Pregnancy testing in horses is a common practice in equine breeding and ownership. It helps confirm if a mare has successfully conceived after breeding. Knowing the pregnancy status allows for proper planning and management of the mare’s health and future, providing valuable information for both individual owners and large-scale breeding operations.
Reasons for Testing
Confirming pregnancy in mares is a routine part of responsible equine management. It allows owners to verify successful breeding efforts, which is useful for optimizing breeding schedules and managing stallion services. Early confirmation helps in making timely decisions about the mare’s ongoing care and nutritional needs.
Knowing a mare is pregnant enables preparation for the upcoming foaling season. This includes adjusting her diet, planning veterinary check-ups, and setting up appropriate foaling facilities. For commercial breeders, this information aids marketing and sales planning by confirming future foals.
Optimal Testing Times
The timing of pregnancy testing depends on the method used, as different tests are effective at various gestation stages. Transrectal ultrasonography can detect an embryonic vesicle as early as 10 to 11 days after ovulation. Initial examinations are often performed between 12 and 16 days post-ovulation to diagnose pregnancy and identify potential twin pregnancies.
Early detection allows for prompt management of issues, such as twin reductions, and helps schedule rebreeding for mares that are not pregnant. A follow-up ultrasound around 25 to 30 days is often recommended to confirm the embryo’s viability and presence of a heartbeat. Hormonal blood tests, such as Pregnant Mare Serum Gonadotropin (PMSG), are reliable from day 45 to 100 of gestation. Estrone sulfate tests are effective from day 60 onwards. Re-testing may be necessary if initial results are inconclusive or if the mare was tested very early in her gestation.
Available Testing Methods
Several methods are available for detecting pregnancy in mares, each with its own benefits and suitable timing.
Transrectal Ultrasonography
This is a widely used and accurate method, often performed between 14 and 16 days after ovulation. This technique involves inserting an ultrasound probe into the mare’s rectum to visualize the uterus and detect the embryonic vesicle. It allows for early identification of pregnancy, assessment of embryonic development, and detection of twin pregnancies, which can be managed early.
Hormonal Blood Tests
These tests offer another approach to pregnancy detection.
##### Pregnant Mare Serum Gonadotropin (PMSG)
One such test measures Pregnant Mare Serum Gonadotropin (PMSG), also known as equine chorionic gonadotropin (eCG). This hormone is produced by endometrial cups in the mare’s uterus starting around 40 days after conception, becoming measurable by day 45 and peaking around day 60, remaining detectable until 100-150 days. While a positive PMSG result indicates the presence of endometrial cups, it does not confirm fetal viability, as the cups can persist even after fetal loss.
##### Estrone Sulfate (E1S)
Another blood test analyzes Estrone Sulfate (E1S), a hormone produced by the fetal-placental unit. This test is accurate for diagnosing pregnancy from day 90 to term, and its presence indicates fetal well-being. Concentrations of estrone sulfate are elevated after 60 days in plasma and 150 days in urine. Unlike PMSG, estrone sulfate levels confirm a viable fetus and placenta.
Understanding Results and Next Steps
Interpreting pregnancy test results is important for subsequent mare care. A positive result indicates that the mare is pregnant, prompting a shift in her management strategy. This includes adjusting her nutritional intake to support fetal development, often involving a gradual increase in feed quality and quantity as gestation progresses. Regular veterinary check-ups are also scheduled to monitor the mare’s health and the foaling process.
Veterinarians can conduct further examinations to confirm fetal viability and assess overall health, helping to prepare for a successful foaling. This planning might include setting up a safe and clean foaling environment and understanding the signs of impending labor. If a mare receives a negative or inconclusive result, it suggests she is not pregnant or the test was performed too early. Re-testing is often recommended, sometimes using a different method or at a later date, to confirm her reproductive status. Further veterinary consultation can help investigate reasons for non-pregnancy or explore options for rebreeding.