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Process of Flushing a Beef Cow
By: Kelsey Morgan
Introduction
The process of flushing a cow, also known as super ovulation, involves hormonal
stimulation of the ovaries and the removal of fertilized eggs for transplant into surrogate
mothers (a female recipient cow that will carry the calf and raise it as her own). This
process must be performed by a veterinarian who is trained in embryology (the study of
the embryo from fertilization to fetus).
The purpose of flushing a cow is genetic advancement. Because female cows typically
only have one calf a year flushing allows for many offspring to come from one female
increasing her genetic pool. This will progress and push forward the genetics of a
valuable dam. This process can be done any time during the female’s estrous cycle. So
long as she is not pregnant she may
be flushed.
This process description will help to
explain how flushing a cow works.
This is explained in the five critical
steps: the hormonal stimulation of
the ovaries, followed by an estrus
cycle, fertilization of the eggs, the
collection of the embryos, and
storage or transplant of embryos.
Figure 1 shows a general overview of
the process that is followed to flush
a cow.
Figure 1 Process of Flushing a Cow
http://www.cruachan.com.au/embryo_transfer.htm
Hormonal Stimulation
The process begins by the injection of GnRH (Gonadotropin Releasing Hormone) for 3
days at 8-hour intervals. This stimulates the production of eggs on the ovaries. Normally
cattle will only produce one egg per ovulation but the hormones injected stimulate the
production of many eggs.
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Estrus Cycle
24 hours after the completion of the hormone injections the cow will go into heat. She is
observed for standing heat (this is when the cow stands when ridden by other cattle).
Heat is defined as the time in the estrus cycle where the cow is receptive to breeding and
when it is close to the time when an egg is to be released.
Breeding
12 hours after standing heat is observed the cow is then bred by artificial insemination.
Artificial insemination is the insertion of a ¼ mL straw of semen that is deposited in the
uterus. She is inseminated twice to ensure that there is enough semen to fertilize all of
the eggs that have developed.
Embryo Collection
The eggs are allowed to divide and develop
for 5 days. This allows the eggs to be stronger
and more stable (gives them more time for
the cells to divide). This time allows the eggs
to move into the oviduct but before they have
attached to the uterus.
The flushing process takes about 1 hour. An
epidermal is given to the cow to relax her
back half. A cathedral is inserted into one
side of the oviduct. Fluids are flushed into
the uterus. The fluids then “flush” the
embryos out of the oviduct and into a large
test tube and repeated on the opposite side.
This process is represented in figure 2. It
displays the basic set-up of how the flushing
fluid works to remove the eggs from the
donor cow.
Figure 2 Process flow of embryo collection
http://www.bairnsley.com/Breeding%20-%20ET.htm
Storage/ Transplant of Embryos
After the eggs are removed, they are graded on quality. The veterinarian looks at the
eggs under a microscope and grades the eggs as 1, 2, unfertile or unviable quality. The 1
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and 2 graded eggs are kept for implantation while the latter two are disposed of. There
are two possibilities that can be done to the eggs.
The eggs may be frozen in liquid nitrogen. This allows the eggs to be frozen indefinitely.
They can be stored for long periods of time and placed in recipient cows when they are
available. They may also be directly implanted into a recipient cow. This entails the
recipient cows being in sync at the same time as the donor cow. The recipient cow must
be in the same stage of estrus so that when the egg is implanted it will attach to the
uterus and begin to develop.
Conclusion
Reproduction is the defining reason of our existence and the variation that we observe
in the different breeds and type of cattle. Flushing is just one that we are able to have
genetic advancement in the cattle industry. The flushing process involves five crucial
steps: the hormonal stimulation of the ovaries, estrus cycle, fertilization of the eggs,
collection of the embryos, and storage or transplant of embryos. Ultimately breeders
that are looking to further improve the genetics of their herd use this process in valuable
genetic cattle.