Equine endometritis: a review of challenges and new approaches

In vitro effects of different ozone preparations on microorganisms responsible for endometritis in the mare

Infectious endometritis is considered one of the major causes of infertility and it can affect up to 60% of barren mares. It is characterized by the presence of one or more microorganisms in the reproductive tract and it is treated with the administration of antibiotics, ecbolic agents and uterine lavages. Ozone, thanks to its antimicrobial properties that are based on its high oxidative potential, could represent an effective alternative treatment for endometritis. The aim of this study was to test in vitro the bactericidal and fungicidal properties of different ozone formulations, either as gas (experiment 1) or dissolved in two liquid matrices (experiment 2), specifically distilled water or oil (Neozone 4000, Cosmoproject, Parma, Italy), onto 6 different species of microorganisms isolated from mares with clinical endometritis, namely Escherichia coli, Staphylococcus aureus, Streptococcus equi subsp. Zooepidemicus, Pseudomonas aeruginosa, Klebsiella pneumoniae and Candida albicans. In the first experiment, 3 clinical antibiotic-resistant strains per each species were exposed to different conditions: to O2O3 gas mixtures (15 and 40 μg/ml for 1, 3 and 5 min), to 100 % O2 or left untreated. The results showed a reduction of the microbial count of over 99,9% for every pathogen, time and concentration of O2O3 gas mixtures tested. Furthermore, gaseous ozone showed both a time-dependant effect (5 vs 3 vs 1 min of exposure) and a concentration-dependant effect (40 vs 15 μg/ml) at 1 and 3 min, while after 5 min no differences were observed. In the second experiment, minimum inhibitory concentration (MIC), and minimum bactericidal/fungicidal concentration (MBC, MFC) of ozonated distilled water and ozonated oil were evaluated. Ozonated oil showed a bactericidal/fungicidal activity against all the strains tested (MIC range 12.5-25 % v/v, MBC/MFC range 12.5-50 % v/v) while ozonated distilled water didn't show an observable antimicrobial effect, discouraging its use as an antimicrobial agent for the treatment of endometritis. The results of this in vitro study indicate that both gaseous ozone and ozonated oil exerted remarkable antimicrobial activities and are promising alternative treatments for infectious endometritis, even when caused by antibiotic-resistant bacteria, and encourage further experiments in an effort to scale down or even prevent the use of antibiotics in equine reproduction.

A simplified fixed-time insemination protocol using frozen-thawed stallion spermatozoa stored at 17°C for up to 24 h before insemination

BACKGROUND

Insemination of mares with frozen-thawed spermatozoa requires intensive management and results in 40%-60% per cycle pregnancy rates.

OBJECTIVES

To determine if satisfactory fertility is possible for frozen-thawed semen after processing it through a microfluidic device, followed by storage at 17°C for up to 24 h before fixed-time insemination.

STUDY DESIGN

Uncontrolled field trials.

METHODS

A pilot study evaluated the motility of frozen-thawed spermatozoa after centrifugation and storage (17°C) in two different media for up to 48 h. Subsequently, the motility of frozen-thawed semen processed through a microfluidic device, resuspended in two different media during storage (17°C) for up to 24 h was evaluated. The fertility of frozen-thawed spermatozoa, after microfluidic sorting and storage at 17°C for up to 24 h, was evaluated after fixed-time insemination in a commercial embryo programme. Experiment 1: Frozen-thawed spermatozoa (N = 5 stallions) were centrifuged and resuspended in Botusemen Gold™ or SpermSafe™ and stored (17°C) for up to 48 h. Sperm motility was evaluated by CASA at 0, 6, 24 and 48 h. Experiment 2: Frozen-thawed spermatozoa (N = 4 stallions) underwent microfluidic sorting and storage (17°C) for up to 24 h in both media. Sperm concentration and motility were evaluated at 0, 16 and 24 h. Experiment 3: Fertility of frozen-thawed spermatozoa (N = 3 stallions) was evaluated after insemination of 42 mare cycles at 6, 16 and 24 h after thawing, microfluidic sorting and storage before fixed-time insemination.

RESULTS

The stallion significantly influenced sperm motility, but there was no effect of media on motility parameters. Storage time significantly affected sperm motility after centrifugation but not after microfluidic sorting. Storage time had no effect on the overall embryo recovery rate (52%, n = 42).

MAIN LIMITATIONS

Field trial with small mare numbers and no control at time = 0 h.

CONCLUSIONS

Fixed-time insemination of frozen-thawed spermatozoa after microfluidic sorting and storage at 17°C for up to 24 h produced satisfactory embryo recovery rates.

Endometrial expression of antimicrobial peptides as markers of subclinical endometritis in mares

BACKGROUND

Endometritis is a major cause of subfertility in mares. Multiparous old mares are more susceptible to developing endometritis given that ageing is associated with an altered immune response and with inadequate physiological uterine clearance after breeding, which can lead to degenerative changes in the endometrium. Molecules such as antimicrobial peptides (AMPs) have been proposed as endometritis markers in the equine species.

STUDY DESIGN

Cross-sectional.

OBJECTIVES

To investigate the endometrial expression of defensin-beta 4B (DEFB4B), lysozyme (LYZ) and secretory leukocyte peptidase inhibitor (SLPI) genes in mares either affected or not by subclinical endometritis, due to the role of these AMPs in the immune response to bacteria and inflammatory reactions.

METHODS

Endometrial biopsy for histopathological and gene expression examinations was performed on 26 mares. The inclusion criteria for the normal mare group (NM, N = 7) were 2-4 years of age, maiden status, no clinical signs of endometritis and a uterine biopsy score of I, while for mares affected by subclinical endometritis (EM, N = 19) the inclusion criteria were 10-22 years of age, barren status for 1-3 years, no clinical signs of endometritis and a uterine biopsy score between IIA and III.

RESULTS

A significantly higher expression of LYZ (NM: 0.76 [1.84-0.37] vs. EM: 2.78 [5.53-1.44], p = 0.0255) and DEFB4B (NM: 0.06 [0.11-0.01] vs. EM: 0.15 [0.99-0.08], p = 0.0457) genes was found in endometritis mares versus normal mares. Statistically significant moderate positive correlations were found between the level of expression of LYZ gene and both the age (r = 0.4071, p = 0.039) and the biopsy grade (r = 0.4831, p = 0.0124) of the mares.

MAIN LIMITATIONS

The study investigated a limited number of genes and mares, and the presence/location of the proteins coded by these genes was not confirmed within the endometrium by IHC.

CONCLUSIONS

If the results of this study are confirmed, LYZ and DEFB4B genes can be used as markers to identify mares that are affected by subclinical endometritis.

Prevalence of Microbial Isolates Cultured from Endometrial Swab Samples Collected from United Kingdom Thoroughbred Mares from 2014 to 2020

Determining whether endometrial microbial isolates are pathogens, contaminants, or even part of the "normal" microbiome is extremely complex, particularly given the absence of "gold standard" tests for endometritis. Population-level benchmarking and temporal monitoring can provide novel insights and a wider context to improve understanding. This study aimed to (i) estimate the prevalence of endometrial isolates from swabs of Thoroughbred broodmares in Newmarket, UK between 2014 and 2020; and (ii) evaluate the effects of year, mare age, and cytology findings on isolate prevalence. Generalised linear mixed models with a logit link, both null models and models using year of sampling, mare age, or cytology findings as predictors, were fitted to estimate isolate prevalence. Over the 7-year period, data were available from 18,996 endometrial-swab samples from 6050 mares on 290 premises. The overall isolate prevalence was 35.5% (95% confidence interval (CI) 33.0-37.9), and this varied significantly between years. The most prevalent isolates were β-hemolytic Streptococcus (17.9; 95% CI: 17-19) and E. coli (10.3%; 95% CI: 9.0-11.6). Isolate prevalence increased with mare age except for E. coli isolates, and with increasing category of cytology findings except for α-hemolytic Streptococcus isolates. The results provide novel estimates of isolate prevalence and highlight knowledge gaps around potential complexities in the interpretation of findings.

