Embryo transfer in mammals

Summary

Embryo transfer refers to the process of transferring the embryo developed in vivo or in vitro to the corresponding part of the synchronized recipient, and this foreign embryo can be implanted in the recipient's uterus and continue to grow and develop, and finally give birth to normal offspring, commonly known as artificial insemination or borrowing the abdomen to carry a fetus, which is an important foundation of gamete and embryo bioengineering technology. The use of embryo transfer can develop the breeding potential of female animals with excellent genetic characteristics and expand the herd of good breeders faster. The use of embryo transfer can make cows, horses, pigs and other fine female animals free from the long gestation period, the embryo can be taken out soon after the estrus again, breeding and fertilization, which can produce more offspring within a certain period of time. In addition, because embryos can be stored for a long time and transported over long distances, they also provide better conditions for the establishment of livestock gene banks, the introduction and exchange of breed resources and the reduction of disease transmission.

Principle

The principle of embryo transfer is based on the synchronization of oestrus in the donor (fertile) and the recipient (infertile), where the changes in the reproductive systems of the donor and the recipient are the same in the days following oestrus, and the physiological state is the same during the same period of time (corresponding to the lifespan of the cyclic corpus luteum), which provides a solid basis for the success of the embryo transfer. The embryo, on the other hand, is free in the fallopian tube and uterine cavity for a considerable period of time prior to implantation in the early stages of development, and its development depends on its own yolk for nourishment, which makes it easy for it to survive after removal, and to continue to develop when it is put back. There is no or very little immune rejection of embryos transferred between the same species, which allows the embryo to survive in the recipient. The embryo must establish a physiological and organizational connection with the recipient's uterine lining in order to ensure future development.

Appliance

Embryo transfer is often used to develop the reproductive potential of female animals with excellent genetic characteristics, to expand the herd of good breeders faster, to establish gene pools of domestic animals, to introduce and exchange breed resources, and to reduce the spread of diseases.

Operation method

Embryo transfer in mammals

Principle

The principle of embryo transfer is based on the synchronization of oestrus in the donor (fertile) and the recipient (infertile), where the changes in the reproductive systems of the donor and the recipient are the same in the days following oestrus, and the physiological state is the same during the same period of time (corresponding to the lifespan of the cyclic corpus luteum), which provides a solid basis for the success of the embryo transfer. The embryo, on the other hand, is free in the fallopian tube and the uterine cavity for a considerable period of time prior to implantation in the early stages of development, and its development depends on its own yolk for nourishment, which makes it easy for it to survive after removal, and to continue to develop when it is put back. There is no or very little immune rejection of embryos transferred between the same species, which allows the embryo to survive in the recipient. The embryo must establish a physiological and organizational connection with the recipient's uterine lining in order to ensure future development.

Materials and Instruments

Equipment:
① Disposable sterile gloves
② Surgical forceps
③ Syringe
Reagents:
① Materials: donor and recipient animals
② Gonadotropins
③ Flushing solutions: Duchenne phosphate buffer (PBS), Brinster's medium-3, synthetic oviduct fluid (SOF), Whitten's medium, Ham's F-10, and TCM-199.

Move

The basic process of embryo transfer can be divided into the following steps:
I. Preparation of donor and recipient animals
(1) The selected donor should not only be of breeding value, but also needs to be in an advantageous state in terms of reproductive function, and the utilization rate of embryos can be improved through artificial supernumerary ovulation as well as embryo splitting methods.
(2) Recipient animals should have excellent reproductive performance and health status, and be of medium to high body size.
(3) Select females with the same time of natural estrus and donor estrus, and the time of estrus of both should not be more than 1 day.
Supernumerary Ovulation
At the appropriate time in the female's estrous cycle, use exogenous gonadotropins to treat her ovaries, inducing a large number of follicles on her ovaries to develop at the same time and discharging a number of eggs with the ability to be fertilized.
C. Simultaneous est rus
(1) Control the duration of the luteal phase
(2) Use progesterone and its analogs to maintain a certain level of progesterone or its analogs in the blood to inhibit follicular development and estrus in the female, artificially prolonging the luteal phase and delaying the time of estrus. (3) Use prostaglandin F2 and its analogs to dissolve the corpus luteum to lower the level of progesterone, artificially terminating the luteal phase, and to facilitate the release of pituitary gonadotropins, thus causing the female to enter the follicle earlier than expected. This will make the female animals enter the follicular phase of ovulation and estrus in advance.
Fourth, the breeding of donor females
After the super-exclusion of the female animals, according to the needs of breeding, select the semen of good male animals at the appropriate time for artificial insemination. In order to get more embryos with normal development, semen with high viability and high density should be used, and the number of inseminations should be increased to 2-3, with an interval of 8-10 hours between two inseminations.
V. Embryo Collection and Examination
(1) The embryos are washed out of the reproductive tract with a douche solution and collected in a vessel.
(2) The collected rinse solution should be left for 10 minutes to allow the embryo to sink before examination.
(3) Use a pipette to place the egg or embryo in fresh culture medium for morphological observation.
(4) After collecting suitable embryos, those for short-term use can be cultured in vitro under the condition of body temperature in the culture medium so that they can continue to develop; if they need to be used for a long period of time, they should be treated with cryopreservation or freezing, so as to make the embryos stop developing and delay the time of their survival in vitro.
VI. Embryo transfer
The location of embryo transfer should be determined according to the normal developmental rate and running position of the embryo in the body of the animal (generally, the embryo with less than 8-cells is transferred into the oviduct).

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