Embryo transfer is the most advanced method for breeding the excellent breeds of grass-eating livestock, such as cattle and sheep. The so-called embryo transfer is through the superovulation technology of the fine breed cattle and sheep embryos (about 7 days of fertilized eggs), artificially transplanted to the general species of cow sheep in the womb develop into a fetus, and finally produce excellent varieties of cattle and sheep the process of. This technology is particularly important for the improvement of the low performance varieties of cows, beef cattle, goats and sheep in China. From a technical point of view, the owner of the embryo provides a donor, and the owner of the embryo accepts the recipient. The current foreign donor species that are currently participating in the improvement of herbivorous livestock breeds in China are: Holstein cows, Limousin, Charolais, Angus beef cattle; Boer goats, Dorset, Suffolk, Texel, German Merino, Dorper sheep. The recipients are mainly low-yield dairy cows, yellow cattle, crossbred cattle, local goats and sheep throughout China. In embryo transfer, the donor gene is required to have high purity, good personal appearance, strong reproductive function, healthy receptors, and no reproductive disease. It is best to have a history of production. The age of 2 to 6 years is preferred. Embryo transfer technology is divided into frozen embryo transfer and fresh embryo transfer. The frozen embryo transplantation is to first perform superovulation on the donor, and then produce embryos to freeze after mating, and perform off-site or local transplantation at other times. Embryo transfer refers to the production and transplantation of embryos at the same time and place. In contrast, fresh embryo transplantation has a pregnancy success rate that is about 10% higher than that of frozen embryo transplantation. Among them, the success rate of the embryo transfer of Boer goats is more than 60%, and the success rate of pregnancy with frozen embryo transplantation is only about 30%; the success rate of fresh embryo transfer of sheep, cows and beef cattle can reach 60%. The pregnancy success rate is about 50%. Embryo transplantation has strict technical regulations. The donor's body condition, reproductive function, super-discharge of used drugs, and technical personnel's practical experience can affect the quantity and quality of embryo production; the body condition of the recipient, reproductive function, and technical personnel. The practical experience also affects the success rate of pregnancy after transplantation. The process of embryo production is: selecting donors, estrus in the same period, playing superovulation drugs, mating, embryos, and cryopreservation; the embryo transfer process is: selecting recipients, estrus synchronization, thawing embryos, and transplantation. At present, China is mainly engaged in embryo transfer work of agricultural scientific research institutions of scientific research personnel, professional teachers and some of the enterprise technicians specialized in embryo transfer work. Due to the short history of embryo transplantation technology in China, the number of technical personnel who can engage in full-scale technical work is limited, and they cannot meet the needs of low-quality cattle and sheep breeds throughout the country. Therefore, the Ministry of Agriculture is taking measures to encourage organizations engaged in embryo transfer to cultivate talents through various channels to expand the team of embryo transfer in China, improve the technical level of technical personnel, and accelerate the progress of the improvement of China's cattle and sheep breeds.
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