Use of cytobrush for bacteriological and cytological diagnosis of endometritis in mares

Background and Aim

A combined microbial and cytological examination of uterine samples is the main diagnostic method for endometritis in mares. This study aimed to describe a procedure for using the same uterine cytobrush (CB) for both bacteriological and cytological evaluation.

Material and Methods

The procedure consists of rolling the CB onto a sterilized glass slide immediately after collection and before the transfer into a sterile saline solution. In Experiment 1, a comparison between bacteriological results of the cotton swab (CS) and CB or pellet was made in 10 mares; in Experiment 2, bacteriological and cytological results were compared between different processing methods of CB in 28 mares; in other 6 mares, a CB was processed for cytology only, to investigate the reasons for the low cellularity of the pellet.

Results

The agreement between culture results from the CB and CS was evaluated, and a comparison between the cytological data obtained by different processing methods of CB was performed. The perfect agreement between the CB and CS microbiological results was found. The described procedure enables useful diagnostic smears for cytology. Moreover, the seeding of both the tip of CB and the saline solution used for the transport produced accurate bacteriological results.

Conclusion

The protocol described in this study for the use of CB for both cytological and bacteriological analysis could be used for the diagnosis of endometritis. To maximize diagnostic sample quality, cytology slides must be prepared with meticulous care in the field to preserve cellular integrity and minimize artifacts.

Frequency of potentially pathogenic bacterial and fungal isolates among 28,887 endometrial samples from mares, with an emphasis on multi-drug resistant bacteria in Germany (2018-2022)

Antimicrobial-resistant bacteria pose a serious threat to the wellbeing of animals and humans. In equine reproduction, endometritis caused by facultative microbial pathogens is a condition, which is usually treated with antibiotics. Data from Germany on prevalence of facultative pathogenic microorganisms cultured in samples from the equine uterus and the frequency of multi-drug resistant (MDR) bacteria is lacking. The aim of the study was to provide representative numbers for both. Microbiological culture results (n = 28,887) of endometrial samples submitted to a large veterinary diagnostic laboratory from 2018-2022 were analyzed. An average of 25.9 % of the culture results showed growth of facultative pathogenic bacteria. The dominant isolated bacteria were β-hemolytic streptococci (79.7 %) followed by Escherichia (E.) coli variatio haemolytica (5.2 %). E. coli were cultured in 4.3 % of the samples and occurred more often than Klebsiella pneumoniae (3.9 %), Candida species (2.9 %), Pseudomonas aeruginosa (2.0 %), and Staphylococcus aureus (1.5 %). Antibiotic susceptibility testing revealed sensitivity of β-hemolytic streptococci towards penicillins in almost 100 % of the cultured samples (99.5 %). E. coli-isolates were sensitive to gentamicin in 96.2 % of the cases. The frequency of multidrug-resistant extended spectrum beta-lactamase (ESBL)-positive bacteria and methicillin-resistant Staphylococcus aureus (MRSA) was 3.1 % of all positive culture results. The number of ESBL-positive isolates (n = 159) and MRSA was stable from 2018-2022. In conclusion, the situation regarding occurrence of MDR bacteria in Germany is favorable, but should further be monitored.

Success of different therapies for bacterial endometritis in stud farm practice

Bacterial endometritis is a major problem in equine reproduction usually treated with antibiotics, however reports of success rates are scarce. This study collected data from mares diagnosed with intrauterine bacterial growth and compared the outcome of different therapies for bacterial endometritis in German stud farm practice. Data on mares with positive uterine culture results were collected retrospectively in veterinary practices (n = 5; 2018-2022). Information relating to 30 factors (mare, diagnostics, therapy, pregnancy rate) of bacterial endometritis cases (n = 772) were recorded and analyzed. Possible effects on treatment success (positive pregnancy result in the first cycle after treatment) were tested by binomial logistic regression. In most cases β-hemolytic streptococci were detected (n = 707). Treatments for the endometritis included trimethoprim-sulfonamides (n = 409), procaine-penicillin (n = 227), marbofloxacin (n = 53) or no antibiotics (n = 59) and most antibiotics were administered systemically (n = 711) rather than locally (n = 23). Uterine lavage was reported in 49 % of mares. Uterotonic drugs were administered in 42.2 % of mares. Breeding programs included artificial insemination (AI) with chilled semen (n = 667), AI with frozen semen (n = 169), transfer of fresh (n = 112) or cryopreserved (n = 27) embryos and natural cover (n = 27). In the first cycle after treatment, the pregnancy rate was 47 % and it rose to 69 % by end of the season. Treatment success was affected by duration of antibiotic treatment, veterinary practice, and presence of clinical signs. In conclusion, reported treatment practices in German stud farm practice resulted in acceptable pregnancy results and the multiple binomial logistic regression approach identified factors affecting the pregnancy outcome in this dataset.

Isolation of lactic acid bacteria from the reproductive tract of mares as potentially beneficial strains to prevent equine endometritis

Endometritis, the inflammation of the endometrium, is the leading cause of subfertility in mares, and therefore responsible for major economic losses in the horse industry worldwide. It is generally treated with uterine lavages combined with ecbolic agents and local or systemic antibiotics. However, since antibiotic overuse has been associated with antimicrobial resistance in mares with persistent endometritis, new prevention and treatment alternatives are needed. One such alternative could be the use of probiotic lactic acid bacteria (LAB) isolated from the host. Thanks to their species specificity, resident microbiota may restore ecological equilibrium within the host, and therefore, help prevent infections and improve physiological functions. In the present study, 257 bacterial strains were isolated from 77 healthy mares, and 88.76% (n = 228) of them were phenotypically classified as LAB. Within this group, 65.79% were able to inhibit at least one strain from each of the genera that most commonly cause equine endometritis (Streptococcus equi subsp. zooepidemicus, Escherichia coli, and Staphylococcus spp.). Five strains (RCE11, RCE20, RCE91, RCE99, and RCE167) were selected on the basis of their beneficial properties: ability to autoaggregate and adhere to equine epithelial cells, high inhibition of and co-aggregation with all the bacteria isolated from clinical cases of endometritis evaluated, and negative co-inhibition between one another. All five were finally identified as Enterococcus spp., namely E. faecium (two strains), E. hirae (two strains), and E. gallinarum (one strain). Further studies will assess their safety and biotechnological potential for the design of a multi-strain probiotic formula to prevent equine endometritis.

Uterine microbial ecology and disease in cattle: A review

Due to the critical contribution of the uterine-associated microbiota in reproductive health, physiology, and performance, culture-independent methods have been increasingly employed to unravel key aspects of microbial ecology in the uterus of cattle. Nowadays, we know that bacterial diversity is crucial to maintain uterine health, however, there is still no consensus on the exact composition of a healthy uterine microbiota (or eubiosis). Generally, loss of bacterial diversity (or dysbiosis) contributes to the development of uterine infections, associated with increased relative abundances of Bacteroides, Fusobacterium, Trueperella, and Porphyromonas. Uterine infections are highly prevalent and gravely influence the profitability of cattle operations, animal welfare, and public health. Thus, understanding the dynamics of uterine microbial ecology is essential to develop effective strategies focused on preventing and mitigating the adverse effects of uterine dysbiosis as well as assisting in the process of restoring the core, healthy uterine microbiota. The aim of this review is to summarize research conducted in the microbial ecology of bovine uteri. We discuss the origin of the uterine microflora of healthy cows and the factors influencing its composition. In addition, we review the biology of specific pathogens that are known to increase in abundance during the occurrence of uterine disease. Lastly, we provide an overview of the bacterial biofilm in the bovine endometrium, and we briefly summarize the rationale for the use of probiotics to prevent uterine disease in cattle.

