The use of gonadotropins and steroids, if the period of follicular wave development is not known, can accelerate the first ovulation and estrus week of the cow after delivery, but the results are inconsistent. It can cause confusion when given certain treatments. In the early postpartum period, the development of ovarian follicles and ovulation are not related to estrus. In addition, it is easy to make the average estrus identification efficiency of the cow only 40% to 60%. Therefore, physiological anestrus cannot be distinguished from the identification of anestrus, especially for a fixed number of days after delivery. Pay close attention to the response and characteristics of the ovaries. It is very important to observe the ovaries of cows with B-ultrasound after delivery. In order to have an effective effect on postpartum cows, it is necessary to find a suitable treatment time. The time of the first estrus of cows after delivery, in addition to the prolongation of the postpartum estrus due to old age and weakness, malnutrition, improper feeding and management, and the environment will also delay the estrus of cows after delivery, resulting in ovarian hypofunction and slow recovery of reproductive organs, which will affect the delay of estrus after delivery in cows. Use B-ultrasound to observe the condition of their ovaries after delivery. In order to make the cows estrus normally after delivery and shorten the calving interval, in addition to strengthening feeding management, 25 mg of prostaglandin (PGF) and oxytocin are injected into the cows' muscles 25 days and 40 days after delivery, respectively. The cows' B-ultrasound observation shows that the estrus time after delivery can be significantly advanced, thus shortening the delivery interval and improving the cow's fertility.

For cows whose ovaries are in a dormant state after delivery, with no functional corpus luteum or poorly developed corpus luteum, gonadotropins such as PMSG or LHRH can be used to stimulate the cow's ovarian function and promote follicle development, which can be clearly observed on B-ultrasound for cows. Oxytocin (OT) can shorten the first estrus after delivery, and PGF can significantly shorten the time from calving to the first mating. The lack of crude protein in postpartum cows reduces the secretion of FSH and LH and the response of ovarian follicles to GnRH, thereby affecting the growth and development of ovarian follicles.