"Ostophoresis" is an abbreviation for embryos or fertilized eggs. Its characteristic is that the fertilized egg is taken out from the excellent cow (donor), cryopreserved and transported, and then other cows (recipients) are transplanted into the uterine horn or fallopian tube to develop and deliver. The yak has similar characteristics as the donor cow. Therefore, it has an extremely important practical value for the full play of the reproductive potential of excellent cows, the promotion of the use of excellent female gametes, and the acceleration of herd improvement. It also plays an important role in the study of animal genetics and reproductive physiology. The egg migration process includes superovulation, embryo collection, embryo preservation, and embryo transfer. (a) Superovulation is also called "superovulation." Refers to the hormone treatment of the donor cow, so that it can estrus, and can discharge a large number of mature eggs, a reasonable method of artificial insemination, in order to obtain a stable number of transplantable embryos. Treatment method: 9-13 days after the cow's estrous started intramuscular injection of follicle stimulating hormone (FSH), each dose of 50IU, twice daily, each time interval of 12h, continuous injection of 4 days, a total of 8 times. At the 48h, 60h and 72h after the first injection of follicle stimulating hormone (FSH), chloroprevalonol was intramuscularly injected. 2mg. It was observed that cows developed estrus 30 to 60 hours after the first use of cloprostenol. The duration of superovulation treatment is not the same as the use of hormones. On the 16th day of the sexual cycle, intramuscular injection of 2 500 IU of fertile equine serum, 2000 IU of intravenous human chorionic gonadotropin (HCG) at 20-21 days; On the 8th to 14th days of the cycle, intramuscular injection of 2000 IU of gestational horse serum was performed. After 48 hours, prostaglandin F2a (33 mg) was injected intramuscularly. The number of super-discharges is related to the dose of hormone. The dose is too large and the number of ovulation is too much, which can easily damage the ovarian function. Usually, it is appropriate to use about 10 eggs per female steak; when the number of ovulation is 11-21, fertilization rate, recovery rate and conception rate can be reduced. For super-disposed cows, the estrus performance of the cows should be carefully observed and should be observed 2-3 times a day. Because there are more cross-cattle cows in the herd, it can be checked with an opener to ensure accuracy. When the cervix is ​​fully opened and a proper amount of mucus flows out, it is estrus. The artificial insemination time begins when the cow receives another cow's climb. The frequency of artificial insemination and number of insemination times for superovulated cows were reported differently. They were inseminated 12h or 24h after the estrus was superovulated, and were inseminated at 48h after treatment with cloprostenol. Regarding the frequency of insemination, there are three times (8h, 16h, and 24h) of insemination for one insemination, and it is generally believed that increasing the number of artificial inseminations for superovulation cows can increase the fertilization rate of the superovulated cows. (b) Embryo collection is also referred to as "occupation." Usually the time of embryo collection is 3-7 days after the cow is estrus. There are two methods of embryo collection, surgical and non-surgical. The non-surgical collection method has been widely used. German-style second-way picking tubes are used for non-surgical collection of embryos. Operation method: The cow stands Baoding. Local anesthesia or use a low dose of general anesthetic to make it quiet. Pull out the accumulated feces in the rectum. Thoroughly and thoroughly cleanse the hindquarters of cows with 0.1% benzalkonium bromide and wipe the vulva with 75% alcohol. Insert the stainless steel core in the two-way picking tube to make it straight, direct the straight oviduct into the vagina to the vaginal vault, and assist the other hand in the rectum. Slowly insert the catheter into the uterus, about 5cm into the horn of the uterus, pull out the inner core of the oviduct about 2cm, and then let the tube fall along the direction of the uterine horn and enter the deep part of the uterine horn. In this process, the assistant takes out about 2cm of the inner core, and the operator will send the tube into the uterus for the appropriate length until the tube is sent to the proper position of the uterine horn. One way in the picking tube is the "air path", that is, through it to inflate the balloon; the other way is the "water path." That is, infusion into the uterus and recovery of the flushing fluid. The inflated balloon fixes the uterine horn near the big corner of the uterine horn. At this time, the stainless steel inner core of the oviduct was completely withdrawn, and 20--30 ml of the flushed egg was injected into the uterine horn through the oviduct via a 50 ml syringe, and then the flushed egg was drawn into the syringe. Ovum fluid gradually increased from 20ml to 50ml, and each side of the uterine horn shared 500ml of flushed egg fluid. The recovered oocytes were gently injected into a 500 ml egg collection cup and allowed to stand for 30 min. The upper liquid was slowly aspirated. The remaining 30 ml of flushed eggs were placed in a plurality of petri dishes with a diameter of 10 cm and examined one by one under a microscope. The embryos that have been examined are moved into the culture fluid and stored. (c) Genes used for embryo conservation and flushing of embryos are common. More suitable are inactivated phosphatidylserine buffers (pbs). Its composition: sodium chloride 8g, potassium chloride 2g, disodium hydrogen phosphate 1.15g, potassium dihydrogen phosphate 0.2g, calcium chloride O. 1g, 0.1 g of magnesium chloride, 32 mg of sodium pyruvate, 1 g of glucose, 4 g of bovine serum albumin, 25 mg of kanamycin, 5 mg of phenol red, and 1,000 ml of distilled water. Calf serum 20%, pH 7.2, stored at -20°C. (IV) Transplantation techniques Transplantation techniques include surgical methods and non-surgical methods. Nowadays, non-surgical transplantation is widely used. Embryos that are flushed out should first be assessed for quality using a combination of morphological observation and in vitro culture, before finally determining whether they are transplantable embryos. Morphological observations were performed under a stereomicroscope and amplified 80-fold. The standard for transplantable embryos is that the embryonic development coincides with the date of collection; the morphology is typical, the zona pellucida is intact or slightly damaged; the embryo structure is clear, or the defect is slight; the cell highlights the whole or dark part of the embryo not exceeding one fifth of the total embryo volume. . In vitro culture: Embryos with too large proportion of dark color or overemphasized whole embryos are incubated at 37°C for 2-4 hours, if they are transplantable embryos. The embryos cultured in PBS were grasped by the rectum to the cervical insemination method and injected into the deep part of the uterine horn.