The effect of postbreeding uterine lavage on pregnancy rate in mares

Persistent Breeding-Induced Endometritis in Mares - a Multifaceted Challenge: From Clinical Aspects to Immunopathogenesis and Pathobiology

Post-breeding endometritis (i.e., inflammation/infection of the endometrium), is a physiological reaction taking place in the endometrium of mares within 48 hours post-breeding, aimed to clear seminal plasma, excess sperm, microorganisms, and debris from the uterine lumen in preparation for the arrival of an embryo. Mares are classified as susceptible or resistant to persistent breeding-induced endometritis (PBIE) based on their ability to clear this inflammation/infection by 48 hours post-breeding. Mares susceptible to PBIE, or those with difficulty clearing infection/inflammation, have a deficient immune response and compromised physical mechanisms of defense against infection. Molecular pathways of the innate immune response known to be involved in PBIE are discussed herein. The role of the adaptive uterine immune response on PBIE remains to be elucidated in horses. Advances in the pathobiology of microbes involved in PBIE are also revised here. Traditional and non-traditional therapeutic modalities for endometritis are contrasted and described in the context of clinical and molecular aspects. In recent years, the lack of efficacy of traditional therapeutic modalities, alongside the ever-increasing incidence of antibiotic-resistant microorganisms, has enforced the development of non-traditional therapies. Novel biological products capable of modulating the endometrial inflammatory response are also discussed here as part of the non-traditional therapies for endometritis.

Effect of a povidone-iodine intrauterine infusion on progesterone levels and endometrial steroid receptor expression in mares

Background

Intrauterine infusions have been widely used for the treatment of endometritis in the mare. Nevertheless, their consequences on endocrine and endometrial molecular aspects are unknown. We studied the effect of a 1% povidone-iodine solution intrauterine infusion on progesterone levels, endometrial histology and estrogen (ERα) and progesterone (PR) receptor distribution by immunohistochemistry.

Methods

Fourteen healthy mares were used in this study. Estruses were synchronized and seven mares were treated with intrauterine infusions at days 0 and 2 post ovulation of two consecutive estrous cycles. Uterine biopsy samples were taken on days 6 and 15 post ovulation.

Results

The treatment did not induce an inflammatory response indicating endometritis, neither affected the ERα. However, it reduced the percentage of PR positive cells (PPC) on day 6 (deep glandular epithelium, control: 95.7 vs. infused: 61.5, P < 0.05). Treated mares tended to have lower progesterone levels on day 2 (3.9 ng/ml vs. 6.6 ng/ml, P = 0.07), and higher levels on day 15 compared with controls (4.4 ng/ml vs. 1.3 ng/ml, P = 0.07).

Conclusion

a 1% povidone-iodine infusion during days 0 and 2 post ovulation in healthy mares did not induce histological changes indicating endometritis, but altered progesterone concentrations and reduced the expression of endometrial PR at day 6 without affecting the ERα. These changes could reduce embryo survival.

Advances in the diagnosis and treatment of chronic infectious and post-mating-induced endometritis in the mare

CONTENTS

Rapid physical uterine clearance is paramount for fertility. Mares that are unable to clear the by-products of insemination or foaling quickly may develop post-mating-induced or acute endometritis. If endometritis is not promptly resolved, the infection can become chronic. Endometritis can be difficult to identify because clinical signs, ultrasonographic and laboratory findings can vary between uterine pathogens. Some micro-organisms are associated with an influx of neutrophils and fluid into the uterine lumen while others are associated with only heavy debris on cytological specimens. Identifying the inciting cause may require more than swabbing the endometrium. Culturing endometrial biopsy tissue or uterine fluids are more sensitive methods for identifying Escherichia coli than culture swab while endometrial cytology identifies twice as many mares with acute inflammation than uterine culture swab. While post-mating-induced endometritis is classically treated with uterine irrigation and ecbolics and acute endometritis is treated with either systemic or intra-uterine antibiotics, these therapies are not always effective in resolving chronic uterine inflammation or infections. Mucolytics can be used to break up mucus produced by an irritated endometrium, steroids can modulate the inflammatory response associated with insemination and buffered chelating agents can remove biofilm, a protective mechanism used primarily by gram-negative organisms and yeast to evade the host immune response.

