Embryo transfer involves collecting embryos from a donor cow and transferring them to a recipient cow. It can help improve fertility in cows experiencing issues like repeat breeding or infertility due to infections. The process involves synchronizing the donor and recipient's cycles, superovulating the donor, collecting embryos 7 days after insemination, and transferring high quality embryos into the recipient. Embryo transfer has been shown to increase pregnancy rates in repeat breeder cows by minimizing the impact of poor egg quality or uterine issues.

1. Embryo Transfer and
Infertility Management
welcome
Prepared by:
Dr. Sushil Dhakal
Department of veterinary theriogenology,
Institute of agriculture and animal science,
Tribhuvan University
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2. Embryo Transfer:
• Embryo transfer is the process by which an embryo is collected
(flushed) from one female (the donor) and transferred to another
female (the recipient).
Embryo:
• An embryo is an egg that has already been fertilized by a sperm cell
and is in the earliest stage of development.
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3. Infertility:
• Infertility is a temporary disturbance in reproductive function
wherein the animal cannot become pregnant.
• Or,
• Infertility is the Diminish or absent capacity to produce viable
offspring’s.
• It can be due to malnutrition, infections, congenital defects,
management errors and ovulatory or hormonal imbalances in the
female.
• Some of the most common disorders include Repeat breeding, Anestrus,
Ovarian cysts, and Early Embryonic loss.
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4. Different treatment approaches like:
• Nutritional management,
• Deworming,
• Intra-Uterine infusion of antiseptics and antibiotic,
• Hormonal therapy:
 For example: treatments including gonadotropin-releasing hormone (GnRH),
progesterone formulation (controlled internal drug release; CIDR), exogenous
estradiol benzoate, prostaglandin (PG).
And combinations of these, depending upon the cause of infertility have been
implemented, and improved conception rates are reported .
• Remarkably, it has been proposed that embryo transfer could be used as an
assisted reproductive technology to improve the conception rate of infertile
animals.
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5. Embryo transfer and Repeat breeding:
• Repeat breeding is one of the most critical reproductive disorders in
cattle.
• Repeat breeders are generally described as sub fertile animals without
any anatomical or infectious abnormalities that do not become pregnant
until after three or more breeding attempts, or that remain infertile after
numerous services(Seidel, 1981).
• Embryo transfer (ET) following artificial insemination (AI) could be
used as an assisted reproductive technology to improve the conception
rate of repeat breeder cattle (Yaginuma et al., 2019).
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6. Contd…
• Once pregnancy is established, embryonic trophoblast cells produce
and secrete interferon tau (IFNT), a well-known pregnancy recognition
signal in ruminants (Yaginuma et al., 2019).
• This would induce maternal recognition of the embryo and result in the
suppression of luteolytic PGF2α from the uterus.
• Furthermore, IFNT also plays a role in regulating embryonic
development and elongation in ruminants (Yaginuma et al., 2019).
• Therefore, it is speculated that the higher pregnancy rate of Embryo
Transfer following AI in repeat breeder cattle is due to the increased
release of IFNT from the added embryos (Yaginuma et al., 2019).
• However, the exact reason why this technique improves the conception
rate in cattle with reduced fertility is unknown.
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7. Uterine infection and Embryo Transfer :
• In cases of subclinical or recurrent endometritis,
repeated superovulation and embryo transfer may
result in the “rescue” of viable embryos from the toxic
environment to develop in the healthy uterus of the
recipient.
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8. Aged repeat breeder and Embryo Transfer:
• Problem likely due to “worn-out” uterus.
• Normal super ovulatory treatment and transfer of embryos to uterus of
younger recipient is often effective.
Chronic abortion and Embryo Transfer:
• Embryo transfer can be done after the recovery of the embryo before
the abortion-causing condition is active.
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9. Cystic ovarian disease and Embryo Transfer:
• Embryos with superior genetics can be embryo transferred from a cystic
ovarian diseased animal to a healthy recipient
• This can be done by Super ovulatory treatments based on the insertion
and removal of a progestin implant.
