I have 2 mares. Neither actually bucks when in season but can get sore backs. My vet had a feel inside the older mare when she was in season and told me that one of her ovaries was inflamed which would make her sore. This could be causing the bucking in your mare, she might just be trying to tell you it hurts. If mine are really sore I don't ride them for a few days.
It's like period pain, they get tenser and sore over the loins when they're in season and like people it affects some more than others. Al couldn't work Bee when she was in season, she was too sore and would buck a lot and feel funny behind.
I think a mares ovaries swell to twice the usual size when the mare is in season and they are positioned just behind the back of the saddle so really that explains why she bucks when shes in season.
As above. You could try bute and if it stops the bucking, there's your answer. If you have period pains you take ibuprofen and soldier on and feel the better for it, and this can work for mares as well.
Just a note on the use of bute for back pain - about 2 years ago the Horse and Hound did a veterinary article on recent research, and one of the findings was that bute actually made a horses back more sensitive for the first 3 days and didn't have a pain reducing effect until after that period. This means that bute may not be suitable for a mare with back pain associated to her being in season.
I had a mare who appeared to be sore over her ovaries especially in spring/when her seasons started. I put her on Oestress and the change (for the better) was amazing. She was obviously so much more comfortable. Obviously that kind of thing doesn't work for all mares, but might be worth a try.
I put my mare on 'herbal mare' a supplement which I get from Natural Horse Supplies, I had awful problems with her bucking, had tack checked, teeth, physio, everything I could think of, this was a last resort with no real hope of any improvement. She stopped bucking, it's the only stuff she will eat, which makes me think maybe her diet is lacking without it. I did take her off it as I was so convinced that it wouldn't do anything for her, and she started bucking again.
I Purchased a bag of Hilton Herbs Angus Cactus (looks like peppercorns) for £8 from saddlers at the beginning of the year and now have completely different horse!! Much less sensitive and tight through her back when in season and doesn't even squirt anymore!
I have fed about 20g once a day since March this year and I am only just 1/4 into my second bag, so works out very cheap too!
I was told that for maximum effect you have to start it before they have their first season if poss and continue until the last one in the autumn.
This worked much better for me that a couple of branded mare supplements I tried - I would guess that is due to feeding it raw, undiluted, the horse is getting more, rather than that it acutally being any better.
Mine doesn't buck but she sure will bite you to within an inch of your life if you go anywhere near her girth, back or flanks when in season. if I can get on her and do some light riding she will ease up and relax. I found NAF Oestress to be very good
Thanks everyone for your replies. This is a horse I am thinking of buying and it's putting me off a bit. I've had mares for 20ish years and never had a problem when in season. But I know they are all different. She's a real sweetheart otherwise.