Clinical and subclinical endometritis in the mare: both threats to fertility

Endometritis, a major cause of mare infertility arising from failure to remove bacteria, spermatozoa and inflammatory exudate post-breeding, is often undiagnosed. Defects in genital anatomy, myometrial contractions, lymphatic drainage, mucociliary clearance, cervical function, plus vascular degeneration and inflamm-ageing underlie susceptibility to endometritis. Diagnosis is made through detecting uterine fluid, vaginitis, vaginal discharge, short inter-oestrous intervals, inflammatory uterine cytology and positive uterine culture. However, these signs may be absent in subclinical cases. Hypersecretion of an irritating, watery, neutrophilic exudate underlies classic, easy-to-detect streptococcal endometritis. In contrast, biofilm production, tenacious exudate and focal infection may characterize subclinical endometritis, commonly caused by Gram-negative organisms, fungi and staphylococci. Signs of subclinical endometritis include excessive oedema post-mating and a white line between endometrial folds on ultrasound. In addition, cultures of uterine biopsy tissue or of small volume uterine lavage are twice as sensitive as guarded swabs in detecting Gram-negative organisms, while uterine cytology is twice as sensitive as culture in detecting endometritis. Uterine biopsy may detect deep inflammatory and degenerative changes, such as disruption of the elastic fibres of uterine vessels (elastosis), while endoscopy reveals focal lesions invisible on ultrasound. Mares with subclinical endometritis require careful monitoring by ultrasound post-breeding. Treatments that may be added to traditional therapies, such as post-breeding uterine lavage, oxytocin and intrauterine antibiotics, include lavage 1-h before mating, carbetocin, cloprostenol, cervical dilators, systemic antibiotics, intrauterine chelators (EDTA-Tris), mucolytics (DMSO, kerosene, N-acetylcysteine), corticosteroids (prednisolone, dexamethasone) and immunomodulators (cell wall extracts of Mycobacterium phlei and Propionibacterium acnes).

Effect of type of semen, time of insemination relative to ovulation and embryo transfer on early equine embryonic vesicle growth as determined by ultrasound

Embryonic vesicle growth in the mare is easily monitored by ultrasound. Apart from pregnancy diagnosis, assessment of the embryonic vesicle in practice is also useful to evaluate its viability. Although subject to individual variation, embryo growth rate follows a constant pattern in the early stages of development in relation to embryonic age. Previous studies have shown a significant effect of some factors routinely used in practice, such as post-ovulation insemination and embryo transfer, on embryonic growth and the time in which the vesicle is first detected. This study attempts to confirm previous results in different settings and characterise the causes for this delay in growth. A total of 159 pregnancies from different mating protocols: (1) pre-ovulation natural mating, (2) pre-ovulation natural mating and transfer into recipient mares, (3) post-ovulation natural mating, and (4) post-ovulation AI with frozen/thaw spermatozoa were evaluated ultrasonographically from day 12 to 19 of pregnancy and vesicle diameters recorded. Regression analysis between embryonic vesicle diameters and embryonic ages was performed for each group and mean vesicle diameter at different age periods among groups were tested for statistical difference with a general linear model of variance. There was no significant difference between groups 1 and 2 (P=0.73) or between groups 3 and 4 (P=0.71). However both pre-ovulation groups (1 and 2) had larger vesicle diameters (P<0.000) at any embryonic age analysed than either of the post-ovulation groups (3 and 4). In conclusion, post-ovulation inseminations produced pregnancies with smaller vesicle diameters equivalent to approximately 1 day's growth.

Common procedures in broodmare practice: what is the evidence?

Many procedures performed as part of routine broodmare practice are based on sound clinical judgment and experience or scientific evidence; however, others are based on perceived problems and needs to address them. This article presents four procedures commonly used in broodmare practice, for which there is questionable evidence to substantiate their use.

