Christy, well, ah... Is a total hussy!
She will keep her tail up and out and usually off to the side, she will pee forcefully, she will pee frequently, she will squat a bit when she pees... She is short tempered, not as calm and quiet as normal. Whinny's a lot! Goes nutsy when she sees a male horse, doesn't have to be a stallion either, can be a gelding...
She will be sore on her back, by her flank for a day or two. Does not want to be saddled, especially does not want the girth! She also doesn't want to be brushed on her belly or back. Chest, neck, rump are fine, just leave her belly and back alone.
She also has a slight discharge. Nothing much, and many mares don't have a discharge. Also, her poo is a wee bit softer. Not diarrhea at all, but more watery than normal.
And yes, she will buck under saddle because the darn thing hurts when she is sore. I just don't ride when she is sore on her back.
I was going to have a marble put in, but by the time I got around to it, well, it's really too late now. That is a stainless steel appricot to plum size marble that is inserted by the vet into the uterus. It makes the hormones respond as if they are pregnant. So, no heat cycles, and no moody behavior. Also no side effects from the marble. Occasionally the mare will expel the marble, but most keep it in for about 8 months according to my vet. Isn't terribly expensive either. I definitely plan on having this done next spring!
Does not damage the horse in any way, and they can still get pregnant later on, just not when the marble is in there.