The technique in which the cow is induced to ovulate 6 to 7 ova per oestrous cycle by injecting gonadotrophic hormones like FSH and LH is called superovulation. These eggs are allowed to fertilize and then the embryos are transferred to the uterus of the surrogate mother.
SOET involves the following steps:
1. Selection: The first step involves the selection of donor cows and recipient cows. After selection, both of them must be synchronized, so that they are at the same phase of the estrous cycle.
2. Induction of superovulation in donor cow: In this step, the donor cow is made to ovulate 6-7 ova per estrous cycle (20 -21 days) by injecting a mixture of FSH and LH. This process of production of more eggs is called superovulation.
3. Artificial insemination and recovery of embryos: The superovulated cow is artificially inseminated with semen for superior quality bull and repeated several times. The fertilized eggs are allowed to develop into an embryo. The embryos at 8-32 cells stage are recovered from the donor by nonsurgical techniques. The recovered embryos can be stored in liquid nitrogen at -196 0C is called cryopreservation.
4. Transfer of embryos: Good quality embryo is selected and transferred to the uterus of a synchronized recipient cow called surrogate mother for pregnancy and parturition.
5. Pregnancy diagnosis: After embryo transfer between 1-3 months, pregnancy is confirmed in the surrogate cow by palpation.
This technology has been used for cattle, sheep, rabbits, buffaloes, mares, etc. High milk-yielding breeds of females and high-quality meat-yielding bulls have been bred successfully.