This article is based on an episode of Behind the Breeding, the StallionApp podcast, featuring Thai Hua of Botupharma USA. The conversation explores uterine biofilms, difficult-to-breed mares, and the challenges of treating mares when conventional testing doesn't provide an obvious answer.
When a mare repeatedly fails to become pregnant, finding the reason can be frustrating, expensive, and sometimes surprisingly difficult. We spoke with Thai Hua of Botupharma USA about uterine biofilms, and the challenges of managing mares that don't respond to conventional treatment.
For mare owners, few things are more frustrating than a mare that simply won't get pregnant. Getting mares pregnant is crucial to any breeding program, and a mare that isn't taking is a huge source of stress for breeders. Not only can things become expensive, hopes and dreams can be trashed during a season of "not pregnant" ultrasounds.
A mare that wouldn't get in foal
A mare may cycle normally, appear to ovulate appropriately, and seem healthy, yet pregnancy after pregnancy fails to materialize. Every additional breeding cycle means more veterinary work, semen, transportation, and time. That was the situation I found myself in with one of my own mares this breeding season.
After two unsuccessful breedings, I had her evaluated with culture and cytology. Neither provided an obvious answer. What I had noticed, however, was that she developed a small amount of uterine fluid early in her cycle, which subsequently disappeared. The fluid was never present at the time of breeding, or even the day before. The mare never retained fluid after breeding either.
I had previously purchased BotuKiller after seeing it discussed online, although I hadn't used it. With the mare proving difficult to get in foal, I decided to try it as part of her management. After the infusion, she had no fluid the following day, and I subsequently bred her. When I checked her at 11 days, she was pregnant.
That result may or may not have been connected to the treatment — but it provided the reason for a conversation with Thai Hua, COO of Botupharma USA, about what BotuKiller is intended to do and why uterine biofilms have become a topic of interest in difficult-to-breed mares.
What is a uterine biofilm?
One of the most useful explanations Thai gave during our conversation was an analogy for understanding biofilms.
Imagine walking along a creek bed and stepping on a slippery rock. The rock is slippery because algae and other organisms have created a layer over its surface. According to Thai, bacteria can behave similarly inside the uterus.
Bacteria can establish themselves within a biofilm — a protective matrix that can make them more difficult to eliminate. The idea behind targeting a biofilm is therefore different from simply trying to kill bacteria directly.
As Thai explained it, if bacteria are protected within a biofilm, treating the mare with an antimicrobial without addressing that protective layer may not completely resolve the underlying problem.
If you don't get rid of the biofilm and you infuse with antibiotics... you could potentially just be dealing with the symptoms.
The theory behind BotuKiller is that disrupting the biofilm can expose the bacteria, potentially allowing subsequent treatment to work more effectively. Importantly, a negative culture does not necessarily mean that a mare has no bacteria present. As discussed in the podcast, bacteria associated with a biofilm may not always be detected through routine testing.
That distinction is particularly interesting in mares that have a history of breeding difficulties but don't have an obvious positive culture.
What is BotuKiller?
According to Thai, BotuKiller is a uterine infusion intended to disrupt biofilm. He described its principal ingredients as including:
- DMSO
- Sterile water
- Tris-EDTA
- Hydrogen peroxide
It is infused into the uterus and left in place, rather than being flushed straight back out. The protocols below — which Thai described during the interview — differ depending on whether the mare is being treated before or after breeding.
When is BotuKiller used?
One of the questions I particularly wanted to clarify was whether BotuKiller is intended to be used only alongside antibiotics. The answer from Thai was that it can be used in different circumstances, depending on what is happening with the mare. In particular, he described protocols for mares with visible uterine fluid, both before and after breeding.
Before breeding
The protocol described in the interview was:
- Lavage the uterus with lactated Ringer's solution.
- Infuse two bottles of BotuKiller.
- Leave the infusion for approximately 24 hours.
- Re-examine the mare.
- If fluid remains, lavage again and administer another infusion of one bottle of BotuKiller.
The process can be repeated up to three times if fluid persists. Thai said that, in his experience, many mares will be clear after the second infusion.
After breeding
The post-breeding protocol he described is different. BotuKiller is used only when uterine fluid is present after breeding.
If fluid is identified six hours after breeding, the described protocol is to:
- Lavage with lactated Ringer's solution.
- Infuse one bottle of BotuKiller.
- Recheck the mare after approximately 24 hours.
- If fluid remains, administer another bottle.
If the fluid has cleared, no further BotuKiller infusion is called for under the protocol described in the interview.
What if the mare has a positive culture?
Another important part of our conversation was what happens when a mare does have a positive culture and an appropriate antibiotic has been identified. Thai said that BotuKiller can be used in conjunction with antibiotics rather than treating the two as mutually exclusive options.
