Management
Keep Records of Twins or Other Multiple Calf Births
By Glenn Selk, Oklahoma State University emeritus extension animal scientist
As producers work through this (or any) calving
season it is very important to record any multiple
births that may have occurred. Estimates of the
percentage of beef cattle births that produce
twins vary. One estimate (Gilmore) puts the
percentage at about 0.5% or 1 in every 200
births. Approximately one-half of the sets of
twins should contain both a bull and a heifer
calf. Make sure to write down these calf numbers
of twin births while they are still nursing the
cow. Be certain to not retain the heifer born
twin to a bull as a replacement female.
Freemartinism is recognized as one of the most
severe forms of sexual abnormality among
cattle. This condition causes infertility in most
of the female cattle born twin to a male. When
a heifer twin shares the uterus with a bull
fetus, they also share the placental membranes
connecting the fetuses with the dam.
A joining of the placental membranes occurs
at about the fortieth day of pregnancy, and
thereafter, the fluids of the two fetuses are mixed.
This causes exchange of blood and antigens
carrying characteristics that are unique to each
heifers and bulls. When these antigens mix, they
affect each other in a way that causes each to
develop with some characteristics of the other sex.
Although the male twin in this case is rarely
affected by reduced fertility, in over ninety
percent of the cases, the female twin is completely
infertile. Because of a transfer of hormones or a
transfer of cells, the heifer’s reproductive tract
is severely underdeveloped and sometimes
even contains some elements of a bull’s
reproductive tract. A freemartin is genetically
female but has many characteristics of a male.
The ovaries of the freemartin do not develop
correctly, and they remain very small. Also,
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. Usually, the
vulva is normal except that in some animals…
large tufts of vulvar hair exist. The cattleman
can predict the reproductive value of this heifer
calf at birth and save the feed and development
costs if he is aware of the high probability of
freemartinism. (Source: “The Causes and Effects
of Freemartinism in Cattle” by Laurie Ann Lyon.)
To dissuade any worries about embryo
transfer calves, it is important to remember
that the mixing of the fluids between fetuses
does not occur until about day 40 of the
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