Progesterone Device Use Improves Ovum Pick-Up Efficiency in Acyclic Donors

The aim of this study was to evaluate follicular dynamics and ovum pick-up (OPU) efficacy in untreated mares or mares treated with an intravaginal progesterone (P4) device during seasonal anestrus (acyclic) and during the breeding season (cyclic). Six mares (mean age = 5 years), were recruited into an ovum pick-up scheme that was performed every 14 days with and without the P4 device, during the acyclic and cyclic phases. Aspirations amounted to seven procedures with or without the P4 device during each phase. Five ultrasound assessments were performed at each interval between the OPUs. Data on follicular number and diameter as well as the numbers of recovered and the percentage of recovered oocytes were also collected. The number of follicles from mares in the acyclic phase was higher (P < .005) regardless of the treatment. However, the follicular diameter was smaller for the P4 group (P < .005) from the 2nd to the 5th evaluation post-OPU procedure. The percentage of oocytes recovered during the acyclic phase was higher for mares treated with the P4 device (P < .005). The P4 device resulted in follicles with smaller diameters and facilitated OPU efficacy.

Effect of Sampling Method on Detection of the Equine Uterine Microbiome during Estrus

Bacterial endometritis is among the most common causes of subfertility in mares. It has a major economic impact on the equine breeding industry. The sensitivity of detecting uterine microbes using culture-based methods, irrespective of the sample collection method, double-guarded endometrial swab, endometrial biopsy, or uterine low-volume lavage (LVL), is low. Therefore, equine bacterial endometritis often goes undiagnosed. Sixteen individual mares were enrolled, and an endometrial sample was obtained using each method from all mares. After trimming, quality control and decontamination, 3824 amplicon sequence variants were detected in the dataset. We found using 16S rRNA sequencing that the equine uterus harbors a distinct resident microbiome during estrus. All three sampling methods used yielded similar results in composition as well as relative abundance at phyla (Proteobacteria, Firmicutes, and Bacteroidota) and genus (Klebsiella, Mycoplasma, and Aeromonas) levels. A significant difference was found in alpha diversity (Chao1) between LVL and endometrial biopsy, suggesting that LVL is superior at detecting the low-abundant (rare) taxa. These new data could pave the way for innovative treatment methods for endometrial disease and subfertility in mares. This, in turn, could lead to more judicious antimicrobial use in the equine breeding industry.

MicroRNAs in equine Endometritis: A review of pathophysiology and molecular insights for diagnostic and therapeutic strategies

Endometritis plays an important role in mare infertility. Certain infectious agents interfere with the innate immune system of endometrium, causing a systemic inflammatory response that lasts for a long time and circulates via the blood or cellular degeneration, leading to endometritis due to bacterial endotoxins. Different small, non-coding RNA molecules are involved in many biological functions. For instance, microRNAs (miRNAs) are involved in the post-transcriptional regulation of gene expression. These miRNAs are important regulators of gene expression, primarily via inhibiting transcription and translation processes. This manuscript reviews: (1) pathomorphological findings in equine endometritis, (2) the expression and effects of eca-miR-17, eca-miR-223, eca-miR-200a, eca-miR-155, and eca-miR-205 in endometritis and (3) the therapeutic role of miRNA in equine endometritis. The miRNAs have a vital regulatory role in a wide range of inflammatory diseases by regulating the molecular mechanism of cytokines that cause inflammation through signal pathways. This review emphasizes the demand for cutting-edge genetic technologies and the development of novel pharmaceutical preparations to improve our understanding of the genes encoding by these miRNAs. It also focuses on the efficacy of miRNAs for control, early diagnosis, and prevention of endometritis.

Mesenchymal stromal cells modulate infection and inflammation in the uterus and mammary gland

The use of mesenchymal stromal cells (MSCs) is emerging as an efficacious and safe treatment for many infectious and non-infectious inflammatory diseases in human and veterinary medicine. Such use could be done to treat mastitis and metritis, which are the most common disease conditions affecting dairy cows leading to considerable economic losses and reduced animal welfare. Currently, both disease conditions are commonly treated using local and systemic administration of antibiotics. However, this strategy has many disadvantages including low cure rates and the public health hazards. Looking for alternative approaches, we investigated the properties of MSCs using in-vitro mammary and endometrial cell systems and in-vivo mastitis and metritis murine model systems. In-vitro, co-culture of mammary and uterus epithelial cells constructed with NF-kB reporter system, the master regulator of inflammation, demonstrated their anti-inflammatory effects in response to.LPS. In vivo, we challenge animals with field strains of mammary and utero pathogenic Escherichia coli and evaluated the effects of local and systemic application of MSC in the animal models. Disease outcome was evaluated using histological analysis, bacterial counts and gene expression of inflammatory markers. We show that MSC treatment reduced bacterial load in metritis and significantly modulated the inflammatory response of the uterus and mammary gland to bacterial infection. Most notably are the immune modulatory effects of remotely engrafted intravenous MSCs, which open new avenues to the development of MSC-based cell-free therapies.

Relationship between Clinical Uterine Findings, Therapy, and Fertility in the Mare

Persistent breeding-induced endometritis (PBIE) is a major cause of subfertility in horses and the susceptibility is increased by several factors. The aim of this study was to determine the effects of clinical uterine findings and PBIE therapies, respectively, on pregnancy rate in mares. The analysis included records from 220 mares (390 cycles) inseminated at an artificial insemination (AI) center in Switzerland. Gynecological examinations were performed repeatedly before and after AI to determine cervical tone, uterine edema, and intrauterine fluid accumulation. Pregnancy rate was lower (p < 0.001) in barren mares compared to mares of other reproductive status. A more flaccid cervix (p = 0.009) was observed at the time of ovulation in pregnant cycles, but there was no difference (p > 0.05) regarding uterine edema. Intrauterine fluid accumulation reduced pregnancy rate (p = 0.002). Oxytocin administration had beneficial effects on pregnancy rate (p = 0.015), especially for barren mares, while uterine lavage did not have any effect (p > 0.05). The results show that cervical tone and intrauterine fluid accumulation, but not its degree, are useful parameters for assessment of fertility in mares. Oxytocin treatment improved pregnancy rates in mares with PBIE while uterine lavage had a limited effect.

Clinical Aspects of Bacterial Distribution and Antibiotic Resistance in the Reproductive System of Equids

Antibiotic administration is a standard therapeutic practice for the treatment of reproductive disorders of equids. This might lead to undesirable microbial imbalance and could favour the acquisition of antibiotic resistance. Therefore, it is imperative for clinicians to understand patterns of antibiotic resistance when considering and developing treatment regimes. Continued engagement of clinicians with novel alternative approaches to treat reproductive infections would be essential in order to address this rising threat within the One Health perspective. The objectives of the present review were to present the bacterial infections in the reproductive system of equids (horses, donkeys), to upraise the literature related to the issue of antibiotic resistance of bacteria causing these infections and to discuss the topic from a clinical perspective. Initially, the review summarised the various infections of the reproductive system of equids (genital system of females, genital system of males, mammary glands) and the causal bacteria, providing relevant information about horses and donkeys. Subsequently, the clinical therapeutics of these infections were presented, taking into account the significance of antibiotic resistance of bacteria as a limiting factor in treating the infections. Finally, approaches to circumvent antibiotic resistance in clinical settings were summarized. It was concluded that awareness regarding antibiotic resistance in equine reproductive medicine would increase, as we would recognise the multifaceted problem of resistance. Actions and initiatives within the One Health approach, minimizing the potential dissemination of resistant strains to humans and to the environment, with specific applications in medicine of equids should be appropriately instituted internationally.

