Early embryonic death

Early embryo death is one of the important factors affecting the reproduction rate of livestock. The embryonic mortality rate of livestock is about 25% to 40%. Pigs are multiparous livestock, embryo death is more common and the embryo may die at any stage of development, especially before or during the implantation of the embryo to the endometrium, which is the most critical period of pregnancy identification. When sows are in a bad environment, lack of nutrition, disease and so on, embryo death is more serious. The first peak of embryo death in sows is 9-16 days after zygote implantation, and the embryo is easily affected by various factors, with a mortality rate of about 40%-50%. The second peak is in the third week after mating, with a mortality rate of about 30%-40%. However, under normal circumstances, the death of a small number of embryos will not affect the normal progress of pregnancy. The main results are as follows: 1 genetic inbreeding is one of the important causes of embryo death in livestock. The smaller the difference between males and females of the same species, the greater the embryo death. Because inbreeding can lead to low fertilization affinity and weak embryo vitality. Genetic studies have shown that chromosome abnormalities such as triploids are associated with embryonic death. Variations in chromosome structure, such as translocation (boar 38 minutes XYt) and deletion, can also cause early embryo death. Individuals with genotypes composed of bad genes, that is, embryos with genetic defects also die in the early stage of pregnancy. (2) nutritional factors in general, long-term low nutritional level or lack of some nutrients will not only reduce the number of ovulation and fertilization rate, but also lead to embryo death. The embryo death of sows was the most serious at 3 days after mating. If feeding is properly restricted within 7 days after mating (feed intake is controlled at 50%-60% of free feed intake), embryo death can be reduced. However, feed restriction will not only cause severe pain caused by hunger in pregnant sows, but also prolong the retention time of digestive tract contents in the intestines, and the harmful gases (such as H2S) are absorbed into the blood circulation and cause embryo death (Lu Jianwei, 2000). Severe malnutrition in the early stages of pregnancy leads to a decrease in embryo survival (Speer,1990), mainly because some embryos die due to lack of nutrition. High nutritional levels in the early stages of pregnancy can reduce embryo survival by 5 per cent (Hughs,1989). Toplis confirmed that increasing intake in early pregnancy can reduce embryo survival in parturient sows. Because within 3 weeks after mating, fertilized eggs need little extra nutrition to form embryos, sows are given a low level of rations (DE