Spaying a Mare

Has anyone recently (past 5ish years) had a mare spayed? What was the recovery like? What was your experience with your horse after? Ballpark cost?

For context: mare is becoming dangerous to handle when in heat. We’ve tried everything to suppress her cycle (oral Regumate, injectable Regumate, oxytocin, marble, etc) and confirmed via ultrasound on 3 separate occasions that the behavior we are observing correlated with her being in heat. Out of heat she is an easy going, sweet, quiet mare. In heat she is in pain, uncomfortable, and highly irrational and unpredictable. We suspected a possible granulosa cell tumor but can’t find one on ultrasound, and blood work is borderline. Escalating behavioral issues are leading me to explore surgery instead of waiting 6 months to see if a tumor develops. (And no, it’s not a matter of disciplining her more.)

Vet agrees and is getting a consult, but I curious what everyone else’s experience was - if there are others with experience! I know it’s not a very common procedure. TIA.

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I see a lot of people go this route with no improvement. I would get a firm diagnosis first, personally. Did vet see anything abnormal with ovaries?

A lot of these behavioral symptoms overlap with pain responses from unrelated issues – from KS, to PSSM, to pathologies in the hoof.

I admit I’m a skeptic about cycles really making an otherwise healthy horse miserable. In my experience with boarding horses who have had this procedure, the underlying issue wasn’t hormonally related at all – it was something undiagnosed like a lameness issue. I experienced this firsthand with a boarding client who had the nicest mare who just gradually became miserable and unhandleable by all but the best barn staff. She was okay to ride, just unbearable on the ground. Her owner tried everything from ulcer treatment to regumate to depo to the marble – and finally they spayed her. She seemed okay for a few weeks but then went back to being awful again. They donated her to the UNH riding program with the caveat she could be difficult to handle… I saw her a year later and she was a completely different horse. All they changed was her farrier and her feed – her tack went with her.


Thanks. As I mentioned, behavior is only present when mare is in heat. Out of heat she is great. We’ve confirmed this with two specialists via multiple repro exams. Not looking for other possible diagnoses at this time (we’ve tested for and ruled out many, including KS, and vets are confident it’s repro related).

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That’s how it started with this mare too, for what it is worth.

Just my experience, worth what you paid for it! But the spaying didn’t work for this particular horse, so there is that.


I have had a lot of mares. Own a mare now and ride two young, green mares for a trainer. With all of them, I notice when they’re in heat, but their behavior doesn’t change other than being a little distracted or more focused on their friends for a couple of days. They still do their jobs. So I’m sorry you seem to have a mare that, apparently, really responds to her hormones.

I’ve known only two mares that were spayed, both in the last few years. One was a trail horse and while I never saw the mare act out, the owner claimed she was a B*tch in heat. She was spayed and nothing changed. I’m sure it was a lack of training and horsemanship in that case.

The other horse was an Oldenburg we raised and showed but later gave to our vet, who wanted a broodmare. She discovered the tumor when she couldn’t get the mare in foal, so it was spayed and became a trail horse. But the presence of the tumor did not affect the mare’s temperament. At all. Ultimately my anecdotes are probably not helping, other than to encourage you to consider all the options before putting your mare through a procedure that might not change anything. (And it’ll cost you $$$).


What exactly is borderline? Testosterone?

The problem with spaying is that often you can put the mare in perpetual heat due to how the hormones work. I actually tried to find the article that explained this, just the other day. there were tests that needed to be done to check various hormone levels to tell you if the spaying was going to prevent all heats, or cause continuous estrus, and now I can’t find it. You definitely don’t want to cause the latter.


Testosterone was slightly elevated, AMH and inhibin were normal. This was explained to me as a possibility, but also that she will no longer be able to produce follicle or ovulate so to the extent ovulation is physically painful to her (which we think it is) it will solve that issue.

That is why I’m curious if others have first hand experience with what kind of mare they ended up with after.

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Following out of pure curiosity!

I have a mare who, when she goes into heat, is exceptionally distracted and anxious. Luckily, Regumate works like a charm for her. When she was in foal, she was the most relaxed and happy horse you ever saw. Spaying is not something I would consider (given she does well on Regumate and has exceptional bloodlines),but I am curious if there are people out there with firsthand experience with a spayed mare. Your horse sounds like she might be a good candidate for it though.

Can’t really answer your question, as I don’t think I’ve ever known a spayed mare. I’ve known a few with various levels of… knowing full well when the are in heat.

Interesting what @beowulf is saying about underlying issues. The two most troublesome mares in heat I can think of in recent memory, probably weren’t the most “body sound” either. Well managed for their jobs (one was jumping GP, one pleasure riding) but with something underlying. Perhaps the changes accompanying their cycle “pile on” to make it extra uncomfortable.

Speaking of the changes with the cycle: (Be warned I’m probably going to muck up this explanation) The ovaries actually move during ovulation…kind of curl or roll up higher (if I’m remembering correctly). They normally hang from a sort of “curtain” of connective tissue under the lumbar spine. Apparently sometimes this normal movement can get muddled up or “stuck” because of adhesions in the connective tissue. If you have access to an osteopathic vet or osteopath/vet team, some of them will do ‘ovary manipulations’ aimed at releasing these adhesions. I’ve personally never seen this done, but read some good testimonials. Incidentally, one of the mares I spoke of above, the vet found one ovary to be sitting abnormally high. He didn’t specifically manipulate, but she did seem better for the next couple of cycles. Maybe another avenue to look into.