Amniotic Mesenchymal-Derived Extracellular Vesicles and Their Role in the Prevention of Persistent Post-Breeding Induced Endometritis

Persistent post-breeding induced endometritis (PPBIE) is considered a major cause of subfertility in mares. It consists of persistent or delayed uterine inflammation in susceptible mares. There are many options for the treatment of PPBIE, but in this study, a novel approach aimed at preventing the onset of PPBIE was investigated. Stallion semen was supplemented with extracellular vesicles derived from amniotic mesenchymal stromal cells (AMSC-EVs) at the time of insemination to prevent or limit the development of PPBIE. Before use in mares, a dose–response curve was produced to evaluate the effect of AMSC-EVs on spermatozoa, and an optimal concentration of 400 × 106 EVs with 10 × 106 spermatozoa/mL was identified. At this concentration, sperm mobility parameters were not negatively affected. Sixteen susceptible mares were enrolled and inseminated with semen (n = 8; control group) or with semen supplemented with EVs (n = 8; EV group). The supplementation of AMSC-EVs to semen resulted in a reduction in polymorphonuclear neutrophil (PMN) infiltration as well as intrauterine fluid accumulation (IUF; p < 0.05). There was a significant reduction in intrauterine cytokine levels (p < 0.05) for TNF-α and IL-6 and an increase in anti-inflammatory IL-10 in mares in the EV group, suggesting successful modulation of the post-insemination inflammatory response. This procedure may be useful for mares susceptible to PPBIE.

The Role of NF-κB in Endometrial Diseases in Humans and Animals: A Review

The expression of genes of various proinflammatory chemokines and cytokines is controlled, among others, by the signaling pathway of the nuclear factor kappaB (NF-κB) superfamily of proteins, providing an impact on immune system functioning. The present review addresses the influence and role of the NF-κB pathway in the development and progression of most vital endometrial diseases in human and animal species. Immune modulation by NF-κB in endometritis, endometrosis, endometriosis, and carcinoma results in changes in cell migration, proliferation, and inflammation intensity in both the stroma and epithelium. In endometrial cells, the NF-κB signaling pathway may be activated by multiple stimuli, such as bacterial parts, cytokines, or hormones binding to specific receptors. The dysregulation of the immune system in response to NF-κB involves aberrant production of chemokines and cytokines, which plays a role in endometritis, endometriosis, endometrosis, and endometrial carcinoma. However, estrogen and progesterone influence on the reproductive tract always plays a major role in its regulation. Thus, sex hormones cannot be overlooked in endometrial disease physiopathology. While immune system dysregulation seems to be NF-κB-dependent, the hormone-independent and hormone-dependent regulation of NF-κB signaling in the endometrium should be considered in future studies. Future goals in this research should be a step up into clinical trials with compounds affecting NF-κB as treatment for endometrial diseases.

The effect of dexamethasone and flunixin-meglumine on ovulation, endometrial oedema, and inter-ovulatory interval length in the mare

The use of flunixin-meglumine (a potent non-steroidal anti-inflammatory drug) during the critical period of intrafollicular prostaglandin production before ovulation (24 and 36 h after hCG treatment) results in a high rate of ovulatory failure and formation of haemorrhagic anovulatory follicles (HAF) in the mare. Dexamethasone is commonly used to prevent persistent mating-induced endometritis in susceptible mares, but the effect on ovulation blockage within the pre-ovulatory critical window of intrafollicular prostaglandins production following hCG administration has not been determined. Six mares were followed during four consecutive cycles in a crossover design; once in oestrus with a follicle of >32 mm in diameter, mares were treated with hCG (Hour 0) and assigned to one of 4 groups randomly: 1) FM, mares received 1.7 mg/kg flunixin-meglumine at Hour 24 and 36; 2) CON, mares received no further treatment. 3) DEX1, mares received 0.1 mg/kg dexamethasone at Hour 24, and 4) DEX2, mares received 0.1 mg/kg dexamethasone at Hour 24 and 36. For all groups, ovulation and HAF rates, endometrial oedema profiles and the inter-ovulatory intervals (IOI) were determined and compared statistically. All CON and DEX mares ovulated normally and did not form any HAF. On the contrary, FM mares developed a HAF in 83% of cycles (P < 0.01). The endometrial oedema score was lower following DEX administration than FM (P < 0.05). The mean IOI was longer (P < 0.05) in DEX1 and DEX2 groups (26.5 and 26 days, respectively) than in CON and FM groups (21.5 and 22 days, respectively). In conclusion, dexamethasone treatment given either once or twice during the critical window of hCG-induced ovulation did not block or delay ovulation, but had a similar ovulation rate than untreated control mares. However, the inter-ovulatory intervals of dexamethasone treated mares was longer than control and FM treated mares. Finally, dexamethasone treatment was more effective in reducing endometrial oedema than FM.

Reproductive Microbiomes in Domestic Livestock: Insights Utilizing 16S rRNA Gene Amplicon Community Sequencing

Advancements in 16S rRNA gene amplicon community sequencing have vastly expanded our understanding of the reproductive microbiome and its role in fertility. In humans, Lactobacillus is the overwhelmingly dominant bacteria within reproductive tissues and is known to be commensal and an indicator of fertility in women and men. It is also known that Lactobacillus is not as largely abundant in the reproductive tissues of domestic livestock species. Thus, the objective of this review is to summarize the research to date on both female and male reproductive microbiomes in domestic livestock species (i.e., dairy cattle, beef cattle, swine, small ruminants, and horses). Having a comprehensive understanding of reproductive microbiota and its role in modulating physiological functions will aid in the development of management and therapeutic strategies to improve reproductive efficiency.

Comparison of systemic trimethoprim-sulfadimethoxine treatment and intrauterine ozone application as possible therapies for bacterial endometritis in equine practice

Bacterial endometritis is one of the major problems in equine reproduction and usually treated with antimicrobial drugs. The study aimed to compare the effects of intrauterine ozone application and systemic antibiotic treatment (trimethoprim-sulfadimethoxine) on intrauterine bacterial growth and possible side effects on the endometrium in a clinical setting. Mares (n = 30) with signs of endometritis (positive uterine bacterial culture and cytological findings) were assigned randomly to different treatments: intrauterine insufflation of an ozone-air-mix (240 ml, 80 μg ozone/ml) twice at a 48 h-interval (Ozone; n = 10), systemic antibiotic therapy with trimethoprim-sulfadimethoxine (30 mg/kg, p.o., twice daily) for 5 days (TMS; n = 10), or intrauterine insufflation of air (240 ml, sterile-filtered) twice at a 48 h-interval (air; n = 10). Endometrial biopsy for histological examination was obtained before the treatment. Histological examination revealed no differences among groups. A control examination, including transrectal ultrasound, bacterial culture, cytological evaluation, and biopsy, was performed 7 days after the last treatment. Overall bacterial growth was reduced in every group after the treatment (p < 0.05), irrespective of the therapy [Ozone: 4/9 (positive culture after treatment/number of mares), TMS: 3/10 and Air: 6/10; p > 0.05]. However, Ozone and TMS (p < 0.05) were more effective in reducing growth of gram-negative bacteria as compared to Air (p > 0.05). No effects on the number of polymorphonuclear granulocytes (cytology) were observed (p > 0.05). In conclusion, trimethoprim-sulfadimethoxine and intrauterine ozone insufflation are safe treatment options for bacterial endometritis in mares but the efficacy of both treatments in reducing bacterial growth did not result in a complete absence of intrauterine bacterial growth.

