Mare was bred on day three, showing heat. Vet bred AI. (Doc thought maybe a bit early, 3.0 follicle and a 2.8 on other side. Cervix a 1-2 ) HCG'd. Still in on day five, so doc checked again, and said cervix a 3-4 and on the floor. A 3.5 -38 follicle and a regressing 2.5, he thought. No ultrasound this time. (?) We ordered another shipment. Mare bred on day six and seven of her showing heat cycle. Doc unable to come and check her to say where we were after this. Palpation indicated cervix open and on the "floor" last two times bred, I was sure the last one was unnecessary...but she showed to the teaser for a couple more days. She DID have those two follicles when checked with ultrasound pre-breeding on the third day of heat. I am not looking forward to shipping again. Is it highly likely though, that we did not "catch" her as she continued to show to the teaser?
There are several points worthy of note here. The first is that research has shown unpredictable results in stimulation of ovulation following the administration of hCG with a follicle smaller that 3.5 cm in diameter. Deslorelin products however can be given on a 3 cm follicle, so are you sure that it was hCG that was given and not Deslorelin?
The next point to consider is are you sure that this mare is out of transitional phase? Development of follicles that regress rather than ovulate is typical of transitional phase, and it is that time of the year...
The third factor to consider is that when a mare ovulates, it is not until the CL is formed and producing sufficient levels of progesterone that one will see the onset of resistance from the mare to the stallion's advances - it is progesterone that causes that behaviour - and it will typically take 1-2 days to achieve those levels, so it is normal for a mare to be receptive to the stallion for a day or so after ovulation - it is not the mare conceiving that causes her to no longer show receptivity.
If I had to put money on one of the options, it would be that you are dealing with transitional phase...
Next question then...can they conceive on a transitional phase? We do know the mare had a seven day heat 21 days earlier. Oh...and it WAS HCG and not the other product you mentioned. I"ll remember that fact. Yup.
Transitional phase - by definition - is the phase between the winter anestrus period and the regular cyclical season. The end of transitional phase is heralded by the first ovulation of the year, so technically, the mare cannot conceive during transitional phase, only with the ovulation that ends it.
Without discovering if there is a functional CL present, you cannot determine if the mare has passed through transitional phase or not.
Whew...that's a landmine of nomenclature! A Catch-the-mare-22! We'll have her checked at fourteen days. Thanks so much for your input.
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