# Pregnant mares in heat?



## Left Hand Percherons

You've never confirmed her infoal so there is a good chance that she was never pregnant. There's really only a small window at the end of a heat cycle when a mare can settle so if she was covered at the start, she never was going to be in foal.


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## SunnyDraco

Left Hand Percherons said:


> You've never confirmed her infoal so there is a good chance that she was never pregnant. There's really only a small window at the end of a heat cycle when a mare can settle so if she was covered at the start, she never was going to be in foal.


Depends on when a mare ovulates, majority ovulate at the end but there are mares that ovulate at the beginning. Which means covering only at the end is too late for them, you also increase your chances for a filly if covering takes place before ovulation as the Y chromosome sperm tend to burn themselves out quicker with more speed over endurance. It also depends on the longevity of the sperm. Sometimes sperm is still viable for an unusually long time which has several factors that determine a sperm's longevity (like the temperature and viable environment of the mare's uterus). 

Last spring I know a mare that has really awful heat cycles. Every 10 days. That was really hard getting her bred (took 2 breeding seasons to finally get her weirdly wired system to settle) but it was finally accomplished. But according to frequent early ultrasounds and fetus measurements, the conception did not occur with the heat cycle she was last covered on (last covering at the end of the cycle) but conception occurred for the following heat cycle 10 days later (which she was not covered). Sperm can last longer than what typical science says it can last for (which is an average).


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## SunnyDraco

@daystar88

Pregnant mares can still behave as though they are cycling even though they really aren't which is why using heat cycles alone is not a reliable indicator of pregnancy (false pregnancies will prevent mares from continuing cycles just by hormones alone without producing a foal and some pregnant mares will still seem to continue to cycle even though they are pregnant. A pregnant mare's hormones are out of whack, brings about odd behaviors and moods. Some pregnant mares will even allow mounting, which is actually quite bad if there is penetration as that greatly increases risks of infection (infections will cause a variety of fatal or damaging problems, like spontaneous abortion or red bag delivery as just a couple potential problems)

To save everyone from the guessing game, get a vet out to check the mare so your mom knows if her young filly is pregnant;-)


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## Smilie

SunnYDraco, do you have alink that gives statistics of mares ovulating at the beginning of their heat cycle? Just curious, as I never heard of it, and my equine vet would start to check follicle size around day 3 of heat, to track when it got near ovulation size, so semen could be ordered at the right time
Yes, sperm can remain viable in a mare for a while, but 10 days sounds also unusal, or at least, also something I never heard about. The ovum itself, remains viable for only about 24 hours after ovulation

Anyway, here is the info I am familiar with. We never bred our mares until they had been in heat for three days




Number of days in estrus The average equine estrous cycle is 20.6 days, and the average duration of estrus is 5.7 days. McCue noted that "46%, 32%, and 12% of mares ovulated within 24, 48, or 72 hours, respectively, prior to the end of estrus, while 10% of mares were out of estrus before ovulation occurred.'

Yes, mares can still allow a stud to mount, while in foal at times, but they are not cycling, as in having viable follicles
At any rate, just because this filly was bred twice, in no way means she was ever in foal


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## Smilie

I see where the extreme end of the sperm remaining viable in the mare, is 7 days, so possible, but not usual Depends on the stallion, with 24 to 72 hours the norm

As the Sperm Turns | TheHorse.com


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## Yogiwick

Don't know much about breeding young horses. I'm wondering if her age made it a little harder for her to take? Sort of how an older mare may take a little longer as well (different reasons of course).

I'm guessing she's not bred due to the multiple factors against it but yes, ALWAYS check!! Glad that is the game plan.

I will say that my ewe's are due in a few weeks (yikes what happened! lol) and I was looking at one of the yearlings in particularly thinking she literally does NOT look pregnant. None of them really do, even the older ones this year, it's a little odd. Was planning out for the end of the month then my mom was like "noo earliest was March 13, so they can go any day!". She does not look at all pregnant but based on a young maiden and it's still SO early I wouldn't base anything off of that.


