What is an
? An embryo is an egg that has already
been fertilized by a sperm cell.
? It is an organism in the early stage
? Embryo transfer is a bio-technique
where embryos are collected from the donor females and transferred into the
uterus of recipient which serves as foster mother for its development
throughout the remainder period of pregnancy’.’
? Multiple injections of hormone to
stimulate and multiply the ovulations in the cow that you want to get the
embryos from (cruachan.com)
v The first successful embryo transfer
was carried out in rabbit (1890) by Heap.
v First lamb by ETT – 1949 by Berry.
v First calf by ETT – 1951 by Willet et
v In swine – 1951 by Kvansnickii.
v In Asian buffalo – 1983 by Drost et
involved in embryo transfer
Selection of donorSelection of recipientEstrus synchronization of donor
and recipientSuperovulation of donor with high quality semenArtificial insemination of donorEmbryo collectionEvaluation of embryoTransfer of embryo / cryopreservation of embryo /
criteria of donor
v Superior individual performance
productive performance of offspring
v Regular cyclicity
v Ovaries must be free (no adhesions)
v Intact tubular genitalia (free from
any sort of abnormalities)
v Younger (4-8 years of age)
v Healthy and have good body weight.
v Normal postpartum history.
criteria of Recipient
? Healthy, free from infection and have
good body weight.
? Regular cyclicity.
? Intact genitalia
? Must have good cyclic CL of desired
stage at the time of embryo transfer.
? Exhibit calving ease, and that have
good milking and good mothering ability.
Synchronization of Donor
? 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 recipient
must be identical in order for the embryo to survive the transfer.
? Prostaglandins (PGF2) is the hormone
used to synchronize the estrous cycles of the donor and recipient cows.
? For optimum response gonadotropin
treatment is initiated during mid-luteal phase i.e on days 9-14 (if we consider
day 0 as estrus) of a normal estrous cycle.
? Donor cows can be superovulated
repeatedly at approximately 6-8 weeks intervals.
of Donor (A.I)
? Donor should be inseminated
artificially 2-3 times at 12 hours, 24 hours, and 36 hours interval, beginning
at 8-10 hours after the onset of estrus. This is required because ovulation can
occur over an extended time period.
? Fresh semen is preferred.
? If frozen semen- then use double
insemination dose at each insemination.
? Embryo can be collected by following
Surgical method – sheep, goat
& swine (mid ventral incision.Non- surgical methodLaparoscopy
? After the A.I the embryos are allowed
to grow for 6 days.
? On the 7th day, the
embryos are ready to be removed. This process is called “FLUSHING”
? An injection of lidocaine is given
prior to flush.
? The uterine horn is filled with flush
media and massaged to allow the embryos to flow out of the tract.
? After the embryos have been flushed
out, uterus injected with penicillin to kill any missed embryos or infection.
In the lab,
embryos are separated from the flush media and examined under a microscope to determine their quality and
stage of development.
Embryo (Introduction to recipient)
? Recipient should be in estrus within
12hours of the donor so that it should posses good CL at the time of transfer.
? To maximum success rate of the
transfer, the recipient’s estrus should be in sync with that of the donor.
Process of Transferring Embryos
q The recipient is palpated to determine the
presence and location of the CL (right vs. left). Recipient is administered an
epidural (lidocaine) to relax the muscles in the pelvic area.
Embryo (Introduction to recipient)
q Preferred in sheep, goat and pigs.
q Surgical transfer requires a small
cut in the cows flank
q The uterus is pulled out and a small
hole is made to the uterus. A small catheter is placed in through the hole and
the embryo released.
2.Non- surgical method:
? Mostly used for cattle and mare.
? Flused embryos that pass inspection
are loaded into an AI straw.
? If the embryo is frozen it is thawed
in a warm water bath (92F) FOR <30 sec and placed in specially designed transfer gun and covered with a sterile sheath. ? The transfer gun is passed through the vagina, cervix and into the uterine horn on the side as the CL. The embryo is deposited 1/3 the way up the uterine horn. Storage and cryopreservation of embryo q Embryos can be maintained at near body temperature in the media used for flushing during the period between recovery and transfer. q If embryos are to be held longer than 2 hours u pto 10 hours ., a media containing 20% heat treated serum should be used as holding medium q If embryos are cooled at 5c(I.E. refrigerated) they can be maintained for 2-4 days . q Cryopreservation of embryo is performed for longer period of time. q Cryoprotectants like glycerol, glycol, and DMSO to be added Applications of EET v Faster genetic improvement. v Genetic screening. v Disease control. v Import and export. v Circumvention of infertility. v Twinning in cattle v Conservation of endangered species v Research; production of cloned and genetic engineering.