Embryo
Transfer Technology (ETT)
Embryo transfer is a
technique where embryos are collected from the donor females and transferred in
to the uterus of recipients which serves as a foster mother for its development
throughout the remainder period of pregnancy.
ET refers to the technique by which fertilized ova
collected from the reproductive tract of a genetically superior female (donor)
are transferred to that of another female (recipient) which may be genetically
inferior.
What is Embryo?
A fertilized ovum which will eventually
develop into the offspring.
After 9 to 10 days of age it will hatch
and break out of its protective “shell-like” coating (the zona).
What is Superovulation?
The result of treatment of a donor with
gonadotropin (FSH or PMSG) to produce more than a single ovum.
Superovulation can be defined as increased ovulatory
response by exogenous hormone therapy, above a level that would be expected to
occur naturally.
What is Synchronization?
Matching
the estrous cycle of a donor and a recipient by the injection of prostaglandin
(PGF2 alpha) to stimulate the onset of estrus (heat).
Milestones in ET
ü 1890 The first successful embryo transfer was
carried out in rabbit by Heap.
ü 1930 Collection of first bovine embryo
ü 1949 First lamb by ETT by Berry
ü 1951 First calf by ETT by Willet et al.
ü 1964 First non-surgical collection
ü 1983 Successful ET in Asian buffalo by Drost et
al.
ü 1987 India’s first ET calf was born at
Delhi, India’s first ET buffalo calf was born at SAG, Bidaj through
non-surgical embryo transfer.
History of Embryo transfer
|
Events |
Species |
Scientist |
Year |
|||
|
First
successful ET |
Rabbit |
Walter Heape |
1890 |
|||
|
First
successful ET |
Rat |
JS Nicholas |
1933 |
|||
|
First
successful SOV |
Cattle |
Casida |
1940 |
|||
|
First
successful ET |
Sheep and Goat |
BL Warmick
& RO Berry |
1949 |
|||
|
First
successful ET |
Pig |
AV Kvansnickii |
1951 |
|||
|
First ET
reported in cattle |
Umbaugh |
1949 |
||||
|
First
successful ET |
Cattle |
EL willett |
1951 |
|||
|
Baby girl born
through ET |
Steptoe &
Edwards |
1979 |
||||
|
Calf -Frozen
thawed Embryo |
Cattle |
Wilmut &
LEA Rowson |
1973 |
|
||
|
Calf born by
ET |
Buffalo |
Drost |
1983 |
|
||
|
Calf born by
IVF |
Buffalo |
Madan et al |
1990 |
|
||
|
Calves through
surgical and non-surgical ET in Asia/India Calf born by
frozen thawed embryo |
Buffalo |
Misra et al Misra et
al., |
1988 1991 |
|
||
First calf using
vitrified embryo
Live animal (OPU/IVF)- Neglia et al., 2004
Ovaries of slaughtered buffaloes- Duran et al., 2004
Buffalo calves born through surgical &
non-surgical ET in India/Asia (Misra et al., 1988)
First buffalo calves born through frozen thawed embryo
(Misra et al., 1988)
Applications of ET
•
Faster genetic improvement/Increase
the number of offspring from a genetically superior female
•
Genetic screening of bulls for
inherited defects. Mating a bull to six or eight of his superovulated daughters
will exhibit the recessive genes a bull carries more accurately and in much
less time than by testing the population at large.
•
Disease control. Many
diseases present in the dam will not be transmitted by the embryo
•
Import and export of
frozen embryos at minimal cost.
•
To obtain offspring from valuable
females that are infertile due to disease or injury.
•
Twinning in cattle,
although 12-15% of the offspring will be freemartins (i.e. infertile females).
•
Conservation of
endangered species
•
Long-term storage by
freezing
•
Research;
production of clones and genetic engineering
•
Rapid genetic change within a small
population
Useful in utilising low
producer animals by making them recipient or surrogate mother.
Futuristic perspectives of embryo
transfer
•
Monoclonal
antibodies
•
Recombinant
DNA technology
•
PCR
•
Transgenic
procedures
•
Embryonic
stem cell research
•
Estrus
and ovulation synchronization
•
Cryopreservation
of mammalian embryos
•
IVM
& IVF
•
Cloning
by nuclear transplants
•
Twinning
•
Sexing
•
OPU
•
Embryo
bisections
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