Serological and Uterine Biomarkers for Detecting Endometritis in Mares

Serological analysis may provide relevant information on endometritis diagnostics. Therefore, mares scheduled for AI with refrigerated semen, at the time of heat signs, underwent blood and uterine fluid samplings using a swab, uterine lavage for culture analysis, and treatment with human chorionic gonadotropin to induce ovulation. After 24-28 h, the mares were inseminated and, if positive at the culture test, treated with antibiotics chosen based on the susceptibility test. Uterine cells obtained by swabs were used for cytological examination with both classical and fluorescence techniques. Blood serum and uterine fluid samples were analyzed for assessing parameters related to redox balance, inflammation, and protease regulator potential. In blood serum, total antioxidant capacity, measured as the ferric reducing ability of plasma (FRAP), was significantly lower in cytologically endometritis-positive than -negative mares. In the uterine fluid, total thiol levels (TTL), nitric oxide metabolites (NO_x), protease activity and total protein content varied significantly between groups. Although the cytological examination was more capable of discriminating between endometritis-positive and -negative mares in relation to the parameters examined, no statistically significant differences emerged in terms of pregnancy rate in relation to cytological and culture diagnosis as well as in mares diagnosed as positive and negative for endometritis.

Effects of Intra-Uterine Fluid Accumulation after Artificial Insemination on Luteal Function in Mares

After breeding or artificial insemination, especially with frozen/thawed semen, mares often develop a persistent uterine inflammation, which is diagnosed by intra-uterine fluid accumulation. Here, we explored whether intra-uterine fluid accumulation affects corpus luteum function and tested the hypothesis that intra-uterine fluid accumulation after artificial insemination alters blood flow in the corpus luteum and plasma progesterone concentrations. A total of 40 Standardbred mares were artificially inseminated with frozen-thawed semen 30 to 36 h after induction of ovulation, and cases with or without intra-uterine fluid accumulation were detected by ultrasound 12 h after insemination. Luteal blood flow was measured by Power Doppler ultrasonography 3 and 6 days after ovulation, progesterone concentration was measured in peripheral plasma by ELISA 6 days after ovulation, and pregnancy was diagnosed by ultrasonography 14 days after ovulation. Luteal blood flow increased between 3 and 6 days after ovulation, but blood flow did not differ significantly between cases with (n = 28) and without (n = 25) intra-uterine fluid accumulation after insemination. Surprisingly, progesterone concentrations were higher in cases of intra-uterine fluid accumulation than cases without (9.3 ± 1.1 vs. 6.6 ± 0.5 ng/mL, p = 0.048). Pregnancy was less likely in cases with intra-uterine fluid accumulation than in cases without (10/28 vs. 17/25, p = 0.019), and there was a negative correlation between the severity of intra-uterine fluid accumulation and per cycle pregnancy rate. These data suggest that although intra-uterine fluid accumulation increases the secretion of progesterone, pregnancy is more dependent on uterine health than ovarian function.

Lethal variants of equine pregnancy: is it the placenta or foetus leading the conceptus in the wrong direction?

Embryonic and foetal loss remain one of the greatest challenges in equine reproductive health with 5-10% of established day 15 pregnancies and a further 5-10% of day 70 pregnancies failing to produce a viable foal. The underlying reason for these losses is variable but ultimately most cases will be attributed to pathologies of the environment of the developing embryo and later foetus, or a defect intrinsic to the embryo itself that leads to lethality at any stage of gestation right up to birth. Historically, much research has focused on the maternal endometrium, endocrine and immune responses in pregnancy and pregnancy loss, as well as infectious agents such as pathogens, and until recently very little was known about the both small and large genetic variants associated with reduced foetal viability in the horse. In this review, we first introduce key aspects of equine placental and foetal development. We then discuss incidence, risk factors and causes of pregnancy loss, with the latter focusing on genetic variants described to date that can impact equine foetal viability.

Interaction of sperm cells with the female reproductive tract in cattle: Focus on neutrophil extracellular trap formation

After insemination of cows, either naturally or artificially, the deposition of semen into the vagina or uterus results in an immune reaction which is based on polymorphonuclear neutrophil activity. Sperm must be resistant to immune system actions of the female for an adequate time to allow fertilization to occur. Neutrophils, however, either directly phagocytize sperm through cell-cell attachment or entrap sperm cells in neutrophil extracellular traps (NETs), structures consisting of neutrophil nuclear DNA and associated proteins. In this review article, the interaction of neutrophils and sperm cells in t cattle will be described, with a special focus on the formation of neutrophil extracellular traps (NETs).

The correlation of endogenous progesterone concentration in diestrus on early pregnancy rate in Thoroughbred mares

AIM

The aim of this project was to test the hypothesis that progesterone concentration 5 days after ovulation did not differ between pregnant and nonpregnant Thoroughbred mares on stud farms located in the Waikato region of New Zealand.

METHODS

A prospective cohort study was performed involving five stud farms in the Waikato region of New Zealand during the 2018 breeding season. A total of 275 mares were enrolled in the study. Mares were served by 34 individual stallions. Blood samples were taken from each mare 5 days after ovulation (D0) and measured for progesterone concentration. Early pregnancy was confirmed at D14 by transrectal palpation and ultrasonography of the mares reproductive tract.

RESULTS

Progesterone concentration at Day 5 post-ovulation was higher in mares determined to pregnant at Day 14 of gestation than in mares determined to be non-pregnant at Day 14 (6.4 ± 3.0 ng/ml vs 5.5 ± 3.3 ng/ml respectively; P=0.02). A negative association between increasing mare age and pregnancy rate was found but mare age had no effect on progesterone concentration at D5.

CONCLUSIONS

In this study we found that although higher serum progesterone concentration at Day 5 post ovulation was associated with a higher pregnancy rate at Day 14, no predictive or definitive minimum required progesterone concentration could be identified. Additional studies are required to determine if a synthetic progestogens can serve to supplant natural progesterone to increase pregnancy rate in naturally bred mares.

Relationship between Oxidative Stress and Endometritis: Exploiting Knowledge Gained in Mares and Cows

Simple Summary

Endometritis is a widespread pathology in mares and cows and one of the leading causes of reproductive efficiency decline. Although localized in the innermost layer of the uterus, this inflammation involves the release of bioactive molecules and by-products related to molecular damage. Among the bioactive substances, a primary role is played by the reactive oxygen and nitrogen species, which, while exerting an antimicrobial effect, can amplify the inflammation, sometimes causing unwanted and self-aggravating effects. Part of these substances enters the bloodstream, with implications that range from sustaining distant effects on organs and tissues to being used as diagnostic biomarkers. The research carried out on this matter in cows and mares has maintained certain independence due to its species specificity. This review aims to collect and analyze the information available in these species to enhance diagnostics and provide new insights to prevent and treat this pathology.

Abstract

The etiopathogenesis of endometritis in mares and cows differs significantly; this could depend on a different sensitivity and reactivity of the uterus but also on endocrine and rearing factors and different stress sources. In both species, microorganisms and the immune system play a primary role in the generation of this pathology. Microbiological and cytological tests support clinical examination and significantly improve diagnostic accuracy. For both species, during the inflammation, immune cells invade the endometrium and release bioactive substances to contrast primary or secondary pathogen contamination. These molecules are traceable to cytokines, chemokines, and prostaglandins as well as reactive oxygen and nitrogen species (ROS and RNS), collectively known as RONS. The RONS-mediated oxidation causes morphological and functional alterations of macromolecules, such as proteins, lipids, and nucleic acids, with the consequent production of derivative compounds capable of playing harmful effects. These bioactive molecules and by-products, which have recently become increasingly popular as diagnostic biomarkers, enter the bloodstream, influencing the functionality of organs and tissues. This review has collected and compared information obtained in cows and mares related to the diagnostic potential of these biomarkers that are assessed by using different methods in samples from either blood plasma or uterine fluid.

