In equine reproduction there are various factors which can reduce the probability of success, and that is when the hand of the Veterinarian must intervene to solve these problems.
The final objective of reproduction in any species is to obtain a new offspring. For this to be achieved is not always a simple task, since there may be reproductive pathologies which affect fertility. As for the mare, it may present problems in the ovaries, oviduct, uterus, among others.
According to Brinsko et al, 2010, one of the major causes of infertility in the mare is endometritis, which is developed by some of these events: childbirth, examination of the reproductive tract, artificial insemination, natural mating, and self-contamination by a poor perianal conformation. When the uterus is exposed to contamination, its defense mechanism is activated, this being the migration of polymorphonuclear cells to the uterus and its contraction increases to eliminate the contents of the lumen and improve the uterine environment. (p. 74.)
It should be taken into account that endometritis in Mares is inflammation of the endometrium, the endometrium being the part of the uterus that is exposed to the uterine lumen; In some cases these inflammations generated by foreign agents, whether chemical, bacterial, fungal or fecal material or others, can become an infection, because some of the body’s defense barriers fail and cannot counteract this situation and it is there where infectious endometritis is generated.
When a mare is serviced either by natural mating or by insemination, there will be a peak of inflammation in the uterus which occurs 8 to 12 hours after service, this having a resolution on its own in normal mares within 24 hours. (McCue, P and Ferris, R, 2016)
In some cases you can find mares suffering from Persistent Post-Mat Endometritis, which can be diagnosed by observing the uterus with fluid accumulation about 48 hours after service. This tends to happen due to a failure of the uterus to empty itself, which will generate a decrease in the pregnancy rate.
Generally, persistent endometritis in mares occurs in pluriparous animals, which have several births, or in mares of advanced age, where they tend to have difficulty relaxing the cervix during estrus, causing the expulsion of fluid from the uterus to be prevented.
This is one of the reasons why we monitor mares in estrus with the ultrasound, since if we see an exaggerated accumulation of fluid in the uterus before service, it would be indicative of a possible candidate for Persistent Post-Mat Endometritis.
When a mare’s reproductive tract constantly receives polluting agents, chronic endometritis can occur. The way this happens can be due to two factors, one is that the uterus has frequent contamination and two, that the tract’s own defense system does not provide good drainage or elimination of microorganisms.
When one of these two factors is met and there is the presence of contaminating agents as we mentioned at the beginning, we begin to run the risk of infections, which is a big problem in meeting our objectives of obtaining a calf.
Infectious endometritis is caused by pathogenic microorganisms which multiply in the uterus, causing infertility and which are alterations that must be treated as soon as possible to reduce damage to the reproductive tract. These infections can be caused by bacteria or fungi.
The most common bacterial agents are Streptococcus Zooepidemicus, Escherichia Coli, Pseudomona Aeruginosa, Klebsiella Pneumoniae. While the fungi that cause fungal infections tend to be the yeast Candida Albicans, Aspergillus Fumigatus and Mucor. (McCue, P and Ferris, R, 2016)
It is important to keep in mind that this type of pathology must be treated in advance and that should lead us to think that when checking a mare for the first time, its vulvar conformation should be visually evaluated, since from there we can begin. whether or not to presume infectious endometritis. There are signs of possible uterine infection that can be observed visually without the need for medical tools, such as purulent vulvar secretions, finding exudate material in the tail, moisture in the ventral commissure of the vulva; On the other hand, when the rectal evaluation is done, the abundant presence of fluid during estrus can be detected and which is confirmed by ultrasonography. By using a vaginal speculum, it can be observed if there is inflammation and irritation, presence of urine, discharge from the uterus through the cervix.
When a mare with endometritis is examined with an ultrasound, an exaggerated accumulation of fluid can be observed. This fluid tends to look echogenic, that is, it looks cloudy with white dots, the uterine cells are enlarged, and in some cases very echogenic dots or lines are observed. bright.
