When a mare reabsorbs after 21 days or after 40 days when will she be ready to breed again? How long does it take to reabsorb a embryo at these stages?
Sandy Posted From: 188.8.131.52
Posted on Thursday, July 29, 2004 - 04:26 pm:
My mare was palped at day 36 and vet said that he was pretty sure she was in foal, although it did not feel like a 30+ day pregnancy. The cervix just wasn't tight enough, but he was going to say that yes, she was pregnant. I had her palped again at day 90, and she was found open. I did not see the mare have any heat cycles during that 60 day period between the exams. Vet recommended giving her a Lutalyse injection to bring her back into heat so we could get her re-bred. Well, here we are, 9 days later after giving her the injection, and still no heat. When does a mare start having heat cycles again after absorbing, and why didn't the shot work? This is the first time one of my mares has ever absorbed, so I'm just really unsure of what to expect and what to look for.
Jos Posted From: 184.108.40.206
Posted on Thursday, July 29, 2004 - 05:20 pm:
If a mare loses her pregnancy prior to about day 30-35, then she will be likely to come back into estrus ("heat") as soon as the CL left from the previous ovulation has regressed. This generally means that if she lost the pregnancy prior to 14 days, she will come back into estrus on the same schedule as she would if she hadn't been bred; on the other hand, if she loses the pregnancy after that point, she will generally lag behind by the same number of days as she was behind her regular schedule when she lost the pregnancy. There can be variables (such as a retained CL) but generally, it will be as described. Note that these mares will probably respond to prostaglandin by coming into estrus in 3-5 days.
Around day 30-36 of pregnancy some structures form called the endometrial cups. These secrete a hormone called equine chorionic gonadotropin or eCG. eCG is responsible for the encouragement of the production of further follicles, some of which ovulate, and some simply becoming CL's without ovulation. the end result is that there is an increased production of the hormone progesterone, which is secreted by the CL's. These structures will remain in place until about 120-150 days of pregnancy.
If a mare loses her pregnancy after the formation of the endometrial cups, she will not return to estrus until they have regressed at the 120-150 day mark. Neither will the mare respond to a single dose of prostaglandin by coming back into estrus, as there are multiple CL's that must be destroyed, and hence, multiple doses of prostaglandin will be required, and even then, some mares will still not come back into estrus until later when the CL's have naturally disappeared.
WRT your mare that was checked not in foal at 90 days... I would encourage you to have the mare checked again using ultrasound, or a blood test for the hormone estrone sulfate. Around 90 days, the pregnancy can become difficult to reach, as the weight drops it over the edge of the pelvic brim out of reach of the palpator. As your vet gave you prostaglandin to use at that time, which is unlikely to work to bring the mare back into estrus (because of those endometrial cups), my feelings are that perhaps he is not very experienced in the field of equine reproduction, and you might be better off finding someone that is to check the mare again. The good news is, that in the event that she is pregnant, even though you gave her the prostaglandin, she is likely to still be pregnant because of those endometrial cups!
In the event that she is again found to be not pregnant, repeated dosing with the prostaglandin may result in a return to estrus, or you may need to wait until the endometrial cups and CL's have regressed naturally.
Sandy Posted From: 220.127.116.11
Posted on Saturday, July 31, 2004 - 12:43 pm:
Thanks Jos. I had wondered whether or not this mare is still indeed pregnant. I have owned her for 7 years and this will be her 4th foal with us so I know what she is like when pregnant and she is exhibiting all of the behaviors of pregnancy. I am glad to hear that giving her the shot of prostaglandin would not have aborted the pregnancy as that was definitely a concern for me.
As for my vet....I have used him exclusively for the last 12 years and he has never been "wrong" yet. But I guess there is always a first time for everything. In the case that she is still open, what is the recommended repeat dosing with prostaglandin for attempting to bring her back into estrus? I hate the thought of having to wait 150 days, as that would put breeding quite late into the season.
Jos Posted From: 18.104.22.168
Posted on Saturday, July 31, 2004 - 12:54 pm:
First point... "likely to still be pregnant"... not "would not have aborted"... no guarantees...
