Anatomical, cytogenetic and behavioural studies of freemartin ewes

The external phenotype and reproductive behaviour of 21 freemartin sheep and two male pseudohermaphrodite sheep were recorded with the aim of identifying any characteristics which might be used to predict a failure to breed. The size and shape of the vulva and clitoris, the length of the vagina, the size of the teats, the presence or absence of inguinal gonads, and the ultrasonographic characteristics of the inguinal gonads were recorded. A subjective assessment of the masculinity of each animal's body form was also made, and its behavioural responses to a virile ram and to an oestrus ewe were recorded. A number of physical and behavioural abnormalities were detected but the only consistent finding in all 23 animals was a short vagina which varied in length from 3.1 to 7.0 cm, compared with 10 to 14 cm in normal animals.