractility was also assessed daily in 20 nonbred and 27 pregnant mares from Day 0 to Day 17. For the nonbred mares, a biphasic profile in contractility occurred during the estrous cycle as indicated by the following significant changes: a decrease between Days 0 and 2, an increase between Days 2 and 4, a plateau between Days 4 and 7, a decrease between Days 7 and 11, an increase between Days 11 and 13, and a decrease between Days 14 and 16. For pregnant mares, contractility increased (P<0.05) prior to the late-diestrous increase for nonbred mares. In addition, a significant reduction in contractility was detected on Day 5 in these mares compared with that in the nonbred mares. Contractility in the uterine body in 7 mares was assessed every 5 minutes after departure of the embryonic vesicle from the uterine body. Levels of contractility in the uterine body were lower (P<0.05) 55 minutes after the vesicle had exited the body than 相似文献   

The effect of postbreeding uterine lavage on pregnancy rate in mares

One stallion and 54 mares were used in an experiment to evaluate the effect of postbreeding uterine lavage on pregnancy rate in mares. All mares were inseminated with 250 x 10(6) progressively motile sperm every other day during estrus until detection of ovulation. Mares (n = 18) were randomly assigned to one of three treatment groups: 1) no postbreeding uterine lavage (control); 2) uterine lavage at 0.5 h postbreeding; or 3) uterine lavage at 2 h postbreeding. A dilute solution of povidone-iodine (PIS; 0.05%) previously determined to render spermatozoa immotile in vitro was used to lavage the mare uteri. One liter PIS, prewarmed to 40 degrees C, was used for each lavage. Pregnancy status of mares was determined at 21 d and 36 d post ovulation, using transrectal ultrasonography. The pregnancy rate of Group 1 (66.7%) was higher than that of Group 2 (22.2%; P<0.05) or Group 3 (33.3%); P<0.10). The pregnancy rates of Groups 2 and 3 were similar (P>0.70). Evaluation of endometrial biopsies obtained from a separate set of mares (n = 3) on Day 6 post ovulation, both before and after uterine lavage, revealed no difference in the accumulation of inflammatory cells, suggesting adverse effects of lavage on fertility may have been due to excessive removal of spermatozoa from the uterus during the lavage process or damage to oviductal spermatozoa.     

Lysozyme, alkaline phosphatase and neutrophils in uterine secretions of mares with differing resistance to endometritis

A study was conducted to 1) determine differences in the inflammatory response following bacterial challenge between normal mares and mares with chronic endometritis and 2) to determine if enzyme activity in uterine fluid can be used to evaluate degree of inflammation in the equine uterus. Six normal mares (Group 1) and four mares with chronic endometritis (Group 2) received an intrauterine infusion of beta-hemolytic streptococci on the second day of estrus. Neutrophil concentration as well as lysozyme and alkaline phosphatase activity were determined in uterine secretions obtained by placing tampons in the uterus of mares. All mares had a similar inflammatory response following bacterial challenge of the uterus, as indicated by a neutrophil response of the same magnitude. Neutrophil numbers, lysozyme and alkaline phosphatase concentrations were all increased 12 h postinoculation and declined rapidly to normal preinoculation values by 48 h after inoculation. In spite of the similarity of the clinical signs, neutrophil concentrations and enzyme activity, mares in group 1 demonstrated a markedly higher ability to eliminate the infection than mares in group 2. It is concluded that factors other than neutrophil numbers, lysozyme and alkaline phosphatase activity account for the inability of the mare to eliminate uterine infections.     

Does artificial insemination with chilled, extended semen reduce the antigenic challenge to the mare's uterus compared with natural service?

Uterine response in infection-resistant mares (n = 5) at 48 h after AI was compared with that following natural service in these same mares, and after AI in infection-susceptible mares (n = 6). In the resistant mares, small amounts of uterine fluid were detected and bacteria were isolated infrequently at 48 h after breeding, but cytological examination of uterine flushes revealed that a significant degree of endometritis was present. There was no difference in the degree of inflammatory response by 48 h after AI or natural mating. In 4 of the 6 susceptible mares moderate to large accumulations of intrauterine fluid were detected at 48 h after AI, and massive uterine neutrophilia was present in all 6 mares. It was concluded that there was no evidence that using conventional AI techniques limited the inflammatory response of the mare's uterus.     

High concentrations of myeloperoxidase in the equine uterus as an indicator of endometritis

Intraluminal fluid and excessive abnormal hyperedema are regularly used for the diagnosis of endometritis in the mare, which is routinely confirmed by the presence of neutrophils on endometrial smears. Studies show a relation between neutrophils and myeloperoxidase (MPO), an enzyme contained in and released by neutrophils during degranulation or after cell lysis. This enzyme has been found in many fluids and tissues, and associated with different inflammatory pathologies in the horse. The aims of this study were to assess the presence and concentration of MPO in the equine uterus, and to investigate its relation with neutrophils, and other clinical signs of endometritis. Mares (n = 51) were evaluated for the presence of intraluminal fluid and excessive endometrial edema before breeding, and a small volume lavage and cytology samples were obtained. From 69 cycles, supernatant of the uterine flushes was analyzed with a specific equine MPO ELISA assay to measure MPO concentration. Cytology samples were used for the diagnosis of endometritis. Myeloperoxidase was present in the uterus of all estrus mares in highly variable concentrations. Myeloperoxidase concentrations were significantly (P < 0.05) higher in samples with positive cytologies and in the presence of intraluminal fluid. Occasionally, some samples with negative cytologies showed high MPO concentration, but the opposite was never observed. Cycles presenting hyperedema weren't associated with high concentration of MPO, intraluminal fluid, or positive cytology, making it a poor diagnostic tool of endometritis.