The gestation of a horse is significantly longer than the gestation of humans. Ranging from 320 to 380 days, the average gestation length falls between 330 to 345 days.
A horse embryo can be seen by ultrasound as early as 12 to 14 days after conception. Between days 15 and 17, the embryonic vesicle becomes more fixed to the wall of the uterus, and the embryo is easier to visualize.
The heartbeat is detectable on ultrasound imaging to verify the presence of a viable fetus between days 24 and 28.
Check out our recent posts below throughout the season to learn more about reproductive health and breeding methods, and select “Read More” below to see all our Breeding/Reproduction blog posts.

The Pregnancy Wheel, developed by the University of Guelph, is a great online resource with information covering a mare's pregnancy through all three trimesters and the foaling window.

Customizable to a mare's breeding date, the Pregnancy Wheel provides an overview of fetus growth and milestones during each month, while offering considerations on risk factors and mare management during each trimester.  

Education Blogs

We heard from a Foal Patrol follower earlier this week asking about maternal genetic influence in Thoroughbreds. Although research is ongoing and there is no definitive answer to this question, this article by Anne Peters available from the BloodHorse summarizes a 2015 study that suggested a mother’s influence may actually be more important than a father’s influence when it comes to racing ability. Again, this information is limited to one research study from hundreds centered on genetics, but we think you'll find it an interesting read. Enjoy!

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From reproductive endocrinology and placenta physiology to broodmare nutrition, learn more about equine reproductive health in this podcast featuring Dr. Barry Ball. With more than 35 years in equine reproduction research, Dr. Ball reflects on the evolution of theriogenology, the veterinary medicine specialty focused on reproduction, over his long career. A big thanks to The Horse for allowing us to share this podcast with our Foal Patrol followers.

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In response to a great question from a Foal Patrol fan in Ohio about fetal sexing, we think you will enjoy this video in which Rood & Riddle Equine Hospital's Dr. Tom Riddle explains how to determine if a mare is pregnant with a filly or colt. 

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