Twinning in Cattle


Mac Winslow
Dr. Farin
ANS 220 3
December 1996

Due to the continual fluctuation of the cattle market cattle producers
have been searching for ways to improve their production and increase their
profits any way possible. For years genetic engineers have been working hard on
improving economic efficiency in cattle. It is their hope that through genetic
research they can improve the yield and the income of cattle producers around
the world. Research has shown that twinning is one way that farmers can increase
their yield . Twinning has a significant influence on producers as well as
people who are involved in all realms of agriculture. The reason for this large
impact at this time is the fact that the occurrences are limited. However, many
producers have a vision that twinning can be more than a once in a blue moon
occurrence. These producers see twinning as a way to dramatically increase their
yield per calving season. Producers will increase their income due to more
weight per year per cow. It is necessary ;however, that the producer be well
educated on how to handle twinning, in order for it to be successful for them.
Many agencies see twinning as an economic move upward. The American
Breeder Service has made efforts to produce semen as well as embryos with high
predicted breeding values available to producers. They have been recorded based
on twinning probabilities and ovulation rates. A large amount of work on
twinning has also been done by the Meat and Animal Research Center. Since the
early eighties, they have located cattle with a high frequency of twinning and
been forming a breeding foundation based on this characteristic. “We believe the
time has come to make some of these unique genetic resources available to the
beef industry through artificial insemination and embryo transfer” (Gregory 23).
An extensive amount of research has been done using embryo transfer in cattle.
In one study recipients were implanted with either a single embryo, two embryo
in one uterine horn, or one embryo in each uterine horn. It is also possible to
split embryos using a micro manipulator and implant each half to produce
identical twins. On the average about 16% of the cows implanted with two embryos
produced twins. When two embryos were implanted, and one was placed in each horn,
conception rates were comparable with the prior method, however the twinning
rate was much higher when the embryos were in separate horns (73% vs. 45%). For
the most part, when one embryo was split in an attempt to produce identical
twins, only one of the offspring survived birth (Davis 302).
Many producers see twinning as a possible advancement in
economic prosperity for themselves. Scientists have increased the possibility of
successful twinning through extensive genetic research. They now also able to
inform the producer of twins through the use of proper palpation techniques as
well as ultrasound. Blood can be analyzed in labs to determine fetal weight gain.
In addition nutritious feeds and technology that aids in calf survival have made
the possibility of high twinning success rates closer to being reality. These
factors enable the genetic possibilities to be an asset to producers (Gregory
23-24).
“Increased frequency of twinning should increase efficiency of beef
production” (Davis 301). Results from twinning are very appealing to a farmer
who can use one brood cow to produce two calves per year. Reports show that beef
cattle can wean a higher total weight per cow. A twin’s average daily gain
depends on the environment as well as genetics (Cady 950-956). Single born
calves are reported to have birth weights of 25% more than a twin calf. Over
time, however, the twin calves approach the weight of the single calves. At
weaning the weight gap decreases to only about 15%. Despite this seemingly large
difference in weaning weights, it should be realized that there are two calves
to sell from a set of twins as compares to one from a single birth. In addition
to their size, twin calves consume less rations of fees than their counterparts.
From these conditions, promise for economical stimulus is easily seen,
especially in beef cattle (Cundiff 3133-3135).
Despite all of these draw backs, work is being done to help twinning
become profitable, instead of problem causing. A gene has been researched that
causes twinning in cows. This gene could be selected for through expected
progeny difference scores just like someone might select for birth weight. This
gene would not only make the offspring of the bull more likely to have twins,
but it would also help her to be maternal to both of the offspring instead of
nurturing