I did a search but didn’t find anything terribly recent. If you’ve done it, what were the symptoms that prompted you to consider it and what were the the results/recovery? tia!
Many moons ago (35-ish years ago) I had a mare that all of a sudden started getting balky and very tense for a few days a month. Duh, it finally sunk in that his was happening about every 21 days and when she was in heat. Of course, I was told she was just a bitchy mare which I knew was not true. I got her as a long yearling and had done all training myself up to that point with absolutely no training issues. We had issues when she was in heat but as soon as she ovulated, it was like someone flipped a switch and she went back to her normal calm, cooperative self. Each month, the behavior got a bit more intense. Luckily she was a very good egg and although balky and kicking out, she didn’t ever unload me or even try.
I hurt my back (unrelated to horse’s behavior) and decided, since I couldn’t ride, I would start with getting a repro exam done (August). All they could see on the ultrasound was multiple follicles. They gave her the shot to shed those follicles and then she sat until December when I had her rechecked. Her left ovary was 3 times the size of the right one. I decided then and there I wanted her spayed but my vet said we don’t do that. The technique of the day was to go through the vagina to snag the ovaries and they had a mare that had a large tumor and she bled out so they were not longer doing that procedure. He referred me to the larger equine vet hospital and that vet was no longer doing spays that way either.
The referral vet had developed his own procedure which involved general anesthesia and making an incision on each side of the udder but with that he could visualize the ovary and not just dig around blind. So…my mare was sort of a guinea pig. However, she came through with flying colors. She had a month in a small pen with some hand walking and was good to go back to work after a month. She initially had some kicking out until she realized she didn’t hurt any more and got back to her usual calm training. She still acted like she was cycling…just usual mare behavior. No changes under saddle.
She had a solid tumor (leiomyosarcoma) on that ovary but I had him take both. That ovary was about the size of a lemon (in the dead of winter) and I am sure when she was building a follicle, it hurt like hell. Besides the under saddle trouble, before the spay she would get very angry with her pasture mate and she tried to savage him a couple times through the fence. She did manage to grab his chest a couple times…poor guy couldn’t figure out what he had done.
Anyway, I know the spay procedure is quite different now. I believe most are done endoscopically. But at the time, this worked and it definitely cured the problem. The vet was skeptical (you know these women and placing their woman problems on their horses 
) but did the surgery and did a good job. He didn’t think it would ‘cure’ her but it did.
Susan
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I had my last horse spayed in 2021. I have a thread about it here: Spaying a Mare
The biggest red flag was that she was constantly in heat. I don’t mean cycling frequently, I mean she went into heat in April 2021 and would not come out of it. Peeing, squealing, winking, etc. Constantly. She was grumpy to touch, balky and spooky under saddle, and explosive on the ground. She had a shifting lameness behind that at the time, we did not connect to the heat symptoms and did a lameness eval on that. Repro vet saw her for the heat symptoms. She had very large follicles, but nothing else notable. Blood panel was mostly normal. Vet gave her a shot to bring her out of heat, and started on regumate. Instant difference. Sound, happy, agreeable - it was night and day. Somewhere in there we also ruled out a bunch of other potential causes (ulcers, kissing spine, her feet) because I was losing it a bit chasing whatever was going on.
I would have just kept her on regumate, but she would cycle through it. Didn’t matter how high the dose, if it was orally syringed or injected regumate. We could not prevent her from cycling through it and then we would need to give her a hormone to bring her out of heat because she couldn’t on her own. It stumped two repro vets and the therio specialist at Cornell and they suggested spaying. It was laproscopic and recovery was pretty simple. I think a week of hand walking, a week small paddock turnout, a week of normal turnout, and then back under saddle.
Behavior on the ground improved a lot after spaying and physically she seemed a lot more comfortable, but she never went back to how she was under saddle before she went into that heat Spring 2021. She is very happily living as a tease mare at a breeding farm.
I did it with one, many years ago. Homebred mare who was just always tense in her back and a bit reactive. Always had lots of follicles when we would check her. Was better on regumate, but kept having to increase the dose to maintain a more normal behavior. Did the spaying because she also had very bad OCD in her hocks that we had removed when she was 2. As a responsible breeder, I decided she really should not be reproducing given her OCD (knew a few others out of her sire who also had OCD).
She did have abnormalities on her one ovary when they removed it. Not sure it made a huge difference in her after the spaying. In hindsight, I wonder if she had OCD issues elsewhere. I sold her as a jumper with full disclosure. Unfortunately she bounced around a bit…finally someone decent bought her who was trying to do right by her. She tracked me down…and the full history had never been shared with her (she thought she could at least have a well bred broodmare). She sent her to get a full vet workup. At that point they found her nuchal ligament was badly torn (chronic). She was put down at that point.
