Freemartin testing is available through Diagnostics GeneMark. It will identify Freemartins so you can save the time and expense of rearing infertile heifers.
Blood samples in purple top blood tubes only are accepted for this testing.
Heifer calves that have a male twin are virtually always infertile and called Freemartins. The male twin may have died during pregnancy or be stillborn, so it may not be obvious that a heifer is a twin and potentially a Freemartin.