• If the cystic ovarian condition appears to be hereditary, no propagation
should be attempted.
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10. Adhesions of ovaries or blocked oviducts and Embryo
Transfer:
• Superovulation increases the chances that at least a few ova will be
picked up if there are adhesions.
• A combination of superovulation with surgical recovery or laparoscopy
helps to diagnose the cause of the infertility and can result in recovery
of viable embryos for transfer.
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11. Steps Involved in Embryo Transfer:
• Selection of a Donor
• Selecting a Recipient
• Synchronizing the Estrous Cycle
• Superovulation of the Donor Cow
• Inseminating the Donor Cow
• Embryo Collection
• Embryo processing and Grading
• Storage of Embryo
• Transferring Embryos
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12. Selection of a Donor:
• Embryo Transfer begins with the selection of a donor cow.
• The donor cow will contribute the embryos to be transferred
• The donor cow have superior characteristics like ; High milking ability,
High growth rate and outstanding reproductive capacity.
• Has regular, normal estrous cycles.
• The donor cow must be disease free.
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13. Selecting a Recipient:
• Recipient cows serve as surrogate mother to the calves ,but contribute no
genetic information.
• Recipient females should be in good body condition and health, on a
proper plane of nutrition, and on a sound herd health program.
• The recipient cow must be able to maintain her pregnancy to term and
produce adequate milk supply for her calf.
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14. Synchronizing the Estrous Cycle:
• Once the donor and recipient cows have been selected, they must be
synchronized so that 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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15. Superovulation of the Donor Cow:
• Donor females are super ovulated, which allows them to ovulate more than
one oocyte.
• The Select Synch CIDR® protocol, is frequently used to synchronize the
estrous cycle .
• This involves giving an injection of gonadotropin-releasing hormone (GnRH)
and inserting a CIDR® vaginal insert (Controlled Internal Drug Release
device).
• The GnRH synchronizes the next follicular wave, and the CIDR® releases
progesterone, which prevents ovulation from occurring while it is inserted.
• Seven days later, the CIDR® is removed, and an injection of prostaglandin
F2α (PGF2α) is given, which causes the corpus luteum (CL) on the ovary to
regress and allows the cow to begin estrus.
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16. Contd…
• This estrus, called the “marker heat,” is indicative of her ability to
ovulate and signals that she is properly synchronized.
• Only females showing this marker heat should continue in the
protocol.
• Nine to eleven days after the marker heat, a series of injections of
decreasing amounts of follicle-stimulating hormone (FSH) are
administered.
• This encourages multiple follicles to grow, which leads to the
ovulation of multiple oocytes.
• Following the FSH injections, two injections of PGF2α are
administered 12 hours apart.
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17. Inseminating the Donor Cow:
• Donor cow is inseminated after the signs of estrus is seen.
• Females are typically inseminated with one straw of semen at the
initiation of estrus.
• Two straws 12 hours later; and again with one straw 24 hours after the
initiation of estrus .
• This provides an adequate number of live sperm to fertilize all oocytes
shortly after ovulation.
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18. Embryo Collection:
• Embryos are flushed 7 days after estrus.
• An injection of Lidocaine is given in to the spinal cord near the tailhead.
before the embryo flushing process begins.
• This eliminate the muscular contractions and relieves pain.
• A catheter, which is placed over a metal stylette, is inserted through the
cervix, similar to passing a rod used for AI .
• Once the tip of the catheter is in the uterine body, a bubble, or cuff, is
inflated to help keep the catheter in place and prevent fluid from leaking
out of the uterine body.
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19. 9/28/2021 19
Parish, J. A., & Karish, B. (2019).
Prepared by Dr. Sushil Dhakal

20. Contd…
• The metal stylette is then removed, and tubing is attached to the
catheter to connect it to the bag of flushing media .
