A Free-Martin

Press, Volume CXI, Issue 32708, 10 September 1971, Page 15

A Free-Martin

Where a cow has twins of different sexes it is very unlikely that the female will be fertile. A reader of these pages has recently asked a question about this phenomenon. Professor I, E. -Coop, professor of animal science at Lincoln College, said this week that in this situation the chances of the female being infertile was “11 times out of 12.” If one calf was bom much earlier or later than the other, this could help the chances of the female

being normal, but it would still be “a pretty risky business.” The situation develops, according to Professor Coop, because the two calves have a common blood circulation or supply. While the foetuses are developing the sex glands are also forming but the female calf is coming.under the influence of the testicular hormones from the male twin. There is a tendency for the testicular development in the male to be earlier than the ovarium development in the female, with the result that this tends to create a “maleness” in the female twin, so that when it is born its sex organs are not properly developed. The male hormones exercise a greater influence than the female hormones. Consequently selection for twinning on the female side should only be done where both members of a pair are females. Professor Coop said that this condition known' as a “Free-Martin” did not occur in sheep and in fact was not known to occur in other animals, apart from goats.