What is anEmbryo?? An embryo is an egg that has alreadybeen fertilized by a sperm cell.? It is an organism in the early stageof developmentDefinition:-? Embryo transfer is a bio-techniquewhere embryos are collected from the donor females and transferred into theuterus of recipient which serves as foster mother for its developmentthroughout the remainder period of pregnancy’.’? Multiple injections of hormone tostimulate and multiply the ovulations in the cow that you want to get theembryos from (cruachan.com) History ofEmbryo Transferv The first successful embryo transferwas carried out in rabbit (1890) by Heap.
v First lamb by ETT – 1949 by Berry.v First calf by ETT – 1951 by Willet etal.v In swine – 1951 by Kvansnickii.v In Asian buffalo – 1983 by Drost etall Stepsinvolved in embryo transferSelection 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 / Micromanipulation 1.Selectioncriteria of donorv Superior individual performancev Good productive performance of offspringv Regular cyclicity v Ovaries must be free (no adhesions)v Intact tubular genitalia (free fromany sort of abnormalities)v Younger (4-8 years of age)v Healthy and have good body weight.
v Normal postpartum history.2.Selectioncriteria of Recipient? Healthy, free from infection and havegood body weight.? Regular cyclicity.? Intact genitalia? Must have good cyclic CL of desiredstage at the time of embryo transfer.? Exhibit calving ease, and that havegood milking and good mothering ability.
3.EstrusSynchronization of Donor? Once the donor and recipient cowshave been selected, they must be synchronized so they are on the same phase oftheir estrous cycle.? It is important to synchronizeestrous cycles because the reproductive environments of the donor and recipientmust be identical in order for the embryo to survive the transfer.
? Prostaglandins (PGF2) is the hormoneused to synchronize the estrous cycles of the donor and recipient cows.Time ofsuperovulation? For optimum response gonadotropintreatment is initiated during mid-luteal phase i.e on days 9-14 (if we considerday 0 as estrus) of a normal estrous cycle.? Donor cows can be superovulatedrepeatedly at approximately 6-8 weeks intervals. 5.Inseminationof Donor (A.I)? Donor should be inseminatedartificially 2-3 times at 12 hours, 24 hours, and 36 hours interval, beginningat 8-10 hours after the onset of estrus.
This is required because ovulation canoccur over an extended time period.? Fresh semen is preferred.? If frozen semen- then use doubleinsemination dose at each insemination. 6.EmbryoRecovery? Embryo can be collected by followingmethods;Surgical method – sheep, goat & swine (mid ventral incision.
Non- surgical methodLaparoscopyNon-SurgicalMethod? After the A.I the embryos are allowedto grow for 6 days.? On the 7th day, theembryos are ready to be removed.
This process is called “FLUSHING” ? An injection of lidocaine is givenprior to flush.? The uterine horn is filled with flushmedia and massaged to allow the embryos to flow out of the tract.? After the embryos have been flushedout, uterus injected with penicillin to kill any missed embryos or infection.Seperatingthe EmbryosIn the lab,embryos are separated from the flush media and examined under a microscope to determine their quality andstage of development. Transfer ofEmbryo (Introduction to recipient)? Recipient should be in estrus within12hours of the donor so that it should posses good CL at the time of transfer.? To maximum success rate of thetransfer, the recipient’s estrus should be in sync with that of the donor. Process of Transferring Embryosq The recipient is palpated to determine thepresence and location of the CL (right vs.
left). Recipient is administered anepidural (lidocaine) to relax the muscles in the pelvic area. Transfer ofEmbryo (Introduction to recipient)Surgical method:q Preferred in sheep, goat and pigs.q Surgical transfer requires a smallcut in the cows flankq The uterus is pulled out and a smallhole is made to the uterus.
A small catheter is placed in through the hole andthe embryo released. 2.Non- surgical method:? Mostly used for cattle and mare.? Flused embryos that pass inspectionare loaded into an AI straw.
? If the embryo is frozen it is thawedin a warm water bath (92F) FOR <30 sec and placed in specially designedtransfer gun and covered with a sterile sheath.? The transfer gun is passed throughthe vagina, cervix and into the uterine horn on the side as the CL. The embryois deposited 1/3 the way up the uterine horn.
Storage andcryopreservation of embryoq Embryos can be maintained at nearbody temperature in the media used for flushing during the period betweenrecovery and transfer.q If embryos are to be held longer than2 hours u pto 10 hours ., a media containing 20% heat treated serum should beused as holding mediumq If embryos are cooled at 5c(I.
E.refrigerated) they can be maintained for2-4 days .q Cryopreservation of embryo isperformed for longer period of time.q Cryoprotectants like glycerol,glycol, and DMSO to be addedApplicationsof EETv Faster genetic improvement.v Genetic screening.v Disease control.v Import and export.
v Circumvention of infertility.v Twinning in cattlev Conservation of endangered speciesv Research; production of cloned andgenetic engineering.