Assisted repro technologies: embryo transfer

Question 1

What does Embryo transfer mean?

Answer 1

The transfer of an embryo, derived from the mating of genetically proven, valuable parents into a fertile but less valuable recipient. She then carried the pregnancy to term and weaning.

Question 2

What isn’t permitted in thoroughbred horses?

Answer 2

AI and ET

Question 3

What are the 6 steps involved with embryo transfer?

Answer 3

1) Selection- of genetically superior dam/ sire
2) Synchronisation- of donor and host females
3) Superovulation- of donor (not in horses)
4) Insemination- of donor with semen
5) Recovery- removing viable embryos from donor female
6) Transfer -put viable embryos into host females

Question 4

What are the advantages of embryo transfer?

Answer 4

• Maximise reproductive ability of high value animals
• Speed up genetic improvements
• Able to get around infertility issues
• Athletic females able to remain in work
• Less disease risk from moving liver animals

Question 5

Discuss the synchronisation of cycles for ET

Answer 5

• Ideal for the host to be a few days behind donor: allows embryo to settle in and release maternal recognition factors; prevent lysis of CL
• Its ok if host/ donor at same point, but bad if the host is in front of the donor as CL lysis may have already started.

Question 6

What are the methods for synching cycles?

Answer 6

• Progesterone: inhibits HPO axis so FH/ LSH inhibited. Also withdrawal of P4 mimicks lysis of CL
• Use PGF2a to lyse an existing CL, if you administer it to the host a few days after donor then you can get the ideal cycle synch.

Question 7

Why can’t you superovulate the mare?

Answer 7

Because ecG has very low level of affinity. ALso due to the ovulatory fossa- multiple follicles trying to ovulate at one time results in them competing so they are leutinised before they manage to ovulate.

Question 8

Which gonadotrophins are used for superovulation in cattle?

Answer 8

• eCG
• PSMG (pregnant mare serum gonadotrophin)
• FSH

Question 9

How are the eggs collected?

Answer 9

• A non-surgical, trans cervical flush of uterus using a catheter around day 7
• Medium is then filtered
• Transferred to recipient, embryo continues to grow and implant.

Question 10

Why do you collect the eggs between days 6-7?

Answer 10

• Because they have entered the uterus BUT are unattached
• The ZP is still intact, they are more fragile when they have hatched
• Can be collected through catheter with minimal damage.

Question 11

How do you transfer the eggs into the host?

Answer 11

• Transfer it to the horn on the same side as the CL

- Can have non surgical transfer or surgical transfer

Question 12

What are the key points for a successful ET?

Answer 12

• Fertile donors
• Quality embryos
• Cleanliness
• Gentle manipulation of cervix