How do I tell if my horse is pregnant?
Unfortunately, there are no obvious signs of pregnancy in horses, at least in the early stages. If your mare has fairly predictable cycles, you can simply watch her. If she doesn't come into heat within a 4 week window, she may be pregnant. However, this method isn't foolproof, as not all mares have predictable cycles, and for many it's nearly impossible to tell when they're in heat or ovulating (unless you have an ovulation monitor).
Closest thing to an equine pregnancy test
As a horse breeder, you have good reason to want to know if your mare is pregnant. If you have a good vet, you can call them to come out and palpate or do an internal ultrasound on your mare. However, this costs money and is not always safe or convenient. Besides, even your vet may not be able to tell if the pregnancy is in the early stages.
Fortunately, there is a better option. If you are serious about breeding horses and/or other livestock, you may want to purchase your own ultrasound unit. Ultrasound is safer than palpation and just as accurate. You can check your mare any time and as often as you like. Most importantly you can make a timely decision on whether to keep the mare, or cull the herd.
The PregScan from Animark is designed specifically for detecting pregnancy in mares and cows. It is calibrated to detect pregnancy as soon as 14 days after breeding in mares (22 days in cattle)."
The PregScan is proven 98% accurate at this task and is completely external. Learn more.