To prevent abortion in the middle and late stages of pregnancy, after the first mating, the sheep are examined with B-ultrasound. If the ewe is not found to be in estrus for two consecutive estrus periods or is confirmed to be pregnant by pregnancy diagnosis, it can be considered that the sheep is pregnant and can be confirmed by B-ultrasound. The gestation period of ewes is 150 d±5 d. The first three months are the early and middle stages of pregnancy. The embryo is very small and develops slowly. The last two months are the late stage of pregnancy. It can be seen from B-ultrasound observation of sheep that more than 85% of the weight of the fetus is formed at this time. Therefore, the nutritional requirements of ewes in the late stage of pregnancy are more than 10-15% more than those in the early and middle stages to ensure the normal growth and development of ewes and fetuses. Feeding management in the late stage of pregnancy must be strengthened. Do not easily inject drugs or feed moldy and rotten forage and feed. Actively avoid external stimuli such as crowding and rushing of the flock to prevent premature birth, abortion, stillbirth and dystocia.

In short, from the experience gained from decades of artificial insemination and mating in some sheep breeding farms, the effective application of the above measures has improved the conception rate of grazing ewes, and the average conception rate has increased from about 60% of natural grazing to more than 95%; through the rational use of excellent breeding rams, the comprehensive quality and production level of the offspring of grassland grazing ewes have been significantly improved, and the economic value of grassland pastoral production ewes has been fully reflected, which has played a positive role in promoting the improvement of pastoral varieties, increasing the income of farmers and herdsmen, and accelerating the modernization of animal husbandry in grassland pastoral areas. Of course, in the usual feeding and management, it is necessary to use sheep B-ultrasound for regular inspections. The best time for artificial insemination and mating of ewes is about 6 hours after estrus (generally when estrus is found). Under the observation of sheep B-ultrasound, the first mating can be carried out, and the next day, the mating is supplemented. It is advisable to mate twice in each estrus period. Ewes with special goals for flock quality and sheep breeding farms should make a selection plan in advance, and keep relevant data records during mating to improve breeding results.

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