Animal B-ultrasound observation of estrus is a cyclical reproductive physiological phenomenon closely related to ovulation in empty-stomach cows of reproductive age. Complete estrus should have the following four physiological changes:

① Changes in mental state, excitement, sensitivity, increased activity, decreased appetite, and decreased milk production during the peak period of milk production;

② animal B-ultrasound observation of changes in the vulva and reproductive tract, swelling and congestion of the labia, mucus outflow, flushing and smoothness of the vaginal mucosa, and opening of the cervix;

③ Sexual desire manifestations, successive attempts to approach the bull, mount other cows, and accept mounting by bulls and other cows;

④ Ovarian changes, rapid development and maturation of follicles and ovulation

Under certain physiological and pathological conditions, abnormal estrus with incomplete physiological manifestations mentioned above may also occur. For example, quiet estrus: mature follicles and ovulation on the ovaries, but no other external manifestations; anovulatory estrus: estrus manifestations, but no ovulation, or even no mature follicles in the ovaries. The above conditions will interfere with the estrus identification and breeding of cows.

Animal B-ultrasound observation of estrus cycleEstrous is a regular cyclical reproductive physiological phenomenon. The time interval between two adjacent estrus or ovulation is the estrus cycle. Each estrus cycle

① Proestrus, the functional corpus luteum on the ovary in the previous cycle has degenerated, the follicles that are about to ovulate develop rapidly, and other estrus symptoms appear one after another, but the cow does not accept bulls or cows to mount;

② Estrus period, the follicles mature, followed by ovulation, other symptoms are further strengthened, sexual desire is obvious, and accepting bulls and other cows to mount is the most obvious feature;

③ Late estrus, the cow has ovulated, the corpus luteum is forming, and other symptoms begin to subside;

④ Diestrus is the functional period of the corpus luteum of the cycle, and the cow returns to normal. Follicles develop slowly or stop developing, accompanied by follicle degeneration and atresia.

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