When cows are breeding and developing, it is necessary to understand their estrus status. So how do technicians determine whether cows are in estrus? There are mainly four methods:

First: B-ultrasound rectal examination for cows: The estrus period of cows is short (12 to 18 hours). Generally, 1 to 2 breedings are sufficient during the estrus period. It is not necessary to use the B-ultrasound rectal examination for cows to determine the ovulation time. However, some malnourished cows have declining reproductive functions and slow follicle development, so the ovulation time will be delayed. Some cows may also ovulate earlier and irregularly. But most of them have slow follicle development and delayed ovulation. For these cows, their ovulation time cannot be correctly determined without a rectal examination. In order to correctly determine the breeding period, in addition to external observation, it is also necessary to perform a B-ultrasound rectal examination for cows. Through palpation of the B-ultrasound rectal examination for cows, the development of follicles can be checked, which can be divided into four stages.

①Ultrasound observation of cattle during the follicle appearance period: the follicles are slightly enlarged, with a diameter of 0.5 to 0.75 cm. When palpated, they are softened points with no obvious fluctuations. During this period, cattle generally begin to show estrus.

②Ultrasound observation of cattle during the follicle development period: the follicles enlarge to 1 to 1.5 cm, present a small spherical shape, and fluctuate significantly. In the second half of this period, estrus is no longer significant.

③Ultrasound observation of cattle during the follicle maturation period: the follicles no longer enlarge, but the follicle walls become thinner and more tense. During rectal examination, there is a sense of being broken at the touch.

④Ultrasound observation of cattle during the ovulation period: the follicles rupture and ovulate, and the follicular fluid is lost, so the follicle walls become soft and become a small depression. 6 to 8 hours after ovulation, the corpus luteum begins to form, and the depression can no longer be felt. Ovulation usually occurs 10 to 15 hours after the disappearance of sexual desire. Ovulation is more common at night than during the day, and more common in the right ovary than in the left.

The second method: external observation method

① The duration of estrus: In the early stage, the cow is excited and restless, howling, wandering, with reduced appetite, crawling and running, and it is too early to breed at this time. In the middle stage, the cow accepts to be mounted, and the hind legs are spread out. At this time, it should be mated every other day. In the late stage, the cow gradually becomes quiet, and the bull still follows and sniffs. When the bull climbs, the cow drops her buttocks and refuses to climb, but rarely runs. It is just right for breeding at this time.

② The degree of external swelling: The vulva of the cow begins to swell and red in the early stage of estrus, and the vulva swells and becomes obviously shiny in the middle stage of estrus. It is too early to breed at this time. When the swelling basically disappears and wrinkles appear on the vulva, it is the breeding period.

③ Mucus properties: The mucus that flows out of the vagina of the cow during estrus can be called estrus fluid. From the production to the end of estrus, the color of the estrus fluid changes from green to yellow or clear white. From the viscosity, its stringiness increases from small to large, and then from large to small. As a result, breeding is carried out when short yellow or white lines are seen.

④ Changes in the cervix: During the anestrus period, the cervix of a cow is relatively hard, and the rectum feels like a rubber stick. As the estrus period prolongs, the cervix becomes softer and thicker. At the end of estrus, the external opening of the cervix becomes harder, but when the internal opening is still soft, it is suitable for breeding.

⑤ When cows are in estrus, they often show excitement and restlessness, their appetite and milk production decrease, their tail roots are raised, they chase and mount other cows and accept other cows to mount them. The difference between the two is that if the cow being mounted is in estrus, it will stand still and raise its tail. If it is not in estrus, it will often arch its back and run away. When an estrus cow mounts other cows, its vulva twitches and urinates, which is the action of a bull mating. The vulva is red and swollen, and mucus flows out of the vulva.

The third method: the estrus test method: one is to place the vasectomized bull in the herd of cows, test the estrus during the day, and separate the bulls and cows at night. The estrus of the cows can be judged based on the bulls' chasing and mounting and the cows' acceptance of mounting. The other method is to bring the estrus test bull close to the cows. If the cows like to lean on the bulls and bend over and arch their backs, it means that they may be in estrus.

The fourth method: the vaginal examination method: the vaginal examination method uses a vaginal opener to observe the changes in the vaginal mucosa, secretions and cervical opening to judge whether they are in estrus. The vaginal mucosa of estrus cows is congested and flushed, and the surface is smooth and moist. The external cervical opening is congested, relaxed, soft and open, and a large amount of transparent stringy mucus is discharged, like a glass rod (commonly known as a hanging line), which is not easy to break. The mucus is thin at first, and gradually thickens as the estrus time passes, and the amount also changes from small to large. In the late estrus period, the amount gradually decreases and the viscosity is poor, the color is opaque, and sometimes contains light yellow cell debris or trace amounts of blood. The vagina of a cow that is not in estrus is pale and dry, and the cervix is tightly closed, so no mucus flows out.

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