EMBRYO TRANSFER

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8-cell embryo for transfer 3 days after fertilization

EMBRYO TRANSFER

Objectives

Definitions

History

Animal components of

ET Program

Advantages and

Disadvantages of an ET Program

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Contents

Management of

components of ET

Program

Super-ovulation

Flushing Freezing

Transferring

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Objectives

1. To introduce the process of super-ovulation and embryotransfer (ET) in cattle and horses.

2. To provide an overview of the advantages anddisadvantages of ET in cattle and horses.

3. To review the process of ET including flushing,searching, handling, grading, freezing, thawing, andtransferring embryos.

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What is Embryo Transfer

Multiple injections of hormone to stimulate and multiplythe ovulations in the cow that you want to get theembryos from (Cruachan.com)

Step in the process of assisted reproduction inwhich embryos are placed into the uterus of a femalewith the intent to establish a pregnancy (Wikipedia.com)

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History of Embryo Transfer

1890s: First successful embryo transfer

1971: First successful embryo transfer between donkeysand horses

1974: Birth of horse foal following non-surgical embryotransfer to recipient mare

1984: Foals born in Japan produced using frozen embryos

1984: First successful embryo transfer between two equinespecies (zebra-horse)

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History of Embryo Transfer

1990s: Embryo transfer procedure starts to take off inArgentinean polo ponies

2002: University of Sydney claims first sex sortedpregnancy by embryo transfer

(Reproduction-online.org)

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Comparison Of Importing Germplasm As

Postparturient Animals, As Semen Or As

Embryos

Advantages Disadvantages

Post parturient animals

Animals productive

quickly

Expensive

Animals often succumb to disease

Chance of introducing exotic

disease

Complex transportation logistics

Limited immediate genetic

influence if females are imported

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Semen

InexpensiveNeed to grade up to get pure-bred animals*

Low risk of diseasetransmission

Need for Al technology

Hybrid vigor, F1 and F2* Long wait until animals productive

Simple transportationlogistics

Passive immunity fromnative dam

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Comparison Of Importing Germplasm As

Postparturient Animals, As Semen Or As

Embryos

Embryos

Very low risk of diseasetransmission

Need for ET technology

Costs may be lower thananimals

Long wait until animalsproductive

Simple transportationlogistics

Passive immunity fromnative dam

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Comparison Of Importing Germplasm As

Postparturient Animals, As Semen Or As

Embryos

Animal Components of ET

ProgramDonor: animal that donates embryos

Selection criteria are used to select a donor.

Embryo from a donor cow does not guarantee a superiorcalf.

Reproductive soundness

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Animal Components of ET

ProgramRecipient – animal that receives embryo from the donor

Surrogate

Criteria for selection

Pregnancy rates

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ET Process

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Super-ovulation

Process of super stimulating the ovaries with FSH toproduce multiple oocytes.

Includes frequent treatment of females with FSH for aperiod of four days.

Females are administered prostaglandin during the thirdday of FSH injections to regress any CL present.

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Flushing

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Flushing

12-24 hours at a pH of 7.1 to 7.5 when holding mediais changed every few hours. Excessive temperature harmsembryos (39oC).

Embryos are classified by stage of development andgraded based on gross morphological appearance.

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In-vitro Fertilization (IVF)

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Vitrification & Recovery

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Vitrification & Recovery

20(International Livestock Research Institute, 2015)

Freezing

1) Cryoprotectants are used to dehydrate cells and protectthe cells of the embryo during the freezing and thawingprocess.

Direct transfer (DT) embryos- embryos frozen in ethylene glycol

2) Embryos are equilibrated for 5 to 10 minutes incryoprotectant freezing medium.

3) Embryos are frozen in a step-wise procedure in a specialfreezing machine.

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Types of ET

Surgical

Vs. non-surgical transfer, it is more time consuming,expensive, labor intensive, and riskier to the recipientmare but more successful than non-surgical methods.

A surgical incision is made into either:Midventral LaparotomyFlank Incision Procedure

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Types of ET

Nonsurgical

Position embryo in sterile pipette in medium between twoair spaces.

Manually guide pipette through cervix into uterus.

Deposit embryo in uterine body

(Betteridge, 2015)

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The Difference Between Surgical

And Non - Surgical Transfers

Surgical transfer places the embryo further up theuterine horn than non-surgical.

Surgical transfer requires a small cut in the cows flank onthe side of the ovulation.

The uterus is pulled out and a small hole is made to theuterus. A small catheter is placed in through the hole andthe embryo released.

Non surgical is the same as A.I. The embryo is placed inthe side of the ovulation and released from the gun.

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Transferring

Embryos can be transferred in two different manners

A. Same day transfer

B. Transfer of Frozen Embryos

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Process of Transferring Embryo

1. The recipient is palpated to determine the presence andlocation of the CL (right vs. left).

2. If the embryo is frozen it is thawed in a warm waterbath (92°F) for <30 sec and placed in a speciallydesigned transfer gun and covered with a sterile sheath.

3. The embryo is deposited 1/3 the way up the uterinehorn.

4. Pregnancy rates

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Embryonic Development

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Oocyte Zygote 4 cell

8 cell BlastocystMorula

Conception Rate

Rate should be 5-10% higher than artificial insemination, but a lot depends on the condition of the recipients.

A.I. program the conception rate is 60-65%

Embryo transfer program it is expected roughly the same sometimes a bit higher (Cruachan.com)

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Pregnancy Diagnosis

The fetus can be sex scanned between days 56 to 65 of pregnancy as by then subsequent losses should be minimal and it can be useful to know whether a bull or a heifer ET calf is expected (Xlvets.co.uk)

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END

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