Embryo Transfer

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Embryo Transfer in Cattle

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Introduction

• This slide show is a general overview of embryo
  transfer (ET) in beef and dairy cattle.
• It includes a brief discussion of the benefits
  and instructional methods of ET.

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Introduction (continued)

• ET is a expensive procedure, costing around 300
  for each flush and approximately 270 for each
  calf born.
• Students should understand that ET is a
  complicated procedure with a fairly high
  difficulty level.
• ET should only be performed by trained
  professionals.

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Objectives

• Explain the benefits of embryo transfer.
• Briefly outline the procedure of embryo transfer.

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Reproductive Anatomy
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What is an Embryo?

• An embryo is an egg that has already been
  fertilized by a sperm cell.
• It is an organism in the earliest stage of
  development.

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What is Embryo Transfer?

• ET involves the removal of an embryo from a
  female of superior genetics and the placement of
  the embryo into the reproductive tract of a
  female of average genetics.

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What is the Goal of Embryo
Transfer?

• The goal of ET is to obtain the maximum number of
  genetically superior embryos in a minimum amount
  of time.

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Benefits of Embryo Transfer

• Traditionally, cows produce only one calf per
  year. ET allows the production of many offspring
  within a year from a single cow.

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Benefits (continued)

• ET can increase the genetic potential of a herd
  in a relatively short period of time.
• ET can increase milk production in dairy herds.
• ET can increase weaning weights in beef and dairy
  herds.

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Benefits (continued)

• ET allows other producers to take advantage of
  superior genetics because frozen embryos can be
  shipped almost anywhere.
• ET preserves superior genetics for future
  generations due to embryo freezing.

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Necessary Equipment for
Embryo Transfer

• Plastic media bag
• Foley catheter
• Embryo filter

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Necessary Equipment for Embryo
Transfer (continued)

• Microscope
• Straw
• Rod

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Necessary Equipment for Embryo
Transfer (continued)

• FSH

• Prostaglandin
• (Lutalyse)

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Necessary Equipment for Embryo
Transfer (continued)

• Penicillin

• Lidocaine

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Necessary Equipment for Embryo
Transfer (continued)

• Plastic Sleeve
• Bull Semen

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The Process of Embryo Transfer

• ET begins with the selection of a donor cow.
• The donor cows will contribute the embryos to be
  transferred.

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Donor Cows Have Superior
Characteristics

• High milking ability
• High growth rate
• Outstanding reproductive capacity

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Bull Selection

• Next, a bull with superior genetics should be
  selected.

• Breeding can occur naturally or by artificial
  insemination.

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Recipient Cows

• Finally, recipient cows must be selected.
• Recipient cows serve as surrogate (foster)
  mothers to the calves, but contribute no genetic
  information.
• For this reason, the genetic makeup of the
  recipient cow is not as important as the makeup
  of the donor cow.

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Recipient Cows (continued)

• However, the recipient cow must be able to
  maintain her pregnancy to term and produce an
  adequate milk supply for her calf.

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Synchronizing the Estrous Cycle

• Once the donor and recipient cows have been
  selected, they must be synchronized so they are
  on the same phase of their estrous cycle.
• It is important to synchronize estrous cycles
  because the reproductive environments of the
  donor and recipients must be identical in order
  for the embryo to survive the transfer.

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Synchronizing the Estrous Cycle
(continued)

• The estrous cycle is controlled by the production
  and secretion of hormones at the proper time
  during the cycle.
• Prostaglandin (PGF2a) is the hormone used to
  synchronize the estrous cycles of the donor and
  recipient cows.

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Synchronizing the Estrus Cycle
(continued)

• Prostaglandin is produced naturally by the cow.
  However, a synthetic version called Lutalyse is
  given in one or two injections to synchronize
  estrous cycles.

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Preparing the Donor Cow to be
Flushed

• Before the donor cow is flushed, she is
  superovulated with a series of injections of
  Follicle Stimulating Hormone (FSH).
• Ovulation is the process of releasing eggs.
• Superovulation causes the ovary (the female
  reproductive organ) to produce many follicles.

