Freemartin
A usually infertile heifer born as twin to a bull calf.
Also: free-martin
A freemartin is a female calf born co-twin with a male. In cattle the blood supply of twins in the womb usually joins, and hormones and cells from the male twin pass to the female and stop her reproductive organs from developing normally. More than nine in ten heifers born twin to a bull are infertile, while the bull calf is usually fertile. Farmers check such heifers with a simple physical examination or a blood test before keeping them for breeding. The word is old, and the condition was described by the surgeon John Hunter in 1779. Freemartins are usually raised for beef.