The aforementioned are signs that are part of the parameters to diagnose Infectious Endometritis and that must be accompanied by diagnostic tests to corroborate them, when the patient is in estrus or heat. Commonly the tests that tend to be performed are culture (it will allow us to know if there is bacterial or fungal growth), if there is the growth of pathogenic microorganisms, an Antibiogram is performed to detect which Antibiotic or antimicrobial product the causative agent is sensitive to. of Infectious Endometritis.
Cytology is another test that can be used for diagnosis, this in turn will reveal the presence of polymorphonuclear cells, which are indicators of inflammation.
The uterine biopsy is a test that can indicate the degree of inflammation in the uterus and whether the process is acute or chronic, that is, whether the inflammation of the endometrium has been present for a short or long time, and what would be the fertility percentage of the horse. This test is performed with a special clamp that allows a physical sample to be taken from the uterus.
The sample to perform a culture or cytology can be taken using a uterine swab or a low-volume lavage with which the fluid obtained is centrifuged and what is decanted is used for said tests.
These uterine infections can be clinical or subclinical, that is, when they are clinical they tend to be easier to identify since some of the visible signs described above can be found, while when they are subclinical, no manifestations of disease are observed and in The ultrasound apparently everything is in order, however, the mare is subfertile.
The key to good treatment is an accurate diagnosis, which is why it is important to know exactly the pathology that the patient presents. When referring to how to treat endometritis in Mares, one must take into account knowing the behavior of said reproductive tract and knowing what it needs to improve the uterine conditions to receive the embryo that comes from the oviducts.
There are various ways to address endometritis in Mares, however, one of the fundamental parameters is to eliminate the source of contamination to the uterus, and if it is a pathology that requires surgical resolution, perform it as soon as possible.
Uterine lavage is one of the main tools to treat this pathology, whether infectious or not, since with this technique excess fluid, semen, and inflammatory cells can be extracted and thus clean the lumen of the uterus. It can be done every day of heat if the case in question warrants it. The solutions to use can be physiological solution, lactated ringer’s solution, etc.; All materials to be used must be sterile, so as not to generate further inflammation and contamination. Likewise, the entire washing process must be carried out by a professional and taking the required hygiene measures.
Ecbolic agents are medications used to generate uterine contractions and generate emptying of the uterus, preventing any unwanted remains in it. Oxytocin and prostaglandins are the components used, with oxytocin having an action of around 30 to 45 minutes post injection and prostaglandins approximately 2 to 4 hours post injection.
When there is an infectious, bacterial or fungal endometritis, already diagnosed and aware of the pathogenic microorganisms involved, the necessary medications must be administered to eliminate said infection.
The application of antibiotics or antifungals through infusions directly into the uterus to combat infections is common. The application of systemic antibiotics is another option, and in some cases a combination of both routes can be chosen and be more effective in resolving the pathology.
Preventive management is very important to take into account in this type of problem mares and in my personal opinion I recommend it for most cases. Some steps to consider are administration of steroidal anti-inflammatory drugs such as Dexamethasone, performing a single riding service or of Artificial Insemination to the mare, perform uterine washings 4 to 6 hours after service and the application of ecbolic agents (in the case of using prostaglandins before ovulation), all of this with the purpose of creating a better uterine environment.
Nowadays there are many techniques and products to use to achieve pregnancy in the mare, it is essential to remember that there is no specific work protocol to be successful, since each case is different, the crucial thing is to use the work tools with those we have and analyze the case to obtain the best result in the shortest time possible.
University of Zulia, Faculty of Veterinary Sciences (FCV). Venezuela.
Member of the College of Veterinary Doctors of the state of Zulia, number 2483
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- Brinsko, S.P., Blanchard, T.L., Varrer, D.D., Schumacher, J., Love C.C., Hirricks, K. and Hartman, D., 2010. Manual of Equine Reproduction. 3rd Edition. Mosby Elsevier, Oxford.
- McCue,P., Ferris, R., 2016. Formulary and Protocols in Equine Reproduction.