The anestrus of dairy cows can be divided into temporary or long-term. It is related to factors such as lack of lactation, low nutritional level, old cows, genetic defects, etc., and is directly affected by reduced pituitary function, ovarian hypoplasia and ovarian atrophy. These functional disorders can basically be diagnosed through B-ultrasound examination of cattle. Nutrition is closely related to reproduction. Cows are given 50% of the standard feed in their early years and are restricted to feed, which inhibits physical maturity and delays the first estrus. Long-term poor feeding conditions affect the growth of cows. Some cows are not big at the age of 2. The reproductive system such as the uterus and ovaries are very small when examined by B-ultrasound of cows, and estrus is not seen for a long time. Long-term lack of green feed, lack of vitamin supplementation, or long-term stress state of cows may inhibit the functional development of ovaries and make them not estrus. On the other hand, due to abnormal nutritional metabolism, high-yielding dairy cows may affect the reproductive endocrine function, resulting in no estrus or abnormal estrus performance of cows, which can be observed more clearly on B-ultrasound of cows. Therefore. The reproduction of high-yielding dairy cows should be taken seriously. When B-ultrasound is used to observe the presence of a persistent corpus luteum on the ovary, the cow does not show estrus. Or it may be caused by an ovarian corpus luteum cyst. The corpus luteum of the cyst continues to secrete progesterone, which can inhibit the secretion of gonadotropin from the pituitary gland, so that the ovarian follicles cannot develop, and the cow will not show estrus. This process is more obvious when observed on B-ultrasound for cows.

Abnormal estrus may be caused by malnutrition, poor feeding management, hormone secretion disorders, diseases, etc. This type of disease can be clearly judged by B-ultrasound for cows. The common ones are as follows: quiet estrus, short estrus, intermittent estrus, continuous estrus, post-pregnancy estrus, and estrus. Most of them are caused by endocrine disorders in cows.

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