A set of twins could be viewed as a bonus calf to some beef producers, but when the set is comprised of one female calf and one male calf, there could be problems.

Glenn Selk, Oklahoma State University Cooperative Extension emeritus animal scientist, says if born as the other half of a mixed-gender set of twins, a heifer calf could be what's called a freemartin, possessing "freemartinism" – a condition that causes infertility.

Freemartinism is recognized as one of the most severe forms of sexual abnormality among cattle, Selk says. That's why it's a good rule of thumb to never retain a heifer as a replacement female if she is born as a twin to a bull.

"When a heifer twin shares the uterus with a bull fetus, they also share the placental membranes connecting the fetuses with the dam," Selk explains. "A joining of the placental membranes occurs at about day 40 of pregnancy, and the fluids of the two fetuses are mixed thereafter."

To read more from Selk, click here.

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