# Mare Heat Cycles



## wildhorses (May 25, 2009)

After many years of pasture breeding, I have decided to try hand breeding. My numbers are down to a more manageable amount to try to hand breed. But I am just used to throwing the stallions out into the pasture and letting them do their business!

Can someone explain to me the pattern of the heat cycle? How many days in between heat cycles, how many days mares are in heat, how many days to breed during their cycle, how many days after foaling do they go through their foal heat cycle, etc?

Any help would be greatly appreciated! Thanks!


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## Fantasia (May 26, 2009)

Hi - i usually work on either 21 days since beginning of cycle or 14 days after mares go out between cycles. Mares will vary with their length of cycles so using those dates will give you a good guideline as to when they may be thinking about coming back into heat. As season progresses, the 21 day, 14 day rule will end up being pretty much the same day.

Length of cycle will vary - in spring anything from 5 -14 days, shortening as the summer progresses. Each individual mare will be different.

I usually start breeding on the third day and then every second day

Most mares have their foal heat between 5-7 days post foaling. Personally I don't breed on this heat.

Hope that helps


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## Just Us N Texas (May 26, 2009)

Mare heat cycles are usually in 9 out 9, making it an 18 day cycle. After foaling, they can be bred back on the 9th day. Many people skip that breeding and go for the 27th day. However, minis are slightly different in their heat cycles, and this is just a rule of thumb to go by. We just bred a mare for clients, on her foaling heat, and she was in, and ready for breeding on her 12th day. Mares, like all females, are different, and this is just a rule of thumb as I stated previously.


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## rabbitsfizz (May 26, 2009)

The generally accepted time is 21 days from the _start_ of the mare's heat cycle, ignoring however long she is in season because, as has been mentioned, mares vary wildly, and vary again as they are affected by the time of year (hours of daylight is what affects that!!)

So it is all a bit of a lottery unless you have a scanner and can tell when the mare is about to ovulate....

I also breed on the third day and then every other day of the season, making sure I get the very last day.

Once the mare has shed her egg she will go off season, so you have around 36 hours (or whatever figure people are using at the moment!) to fertilise the egg once it has been released.

It will take her roughly 21 days to reach this point again if she has not been fertilised successfully, and as we do not, many of us, have the luxury of a scanner, we use the most noticable point of reference, which is when she becomes receptive, or "stands" after a couple of weeks of attempting to kill the stallion!!!

Having bred both ways now I can tell you that there is little difference, so long as your stallion is happy out with the mares, between knowing the dates from writing them down when you notice a mare in season, and knowing the dates from hand breeding a mare.

The mares still have their foals exactly when they are ready, and still completely ignore the days that _we_ think that they are due!!!


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## wc minis (May 26, 2009)

I just started teasing my mares this weekend. On Saturday, one mare, she was in and we hand bred her and than teased her Sunday and Monday and she was out. So I must have just caught her on the last day. I am hoping she took with the one breeding


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## rabbitsfizz (May 26, 2009)

Or she may just have had one of those "here today, gone tomorrow" seasons!!

There is no law of averages for the length of a mare's season, my Arabs normally (HAH!!) went three or four days, my Minis "normally" go .....well, anything from three to fifteen and running one season into another, basically





As a rough estimate you can often go ten days from the last day she accepted the stallion to the (roughly) start of the next season, but it is not an exact thing, just a guide to when to next tease.


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## minie812 (May 26, 2009)

Speaking of heat cycles. Is there any truth that if you wait farther into the heat cycle the more likely for a filly? Wondered if there is truth to it or a ole' wives tale?


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## Nathan Luszcz (May 26, 2009)

The thought is that XX (female) sperm are more robust than XY (male) sperm, and therefore last longer. So if you breed earlier in the cycle, only the XX would survive long enough to fertilize the oocyte.

This is technically true (XX are more robust) but practically false (the difference is not noticable).

The mare's cycle is approximately 21 days, 14 days of diestrus and 7 of estrous. Ideally you start breeding three days after the beginning of estrous, every other day, until she goes out of heat.

If a mare ovulates 9 days post foaling, the foal heat breeding will not be successful. The mare needs to ovulate more than 10-11 days post foaling for the uterous to have time to repair itself from the stress and damage of the previous pregnancy.


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## rabbitsfizz (May 27, 2009)

Nathan Luszcz said:


> The thought is that XX (female) sperm are more robust than XY (male) sperm, and therefore last longer. So if you breed earlier in the cycle, only the XX would survive long enough to fertilize the oocyte.
> This is technically true (XX are more robust) but practically false (the difference is not noticeable).
> 
> The mare's cycle is approximately 21 days, 14 days of diestrus and 7 of estrous. Ideally you start breeding three days after the beginning of estrous, every other day, until she goes out of heat.
> ...


Not quite so, we used the foal heats as norm with the Arabs and they were, in my mares, always five days after foaling.

I have had mini mares do the same and had successful breedings, too.

But the fact is unless there is a real reason to use this heat it is best not to, as the mare obviously needs time to recover.

"In the wild" of course they are bred on the foal heat, but we are not in the wild!!!

There are loads of myths surrounding fillies and colts, "face the mare into the sun" is one I was told.

Well, hand breeding Arabs can get entertaining, but I tried, I really did....the only time I _knew_ I had managed it, I did get a filly, but I am pretty sure it was a coincidence


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## Nathan Luszcz (May 27, 2009)

Its called involution... and yes, it is quite so. That's the reason why it takes cattle so long to be bred back. Horses are FAR faster, its actually quite amazing. They need about 17 days to involute their uterous. 10-12 of those days need to be pre-ovulation, then another 6.5 days or so after ovulation. Then the embryo enters the uterous, and either finds a hospitable home or a very hostile enviroment. Too soon, and even if there is an embryo, it'll quickly die in the hostile enviroment.

If the mare ovulates too early (>10 days) the cycle will not be successful, even if an embryo is conceived.


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## rabbitsfizz (May 28, 2009)

Nathan I agree that that is the more normal accepted way of thinking.

In practise, however, it is not always so....the mares I have had who conceived, as norm, at five days after foaling prove this.

Had it just been one mare I would have said that, as with a ten month gestation, it is unusual, but we always used the foal heats in the later foaling mares, they always came at up to nine days, and we always got foals when we used these heats.

I have also bred a very late foaling Mini mare on a foal heat that came at five days and she conceived, and had a healthy foal.

I am no longer that keen on using the foal heat, merely because I think it does the mare good to have a rest, but I would not even consider it as infertile.


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## Nathan Luszcz (May 29, 2009)

I never said a foal heat is infertile. But if she ovulates too soon, the uterous can not support a pregnancy. If she holds her folicle long enough, its just as fertile as any other regular cycle.


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