The reasoning he gave is that if the biofilm is disrupted, the antibiotic can be introduced at the same time rather than leaving an interval during which the biofilm could potentially reform.
In other words, the proposed approach is: disrupt the biofilm → expose the bacteria → allow the antibiotic to act.
Exactly what treatment is appropriate, however, depends on the organism involved, the mare's reproductive history, veterinary findings, and the veterinarian's treatment plan.
Since recording the podcast, I have successfully used BotuKiller to treat biofilm-producing uterine infections in two more mares. For these mares, I infused with BotuKiller the day before taking a culture. The culture came back positive — which means we have something we can treat — and was treated with the appropriate antibiotics. Neither mare received subsequent biofilm treatment other than the initial infusion of BotuKiller, which evidently was enough to allow the antibiotics to do their job: both mares were bred on the same cycle after treatment and both are now in foal.
Why not simply use increasingly aggressive treatments?
Our conversation also touched on a practice that has circulated among breeders for many years: using highly caustic substances such as kerosene as a uterine treatment. Thai was strongly critical of this approach. His concern is that although a caustic treatment may appear to produce results in some mares, deliberately damaging or stripping the endometrium is a very different approach from trying to create a healthy uterine environment.
When a mare isn't getting pregnant, the goal isn't simply to make the uterus "clean." The goal is to have a healthy environment capable of supporting pregnancy. For that reason, a treatment that causes substantial tissue irritation or damage deserves careful consideration, particularly when less destructive approaches may be available.
A difficult mare isn't always a dirty mare
Perhaps the most important caution from the conversation was that BotuKiller isn't a magic solution for every difficult mare. Thai was very clear about this. Some mares have reproductive problems that originate outside the uterus. Environmental factors, nutrition, management, timing, reproductive examination, and breeding protocols can all affect reproductive success.
A uterine infusion cannot correct a fundamentally flawed breeding program. As Thai put it, BotuKiller isn't a "band-aid" and isn't going to fix inadequacies elsewhere in the breeding protocol.
That's an important message for any mare owner who has reached the point of trying one treatment after another. When a mare isn't conceiving, it can be tempting to search for the next product, drug, infusion, or breeder recommendation that might solve the problem. But the more complicated the mare becomes, the more important it is to step back and systematically evaluate the entire breeding program.
The danger of Facebook veterinary advice
That brings us to another issue that came up repeatedly during our conversation: social media.
Breeding groups can be incredibly useful sources of experience. They can also be places where treatments are recommended very casually. One frustrated mare owner posts that she can't get her mare pregnant, and within minutes there may be dozens of suggestions.
- Kerosene.
- Antibiotics.
- A particular infusion.
- A treatment that "worked for my mare."
The problem is that two mares with apparently similar breeding problems may have completely different underlying causes. Thai described Facebook as both one of the best and worst places to get advice, depending on who is providing it.
For mare owners, the lesson isn't to ignore the experiences of other breeders. Those experiences can be valuable. But they should be treated as experiences rather than diagnoses.
Start with the goal: a healthy uterus
One of the strongest themes from the conversation was the importance of keeping the end goal in mind: to establish a healthy uterine environment in which a pregnancy can develop. That means avoiding unnecessary inflammation and unnecessary damage while addressing whatever problem is actually preventing the mare from conceiving.
For a mare that repeatedly develops post-breeding fluid, has a history of endometritis, or has unexplained breeding failures, that may require a more detailed veterinary workup and a carefully designed treatment plan rather than simply adding another product to the routine.
Sometimes the answer is still not obvious
My own experience with this mare illustrates why difficult breeding cases can be so challenging.
Her culture wasn't providing a clear answer. Her cytology wasn't providing a clear answer. She wasn't accumulating significant fluid after breeding. Yet she had failed to become pregnant twice.
After using BotuKiller, she cleared the small amount of fluid she had and subsequently tested pregnant. It could have been the treatment. It could have been timing. It could have been that the previous breeding attempts simply hadn't resulted in pregnancy. Or it could have been a combination of factors.
That's the difficulty, the frustration — and the fascination — of equine reproduction.
The bigger lesson for mare owners
For breeders dealing with a difficult mare, the temptation to keep trying different things is understandable. Reproductive management can become expensive very quickly, and after several failed cycles, frustration can take over.
But difficult mares need better investigation, not necessarily more treatments.
Keeping that whole picture in one place is exactly what good breeding records are for — the pattern in a difficult mare is usually only visible across cycles, not within one.
And if a treatment such as BotuKiller is being considered, discuss it with the veterinarian managing the mare. As Thai emphasized during our conversation, it isn't a miracle product and it won't compensate for poor breeding protocols.
You can learn more about BotuKiller via the Botupharma USA website.