Spot those freemartins early
WHILE only a small proportion of ewe lambs with a twin male are freemartins and unable to breed, it may be possible to identify them at a young age.
In the Vet Record, Keith Smith and his colleagues at the University of Bristol, Langford, report that less than 7% of ewe lambs with a male twin become freemartins. But with a high number of sheep twins born it is an important cause of failure to breed. Often they are only identified after failing to breed for one or two seasons, says Dr Smith.
All freemartin ewes in its study had a short vagina of 3 to 7cm (1.2 to 2.8in) in length. Normal animals had a vagina length of 10 to 14cm (4 to 5.7in).
But many also had other physical abnormalities or showed behaviour that could be recognised by producers before attempting to breed them. These included a small, hook-shaped or pronounced tip to the vulva, or a large clitoris. Most of the freemartin ewes also had small or very small teats, adds Dr Smith.
Many of these ewes also showed masculine behaviour in the presence of oestrous ewes and none of them showed normal female behaviour in the presence of a fertile ram.
A farmer or vet could identify these characteristics by observation alone, he explains. *