It takes 6 months for the follicles of ewes to mature (from primordial follicles to mature follicles). In the process of directional follicle development to gonadotropin-dependent follicles, a large number of follicles are atretic, and this process can be clearly seen on sheep B-ultrasound. Although good nutritional conditions cannot prevent the atresia of follicles, good nutrition during the critical period can reduce the number of atretic follicles, thereby increasing the ovulation rate of ewes. Therefore, according to sheep B-ultrasound, the actual number of ovulations of ewes depends largely on the long-term feeding system, including the supply and quality of forage. Of course, the short-term nutritional status before mating will also affect the ovulation rate.

Research in this area plays an important role in guiding sheep production. The ewes are in the negative nutritional balance stage of early lactation in the 6 months before the next mating season. Therefore, according to sheep B-ultrasound, the effect of insufficient nutrition on the ovulation rate during this period can be overcome by short-term good feeding before mating. However, the nutritional limitation of ewes in the first two months of mating cannot be compensated by short-term supplementary feeding alone. This requires us to pay attention to the nutritional level before mating in the practice of mutton sheep breeding. It should at least be kept at the maintenance level or slightly higher than the maintenance level. The nutrition can be judged by observing the body condition of Sheep Using B-ultrasound.

The effect of nutrition on embryo survival rate The lambing rate of ewes is not only affected by the number of ovulations and the number of fertilized eggs, but also by the embryo survival rate. Nutrition in the first month after egg fertilization is a key factor affecting embryo survival rate. Nutritional status before and after ovulation will affect embryo survival. The nutritional status before ovulation affects the quality of the egg, and the nutritional status after ovulation affects the cell division of the early embryo by affecting the formation of ovarian and uterine secretions. Early embryos are sensitive to nutritional factors. It is necessary to frequently use sheep B-ultrasound to observe embryos. Excess or deficiency of certain nutritional factors may affect the survival rate of embryos, especially 11-12d embryos. Of course, the embryos in the early pregnancy can be observed by sheep B-ultrasound.

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