How long will it be before you to know when a horse is pregnant?

A veterinarian can ultrasound a mare at 14 days post ovulation and be able to determine if a mare is
pregnant. An experienced veterinarian can palpate a mare that has not returned to heat post breeding (at 25 plus days) and be able to feel the conceptus. A laboratory based blood test can be done for around 100 dollars and there are also home based urine tests that can detect a pregnancy in a mare that is approximately 40-120 days in foal and another if the mare from a 120 days in foal. The urine based tests were developed in New Zealand.