We have a mare that we cultured and biopsied at the beginning of the season along with a BS exam..everything perfect..no problems. She came into heat on 3/26 ultrasounded on 3/28 with a huge breedable follicle live covered and u/s next day had ovulated. Back into heat on 4/18. Had huge CL on 23rd. Gave Lutalyse and not waiting to rebreed. Talked with previous owner stated that owners before him tried to breed without success..could she have blocked tubes? The vet rec. starting her on regumate as soon as she is out of heat. Have you had much luck with that?
Our first line of attack in this type of a situation - an apparent absence of an obvious cause - is to use the oxytocin protocol that's laid out on our site (follow that link).
Has she been bred to different stallions? I presume she has, but if not, there may be a stallion incompatibility issue.
Does she look "good"? Or is she slow to shed out in spring? Although it's low down on the list of suspected problems, low thyroid function/level is still on it, so you may want to consider that as well.
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