Effect of sperm numbers and concentration on sperm transport and uterine inflammatory response in the mare

Our objective was to determine whether the concentration of cooled sperm inseminated influenced sperm transport and intensity of the uterine inflammatory reaction 2, 4 and 24h after insemination. Experimental subjects were 189 estrous mares with a dominant follicle > or =35 mm in diameter and no bacterial growth or neutrophils detected in uterine smears. Each mare was randomly assigned to receive one of the following intrauterine treatments (volume, 20 mL): insemination with 5x10(6) mL(-1) or 25x10(6) mL(-1) or 50x10(6) mL(-1) sperm diluted in 3 mL seminal plasma (SP) and 17 mL skim milk; seminal plasma or skim milk extender. Mares in a control group received no intrauterine treatment. Mares were slaughtered 2, 4 or 24h after insemination or infusion. Oviducts were separated from the uterus, and uterus and oviducts were then flushed with phosphate-buffered saline (PBS). After flushing, an endometrial sample was collected for further histopathological examination. The grade of uterine fibrosis and the amount of neutrophils in the stratum compactum were evaluated. A sample of each tubal flushing was examined for sperm count, and a sample of each uterine flushing was examined for PMN count. It was concluded that compounds in the insemination dose provoked a uterine inflammatory response, which was more rapid and intense as sperm concentration increased. In contrast, sperm transport through 4h after insemination was not influenced by sperm concentration.

Disease transmission in horses

Bacterial, viral and protozoal infections may cause severe reproductive losses. The present paper reviews the risk factors, clinical signs and preventive measures for the most important venereal or potential sexually transmitted diseases in horses. The stallion and use of semen for artificial insemination represent major risk factors for the transmission of bacterial contaminants of the penis, including Streptococcus equi subspecies zooepidemicus, Pseudomonas aeruginosa and Klebsiella pneumoniae, known to cause endometritis and infertility in the mare. The role of the stallion in disease transmission is also due to the non-clinical manifestation of diseases such as contagious equine metritis and equine viral arteritis. Dourine has been eradicated from many countries, but continues to be a problem in other areas of the globe. Strategies for the prevention of introduction and transmission of diseases in breeding operation are discussed.

Components in seminal plasma regulating sperm transport and elimination

Seminal plasma has been suggested to be involved in sperm transport, and as a modulator of sperm-induced inflammation, which is thought to be an important part of sperm elimination from the female reproductive tract. This article reports on recent experiments on the importance of seminal plasma components in sperm transport and elimination. In Experiment 1, hysteroscopic insemination in the presence (n = 3) or absence (n = 3) of 2 ng/mL PGE showed an increased portion of spermatozoa crossing the utero-tubal junction in the presence of PGE in two mares, while no difference was observed between treatments in a third mare. In Experiment 2, whole seminal plasma, heat-treated seminal plasma (90 degrees C for 45 min), and charcoal-treated seminal plasma were added to: (1) sperm samples during opsonization prior to polymorphonuclear neutrophil(s) (PMN)-phagocytosis assays (n = 5); or to (2) phagocytosis assays (n = 5). Opsonization of spermatozoa was suppressed in the presence of whole seminal plasma, compared with samples without seminal plasma (p < 0.05). Charcoal treatment did not remove the suppressive effect of seminal plasma on opsonization, but heat treatment of seminal plasma reduced its suppressive properties (p < 0.05). The addition of whole seminal plasma to opsonized spermatozoa almost completely blocked phagocytosis (p < 0.05). Charcoal treatment did not remove the suppressive effect of seminal plasma. However, heat-treated fractions of seminal plasma removed the suppressive effect of seminal plasma on phagocytosis (p < 0.05). In Experiment 3, viable and non-viable (snap-frozen/thawed) spermatozoa were subjected to in vitro assays for PMN binding and phagocytosis with the following treatments (n = 3): (1) seminal plasma (SP), (2) extender; (3) ammonium sulfate precipitated seminal plasma proteins with protease inhibitor (SPP+); or (4) ammonium sulfate precipitated seminal plasma proteins without protease inhibitor (SPP-). Treatment was observed to impact binding and phagocytosis of viable and non-viable spermatozoa (p < 0.05). SP and SPP+ suppressed PMN-binding and phagocytosis of viable sperm. This effect was also seen, but to a lesser degree, in SPP- treated samples. Non-viable spermatozoa showed less PMN-binding and phagocytosis than live sperm in the absence of SP. The addition of SP promoted PMN-binding and phagocytosis of non-viable spermatozoa. SPP- treated samples also restored PMN-binding of non-viable spermatozoa. The addition of protease inhibitors removed this effect. In Experiment 4, seminal plasma proteins were fractionated based on MW by Sephacryl S200 HR columns (range 5000-250,000 kDa). Fractionated proteins were submitted to sperm-PMN binding assays. A protein fraction <35 kDa suppressed PMN-binding to live and snap-frozen spermatozoa. A greater MW protein fraction appeared to promote binding between PMNs and snap-frozen spermatozoa. While the addition of protease inhibitors was necessary to maintain the protective effect of seminal plasma proteins on viable spermatozoa, the promotive effect of seminal plasma on non-viable spermatozoa appeared to require some protease activity. It was concluded from these experiments that components of seminal plasma play active roles in transportation and survival of viable spermatozoa in the female reproductive tract and in the elimination of non-viable spermatozoa from the uterus.

