Vet ultrasounded mare at 16 days, says not pregnant, no follicles, has CL. His suggestion was give shot to bring her into heat, as he is certain no pregnancy, so I agree, mare has not come back into heat, shot was given on the June 18. If she was pregnant would the shot make her lose it? What would you suggest we do, or will it take a little longer for her to come back in. She was also ultrasounded at day 10, as she was showing heat, but no follicles were present, and he said she did not look like she had ovulated.
If she was pregnant would the shot make her lose it?
Presuming "the shot" was prostaglandin, yes.
Take a look at the article on this site about why prostaglandin may not work for more information. It may also be that there has not been enough time elapsed since giving the hormone - 3-5 days is the common duration to onset of estrus, and if it was given on the 18th and today is the 22nd then it's still only 4 days. Alternatively, as noted in the article, she may have already come into estrus, ovulated and gone out again is there was a large (>3 cm) follicle present at the time of treatment.
Note that indication of estrus 10 days after prior ovulation, if coupled with physiological signs (relaxed cervix, uterine edema etc.) is suggestive of presence of a uterine irritant - typically a pathogen of some sort - that is causing premature luteolysis of the CL. This may also tie in with a subsequent erratic response to prostaglandin.
When shot was given, she was ultrasounded and no follicle was found. When ultrasounded at 10 days nothing was abnormal looking, could be seen and no follicles present. I am wondering if she is just submissive and pees when teased, as before we bred her this time. We had teased her she acted like she was in squattining, peeing, etc. but when we went to cover her she would not stand. This last cycle, when truely in heat stood like a champ?
If she had recently ovulated when treated - either a mid-cycle ovulation or because she returned to estrus early as per my above post - then there may not have been a functional CL receptive to Prostaglandin F2α at the time of treatment.
Submissiveness is always a possibility, but good ultrasound evaluations should enable you to rule that out (or in).
That is why the Ultrasound was done at day 10, because if she was in heat, had follicle, we were going to do a culture, but the vet said she was not in heat, as no follicles were present, and she had not ovulated. This is why I am thinking she is submissive, as the stallion I teased her with at day 7, when she started acting she was back in heat, was a stallion she had not seen before.
She is still not in heat.
I think I understand this part "she may have already come into estrus, ovulated and gone out again if there was a large (>3 cm) follicle present at the time of treatment" but according to my Vet, the ultrasound showed very, very tiny follicles, which is really confusing me as she should have had a follicle, if she was not pregnant at 16 days post breeding. If she was pregnant, shot was given, would she come in heat, in the 3 to 5 day time frame or would the shot not work, or take longer? So what do I do know?
Next time Vet says not pregnant, and no follicles, but mare should be coming back in. I will wait several weeks, and then reultrasound.
My previous summation may be more likely - that she had a mid-cycle follicle that she had recently ovulated when given the Prostaglandin F2α. If that had happened in the previous 3 or 4 days prior to being given the shot, she would be likely not to come into estrus, or to have follicular presence.
Presuming she is definitely not pregnant (which having received the shot is likely any way you look at it), you might want to discus with your vet the possibility of giving another dose of Prostaglandin F2α, perhaps first checking to make sure there isn't a large follicle present.
Onset of estrus is pregnant when treated carries the same provisos as if not pregnant. If there is no large follicle, and a receptive CL, then 3-5 days. If a large follicle, less; if there is a non-receptive CL, more.
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