This document provides an overview of embryo transfer (ET) in cattle. It describes the ET process, which involves removing embryos from a genetically superior donor cow and transferring them to recipient cows. The goal of ET is to efficiently produce genetically superior offspring. The document outlines the steps of synchronizing donor and recipient cows, flushing embryos from the donor, examining and transferring high quality embryos to recipients. It notes that ET is an expensive but effective way to introduce superior genetics into a herd within a short time period.

1. Embryo Transfer in Cattle
By: Valerie D. Blair and Dr. Frank B. Flanders
Georgia Agricultural Education Curriculum Office
Georgia Department of Education
February 2003
To accompany Lesson 02.421-13.4
* Special thanks to Dr. Russ Page of Reproductive Progress for his assistance with
this slide show.

2. 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.

3. 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.

4. Objectives
 Explain the benefits of embryo transfer.
 Briefly outline the procedure of embryo
transfer.

5. Reproductive Anatomy

6. 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.

7. 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.

8. 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.

9. 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.

10. 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.

11. 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.

12. Necessary Equipment for
Embryo Transfer
 Plastic media bag
 Foley catheter
 Embryo filter

13. Necessary Equipment for Embryo
Transfer (continued)
 Microscope
 Straw
 Rod

14. Necessary Equipment for Embryo
Transfer (continued)
 FSH  Prostaglandin
(Lutalyse)

15. Necessary Equipment for Embryo
Transfer (continued)
 Penicillin  Lidocaine

16. Necessary Equipment for Embryo
Transfer (continued)
 Plastic Sleeve
 Bull Semen

17. The Process of Embryo Transfer
 ET begins with the selection of a donor
cow.
 The donor cows will contribute the embryos
to be transferred.

18. Donor Cows Have Superior
Characteristics
 High milking
ability
 High growth rate
 Outstanding
reproductive
capacity

19. Bull Selection
 Next, a bull with
superior genetics
should be selected.
 Breeding can occur
naturally or by
artificial insemination.

20. 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.

21. 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.

22. 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.

23. 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 (PGF2α) is the hormone used
to synchronize the estrous cycles of the
donor and recipient cows.

24. 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.

25. 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.

26. 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.

27. 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.

28. 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.

29. 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.

30. The Flush (continued)
 Embryo professionals use a non-surgical
method to remove the embryos. The
process requires experience and a patient,
steady hand.

31. 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.

32. The Flush (continued)
 To begin the flush, a catheter is passed
through the cervix into one uterine horn.

33. 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.

34. 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.

35. 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.

36. Injecting Penicillin
 After the embryos
have been flushed
out, uterus
injected with
penicillin to kill
any missed
embryos or
infections.

37. 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.

38. 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.

39. Embryo Size and Quality
 Embryos are
microscopic in size
(about 0.2 mm).
 Only undamaged
embryos at proper
maturity should be
transferred.

40. 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.

41. Transferring the Embryos
 The embryo to be transferred is put into a
small, plastic straw and then loaded into an
embryo transfer gun.

42. 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.

43. 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.

44. 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.

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

46. CLICK HERE FOR EMBRYO
TRANSFER TEST QUESTIONS

47. 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

48. 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 cow’s 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

49. 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.

50. 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.

51. Answer Key
1.) C
2.) D
3.) A
4.) B
5.) B
6.) C
7.) D
8.) B
9.) A
10.) C
11.) B
12.) D
13.) A
14.) C
15.) D
16.) T
17.) T
18.) F
19.) T
20.) F
21.) T
22.) F
23.) T
24.) T
25.) F
26.) F
27.) T
28.) F
29.) T
30.) T