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## daystar88

@SunnyDraco This filly actually belongs to me and I specifically told my mom I didn't want her bred until she was much older. But she doesn't listen. 

Anyway, @Yogiwick I read somewhere that younger horses tend to be most fertile. Maybe that was just for young studs? I'm not 100% sure but I thought they said it was true for fillies as well. 

A vet check WILL happen, I was just curious of anyone had any ideas what could be going on. She wasn't acting full on in heat, because if the gelding went further back than her withers she'd pin her ears back and almost kick at him through the fence. 

I don't know if this helps, but she's pastured with Cowboy and whenever he stands behind her she kicks out at him unless it's his butt facing her. She's never kicked out at me for standing behind her, just and horse that does. He's never had a thought about mounting yet and as soon as I move he's only going to be pastured with his half brother who's a gelding and hopefully a paint gelding I get this summer.


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## daystar88

@Smilie you are correct, there is a good chance she didn't take. I'd honestly be a bit happy and sad about that however since the stud is Cowboy's dad and so far he's produced EXCELLENT correct babies. And with Lacey being a potential barrel horse we've got another multi talented foal in the making. Smokey, the stud, was reining bred. But then again she's too young to breed and I don't want this hard on her at this age.


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## SunnyDraco

Smilie said:


> SunnYDraco, do you have alink that gives statistics of mares ovulating at the beginning of their heat cycle? Just curious, as I never heard of it, and my equine vet would start to check follicle size around day 3 of heat, to track when it got near ovulation size, so semen could be ordered at the right time
> Yes, sperm can remain viable in a mare for a while, but 10 days sounds also unusal, or at least, also something I never heard about. The ovum itself, remains viable for only about 24 hours after ovulation
> 
> Anyway, here is the info I am familiar with. We never bred our mares until they had been in heat for three days
> 
> 
> 
> 
> Number of days in estrus The average equine estrous cycle is 20.6 days, and the average duration of estrus is 5.7 days. McCue noted that "46%, 32%, and 12% of mares ovulated within 24, 48, or 72 hours, respectively, prior to the end of estrus, while 10% of mares were out of estrus before ovulation occurred.'
> 
> Yes, mares can still allow a stud to mount, while in foal at times, but they are not cycling, as in having viable follicles
> At any rate, just because this filly was bred twice, in no way means she was ever in foal


I don't know if there are statistics on number of mares that ovulate early, I have read about one in particular that a breeder explained why they had problems breeding a particular mare as the stud owner they sent her to for breeding didn't cover her until the end of the cycle. The mare didn't take cycle after cycle and two years of trying. The third year the mare owner demanded that they cover the mare at the beginning of the cycle, the stud owner didn't want to but did so reluctantly and the mare finally got pregnant with that cycle. Since the mare cycled in the beginning instead of the end. 

Also, my oldest sister's mare also ovulates at the beginning of the cycle, by the second day of her cycle according to ultrasounds which makes it hard to catch for AI and also requires early covering when doing live cover. 

There are mares that do cycle at the beginning but I do not know if any study has been done to figure out how many. 

As to the longevity of sperm, a reproductive equine vet (that my mom uses for her stallion and mares) has personally studied and found a few rare cases of sperm that lived about 2 weeks. 

The mare that cycled every 10 days was verified by frequent ultrasounds as she was being particularly difficult outside mare for my mom to breed. I have pictures of her somewhere, helped with the hand breeding and went to a few of the vet ultrasounds while I was visiting my parents that first summer of trying to breed her. And when a mare comes into heat before the 14 day post breeding ultrasound, you have vet work done because something weird was going on and it was and the equine repro vet was kinda stumped on her odd system (he thinks that her system might normalize after she has a foal so we shall see since they plan on breeding back again for a second foal). She was a 12 years old maiden the first year of trying to breed her and finally took the following year at 13 years old.


