Cows are in intermittent estrus. Cows are in estrus intermittently and the estrus lasts for a long time. This is caused by the alternating development of follicles. The alternating appearance of follicles on the cow's ovaries can be seen on the cow B-ultrasound. The first follicle to develop degenerates halfway, and another new follicle is developing. The process of follicle degeneration can be clearly seen on the cow B-ultrasound. The two follicles produce estrogen alternately, thus producing intermittent estrus. It is common in early spring and malnourished cows. When the feeding tube is strengthened and the cow enters normal estrus, it can still be bred and conceived.

Post-pregnancy estrus (false estrus): Cows still have external manifestations of estrus after pregnancy, which is called post-pregnancy estrus or false estrus, but when observed by cow B-ultrasound, the production of corpora lutea is seen on the ovaries. There are several situations in which cows go into estrus during pregnancy: some pregnant cows have insufficient progesterone secretion from the corpus luteum and hyperfunction of estrogen secretion from the placenta due to disordered hormone function; some cows are still in estrus in the early stages of pregnancy, and many follicles are still developing in the ovaries, resulting in increased estrogen content. This kind of early abortion caused by estrus after pregnancy is called "hormonal abortion". When identifying estrus for cows that are still in estrus after mating, special attention should be paid to B-ultrasound examination for cows, otherwise it is easy to mismatch and cause artificial abortion.

Except for the infertility of opposite-sex twin infertile cows, the absence of estrus and abnormal estrus of cows can be improved by improving feeding management and eliminating the cause, especially the use of prostaglandins and their analogues for treatment, which can achieve significant results. B-ultrasound examination can be performed first, and then symptomatic treatment can be given to cows.