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Devices that Prevent Cattle from Reproducing
Kelsey Morgan
November 18, 2013
The Pennsylvania State University
Department of Animal Science
Reproductive Physiology
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Every 21 days, female cattle that have reached puberty, cycle and ovulate an egg.
Once ovulated, the egg may be fertilized or die. This occurs provided that the female is
reproductively sound, has proper nutrition and is not previously pregnant. However, to
prevent the development of an embryo these can be techniques performed by man or
naturally occurring events. Many events can also occur to the male that limits his
reproductive capabilities. Prevention of reproduction is utilized for many different
reasons. Castration of bulls enables steers to grow in a more efficient way and allows
them to be more apt to grade choice. Pregnancy in feedlot heifers is undesirable because
if she is taken to the slaughterhouse pregnant, she receives a discount. This is for the
reason that pregnancy changes the developmental priorities in the female, changing from
deposition of muscle to fetal development, ultimately limiting her muscle disposition.
Females can be also altered in their reproductive cycle to enable them to ovulate on a
schedule. This is beneficial if the female is intended for a flushing of embryos or for a
timed breeding schedule.
Preventing reproduction in cattle is a beneficial use for many different reasons. It
allows for increase growth in feedlot heifers and steers, better management of breeding
stock and their genetics as well as herd size management.
The prevention of reproduction in cattle can be used to stop the cow from
ovulating, make her infertile or to abort the embryo/fetus if she has already become
pregnant. One way to abort an embryo is by administering clopsrotenol, more commonly
known as Estrumate, which is hormonally recognized as Prostaglandin F2 (PGF2). This
will effectively terminate the pregnancy when administered one week after mating until
4.5 months into the pregnancy. This drug functions by expelling the fetus 5 to 6 days
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after treatment. In Copeland’s study the researchers induced abortions beginning on day
3. No other fetuses were found by day 9. Once the fetus is aborted, the reproductive tract
returns to estrous following expulsion of the placenta and retraction of the uterus
(Aborting Cattle 2013). Injecting 2 to 5 month pregnant heifers intramuscularly with
PGF2 daily aborted 100% of the heifers. Heifers that were 29 to 52 days pregnant
aborted their embryos after subcutaneous injections. Heifers injected with a single dose
of PGF2a that were 35 to 80 pregnant aborted. 100% abortion can be inflicted on heifers
that are up to 150 days in their gestation by a single dose of 500 g of cloprostenol
(Copeland, et al. 1978). Heifers that go to the processing plant nonpregnant will offer
more profit than those that are pregnant.
Another form of hormonal action that may be taken on livestock is the
administration of progesterone in ovulating cattle. Low levels of progesterone during
early dioestrus have a negative effect on the survival of the embryo. The administration
of progesterone, more commonly known as lutyse, can have detrimental effects on the
formation of the corpus luteum (CL). A research study was performed in Brazil that
determined that the function of the CL was reduced on the first day of postoestrus once
progesterone was administered. When progesterone (P4) was administered long term, on
day two a significant decrease in CL development had been recorded. The function of
the CL is to secrete progesterone and estrogen and indicate to the female’s body that she
is pregnant; if she is not pregnant, the CL will regress forming a scar tissue site on the
ovary. Reduced circulation of progesterone post-ovulation day 3 to 8 leads to a smaller
embryo with reduced secretions of interferon-tau another hormone that aids in
maintaining pregnancy. The function of the CL is important to pregnancy and any
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problem with its formation significantly decreases the female’s chances of becoming
pregnant. Conception rate is greatly reduced with decreased amounts of progesterone
concentrations during early dioestrus (Pugliesi, et al. 2013). This leads to the change in
the expression of endometrial genes, which change the histortroph composition and direct
effects the development and survival of the embryo (Pugliesi, et al. 2013).
Another way to hormonal prevent reproduction is the administration of GnRH
postpartum for 14 consecutive days to stops ovulation. Preventing the release of LH and
FSH stimulates follicular production and growth, and prohibits the cow from expressing
heat. The continuous administration of GnRH will prevent the growth of ovarian follicles,
which prevents the heifer or cow from becoming pregnant. Low levels of progesterone
were also recorded in the experiment group; these low levels prohibit cycling of the
female. (Mattos, et al. 2001). The experimental group determined that the administration
of DESL given 14 days after freshening suppressed ovarian activity and caused plasma
progesterone concentration levels to remain low (Mattos, et al. 2001).
Natural events can also occur in the female that prevent her from breeding. These
can include freemartinism, cystic ovaries, and ovarian cancer. Freemartinism is a
condition that occurs when a twin bull and heifer are developed together in the same
uterus. The hormones from the bull interfere with the female development by stopping
the advanced development of her reproductive tract. The result is a female with a
masculinized reproductive tract. Different levels of severity can occur in freemartins;
some heifers have no development past the cervix or non-functioning ovaries. This can
be detected by a simple test performed by inserting a blunt end probe to measure the
length of the tract. A normal female calf tract would measure 13 – 15 cm while a
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freemartin’s tract would measure only 5 – 8 cm in length (Padula, A.M. 2004). 80 to
95% of twin born females to males are diagnosed as freemartins. (Padula, A.M. 2004).
The other 20 – 5% of heifers are born with no developmental or fertility issues. The
reason for this phenomenon is unknown.
Ovarian cysts are another major contributor of decreased reproductively in cattle.