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## Smilie

Well, that could still be explained, on the mare that failed to get in foal, but did, bred at the beginning of the cycle, that the sperm just remained viable until she did ovulate near the end of her cycle, and the other were just failed breeding attempts-it happens.
Mares come into heat, when that follicle first starts to grow, so I still see where that follicle has to mature, until ovulation, near the end of that heat cycle
All the literature, states mares ovulate just before, or just after going out of heat
There will always be anecdotal observations, with true aberrations occurring in veterinary literature
We hand bred all of our mares, including outside and our own mares. Also bred several by transported cooled semen.
There are sometimes multi ovulations, some time apart, where a second follicle matures and ovulates


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## Smilie

I think, until veterinary literature proves otherwise, the observation of a mare ovulating at the beginning of aheat cycle, remains anecdotal .
The mare that appeared to settle on the third try, bred at the beginning, could merely have had failed breeding's the first two times, with the sperm remaining viable on the third breeding, until the mare ovulated later on in her cycle.
That follicle has to mature, before ovulation'

'An ovarian follicle is a fluid-filled sac surrounded by a group of cells that protect and nourish the ovum (egg). There are thousands of follicles in a mare’s ovaries, but usually only one begins to develop during each estrous cycle. By the sixteenth day of the cycle, the developing follicle has reached the size at which it secretes enough hormone to bring on the external characteristics of heat. Around day 20, the follicle reaches its full size and ruptures, releasing the egg into the fallopian tube (ovulation). The ruptured follicle forms the corpus luteum (CL), which secretes the hormones that prepare the uterus for pregnancy.

http://www.equinews.com/article/follicle-development-and-ovulation-mares

We hand bred all our mares, both those we owned and outside mares. I also bred several mares by transported semen. All ovulated just before going out of heat, or just after. When that follicle first secretes enough estrogen to show heat, it is not near the size for ovulation


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## Left Hand Percherons

Anyone, stallion or mare owner, who can allow a mare to go 2 years trying to get a mare pregnant needs to get out of the business. A simple ultrasound or palpation would of revealed the problem. She obviously was not a proven mare or they would of known how to manage her and not waste 2 years and tons of money.


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## Smilie

This is standard breeding considerations:

A veterinarian should palpate the mare’s ovaries and/or use an ultrasound evaluation of them to monitor the growth and maturity of follicles. Monitoring follicular growth and keeping good records on the history of each mare can help indicate at what follicle size the mare will ovulate and the best time she should be bred. Each mare can vary according to the size of the follicle and when she will ovulate. By keeping accurate records of the growth of the follicle as well as past history this can help indicate at what size the follicle will ovulate. Some mares may ovulate when the follicle reaches a 35 mm or some may ovulate when the follicle is much larger such as 65 mm.

Optimal breeding is every other day while she is in estrus and before she ovulates. A mare will normally ovulate about 24 to 48 hours before the end of estrus. If you are shipping semen, you may want to use the hormone hCG (human chorion gonadotropin) to induce ovulation in order to maximize the chances of the mare’s conceiving. Your best chances to catch your mare (catch referring to conceiving) are inseminating her three days before the end of the estrus cycle to six hours after it. Keep in mind that most semen will live for approximately 48 hours. It is preferred to inseminate the mare at least 36 hours before ovulation.

Thus, very possible, if a mare is bred at the beginning, say day one, of a five day heat cycle, the sperm will still be viable when she does ovulate on the 5th day, but does not mean that she ovulated at the beginning, LOL!


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## daystar88

Left Hand Percherons said:


> Anyone, stallion or mare owner, who can allow a mare to go 2 years trying to get a mare pregnant needs to get out of the business. A simple ultrasound or palpation would of revealed the problem. She obviously was not a proven mare or they would of known how to manage her and not waste 2 years and tons of money.


I stated above what happened. This was not doing but my mom's who just wants to keep producing. Thankfully she said she's done breeding horses and her last mare who's 11yrs should foal in September. 

I specifically told her I didn't want her bred but she doesn't care and wanted a foal. I did NOT want her bred until she was much older AND proven.


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## SunnyDraco

Smilie said:


> Thus, very possible, if a mare is bred at the beginning, say day one, of a five day heat cycle, the sperm will still be viable when she does ovulate on the 5th day, but does not mean that she ovulated at the beginning, LOL!


there are rule breakers to nearly every rule. 

