Freemartinism / XX/XY chimerism - Cattle

Freemartinism in cattle

This DNA test assesses XX/XY chimerism, also known as freemartinism, freemartin, Kween or tetragametic chimerism. It mainly occurs after a mixed-sex twin pregnancy, where shared placental blood vessels allow cells to pass between the male and female fetus.

A female calf can therefore carry both XX and XY blood cell lines. This is often associated with infertility and sometimes abnormal development of the reproductive organs, while external signs are not always clear enough for early identification.

What is tested?

The analysis checks whether female and male chromosomal DNA are both detectable in a pattern consistent with XX/XY chimerism. Blood is the biologically appropriate sample type for this test, because the condition is assessed as blood-cell chimerism.

Practical value of this test

• Early clarity: identify a suspect female twin calf more objectively than by visual examination alone.
• Breeding planning: avoid keeping an infertile freemartin as a future breeding female.
• Farm decisions: support rearing, sale, registration and herd-management choices.