They are most often seen in postpartum dairy cows (Roth, et al. 2012). It has been
reported that cystic ovaries occur during lactation and since this is an extended period of
time for dairy cattle they occur more often. A cyst is defined as a follicle that does not
form a CL for a minimum of ten days. Cysts develop after preovulatory follicles do not
ovulate and continue to remain on the ovary interfering with normal functions of the
ovary (Roth, et al. 2012). To treat cysts, gonadotropins are administered to set luteinizing
hormone (LH) back into a normal schedule because the cause of the cyst is the disruption
of LH release. It is believed that cysts may form from the lack of LH before a
preovulatory surge. Cystic cows will become non-cyclic and do not cycle in normal 21day estrus cycle. Therefore, the cow does not come into heat and is unable to reproduce,
as she is not ovulating to allow for the release of an ovum (Roth, Z., et al. 2012).
Another natural occurring cause of reduced fertility is ovarian cancer that has a
significant effect on the decreased reproductively of female cattle. Normally ovarian
cancer in humans is advertised more however, it is prevalent in cattle as well. One of the
most frequently reported types of ovarian cancer is granulosa-theca cell tumors (GTCTS)
(El-Sheikh Ali, et al. 2013). The disease can be recognized by a blood sample, which
tests for plasma Anti-Mullerian Hormone (AMH) levels. GTCTS is indicated by higher
levels of AMH. The effects of this disease are: ending of estrus cycles and the
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enlargement of the ovary. AMH has been recorded to be at higher levels in mares and
humans that are infected with GTCTS. Unilateral enlargement of the ovary is most often
found on the right side of the reproductive tract; no evidence has been found to indicate
the reason for this prevalence. Due to the lack of an estrous cycle, eggs are not released;
and sperm is not present to fertilize the ovum because no heat is detected. As a result, no
reproduction occurs (El-Sheikh Ali, et al. 2013). A study was performed using two
heifers that had long-term GTCTs. In the first case, the heifer was found to have a smaller
than average uterus, an inactive left ovary missing antral follicles, and an enlarged right
ovary with cyst-like structures with no recognizable follicles. The second case identified
a heifer with an enlarged ovarian mass on the right ovary (Dobson, et al. 2013). A tissue
sample of the ovary revealed that granulose-theca cells formed irregular bodies. Any
combination of these naturally occurring events reduces reproductive ability. While these
instances are beneficial in preventing pregnancy in feedlot situations, they decrease value
in the breeding industry.
Female cattle can be physically altered in their reproductively by performing a
hysterectomy (removal of the uterine body and horns) or ovariectomy (complete removal
of both ovaries). In 1896, two researchers removed the ovaries from feedlot heifers to
avoid an estrus cycle because estrus activity limits growth. They believed that
diminishing estrous activity will increase growth; however, the removal of the ovaries
indicated that ovarian hormones are important in supporting growth. The study exhibited
decreased gains and lower feed efficiency in the ovariectomized heifers (Hamernik, et al.
1958). However, the heifers had to be injected with anabolic steroids because the removal
of ovarian hormones resulted in decreased growth. The injections enabled the
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ovariectomized heifers’ to perform similarly to intact females (Hamernik, et al. 1958).
This is not supported by more recent research as it indicates no decreased growth and
feed efficiency in heifers. The 1896 research also found that the injection of melengestrol
acetate (MGA) blocks ovulation by increasing in follicle size. It appeared that this
allowed for faster weight gain. The endogenous environment of the hysterectomized
heifers promotes growth however, does not show a feed efficiency increase At the
conclusion of the study, it was determined that the hysterectomized heifers was more
advantageous in promoting growth than the ovariectomized heifers.
Females are not the only ones that can be manipulated to prevent reproduction.
Castration is the removal of the testis from the male. There are multiple methods that can
be used to do this. The first method is banding. Through this process the supply of blood
is stopped from entering the testis. This involves placing a small, tight band around the
seminal vesicles above the testis to cut blood circulation off. After a period of time the
testis will die and fall off of the bull resulting in a steer. This is a procedure usually done
on younger bull calves as it causes less stress and chance of infection. It may be
performed on older calves using a single strand of band that is “ratcheted” around the
testicular cord. This process should be done before puberty. Healing takes approximately
6 weeks to completely heal the area where the rubber band was placed. Irritation can
occur as well as swelling above the band. This process however has a lower risk of
infection as well as limited amount of blood loss. The second method is cutting. This can
be done at just about any age. Each testicular cord is injected with a numbing agent. The
bottom of the scrotum is cut off to expose the testicles. Connective tissue is stripped from
around the cords to expose them. A demasculator is then placed around the cord to crimp
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and stop the blood flow while cutting of the testicle below the crimper. Great care is
taken to ensure that the blood flow is stopped as a great amount of blood is supplied to
the testicles. This process is quick and immediately effective allowing for healing to
occur right away. The open wound does allow for a greater risk of infection as well as
for bleeding to begin again. (SD State University. 2013) However, this process is better
for older bulls as it is a much more definite way of ensuring infertility. In herds that use
replacement bulls, bulls are much older at the time of castration and a result is larger
testicular growth. Cutting is a 100% method of castration as banding sometimes breaks
leaving the animal with some latent fertility.
There are many ways to prevent cattle from mating, these include natural
occurring events that limits or prohibits the reproductively of cattle and human
manipulation. The ability to influence cattle’s reproduction is a tool that is essential in the
breeding, beef and show industry. All sectors having different reasons to prevent cattle
for mating. From scheduling a timed breeding, obtaining a higher dollar for a nonpregnant female, and sync a female to calve for a certain age bracket a show are all
reasons that devices that prevent cattle from reproducing is a necessary and important
part of the cattle business.
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Works Cited
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Feedlot Heifers with Cloprostenol (A synthetic Analogue of Prostaglandin F2 ):
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