Untitled Essay Research Paper Mac Winslow
Untitled Essay, Research Paper
Twinning in Cattle
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 ho
w 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 wa
s 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 one of them and abandoning to other one.
“At the present, selection for more twin births in dairy cattle
results in deleterious effects on the dams” (Berepoot 1044). Economic calculations
have mainly been done on beef cattle so far. The calculations for beef cattle is mainly
centered around final sale weight per calving season, rather than milk production as in
dairy cattle. (1044). Dairy cattle producers usually discourage twinning because of milk
loss. Twinning may be directly related to high lactation. Dairy cattle that have superior
milk production tend to have higher twinning rates. Even though these cattle were superior
in milk, they gave less total milk. An increase in hormones which will inhibit lactation
may explain the decline in milk production. Thankfully, this milk decrease does not effect
the lactation results of the dam in future parturitions. Since the return of estrus these
dams takes longer, there is added milk loss due to loss of productivity (Syrstad 255-261).
“in general, there were so many disadvantages that attempts to select
for more twin calves in dairy cattle herds should be discouraged” (Beerepoot 1051).
Twinning in cattle has many positive and negative effects. These
effects depend on the breed of cattle and the purpose for which the cattle are raised.
Producers can move forward in today’s economy through the successful use of twinning.
However, the producer must be ready, willing, and able to deal with the difficulties that
con along with twinning, in order to ensure the survival and success of not only the
calves but of the dams. Selective breeding methods can be utilized to chose a base herd
for a twinning program. At this time, many producers believe that the negative effects
outweigh the benefits. Through continuing research in the area, twinning shall become
a successful and economic way to raise beef cattle. Since twinning research began, the
percentage of beef cattle giving birth to twins has risen by nearly twenty percent.
Through research and education of producers twinning could be one of the beef
industry’s greatest reproductive achievements.
Twinning is often associated with major management problems, such as an
increased frequency of dystocia, retained placenta, and longer rebreeding
intervals.“Dystocia is defined as all calvings for which personal assistance is
needed, and dystocia depends on the size of the calf, its sex, and the age of the
(Beerepoot 1048). “Dystocia accounts for most calf deaths within the first 24 hours
of calving” (Taylor 233). Twin calves have a 15% greater chance of undergoing
dystocia and the chance of a free martin offspring is likely (Hays and Mozzola 7). Twins
have only a 8% less chance of survival, even when there is dystocia. “Twinning has
not been considered [in the past as] desirable in cattle because of increased incidence of
retained placenta, reduction in future reproductive efficiency, weaker calves that are
more difficult to raise, and reduced milk production by the cows after twinning”
(Bearden 100). A cow that retains her placenta has a greater chance of infection and a
longer duration before returning to estrus. Cattle producing twin calves are estimated to
remain open 19-22 days longer than single calvers (Chapin 1-6). The length of gestation in
a cow is, on the average, is seven days shorter in cows birthing twins than is cows that
are birthing singles (Gregory 3135). This can result in a significant loss
in the number of offspring and the quantity of milk a cow can produce in her lifetime.
calvers can also be costly due to the fact that they are subject to different postpartum
nutritional needs (Cundiss 3133).It has also been observed that there is an increased
incidence of abortions during late pregnancy among cows that carry twin fetuses.
“The heritability of twinning is lower. A higher incidence of
twinning has been reported for certain cow families, but long term selection studies to
increase twinning have not greatly increased the twinning rate” (Bearden 100). In
many analysis, repeatability was estimated to be less than heritable, this is assumed to
be due to small negative environmental covariances in adjacent gestation or estus cycles
(Gregory 3214). The genetic correlation between ovulation rates and twinning were found to
be 80% in cattle. Yet, in heifers it had a substantial increase of 10% more. Research by
recording consecutive ovulation rates, can help when establishing a base herd with
emphasis on twinning. Using these records, producers can have a hold on relative twinning.
Sires may also be selected based on the same records from their daughters (Gregory
3212-3218). Ovulation rate in heifers can be used to predict breeding values for twinning.
To pick breeding values a producer should use the average ovulation rate form severa
l estrous cycles. Estrous cycles can be observed at
3 week intervals between puberty and breeding. In recent test analysis genetic correlation
proved to be high with twinning. The analysis was not independent because it had many cows
and several estrous cycles.
“Adjustments in management practices are required to exploit full
potential of twinning to increase efficiency of beef production” (Gregory 3134). Twin
a great deal of care to ensure a safe gestation period and a safe delivery. Recently more
producers have began to use ultrasound to detect the number of embryos, fairly early in
gestation. This saves the producer a great deal of money that would other wise be lost,
because paying a veterinarian is much more economical than loosing two calves. More
postpartum care is also required for the mother and the offspring by the producer. Many
times when a cow gives birth to a pair of twins her maternal instinct only tells her to
take care of one of the calves. Due to this one of the offspring is abandoned and given no
care from the dam. This leads to the death of the abandoned offspring.
Even though good breeding practices have proven to be a major factor,
the environment will also have a large influence on twinning. Part parity seems to have
the largest effect, not considering heritability. One percent twinning was displayed in
cows in their first parity. Yet, 6% twinning was displayed in cattle in their third
parity. This could be directly related to the cattle’s age and the ability of the cow
to maintain a biparous pregnancy. Time is a large factor in beginning and maintaining a
herd that is prone to having a large twinning percentage. Genetically, twinning is not
affected largely by additive variation (Cady 952-956). Age of the mother does not usually
affect the proportion of twins born alive; however, the frequency of natural twinning
increases with age and parity of the dam (Davis 306). Most twinning research has been done
on crossbreeds, which is not a true estimate of all cattle because of possible hybrid
vigor concerning certain traits. Not much research has been done on
in-breeding and between breeds. More will be learned about the genetic variation
responsible for twinning, once these ideas have been researched more.
Works CitedDavis, M.E.; W.R. Harvey; M.D. Bishop; W.W. Gearheart, “Use of embryo Transfer To
Induce Twinning in Beef Cattle:Embryo
Survival Rate, Gestation Length, Birth
Weight and Weaning Weight of Calves”. J. of Anim. Science, 1989. 67: 301-310.Cundiff, L.V.; Gregory, K.E.; Echternkamp, S.E.; Dickerson, G.E., “Twinning in Cattle
III. Effects of Twinning on Dystocia,
Reproductive Traits, Calf Survival, Calf
Growth, and Cow Productivity.” J. of Anim. Science, 1990. 68:3133-3144Bearden, J.W.; M.D. Holland, K.L. Hossner, J.D. Tatum. “Serum Insulin-Like Growth
Factor I Profiles In Beef Heifers With
Single and Twin Pregnancies”. J. of Anim. Science,
1988.66:3190-3196.Cady, R.A., L.D. Van Vleck, “Factors Affecting Twinning and Effects of Twinning on
Holstein Dairy Cattle.” J. of Anim.
Science, 1978.46.950-956.Taylor, Robert E. Beef Production and the Beef Industry. 1984 Burgess Publishing
Company. Minnaepolis.Gregory, J.E. Reproduction in Farm Animals. 1980. Lea & Febinger. PhiledelphiaBeerepoote, R.H. Reproduction of Farm Animals. 1982. Logman Inc, New YorkRussell, Perter J. Genetics. 1996. Library of Congress, Washington DC.