Management
membranes connecting the
fetuses with the dam.”
A joining of the placental
membranes occurs at about
day 40 of pregnancy; thereafter,
the fluids of the two fetuses are
mixed. This causes exchange
of blood and antigens carrying
characteristics unique to each
heifer and bull. When these
antigens mix, they affect each
other in a way that causes
each to develop with some
characteristics of the other sex.
except that in some animals
an enlarged clitoris and large
tufts of vulvar hair exist.”
Freemartinism cannot be
prevented. However, it can
be diagnosed in a number
of ways ranging from
simple examination of the
placental membranes to
chromosomal evaluation.
Beware the hidden freemartin
“Producers need to be aware
that in some cases there
are few if any symptoms of
“Although the male twin in
this case is rarely affected by
reduced fertility, the female twin
is completely infertile in more
than 90% of cases,” Selk says.
The transfer of hormones or
cells can cause the female
twin’s reproductive tract to
be severely underdeveloped,
and sometimes even contain
some elements of the bull
calf’s reproductive tract.
In short, a freemartin is
genetically female but has
many characteristics of a male.
Selk explains the ovaries of
a freemartin do not develop
correctly and typically remain
small, sometimes very much
so. In addition, the ovaries of a
freemartin do not produce the
hormones necessary to induce
the behavioral signs of heat.
“The external vulvar region
can range from a very normal-
looking female to a female that
appears to be male,” he said.“
Typically the vulva is normal
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