Posted on Wednesday, December 27, 2006 - 05:43 pm:
I bred my mare via AI (fresh cooled) last year and she took first try. However, I did breed her twice in her heat cycle, day 3 and day 5. When I bred her on day 3 her cervix was very soft and open, on day 5 I could only insert the pipette and one finger into her cervix and it was not near as soft. So would she have ovulated by this time or do they not ovulate until the cervix is completely closed? Just got to wondering, thanks!
Posted on Wednesday, December 27, 2006 - 09:47 pm:
Most mares ovulate in the last 24-48 hours, not at the very end of estrus ("heat"). Following ovulation, the evacuated part of the ovary (where the follicle was) becomes the corpus luteum or "CL". The CL secretes the hormone progesterone. Progesterone - among other things - causes mares to resist the stallion's advances, and closes the cervix. Follicles on the other hand secrete the hormone estrogen, and estrogen is responsible for encouraging receptivity to the stallion's advances, and relaxing of the cervix.
Putting all the above information together to answer your question - when the mare is in estrus, the estrogen secreted from the follicle encourages the receptivity of the mare to the stallion and relaxation of the cervix. About 2 days before the end of the estrus (receptive) phase, the mare ovulates and the CL forms and starts secreting progesterone. As progesterone levels rise, the mare starts to become "ho hum" to the stallion's advances, and finally (about 2 days after ovulation) rejects his advances, at the same time the elevating progesterone levels cause the cervix to close, thereby keeping pathogens out of the uterus and the conceptus (if there is one) inside.
So your mare is perfectly normal! The last time you bred her, you felt the cervix to be soft around day 3, she probably ovulated day 4, and then when you bred her at day 5 her cervix was starting to close in response to rising progesterone levels, but she was still "teasing" a little as the levels were not yet high enough to prevent receptivity completely.
Two questions. Once the mare HAS ovulated, does one have much of a window when semen in the mare might produce a pregnancy? I seem to remember on a mare two years ago that we tried to impregnate with frozen semen and were told by a vet that we had a six hour window post ovulation. As it turns out, we missed that window or the straw wasn't good. I really don't know which. Country vet with his hands over-full. Cannot always get to the niceties...like checking semen after breeding. In most cases we see a bit that's left get thrown in the truck and lord knows WHEN he will be able to get it back to the office and look at it. Sometimew we hear from him, sometimes we don't.We take it in stride because he's the best around here by a mile and he does get 'em pregnant if he's not knee deep in a colic or whatever. SECOND QUESTION: What's the best way for the mare owner to check the sperm count and motility him/herself? Do we need a microscope, a device, or what? We are planning to use our own stallion next year, and we will just be breeding him to our own mares the first year, but that might change thereafter.
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