Descriptive study of medication usage and occurrence of disease and injury during gestation in Thoroughbred broodmares

The study aimed to (i) describe the use of reproductive therapeutics; (ii) estimate the incidence of disease and injury; and (iii) describe non-reproductive medications administered during pregnancy in Thoroughbred broodmares. A prospective birth cohort was established on seven farms across the UK and Ireland. Details of dams' signalment, breeding history, reproductive management during the breeding season(s) and veterinary-attended episodes of illness or injury and medication usage during gestation were retrieved retrospectively for 275 pregnancies in 235 mares over two breeding seasons. Results are reported at pregnancy-level of mares with data available. Pre-oestrus medications, ovulatory agents and post-covering treatments were administered to 55% (n=85/155, 95% Confidence interval (CI) 47-62), 64% (n=101/157, 95%CI 57-71) and 73% (n=109/150, 95%CI 65-79) of mares respectively. Antibiotics were utilised in 69% (n=75/109, 95%CI 60-77) of post-covering treatments. Of mares with no visible fluid on post-covering ultrasound, 37% (n=24/65, 95%CI 26-49) still received treatment. Thirty-four percent (n=70/203, 95%CI 28-41) of mares suffered at least one veterinary-attended episode of disease or injury, with conditions affecting the musculoskeletal system (23%, n=46/203, 95%CI 17-29) and placentitis (5%, n= 10/203, 95%CI 3-9) most prevalent. Forty-seven percent (n=95/203, 95%CI 40-54) of mares received at least one non-reproductive medication during gestation, antibiotics (25%, n=51/203, 95%CI 20-31) and non-steroidal anti-inflammatory drugs (23%, n=47/203, 95%CI 18-29) being most frequently prescribed. Post-covering treatments often included antibiotics and were sometimes given in the absence of fluid, highlighting a need to further understand therapeutic rationale. Disease occurrence and medication usage during gestation were frequent and warrant additional investigation.

Endometrial and vaginal microbiome in donkeys with and without clinical endometritis

Endometrial and vaginal microbiomes are critical in the study of endometritis, which is an important cause of infertility in donkeys. Our objective was to investigate the difference of the endometrial and vaginal microbiomes between healthy donkey jennies (group C) and jennies with endometritis (group E). Endometrial and vaginal swab samples were collected, and the 16 s rRNA gene amplicon high-throughput sequencing technique was applied to identify the microbial composition in the samples. A similar microbial composition pattern was found between endometrial and vaginal samples, which indicated the impact of the vaginal microbiome on the endometrial microbial environment and health. There was a significant difference of endometrial and vaginal swab samples between the two groups. Ruminococcaceae and Lachnospiraceae were significantly more abundant in endometrial and vaginal microbiomes of group E than in group C. Their dominance was consistent with increased anaerobic bacterial taxa in the functional analysis, which might be associated with the pathogenesis of endometritis in donkeys. Sphingomonadaceae, a bacterial family reported in bovine semen, was statistically more abundant in endometrial microbiome of group E than in group C, which might suggest an association between high abundance of Sphingomonadaceae possibly due to uncleared semen and donkey endometritis. Our study revealed the composition of the vaginal and endometrial microbiomes in healthy and endometritis donkeys. These findings will provide more insights into the pathogenesis of donkey endometritis.

Active components and molecular mechanism of Syringa oblata Lindl. in the treatment of endometritis based on pharmacology network prediction

Antibiotic treatment of endometritis was limited by the inevitable antibiotic residues and risk of bacterial resistance. Therefore, the development of safe and effective strategies for endometritis treatment is urgently needed. Syringa oblata Lindl. (SOL) showed great pharmacological potential against endometritis. However, the active components and underlying mechanism of SOL for endometritis treatment remain indeterminate. In our study, the active components and possible molecular mechanism of SOL against endometritis were predicted through computer data mining and biological networks construction. It was predicted that the main active components of SOL were luteolin, kaempferol, oleanolic acid, and rutin, and their anti-endometritis effect was mainly attributed to the TLRs/NF-κB signaling pathway. Furthermore, a green and efficient deep eutectic solvent combined with ultrasound-assisted extraction (DES-UAE) was performed and optimized to obtain high contents of total flavonoid, rutin, and luteolin. The four predicted active components in the SOL extracts were qualitatively and quantitatively analyzed by LC/MS and HPLC. Finally, the pharmacological effects of SOL and active components have been verified by Staphylococcus aureus-endometritis models in mice. H&E staining and bacterial load in uterus tissues assays initially validated the pharmacodynamic effects of SOL, and quantitative real-time PCR (RT-qPCR) and ELISA results confirmed that SOL and four active components could ameliorate the uterus injury caused by Staphylococcus aureus, the mechanism of action is related to the TLRs/NF-κB signaling pathway.

Genetic Diversity, Biofilm Formation, and Antibiotic Resistance of Pseudomonas aeruginosa Isolated from Cow, Camel, and Mare with Clinical Endometritis

Pseudomonas aeruginosa is a ubiquitous opportunistic bacterium that causes diseases in animals and humans. This study aimed to investigate the genetic diversity, antimicrobial resistance, biofilm formation, and virulence and antibiotic resistance genes of P. aeruginosa isolated from the uterus of cow, camel, and mare with clinical endometritis and their drinking water. Among the 180 uterine swabs and 90 drinking water samples analysed, 54 (20%) P. aeruginosa isolates were recovered. Isolates were identified biochemically to the genus level by the automated Vitek 2 system and genetically by the amplification of the gyrB gene and the sequencing of the 16S rRNA gene. Multilocus sequence typing identified ten different sequence types for the P. aeruginosa isolates. The identification of ST2012 was significantly (p ≤ 0.05) higher than that of ST296, ST308, ST111, and ST241. The isolates exhibited significantly (p ≤ 0.05) increased resistance to piperacillin (77.8%), ciprofloxacin (59.3%), gentamicin (50%), and ceftazidime (38.9%). Eight (14.8%) isolates showed resistance to imipenem; however, none of the isolates showed resistance to colistin. Multidrug resistance (MDR) was observed in 24 isolates (44.4%) with a multiple antibiotic resistance index ranging from 0.44 to 0.77. MDR was identified in 30 (33.3%) isolates. Furthermore, 38.8% and 9.2% of the isolates exhibited a positive extended-spectrum-β-lactamase (ESBL) and metallo-β-lactamase (MBL) phenotype, respectively. The most prevalent β-lactamase encoding genes were bla_TEM and bla_CTX-M, however, the bla_IPM gene was not detected in any of the isolates. Biofilm formation was observed in 49 (90.7%) isolates classified as: 11.1% weak biofilm producers; 38.9% moderate biofilm producers; 40.7% strong biofilm producers. A positive correlation was observed between the MAR index and biofilm formation. In conclusion, the results highlighted that farm animals with clinical endometritis could act as a reservoir for MDR and virulent P. aeruginosa. The emergence of ESBLs and MBLs producing P. aeruginosa in different farm animals is a public health concern. Therefore, surveillance programs to monitor and control MDR P. aeruginosa in animals are required.