Low-dose insemination—Why, when and how

The typical dose for insemination into the uterine body of the mare is > 300 x 10(6) progressively motile spermatozoa (PMS) and an insemination dose of > 200 x 10(6) PMS is recommended for frozen-thawed semen. Low-dose insemination techniques allow for a drastic reduction in the numbers of spermatozoa required to achieve pregnancy. Acceptable pregnancy rates can be achieved with doses ranging from 1 to 25 x 10(6) PMS in volumes ranging from 20 to 1000 microL. Two techniques have been described: hysteroscopic insemination and transrectally guided deep horn insemination using a pipette. Similar pregnancy rates can be attained by either method when 5 x 10(6) PMS are used. Hysteroscopic insemination may provide an advantage when the dose is 1-3 x 10(6) PMS. These techniques have the potential to make more efficient use of frozen-thawed or sex-sorted semen from certain stallions. The use of low-dose insemination to improve fertility of infertile stallions warrants further investigation.

Effect on fertility of uterine lavage performed immediately prior to insemination in mares

OBJECTIVE

To determine the effect on fertility of large-volume uterine lavage with lactated Ringer's solution (LRS) performed immediately prior to insemination in mares.

DESIGN

Prospective randomized controlled study.

ANIMALS

20 mares.

PROCEDURE

Control mares (n = 10) were inseminated with 1 billion (estimated before cooling) progressively motile spermatozoa that had been cooled in a passive cooling unit for 24 hours. Mares (n = 10) in the treatment group were inseminated with 1 billion progressively motile spermatozoa (cooled as described for control mares) immediately after uterine lavage with 4 L of sterile LRS.

RESULTS

There were no significant differences in pregnancy rates or size of the embryonic vesicle on days 12, 13, and 14 after ovulation between control and treated mares.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicate that uterine lavage with LRS can be performed immediately prior to insemination without adversely affecting fertility in mares. This is clinically important, because insemination may be necessary when a mare has inflammation-associated fluid (detectable ultrasonographically) in the uterus; removal of the fluid is desirable, because it adversely affects spermatozoal motility and fertility. This situation typically arises when mares require rebreeding after they have developed persistent mating-induced endometritis or are inseminated multiple times in a 24-hour period (during the period of physiologic mating-induced inflammation), which is a common practice when using cooled or frozen-thawed semen.

Effect of dose and day of treatment on uterine response to oxytocin in mares

To determine the effect of dose and day of oxytocin treatment on intrauterine pressure, 6 normal mares were treated with 10 or 25 IU oxytocin 2 days before ovulation, on the day of ovulation and 2 days after ovulation. Intrauterine pressure (IUP) was measured using micro-tip-catheters (one placed intrauterine, a second and third serving as reference sensors in the vagina and external to the mare) and transmitted by telemetry for 30 min to establish a baseline before saline was administered, iv, and for an additional 30 min after saline administration. Oxytocin was then given, iv, and IUP was recorded for 60 min. No change in IUP was observed after saline injection. The administration of both 10 (n=16) and 25 (n=10) IU oxytocin induced a response (P<0.01). The intensity of response depended on the day of administration (P<0.01) and the dose of oxytocin (P<0.001). The variation of response was significantly greater after 10 IU oxytocin (CV 15.78%) compared with 25 IU oxytocin (CV 6.42%). The uterine response was greatest on Day 2 prior to ovulation and lowest on Day 2 after ovulation. The response was negatively correlated to increasing plasma progesterone (10 IU oxytocin: r = -0.435, 25 IU oxytocin: r = -0.265). There was no correlation between the uterine response and plasma estradiol-17beta concentration (P<0.01). In conclusion the results of this study show that oxytocin administration to mares before ovulation provides a greater response than after ovulation. A decline in the intensity of response after ovulation can be compensated for with a higher dose of oxytocin. Furthermore, the use of the multiple catheter technique is an effective method for assessing changes in uterine pressure.