If all the signs you are seeing with this particular mare, with whom you are familiar suggest pregnancy, I would encourage you to explore further before taking more action to return her to estrus...
The specific dosages and protocol for inducing estrus after the endometrial formation should be discussed with your veterinarian before treatment, and follow his advice. Generally though, it is multiple doses for multiple successive days, which can be hard on the mare. Remember that you are not dealing with a single CL at this stage, but multiple CL's... and note also, that it does not always work as far as bringing the mare back into estrus. Sometimes you just have to wait...
Sandy Posted From: 22.214.171.124
Posted on Sunday, August 01, 2004 - 01:37 pm:
Yes, I do agree that I need to explore the possibility of her still being pregnant before continuing with trying to bring her back into estrus. I will continue to tease her throughout this week, and if I still see no signs of heat, I will have her U/Sd and proceed from there. Thanks so much for the help as I did not know about the multiple CL's. That explains a lot.
Sandy Posted From: 126.96.36.199
Posted on Sunday, August 22, 2004 - 01:18 pm:
Update: I did have my mare u/s'd and she was indeed found open. I decided not to use any more prostaglandin shots to try to return her to estrus as I feel it is just too harsh on the mare.
As of Aug. 20, she returned to heat on her own. Pretty much 120 days after her last heat cycle in which she settled. We are currently breeding her back at this time.
What are the chances of her settling on this cycle? She is exhibiting normal signs of heat and is standing well for the stallion.
Jos Posted From: 188.8.131.52
Posted on Sunday, August 22, 2004 - 11:11 pm:
If she is cycling normally, and ovulates in a normal fashion having been bred at the correct time with good semen, the chances are as good as they were before.
Sandy Posted From: 184.108.40.206
Posted on Monday, August 23, 2004 - 04:41 pm:
I guess that is the question, is whether or not this would be a normal cycle considering the fact of the absorption and the long return to estrus.
Jos Posted From: 220.127.116.11
Posted on Monday, August 23, 2004 - 11:43 pm:
As noted above, once a mare loses a pregnancy after the endometrial cups have formed and are secreting eCG, she will not come back in to estrus until the CL's associated with that eCG secretion are resolved - typically between 120 and a 150 days after the initial ovulation.
In other words your mare is right on schedule, and read the right instruction book...
It is likely therefore that this cycle will be as fertile as any other cycle.
The question you should be considering is why did she lost the previous pregnancy?
How old is this mare?
Was there a clean uterine culture and cytology obtained prior to breeding?
Was there any suggestion of post-breeding endometritis and delayed uterine clearance?
Just some food for thought for starters...
Sandy Posted From: 18.104.22.168
Posted on Tuesday, August 24, 2004 - 04:31 pm:
As of yesterday Aug.23, the mare is out of heat. She exhibited pretty strong signs of heat on the 20th, we bred her live cover on the 21st and teased her yesterday to cover again, and she was definitely saying "no" to the stallion. So, I'm guessing she was only in standing heat for 2 days. So, that makes me wonder about this cycle. I do know that the later in the year it gets, the shorter their cycles get also. So, I guess that could be the cause for the short cycle time.
As to the question of why she absorbed, who knows? I did ask my vet that question and all I was told is, "sometimes it happens, and it happens a lot."
This mare is 10 years old, and has always been an easy breeder. Settling every single time on the first try of the year and this is the first time she has ever absorbed. Although she did abort once, in 2001 at approx. 4-5 mos gestation. But I have attributed that to the fact that she had gotten a very severe laceration to her hip and I gave her a tetanus shot at the time. I figured the pregnancy would be safe considering how far along she was, but she did indeed abort the foal within a week of receiving the shot. I figure she slipped the foal either because of the shot, or because of the fact that she was in extreme pain and was very stressed. She aborted late in the year, so we waited until the following spring (2002) to breed her again, and she did have a healthy full term pregnancy and foaled in 2003. We did not breed her back last year because we sold our stallion and didn't have one to breed her to until this year.
I did not do a culture and cytology prior to breeding because as I say, this mare has never been one to have any problems conceiving and carrying foals to term. I'm just hoping that this mare did indeed read the instruction book and that she settled on this cycle! I'm really depending on this foal next year. Thanks for all your help Jos
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