Mare is coming into heat, doesn't stand for the stallion yet but her follicle is quite large already.

Mare stands for the stallion at the point her follicle is nearly to the point of ovulation, ovulates within 24-48 hours after first day she stands for live cover. Still stands for the stallion a few days after but has already ovulated. 

This mare has been ultrasounded and had her follicle tracked before and during ovulation. She ovulated well before the end of her cycle. In fact, when given a shot halfway between cycles to bring her into heat, she ovulates 3-4 days after the shot so you have to be ready with fresh semen.

Yes, she is a rule breaker from what textbooks say happens. Maybe only 1 out a million mares do this and of those mares maybe only a handful are ever attempted to be bred by AI and actually tracked so why would textbook studies seek out the rare abnomalies when 99.99999% of breeders will never encounter such an odd rule breaker? Just speculation on my part for why a study on rule breakers has not been published


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## Smilie

There are always rule breakers, as in mare that have silent heats, where they are ovulating, but don;t show to a stallion
You can only get those mares bred through using ultra sound
Yes, mares ovulate either before or after they go out of heat, so the point of where they stand for a stallion is mote. 
That egg has a very narrow life stance, once released, and if viable semen is present, will get fertilized. That has zero to do, far as when mares ovulate in that heat cycle
One thing is for sure, that follical has to mature, before it is large enough to produce enough estrogen to generate heat, and then has to mature to a size where it will be released, anywhere from 35 mm on wards. That does not happen in those first days of heat
Of course given shots to manipulate the heat cycle, is going to alterate results
Are we now talking of breeding artificial means, to alterate THE NORMAL HEAT cycle, often used when using transported semen?
That has zero to do with natural live cover


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## Yogiwick

Left Hand Percherons said:


> Anyone, stallion or mare owner, who can allow a mare to go 2 years trying to get a mare pregnant needs to get out of the business. A simple ultrasound or palpation would of revealed the problem. She obviously was not a proven mare or they would of known how to manage her and not waste 2 years and tons of money.


This is for sure not true... Some horses do have issues after all..

OP I don't think the above comment was directed towards you.

"I read somewhere that younger horses tend to be most fertile."

That is ABSOLUTELY true. As with any species age makes fertility decline. I'm simply wondering if a just barely fertile animal is less so simply because it hasn't "fully kicked in yet". Does that make sense?

For example I breed Shetland sheep, they are slow growing and not typically bred until yearlings (to lamb at 2) despite being fertile for breeding the first year. I have never intentionally bred the first year but I've had a few lamb out of season as yearlings (bad sheep!). I wonder if I DID intentionally breed if they would not take as well as the yearlings do? They're still babies. And the rams have never displayed breeding behavior at that age either... It's not that the yearlings aren't young just that the babies are just that.

I fully expect every ewe I breed to lamb in the spring, I would be very concerned if one of my young ewes ran with the rams all fall and did not get bred. My oldest ewe lambed 2 weeks later last year, simply meaning she missed the first heat cycle, she still lambed and in previous years has been right on time, she's nearing her retirement soon so is out of my "worry" range.

But how young is too young as far as fertility? Is it just "boom you have heats you're 100% fertile"? Or does it quickly work up to 100% over the first "x" (depending on species years, months, etc) then gradually diminish with age?


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## Smilie

Many breeding operations require a negative culture on a mare, before breeding her
Sometimes the embryo is reabsorbed, before implantation Some mares require progesterone in addition to amount produced, to keep the pregnancy


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## BritSuisse

Im in a similar boat, although, Early on I had my mare vet checked (it was an 'iffy' confirmation). Now Im sitting here at day 157 in my mares pregnancy and she was flirting with her paddock neighbors (Two young geldings) She was squealing and acting as if in heat-I didnt see her urinate, but when I brought her in for the evening she seemed to have peed on her back legs (typical of her in her cycle) Now Im all worried she lost the foal or maybe had a false pregnancy? I guess its worth a mention that she is a maiden mare (9yrs old) and for the past 5 months during her pregnancy she has NEVER once shown any sign of heat! 
Well I hope all works out with your situation, Keep us posted!


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