The Freemartin

Steve Boyles and Mike Day, The Ohio State University Animal Sciences

At the recent Ohio Beef Expo a producer came up to me and asked about freemartins. He had a good cow that had twins. One of the calves was a bull and the other was a heifer. The producer wanted to know if he should keep the heifer and try to breed her.

Freemartinism, which occurs primarily in cattle, is the sexual modificaton of a female twin by in utero (meaning in the uterus) exchange of blood from a male fetus. It has been assumed that the exchange of blood occurs due to fusing of the placenta between the two fetuses. While sheep, goats, and pigs can have multiple births, rarely is there an exchange of blood between fetuses. Freemartins are characterized by: Continue reading