Embryo Transfer

       Embryo Transfer is also called ovum transfer. In 1890, the idea of embryo transfer was given first time. Its common use started in 1970.

“It is the collection of the fertilized ovum from the donor prior to its attachment/nidation with uterus and transfer into surrogative/recipient mother for completion of gestation period.”

or

“Collection of embryo from donor cows & transfer to the recipient cows where they carry till term or completion of term.”

 

      When embryo is embedded in endometrium of uterus is called as nidation. This term is used in mare and porcine. But in buffalo, cattle, sheep, goat there are specific areas/ cotyledons where attachment of embryo occurs.

       The cow from which we get the embryo is called as donor. The cow in which we transfer embryo is called recipient. In the offspring 50% characters come from mother and 50 % from father. In AI, semen is inseminated in different cows. The genetic potential of male is distributed which is same for all cows but different cows have different potential. In embryo transfer genetic potential of female is being distributed. Every cow produces one egg at the time of estrus. Donor cows are induced to produce more than one egg at the time of estrus, inseminate these eggs and fertilized eggs/embryos are taken from donor. At the same time recipient cows are also prepared which have low genetic potential and one embryo is placed in each cow. In this way more than one calf can be obtained from one donor.

        If donor cow has high potential of production, we do not let it to become pregnant and after two months we get eight eggs. In this way we get 40 embryos in a year (5 times a year). If 60 % is birth rate then we can get 24 calves from donor cow in a year otherwise only one calf in a year.

        The fertilization site in bovine is ampullary isthmus junction in animal. The reason is that this portion contains more ciliary epithelium, increased secretion, and increased suitable environment for fertilization. In mare only fertilized ovum descends down in uterus but in bovine ovum stays for 2-4 days and then descends down. In bitch this duration is 9-10 days. When it descends down, remains in wandering position in uterus for some days and gets nutrition from uterine m1ilk and then gets attachment.

 

Advantages of Embryo Transfer

• It improves the genetic potential.

• It increases the productivity

• It increases the economic benefit

• It increases the disease resistance

• It increases the no. of calves in life time

• It reduces the generation interval.

• It increases the selection intensity.

• Import and export is easier because it is done in the form of embryo transfer in which transportation is easier, genetics is diversified, and cost is decreased.

      The study of physiology and pathology of ovario-uterine pituitary hypothalamic was the main purpose of ET but later it became commercialized.

 

 

Steps of Embryo Transfer

a. Selection of donor

b. Selection of recipient

c. Synchronization of donor and recepient

d. Superovulation of donor

e. Insemination of donor

f. Collection of embryos

g. Evaluation of embryos

h. Transfer or storage of embryos.

 

Selection of Donor

• It should be from known fertile blood line i.e. we must have pedigree record and donor should have calved at least once a year so selection of heifer donor is not required.

• It should have calved once earlier so heifer as a donor is not required.

• Donor should have known calving history or easy calving history.

• It should be regular cyclic animal.

• It should be disease free animal e.g. T.B, brucellosis

• It should be vaccinated animal.

• It should be high producing, reproduction wise normal, and three years of age without any disorder.

 

Advantages of Embryo Transfer

(1): Genetic Improvement:

E.T is best for increasing genetic potential for female while AI is for male. Out of 8-10 embryos, 6-8 are transferable and 3-4 pregnancies occur. If repeated five times a year from15-20 calves will be produced. So donor cow with good potential will produce15-20 calves a year.

(2): Selection Intensity:

ET will increase the selection intensity among the calves. Research says that if a cow gives six calves in a year then selection intensity becomes double.

(3): Planed Mating:

We can plan to select the bull with high genetic potential to mate with the cow which is going to give 8-10 calves.

(4): Genetic Testing:

Commonly it is done to null out the deleterious genes. Cows that are carrier and mated with a carrier bull, offspring will be affected. So such bulls are rejected for AI