Depending on how desirable her offspring would be, breeding her to see how she does after might be helpful.
I have known a few mares who were having behavioral issues and the owners bred them on their vets advice. It worked, one became the most loving puppy dog of a horse after her foal, the other was just overall more amenable to those around her and stopped some of the under saddle antics.

I’m not sure why it works, but according to that vet he has seen it work a lot and hadn’t had much luck with spaying.


I am not seeking alternatives at this time - my vet team has it covered :slightly_smiling_face:

Just looking for first hand experience. Thanks.

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I’ve known 2 spayed mares- not recently, but I’ll relate anyway.
One was owned and spayed by a friend. She bought the horse as a “dangerous” horse, and is a skilled rider and trainer. The mare was sensitive, and had a history of rearing, and was worse when in heat. Spaying her helped, and she became a competitive show horse.

The second one that was spayed was a mare who I had bred and raised, trained and sold as a hunter. She was very competitive at big shows. But she was always a whore. She would leave a trail of pee while you were riding her in the presence of another horse (male or female) when in heat and would masterbate banging her sides into the stall walls, whether or not she was in heat. It was incredible. She was a sexual machine, and normally asexual geldings would act like stallions around her, she was a sexual goddess, knew it, and flaunted it. But would do her job. I got her back after her show career was over and bred her several times. Then she had a reproductive injury, and could no longer be a broodmare. Because she was so VERY “sexy”, I found her a home as a tease mare for a reproductive vet to use to tempt stallions to breed a dummy for collection, a job which she held for some years very successfully. That vet spayed her so that he could “bring her into heat with drugs at any time he needed to to use for semen collection teasing”. I told him that it would not be necessary to do that, as she would tease ANY time, regardless of heat, but he knew better. Turned out that they never had to bring her into heat to tease, she was just the same as a spayed mare as she had been previously. A true “Venus”.


No first hand experience. But a question - why didn’t Regumate work for her? What happened when you put her on it? (E.g. did it not work to suppress her cycles, or did it introduce some new side effect? Or something else?)

What was the purpose of Oxytocin; how was it used?

I would think that your mare on Regumate would give you an idea of what your mare would be like spayed. Unless it didn’t work to suppress her cycle - in which case that in itself is an interesting question.


My family had a large pony mare about 25 years ago when I was a teenager. Between ages 2 and 3, her temperament turned NASTY. She would charge people in the field… including kids trying to get other ponies out of the field. That was really challenging, and a bit scary. The vet recommended spaying her at age 4… this was before the widespread use of Regumate, and the hope was that it would take the edge off her periodic tendency to be aggressive on the ground. Shortly after spaying, we discovered REALLY sad early onset arthritic changes in her hocks… that were progressing VERY quickly. Though they tried injections and bute to support her, and hoped for fusion so she could live a decent life as a family trail pony… she was a truly miserable and unsound pony. She was eventually put down around age 7… hard to know what caused it… likely a combination of breeding, and improper nutrition as a foal or yearling. :cry:

I know you are looking for data on the outcome of spaying only relative to temperament improvement… but count this as one more case of an underlying soundness challenge that was likely the driving factor in terms of temperament issues…


Thank you - that is very helpful!

Regumate did not keep her out of heat - she continued to cycle through it. We tried oral and injectable at various doses and frequencies and it failed to keep her from ovulating.

Oxytocin protocol has some success with preventing ovulation for 1-4 months (also treating cysts). It did not work for her, unfortunately. We did 1cc IM on day 7-14 of her cycle (if you don’t know where they are in their cycle, it’s a month). My understand is it’s more commonly used at the track to keep mares out of heat because it’s pretty inexpensive.

ETA: on Regumate, out of heat, she was lovely and comfortable. The problem was she doesn’t stay out of heat.

That’s really interesting. I agree that spaying might be the best solution at this point. Really interested to hear the results.

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I clip horses at a dressage barn and one of the mares that I clip was spayed last year. The owner was very experienced and responsible and tried everything to no avail, so she had her spayed. And everyone is happier! The mare is moving up the levels in an appropriate manner and is happy and relaxed in her work and with her life. I never saw the mare on a day-to-day basis so I don’t have first-hand information in that sense, but I know for sure that the owner is very happy with the decision.


My SIL had her mare spayed a few years ago due to behavior issues she attributed to heat cycles/hormones, however none of the (limited) testing that was done beforehand was able to pinpoint a specific cause to the behavior.

Since the spay, the mare has seemingly been in heat constantly. I had no idea that was a possibility, so @JB if you find the article you were talking about discussing the cause, I would love to see it. The problem behaviors that the spay was supposed to fix remain.


I hope it goes well for you! I had considered spaying my mare, but the aftercare/stall rest required put me off (just in case it didn’t work), as my mare would not to well on stall rest.