Fluorescence Spectroscopy for the Diagnosis of Endometritis in the Mare

By exploiting the PMN property to produce high quantities of oxygen peroxide to neutralize pathogens, the oxygen peroxide content of uterine cells was measured to diagnose endometritis. After preliminary in vitro studies in which endometrial cells from slaughtered mares were mixed with leukocytes from peripheral blood, endometrial samples were collected by uterine flushing from mares before insemination. Staining endometrial cells with H2DCF-DA was combined with hydroethidine to normalize the fluorescence intensity with the cellular content of the sample. Stained cell smears were assumed as the gold standard of endometritis, and based on this assay, the samples were considered positive (C+) and negative (C−) for endometritis. The amount and the turbidity of fluid recovered by uterine flushing were significantly (p < 0.01) higher in C+ than in C−. Moreover, the oxygen peroxide content of the endometrial cells was significantly higher in the C+ than in the C− group (6.31 ± 1.92 vs. 3.12 ± 1.26, p = 0.001). Using the value of 4.4 as the cutoff level of this fluorescence cytology assay, it was found that only one C− sample exceeded the cutoff level (false positives = 7.7%) while three C+ samples showed values below the cutoff level (false negative = 11.5%).

Evolution of the Concepts of Endometrosis, Post Breeding Endometritis, and Susceptibility of Mares

In this paper, the evolution of our understanding about post breeding endometritis (PBE), the susceptibility of mares, and events leading to endometrosis are reviewed. When sperm arrive in the uterus, pro-inflammatory cytokines and chemokines are released. They attract neutrophils and induce modulatory cytokines which control inflammation. In susceptible mares, this physiological defense can be prolonged since the pattern of cytokine release differs from that of resistant mares being delayed and weaker for anti-inflammatory cytokines. Delayed uterine clearance due to conformational defects, deficient myometrial contractions, and failure of the cervix to relax is detected by intrauterine fluid accumulation and is an important reason for susceptibility to endometritis. Multiparous aged mares are more likely to be susceptible. Untreated prolonged PBE can lead to bacterial or fungal endometritis called persistent or chronic endometritis. Exuberant or prolonged neutrophilia and cytokine release can have deleterious and permanent effects in inducing endometrosis. Interactions of neutrophils, cytokines, and prostaglandins in the formation of collagen and extracellular matrix in the pathogenesis of fibrosis are discussed. Endometritis and endometrosis are interconnected, influencing each other. It is suggested that they represent epigenetic changes induced by age and hostile uterine environment.

The NF-κB signaling pathway in mare's endometrium infiltrated with the inflammatory cells

Endometritis is an important issue decreasing mares' fertility. In the case of endometritis both, inflammatory cells infiltration and proinflammatory molecules production are regulated by various cellular and gene-regulatory mechanisms, including the nuclear factor-κB (NF-κB) dependent pathway. NF-κB signaling pathway has been recently studied in the equine endometrium in the context of endometrosis. Thus, this study aimed to determine gene transcription of NF-κB subunits (RelA; NF-κB1; NF-κB2), proinflammatory molecules (MCP-1; IL-6), and hyaluronan synthases (HAS 1; HAS 2; HAS 3) in endometritis and compare them with the intensity and type of inflammatory cell infiltration. Endometrial samples, collected post-mortem from cyclic mares in estrus or diestrus, were classified histologically and examined using quantitative PCR. Transcription NF-κB subunits genes did not differ with either inflammatory intensity or type of inflammatory cell infiltration. Transcription of MCP-1 and IL-6 genes increased with the severity of inflammation, with the involvement of HAS 3 and HAS 2 genes, as opposed to HAS 1 genes. These proinflammatory molecules and hyaluronan synthases in the equine inflamed endometrium do not seem to be regulated by the NF-κB pathway. Hence, separate signaling pathways for the development and progression of equine endometritis and endometrosis may be suggested.

A Novel Approach to Minimising Acute Equine Endometritis That May Help to Prevent the Development of the Chronic State

One of the most commonly encountered challenges in equine breeding is endometritis, which can be difficult to resolve and causes considerable economic losses to the industry. It is a multifactorial condition, developing as an exaggerated form of the normal physiological response to breeding. Seminal plasma proteins, spermatozoa, bacteria and debris initiate an inflammatory response; the resulting fluid and neutrophils are then cleared from the uterus along with the debris. However, in some mares, the response is prolonged or exaggerated, with much fluid formation and neutrophil infiltration leading to acute endometritis. A bacterial cause has been implicated, although in some cases no pathogenic organisms can be isolated on culture. It has been postulated that any one of a variety of bacteria could be involved, or dysbiosis of the uterine microbiome could be responsible. Repeated episodes of acute endometritis may lead to the pathology associated with chronic endometritis, with mucociliary dysfunction, vascular degeneration and plasma cell infiltration. This review examines the information that is currently available about equine endometritis, particularly about the role of the inseminate in the uterus, and its current treatment. There are some promising lines of research into treatment or prevention that may help to resolve the issue.

Extracellular vesicles in low volume uterine lavage and serum: novel and promising biomarker for endometritis in Arabian mares

Background

Extracellular vesicles (EVs) are a promising biomarker and play a vital role in cell–cell communication. This study aimed (I) to identify and characterize EVs from low volume uterine lavage (LVL) and serum in mares with endometritis, compared to healthy controls and (II) to measure serum levels of interleukin 6 (IL-6), and prostaglandins (PGF_2α and PGE₂). Mares were divided into 30 sub-fertile (endometritis) and 20 fertile (controls). Serum and LVL was collected for EV isolation, and determination of serum levels of inflammatory mediators. Characterization and visualization of EVs were done by electron microscopy, dynamic light scattering and flow cytometry.

Results

Serial ultracentrifugation of LVL and use of a commercial kit for serum were strategies for EVs isolation. Mares with endometritis released higher amounts of larger size EVs. The EVs from mares with endometritis differentially expressed CD9 and CD63, compared to controls. Mares suffering from endometritis evoked higher levels of inflammatory mediators.

Conclusions

Thus, EVs could be used for a better understanding the regulatory mechanisms associated with developing endometritis in mares.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03137-3.

Effect of platelet lysate on uterine response of mares susceptible to persistent mating-induced endometritis

Many mares are susceptible to persistent mating-induced endometritis (PMIE), an important cause of reduced fertility. Platelet lysate (PL) derives from freeze-thawing platelets after concentration, so that growth factors are released from the platelets. Among the advantages of PL compared to platelet-rich plasma (PRP), it can be frozen stored and allogenic use for PL might also be conceivable. Platelet-rich plasma beneficially reduced inflammatory response in PMIE mares when administered 24 h pre- or 4 h post-AI. The aim of this study was to test the effect of PL on inflammatory uterine response in mares susceptible to PMIE. A total of 14 mares susceptible to PMIE (based on presence of fluid or inflammatory cells 24 h after AI) underwent an untreated (Ctr) cycle followed by a treated (PL) cycle. From each mare, 100 mL of citrated whole blood was obtained for PRP production by centrifugation. The resultant PRP was brought to a final volume of 10 mL with platelet poor plasma and frozen at -80 °C to obtain PL. On untreated cycles, mares were inseminated with frozen-thawed semen 36 h after ovulation induction. On treated cycles, PL was thawed, infused into the uterus 12 h after ovulation induction, and AIs were performed 24 h later. The number of neutrophils in uterine cytology (score 1(normal)-3(severe inflammation)) evaluated by optical microscopy, uterine fluid accumulation (height x width) and uterine edema (score 0-3) observed in ultrasonography, were analysed. Pregnancy was evaluated by ultrasonography 14 days after ovulation. A significant decrease (P < 0.05) was observed on cytology score (PL 1.3 ± 0.1 vs Ctr 2.0 ± 0.1), fluid accumulation (PL 79.5 ± 30.1 mm² vs Ctr 342.7 ± 52.9 mm²) and edema score (PL 1.8 ± 0.2 vs Ctr 2.3 ± 0.2) in treated mares. Pregnancy rate in PL-treated cycles (3/12) and control cycles (2/14), were not significantly different (P > 0.05). According to the results, we conclude that treatment with PL in mares classified as susceptible to PMIE appears to reduce the inflammatory response after breeding, based on clinical signs of uterine edema, IUF accumulation and PMNs migration.