A glimpse at sperm function in vivo: sperm transport and epithelial interaction in the female reproductive tract

The process of sperm transport in the female reproductive tract is more than simply a migration of spermatozoa from the site of insemination to the site of fertilization. Rather, it is a complex and dynamic continuum that encompasses phases of sperm distribution within the tract, the accumulation of spermatozoa in reservoirs, the modulation of sperm physiology and acquisition of fertilization competence, the ascent of competent spermatozoa to the site of fertilization, and the elimination of the non-fertilizing sperm population. The dynamic interactions that occur between functional spermatozoa and the luminal fluids and epithelial surfaces of the female genital tract during transit and storage enhance sperm survival and regulate sperm function in the female. The universal nature of this interaction highlights it as a key component of the sperm transport process.

Administration of oxytocin immediately after insemination does not improve pregnancy rates in mares bred by fertile or subfertile stallions

It is probable that reduced pregnancy rates in mares bred to subfertile stallions is attributable, in part, to the reduced number of normal spermatozoa that colonize the oviduct. Administration of oxytocin stimulates both uterine and oviductal contractility. The hypothesis that oxytocin may enhance sperm transport to/into the oviducts, and thereby increase pregnancy rates, was tested in 2 trials. For both trials, fertile estrous mares with follicles > or = 35 mm in diameter were inseminated once at 24 h after administration of 1500 to 2000 U hCG. The inseminate dose was limited to 100 million spermatozoa in order to lower pregnancy rates and thus increase the chance of detecting a treatment effect. Pregnancy status was determined by transrectal ultrasound examination 14 to 16 d after insemination. In Trial 1, 49 mares were inseminated with 4 mL extended semen from 1 of 3 stallions (1 fertile and 2 subfertile males). Immediately after insemination, the mares were administered either 20 U oxytocin or 1 mL saline intravenously. In Trial 2, 51 mares were inseminated with 4 mL extended semen from 1 of 4 stallions (1 fertile and 1 subfertile male used in Trial 1, and 2 additional fertile males). Immediately after insemination, and again 30 min later, mares were administered either 5 U oxytocin or 0.25 mL saline intramuscularly. To test for effects of treatment with oxytocin and for the interaction between semen quality and treatment, a generalized linear mixed regression model was used that accounted for the split-plot design (treatment within stallions), the random effect of stallion, the fixed effect of semen quality, the binary outcome of a single breeding trial, and the varying number of trials per stallion/treatment groups. Three treatment protocols or regimens were used: placebo, 5 U oxytocin injected twice intramuscularly, and 20 units oxytocin injected twice intravenously. Semen was classified as high (fertile stallions) or low (subfertile stallions) quality. No interaction between semen quality and treatment was detected (P > 0.10). The pregnancy rate of mares treated with oxytocin immediately after insemination was 30% (15/50) compared with 50% (25/50) for mares treated with saline immediately after breeding. Administration of oxytocin did not affect pregnancy rates (P > 0.10).

Sperm transport and survival in the mare

Following the deposition of semen in the mares uterus, spermatozoa must be transported to the site of fertilization, be maintained in the female tract until ovulation occurs, and be prepared to fertilize the released ovum. Sperm motility, myometrial contractions, and a spontaneous post-mating uterine inflammation are important factors for the transport and survival of spermatozoa in the mares reproductive tract. Fertilizable sperm are present in the oviduct within 4 hours after insemination. At this time, the uterus is the site of a hostile inflammatory environment. Our data suggest that spermatozoa trigger an influx of polymorphonuclear neutrophils (PMNs) into the uterine lumen via activation of complement. Furthermore, seminal plasma appears to have a modulatory effect on the post-mating inflammation through its suppressive effect on PMN chemotaxis and migration. Spermatozoa that safely have reached the oviduct can be stored in a functional state for several days, but prolonged sperm storage in the female tract is not required for capacitation and fertilization in the horse. The caudal isthmus has been proposed as a sperm reservoir in the mare. The pattern of sperm transport and survival of spermatozoa in the mares reproductive tract are different between fertile and subfertile stallions, between fertile and some infertile mares, and between fresh and frozen-thawed semen. Possible explanations for these differences include a selective phagocytosis of damaged or dead spermatozoa, impaired myometrial activity in subfertile mares, bio-physiological changes of spermatozoa during cryopreservation, and the removal of seminal plasma during cryopreservation of equine semen.