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Preparing the Donor Cow to be Flushed
(continued)

• Follicles are small blister-like structures that
  develop on the ovary containing one egg each.
• When the follicles ovulate, the eggs are
  released.
• Superovulation ensures that many eggs will be
  released because there are many follicles
  present.

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Breeding the Donor Cow

• When the donor shows signs of estrus (the time
  period during the estrous cycle when she will
  allow breeding), she is ready to be bred.
• Some signs of estrus are riding other cows, clear
  vaginal mucus, and pacing the fence.

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Breeding the Donor Cow (continued)

• If using artificial insemination, the donor cow
  should be bred at least twice to ensure that all
  eggs are fertilized.

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The Flush

• Once the donor cow has been bred, the embryos are
  allowed to grow for six days.
• During this time the embryos also travels down
  the reproductive tract from the oviduct (the site
  of fertilization) to the uterus where they can be
  flushed out.
• On the seventh day, the embryos are ready to be
  removed. This process is called flushing.

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The Flush (continued)

• Embryo professionals use a non-surgical method to
  remove the embryos. The process requires
  experience and a patient, steady hand.

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The Flush (continued)

• An injection of lidocaine is given prior to the
  flush to reduce pressure and stress on the donor
  cow and to make the flush easier for the ET
  professional.

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The Flush (continued)

• To begin the flush, a catheter is passed through
  the cervix into one uterine horn.

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The Flush (continued)

• The catheter contains a balloon that is inflated
  with a saline solution in order to seal the
  entrance to the uterus so fluid and embryos are
  not lost.

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Removing the Embryos

• The uterine horn is filled with flush media and
  massaged to allow the embryos to flow out of the
  tract.
• This process is repeated several times in each
  uterine horn.

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Collecting the Embryos

• Embryos are carried out of the reproductive tract
  through plastic tubes and collected in a filter
  with the flush media.
• The pores in the filter are smaller than the
  embryos so excess fluid drains out of the filter
  without losing the embryos.

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Injecting Penicillin

• After the embryos have been flushed out, uterus
  injected with penicillin to kill any missed
  embryos or infections.

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Embryo Statistics

• An average of 7-10 embryos is collected from each
  flush.
• However, the number of embryos obtained from a
  single flush may range anywhere from 0-60.

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Separating the Embryos

• In the lab, embryos are separated from the flush
  media and examined under a microscope to
  determine their quality and stage of development.
  

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Embryo Size and Quality

• Embryos are microscopic in size (about 0.2 mm).
• Only undamaged embryos at proper maturity should
  be transferred.

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Embryo Quality
The embryos on the left are damaged and should
not be transferred.
The embryo on the right is of proper maturity and
quality and should be transferred.
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Transferring the Embryos

• The embryo to be transferred is put into a small,
  plastic straw and then loaded into an embryo
  transfer gun.

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Transferring the Embryos (continued)

• The embryo is then inserted into either the left
  or right uterine horn depending on which ovary
  has a corpus lutuem (CL).
• The CL is a structure on the ovary that secretes
  the hormone progesterone which is needed to
  maintain the pregnancy.

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Transfer Immediately or Freeze

• Embryos should be transferred as soon as possible
  after the flush (within 8 hours at least).
• Embryos can also be frozen for later implantation
  and stored in liquid nitrogen tanks.

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Summary

• ET can be costly, so the return on the investment
  should always be greater than the input costs.
• ET should only be performed using donor cows of
  superior genetics.
• Bull selection should be based on superior
  genetics as well.

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Conclusion

• If the required conditions are met, embryo
  transfer can be a beneficial way to produce
  superior cattle.

