Breeding Horses

Breeding Considerations for Horses


Breeding horses is a large field within the horse industry.  The right bloodlines can fetch some big dollars and lead to very successful competitive horses.  The first thing to consider when deciding to breed your horse, is the health of the parents.  Review the medical history of the stallion and mare to ensure there are no genetic predispositions that could negatively impact the offspring’s health.  Responsible breeding is key.


Once you find an ideal stallion and mare, you have a few options for breeding.  If you own the mare, many breeding farms will have you bring the mare to their facilities where they will take care of the breeding.  Live cover can be dangerous, but often yields the best chances of conception.  Some breeding associations (particularly Thoroughbreds) require live cover to ensure the parentage of the foal.  In some cases, traveling with the mare is not practical due to the location of the stallion so artificial insemination is a good alternative.  Advances in artificial insemination allow breeders access to semen from champion stallions from all over the world.  Semen can be purchased “fresh cooled” where the vials are put on dry ice keeping the sperm viable for about 48 hours or actually frozen which can preserve sperm for years.  The fresher the semen the better chances you have of fertilizing the mare’s eggs.


The first step of the actual process is to have your vet give the mare a full health exam to make sure she is healthy enough for pregnancy.  Broodmares who have had previous foals should be checked for endometritis (inflammation of the uterus).  Keep track of your mare’s heat cycles so you will know when she will be ovulating.  She should be bred about 12-24 hours prior to ovulation for optimal fertility.  Your vet will perform the actual insemination using a long tube that is inserted into the uterus to deposit the semen.  Often times you will want to repeat the process with a second sample the next day to increase odds of conception.  An ultrasound can be performed two weeks after insemination to see if the mare is pregnant and to detect twins.  Horses’ bodies are not designed for carrying twins so twin pregnancy can be fatal to the mare and foals.  In the case of twins, one embryo is usually “pinched off” to ensure the health of the mare and surviving embryo.


The average pregnancy for a horse is about 330 – 345 days (~11 months).  During that time you will need to increase your mare’s nutritional intake.  About 6 weeks prior to birth you should vaccinate the mare so that her milk is full of antibodies to protect the foal once they are born.  The vet should check the mare 4 weeks prior to her due date to make sure the foal is positioned properly and then regularly once she hits the 2 weeks to her due date mark.  Mares will begin “waxing” (secreting from their utter) about 2 days before they give birth but the exact due date is difficult to determine.  Mares typically give birth at night and the labor is very quick – only about 20 to 30 minutes.  In the wild horses giving birth are a prime target for predators so the process needs to be as fast as possible.  If a mare has difficulty and the labor lasts longer you should call your vet.  The mare should stand up after delivery and the umbilical cord will break on its own.  The mare will also deliver the placenta within 3 hours of birth, but if she does not you should call your vet because retained placenta can become toxic to the mare.


The foal should attempt to stand within about 30 minutes of birth and successfully stand to nurse within about 2 hours.  Over the first 24 hours keep an eye on the foal to make sure they are breathing properly, appear bright and alert and that the mare is attentive to them.  Again work with your vet to review your mare’s nutrition because lactation puts some large demands on the mare’s energy requirements.  Early handling of the foal will help the horse become well socialized and mannered as an adult.






Stallion spermatozoa selected by single layer centrifugation are capable of fertilization after storage for up to 96 h at 6°C prior to artificial insemination.


Successful induction of lactation in a barren thoroughbred mare: growth of a foal raised on induced lactation and the corresponding maternal hormone profiles.


Conception rate, uterine infection and embryo quality after artificial insemination and natural breeding with a stallion carrier of pseudomonas aeruginosa: a case report.


Fertility of frozen-thawed stallion semen cannot be predicted by the currently used laboratory methods.


Use of parentage testing to determine optimum insemination time and culture media for oocyte transfer in mares.


Influence of maternal size on placental, fetal and postnatal growth in the horse. I.  Development in utero.


Influence of maternal size on placental, fetal and postnatal growth in the horse.  II.  Endocrinology of pregnancy.