A horse will stop showing signs of heat after their cycle is up. They are only receptive during certain times of their cycle. They will come back into their heat cycle approximately 21 days after the end of their last cycle. They will continue with this pattern until fall. Mares will still cycle in the fall and winter - but their cycles are less noticeable and they often will not stand for the stallion.
A few pointers on breeding:
It is very important to spend the money to get a sonogram done by a vet at around 17 days - you can get a good idea of the status of the pregnancy and it is very important to make sure that the mare is not carrying twins. There is a small window at which point a vet can 'pinch off' one of the embryos. THIS IS IMPORTANT - twinning is very dangerous in horses. Most mares will die during delivery of the foal - as well as the foals. If the mare and the twins survive - the twin foals are usually small and not as healthy as a single foal that has survived the pregnancy. Most people think that twins in horses is a very cool thing. ... it is not and is a very dangerous.
Our neighbor opted to save money and forego the ultrasound for her paint mare. Eleven months later she came home to two beautiful paint babies and her paint mare ..... laying dead in the field. This happens all too often. Sonogram.
I breed foundation quarter horses and breeding is an expensive venture. The cost of vet exams, stud fees, vaccinations, deworming, and special feed for the mare - not to mention the time and money put into the foal - is very costly for a foal that usually only garnishes a $500 - $750 price tag in today's economy. And there is always a chance that the mare may not survive the pregnancy or the delivery. I have lost foals that were a week old and one that was two months old. It is a hard thing to get accustomed to - and an even harder pill to swallow considering the cost that is incurred.
An ULTRASOUND should be done around 17 days.
(Some vets will do this around 14 days - but they will usually come back and soak you for another fee to do it again to check and make sure that twinning has not occurred.)
If the mare has twins - you will be paying for at least two more sonograms to "pinch off" one of the embryos and you will need to check to make sure the other embryo has survived the process and that it is developing correctly.
Deworm, Deworm, Deworm. Use a dewormer that is safe for pregnancy and deworm every six to eight weeks. It is important to rotate your dewormers. Do not use the same type of dewormer twice in a row. Deworm about two weeks before the expected delivery of the foal - this helps the newborn foal as well. Foals will eat their poop - this is common - and if you deworm the mare properly and then again before they deliver - you will not be feeding your new foal worms.
The gestational period for a mare is usually around 11 months. If the mare has foaled before - chances are that she will be right around 11 months and not later or earlier. Check to see when her last foals were born - my mares all deliver about the same time of day each year. (This is not a documented fact - strictly an observance on my part.)
VACCINATE - make sure that the mare has received proper vaccinations for your area and vaccinate 1 month prior to delivery of the foal to pass on the antibodies to the foal.
Use Pneumobort at 5, 7, & 9 months. Check with your vet about the schedule for these. Some vets recommend a 4th dose. This prevents your mare from aborting the fetus early.
Keep the mare off of FESCUE. This is very important. Fescue will cause early abortions in mares.
Make sure you are feeding the mare a quality & well balanced feed ration. Do not increase to a higher protein/higher fat food until later in the pregnancy. Adding this type of food early in the pregnancy will cause the mare to put on too much weight and will be a detriment to her when delivering the foal.
READ UP ON BIRTHING A FOAL! Make sure to have a delivery kit ready about 1 month prior to the birth. There are several items that are imperative that you have on hand.
It is important to have a relationship with a reputable vet before the mare delivers. Your vet will be more willing to make that midnight or early morning call! Some vets will not come out on an emergency basis if you are a new client.
After the mare delivers - give her a warm mash, oat bran is good mixed with rice bran and corn oil - this helps her system to recuperate and also helps her to pass stool. A mare may become "backed up" during the delivery and this is very dangerous in horses and can lead to colic and/or fatal twisting of the intestines.
READ READ READ!
BOOKS on Foaling... and then read them again.
Remember that mares have been having foals since the beginning of time. I put cameras on our mares and stayed in the barn and inevitably the minute I catch a few ZZZZs or go to the bathroom or check the house - or get something to drink - the mare delivers. They wait for that "moment" that you are not watching. They are very good at this. I have had over 30 foals or more in the last three to four years and I have been able to catch only a few actually deliver their foals - and that was because I had to help deliver them!
Again - read, read, read. That is your best offense in helping deliver a healthy foal.
Best of Luck.