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CLICK HERE FOR EMBRYO TRANSFER TEST QUESTIONS
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Name __________________________________      1.)
Which of the following is a benefit of ET?
A. ET is inexpensive and easy to perform
B. ET can be done using any cow on the farm
C. ET preserves superior genetics for future
generations D. ET is an easy way to have
twin calves   2.) If embryos are not transferred
they must be   A. Refrigerated
immediately B. Thrown away C.
Stored in excess flush media D. Frozen in
liquid nitrogen   3.) An embryo is  A. a
fertilized egg B. an unfertilized egg
C. an immature egg D. an organism in the
last stage of development   4.) Which of the
following is used to synchronize estrous cycles
of the donor and recipient cow?
A. Lidocaine B. Lutalyse C. FSH
D. Estrogen   5.) A follicle releases 
A. 2 eggs B. 1 egg C. 0 eggs
D. 4 eggs   6.) Why is it important to
synchronize the estrous cycles of the donor and
recipient cow ? A. to make the transfer
easier on the ET professional B. so the
milk production of the recipient cow will be
adequate C. so the reproductive
environments of the donor and recipient cow are
the same D. none of these are
correct      
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7.) Superovulation causes A. the donor
cow to come into heat sooner B. the
recipient cow to stay in heat longer C.
ovulation to occur earlier D. the ovary to
produce many follicles
8.) The donor cow should be bred at least how
many times prior to the flush when using
artificial insemination?   A. 1
B. 2 C. 3 D. 4   9.) Which of
the following determines which of the recipient
cows uterine horn the embryo will be
placed in?  A. the presence of a corpus
luteum B. the size of the uterine horn
C. the structure of the uterine horn
D. the preference of the ET professional   10.)
What is the antibiotic used to kill any missed
embryos or infection after the flush?  
A. progesterone B. prostaglandin
C. penicillin D. lidocaine   11.)
During a flush, the purpose of inflating the
balloon is to A. expand the uterus
B. seal the entrance to the uterus so fluid
and embryos aren't lost C. stop uterine
contractions D. keep the catheter from
slipping out   12.) Embryo are approximately
______ in size.   A. 1 mm B. 1
in. C. 0.5 in. D. 0.2 mm
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13.) The corpus luteum (CL) is a structure on
the ovary that secretes the hormone
____________ which is needed to maintain
pregnancy.  A. progesterone B.
estrogen C. testosterone D.
FSH   14.) The goal of ET is to   A.
obtain one genetically superior embryo B.
obtain as many embryo as possible regardless of
their quality C. obtain the maximum
number of genetically superior embryos in a
minimum amount of time D.
none of the above are correct     15.) The
total cost of embryo transfer is approximately 
A. 500 per flush and 400 per calf
born B. 150 per flush and 150 per
calf born C. 500 per flush and 100
per calf born D. 300 per flush and
270 per calf born   True / False   T F 16.) ET
involves the removal of an embryo from a
genetically superior cow and placing
t into a cow of average genetics.   T F
17.) Donor cows must possess excellent
genetics.   T F 18.) Prostaglandin (Lutalyse)
is the hormone used to superovulate a donor
cow.   T F 19.) When you observe a cow riding
another cow you can conclude that she is in
estrus.   T F 20.) The only purpose for
waiting 6 days before flushing embryos is to
allow growth and
development.   T F 21.) The most important
characteristic that a recipient cow must possess
is milking ability.   T F
22.) ET professionals use a surgical method to
remove embryos.   T F 23.) An average of 7-10
embryos are collected from each flush.  
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T F 24.) Embryos must be undamaged and at
proper maturity before transferred.   T F 25.)
The uterine horns are flushed only once to allow
embryos to flow out of the tract.   T F 26.)
Filters are designed to keep only the good
embryos and let the bad ones drain off
with the excess fluid.   T F 27.)
Embryos must be examined under a microscope to
determine their quality and stage
of development.   T F 28.) The embryo
transfer procedure has a fairly low difficulty
level.   T F 29.) Recipient cows do not
contribute any genetic material to transferred
embryos.   T F 30.) The donor cow can either
be bred naturally or by artificial
insemination.