Comparative study utilizing different post-breeding treatment regimens in cyclic Arabian mares

BACKGROUND AND AIM

Post-breeding treatment is the most common practice in the reproductive management of mares. Oxytocin, uterine lavage, and intrauterine (I/U) antibiotic are usually used as prophylactic therapy. This study aimed to determine the most efficient prophylactic treatment regimen among six treatment protocols applied during natural breeding of cyclic Arabian mares.

MATERIALS AND METHODS

The current study was conducted on cyclic Arabian mares that were subdivided into three age categories (n=968): Category I (5-10 years, n=380), Category II (11-15 years, n=361), and Category III (≥16 years, n=227). Six prophylactic treatments were applied after 4 h of breeding. According to the treatment regimen, treated mares (n=483) were divided into six treatment groups: A (n=80), treated with I/U antibiotic (1 g gentamicin); B (n=81), I/U lavage (normal saline 500 mL); C (n=83), intramuscular (I/M) oxytocin (10 IU); D (n=82), I/U antibiotic and I/M oxytocin; E (n=78), I/U lavage and I/M oxytocin; and F (n=79), I/U lavage with I/U antibiotic and I/M oxytocin. Non-treated mares were classified as controls (n=485). Ultrasonography was performed to monitor pregnant mares 30 and 60 days after mating, and mares were followed until foaling.

RESULTS

Pregnancy and foaling results reveals that in age Category I, treatment with oxytocin alone or oxytocin with I/U lavage showed the highest pregnancy and foaling rates (p<0.01). In age Category II, the highest pregnancy and foaling rates were observed in lavage treatment (p<0.01), whereas, in age Category III, the good pregnancy and foaling rates were monitored in treatment with oxytocin and I/U lavage (p<0.01).

CONCLUSION

Treatment with systemic I/M oxytocin is ideal in early age group mares (5-10 years of age). However, irrespective of the age categories, all mares exhibited high pregnancy and foaling rates after treatment with systemic I/M oxytocin and I/U lavage with normal saline (0.9%) 4 h post-breeding.

Antimicrobial Resistance in Equine Reproduction

Bacteria develop resistance to antibiotics following low-level "background" exposure to antimicrobial agents as well as from exposure at therapeutic levels during treatment for bacterial infections. In this review, we look specifically at antimicrobial resistance (AMR) in the equine reproductive tract and its possible origin, focusing particularly on antibiotics in semen extenders used in preparing semen doses for artificial insemination. Our review of the literature indicated that AMR in the equine uterus and vagina were reported worldwide in the last 20 years, in locations as diverse as Europe, India, and the United States. Bacteria colonizing the mucosa of the reproductive tract are transferred to semen during collection; further contamination of the semen may occur during processing, despite strict attention to hygiene at critical control points. These bacteria compete with spermatozoa for nutrients in the semen extender, producing metabolic byproducts and toxins that have a detrimental effect on sperm quality. Potential pathogens such as Klebsiella pneumoniae, Escherichia coli, and Pseudomonas aeruginosa may occasionally cause fertility issues in inseminated mares. Antibiotics are added during semen processing, according to legislation, to impede the growth of these microorganisms but may have a detrimental effect on sperm quality, depending on the antimicrobial agent and concentration used. However, this addition of antibiotics is counter to current recommendations on the prudent use of antibiotics, which recommend that antibiotics should be used only for therapeutic purposes and after establishing bacterial sensitivity. There is some evidence of resistance among bacteria found in semen samples. Potential alternatives to the addition of antibiotics are considered, especially physical removal separation of spermatozoa from bacteria. Suggestions for further research with colloid centrifugation are provided.

Alterations in the Expression Profile of Serum miR-155, miR-223, miR-17, miR-200a, miR-205, as well as Levels of Interleukin 6, and Prostaglandins during Endometritis in Arabian Mares

So far the intimate link between serum microRNA (miRNA) and uterine inflammation in mares is unknown. We aimed (I) to investigate expression profile of eca-miR-155, eca-miR-223, eca-miR-17, eca-miR-200a, and eca-miR-205 (II) and to measure concentrations of interleukin 6 (IL-6), and prostaglandins (PGF_2α and PGE₂) in serum of mares with healthy and abnormal uterine status (endometritis). This study was conducted on 80 Arabian mares: young (4–7 years), and old (8–14 years). Mares were divided into 48 sub-fertile (endometritis) and 32 fertile (control) at stud farms. Serum was collected for measuring IL-6, PGF_2α, and PGE₂, as well as miRNA isolation and qRT-PCR. Concentrations of IL-6, PGE₂, and PGF_2α were higher in mares with endometritis compared to control. Age of mares had a remarkable effect on IL-6, PGE₂, and PGF_2α concentrations. Relative abundance of eca-miR-155, eca-miR-223, eca-miR-17, eca-miR-200a, and eca-miR-205 was higher in both young and old mares with endometritis. We noticed that eca-miR-155, eca-miR-223, eca-miR-200a, and eca-miR-205 revealed higher expression level in old than young mares with endometritis. This is the first study that has revealed the changes in cell free miRNA and serum inflammatory mediators during endometritis, and these findings could be used for a better understanding the pathophysiology mechanisms of endometritis in equine.

In vitro antimicrobial activity of selected essential oils against bacteria and yeasts isolated from the genital tract of mares

The aim of the present study, the first to test clinical equine isolates, was to evaluate the antimicrobial activity of commercial essential oils (EOs) obtained from Origanum vulgare, Thymus vulgaris, Cinnamomum zeylanicum, Cymbopogon citratus, Aloysia triphylla and Syzygium aromaticum against Streptococcus spp., Staphylococcus spp., Candida albicans and Rhodotorula spp. previously isolated from uteri of mares with reproductive disorders. T. vulgaris showed the best antibacterial activity against all the selected agents, with MICs ranging from 0.07 mg/mL for S. equi subsp. zooepidemicus to 0.29 mg/mL versus Streptococcus sp. and Staphylococcus spp. isolates and versus C. albicans and Rhodotorula spp., with MICs of 0.46 mg/mL and 1.86 mg/mL, respectively. O. vulgare, S. aromaticum, C. zeylanicum EOs showed good antibacterial activity with MICs ranging from 0.07 mg/mL to 0.29 mg/mL, 0.16 mg/mL to 0.32 mg/mL, 0.07 mg/mL to 0.63 mg/mL, respectively; A. triphylla was the most active EO against Rhodotorula spp. (0.43 mg/mL).

Treatments for Endometritis in Mares Caused by Streptococcus equi Subspecies zooepidemicus: A Structured Literature Review

Bacterial infections are the main causes of endometritis in mares. It is well known that the most common bacterial pathogen is Streptococcus equi subspecies zooepidemicus (SEZ). This structured review was completed according to the PRISMA procedure to search endometritis treatment protocols published between 1990 and 2020 it was our intent to evaluate the actual effects of different treatment protocols for endometritis caused by SEZ. The trials included were collected from Pubmed, CAB and Agricola. Ten articles with 116 horses and 17 different interventions were identified. The results of this structured review indicated that the reported antibiotics, immunomodulatory agents and fresh white blood cell treatments were superior for treating SEZ caused endometritis in mares, whereas oxytocin and uterine lavage alone may not be as effective as presumed. The inclusion and evaluation of more randomized controlled trials may be helpful for further elucidation of the differences.