My BO has a 21 year old thoroughbred mare that she competed on for years in endurance, and now she has a foal out of her every few years. She has been checked by a vet and she is reproductively, and in all other ways, sound. She holds her weight well, carries a foal and foals without complication. She is easy to breed, shows heat obviously. The only quirk is that she typically shows heat and allows breeding three weeks after she was bred successfully. She is like that with every pregnancy.
My BO acquired a stallion last year that complements the mare nicely, so she wanted to have one last foal out of her. She consulted the vet(an equine reproductive specialist) and was given the green light to go ahead.
Her and a couple other mares were bred in late april, early may(early foals are desirable in thoroughbreds), and were ultra sounded open(at 18 days). They were all rebred in late may, the other mares were in foal, but the older mare was again ultra sounded open at 20 days. The barn owner thought she would give it one more chance, so teased her regularly from the middle of June till now. She will start 'flirting' with the stallion, then squeal and lash out violently with a hoof, which is extremely uncharacteristic. There have been no signs of discharge or a foal being aborted at any point, and she is examined every day by the Bo. She has not been in heat at any point.
What is going on with this mare?