A freemartin is a masculinised female born co-twin with a normal male. 11/12 female calves born co-twin to a male will be freemartins. The condition is mainly recognised in cattle, but occurs in sheep, goats and pigs. | A freemartin is a masculinised female born co-twin with a normal male. 11/12 female calves born co-twin to a male will be freemartins. The condition is mainly recognised in cattle, but occurs in sheep, goats and pigs. |