• Flushing media is allowed to flow into the uterine body, where the
technician will massage the uterus to allow the fluid to “pick up” any
embryos present.
• The fluid is then allowed to flow out of the uterus and through a very
fine filter that traps the embryos.
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21. Fig: Embryo Collection
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22. Contd…
• This process is repeated several times, sometimes focusing on one uterine
horn and then the other.
• Once complete, the cuff on the end of the catheter is deflated, and the
tubing and catheter are removed.
• An injection of PGF2α is administered so that if any embryos are missed
in the collection process, they will not develop a pregnancy in the donor
cow.
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23. Embryo processing and Grading :
• The filter used to capture the embryos is rinsed to collect them in a
dish.
• In the lab, embryos are examined under a microscope to determine
their quality and stage of development.
• Embryos are microscopic in size (about 0.2mm).
• Only undamaged embryos at proper maturity should be transferred.
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24. 9/28/2021 24
Fig: Embryo .Parish, J. A., & Karish, B. (2019).
Prepared by Dr. Sushil Dhakal

25. Storage of Embryo:
• Embryos can be freshly transferred or frozen for later use.
• If embryos are to be frozen, they are washed and stored in a cryoprotectant.
• This fluid minimizes the damage done to an embryo when it is frozen.
• Ethylene glycol is used most often.
• Embryos are loaded into 0.25 cc plastic straws and labeled.
• The straws are then placed into a special freezer which decrease the
temperature in a slow, controlled fashion, necessary for embryo viability.
• Once frozen, the straws are placed in labeled goblets and canes and plunged
into liquid nitrogen in a storage tank.
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26. Transferring Embryos:
• When embryos are to be transferred fresh, they are loaded directly into 0.25 cc
plastic straws and transferred using a rod similar to an AI rod.
• To thaw frozen embryos, the straw should be removed carefully from the tank,
held in the air for 10 seconds, and then placed in a water bath between 77 and 86
°F (25–30 °C), which is cooler than the temperature used to thaw semen.
• The straw should remain in the water bath until any ice has melted, approximately
30 seconds.
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27. Contd…
• The cap is removed from the straw and loaded into the transfer rod,
and then a transfer sheath is placed over it.
• The rod is passed through the cervix, and the embryo is deposited in
the uterine horn on the same side that ovulation occurred, as
determined by the presence of a CL on the ovary.
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28. Conclusion:
• The results of different studies are encouraging and indicate that Embryo Transfer
(ET) improves the pregnancy rate during infertility specially in repeat breeder cows
by minimizing the impact of poor oocyte quality and inadequate uterine
environments on fertilization and embryo development during the first 7 days after
AI.
• Thus, ET can be considered an option to improve fertility .
• However, it should be noted that ET cannot be more than a course of action to
improve the pregnancy rate; parturition and feeding should be still carefully
organized in a way best suited to that group of animals.
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29. References
• Parish, J. A., & Karish, B. (2019). Embryo Transfer in the Beef Herd. Mississippi State
University Extension Service.
http://extension.msstate.edu/publications/publications/embryo-transfer-the-beef-herd
• Food and Agriculture Organization(FAO). (n.d.). Training manual for embryo transfer
in cattle. Fao.Org. Retrieved July 29, 2021, from
• Seidel, George E. (1981). Superovulation and Embryo Transfer in Cattle Author ( s ):
George E . Seidel Published by : American Association for the Advancement of Science
Stable URL : https://www.jstor.org/stable/1685333 Superovulation and Embryo
Transfer in Cattle. 211(4480), 351–358.
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30. Contd…
• Nowicki, A. (2021). Embryo transfer as an option to improve fertility in
repeat breeder dairy cows. 231–237. https://doi.org/10.2478/jvetres-2021-
0018
• Yaginuma, H., Funeshima, N., Tanikawa, N., Miyamura, M., Shirasuna, K., &
Hamano, S. (2019). Journal of Reproduction and Development. 65(3).
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