freemartin

A freemartin is a sterile female twin to a male in cattle and other bovines. It occurs when two fetuses of different sexes share a common placental circulation. During pregnancy, the shared blood supply allows hormones and other substances to be exchanged between the male and female fetuses. Specifically, exposure to male hormones can affect the development of the female's reproductive organs.

The result is that the female, while appearing outwardly female, will have underdeveloped ovaries and an underdeveloped uterus. Consequently, she will be infertile and unable to reproduce. This phenomenon is most common in cattle but can also occur in other ruminants like sheep and goats.

The freemartin condition is characterized by a variety of anatomical changes in the female. Her external genitalia may appear normal, but internal examination reveals the underdeveloped reproductive tract. The degree of development can vary, but complete sterility is the typical outcome.

Farmers often recognize freemartins by observing their physical characteristics and by knowing that a twin birth occurred. Because freemartins are sterile, they are not typically kept for breeding purposes. Instead, they are usually raised for meat production. The freemartin condition is a natural occurrence and is not considered a disease.