Blood Test Developed to Predict Foal Gender

Will you be decorating the foaling barn pink or blue?

Equine Science Update Report by: Mark Andrews

Researchers in Iran have developed a blood test to predict whether a foal will be male or female.

Sometimes it can be more than mere curiosity that drives owners to know the sex of a foal before it is born. In particular, the value of in-foal mares at sales may be affected by the gender of the foal they are carrying.

Foetal sexing is possible using an ultrasound scan around 60 to 70 days’ gestation to ascertain the position of the genital tubercle, the precursor of the penis or clitoris. However, the accuracy of the technique depends very much on the experience of the operator.

Ali Kadivar and colleagues at the Shahrekord University in Iran have developed test that requires a single blood sample from the mare. A report of the research is published in the Journal of Equine Veterinary Science.

The test, a nested real-time PCR assay, looks for the SRY (sex determining region Y) gene in the circulating cell-free fetal DNA. Cell-free fetal DNA (ccffDNA) is genetic material that is released by the placenta and circulates in the mare’s blood during pregnancy.

The sex-determining region Y protein (also known as testis-determining factor) produced by the SRY gene controls the processes that make a fetus develop male gonads (testes) and prevent the development of female reproductive structures (uterus and fallopian tubes). So fetuses with the SRY gene will develop into males, and those without will be female.

The research team tested a single plasma sample from each of 28 pregnant Arabian mares between 8 and 20 weeks of gestation. At the time of sampling, the gender of the fetus was unknown. This was only confirmed by direct clinical examination after birth.

Three samples failed to yield sufficient ccffDNA to test. From the remaining 25 samples, the test correctly identified 12 of 14 male pregnancies and 10 of 11 female pregnancies, resulting in a sensitivity of 85.7%, and a specificity of 90.9%. Overall the accuracy of the test was 88%.

The researchers conclude: “Detection of ccffDNA in maternal plasma with a nested real time PCR assay can be used to determine equine fetal sex with a good accuracy by analyzing SRY gene just after 8 weeks of gestation.”

For more details see:

Developing a nested real-time PCR assay for determining equine fetal sex prenatally

Ali Kadivar, Rohollah Dehghani Tafti, Heidar Heidari Khoei, Mahboobeh Heidari Nasirabadi, Naser Shams Esfandabadi, Narjes Cheraghi

Journal of Equine Veterinary Science, Available online 23 February 2016 

doi:10.1016/j.jevs.2016.02.229