The estrus of cows is a rhythmic biological phenomenon. Cattle are animals with multiple estrus cycles throughout the year, meaning they can estrus throughout the year without any seasonality. When the weather is warm and the grass is good, estrus is obvious, and mating is more prone to conception. When imported cattle are observed by ultrasound, follicular development is also better during this period.

In order to accurately grasp the estrus time of cows and improve the detection rate and insemination rate of estrus cows in the herd, artificial insemination personnel and breeders should grasp and be familiar with the basic situation of the cattle they are responsible for. At least 2 careful inspections should be conducted every day, preferably using imported cows and B-ultrasound to observe whether there are estrus cows.

The estrus cows detected by B-ultrasound for imported cattle, regardless of whether they are bred this time, must be registered for the next inspection of these cows. Breeders, grazers, or professional cattle breeders should also pay attention to the dynamics of their cattle, observe whether they are in heat, and promptly fertilize the estrus cows. The key to accurately monitoring the estrus of imported cows is to determine the effectiveness of their conception through ultrasound examination.

Generally, cows in normal estrus have more obvious external manifestations, so external observation combined with vaginal examination can be used to determine. But the estrus duration of cows is relatively short, and if not observed carefully, it is easy to miss mating. It is best to use imported cows for B-ultrasound. In production practice, duty officers, caretakers, and milkers can be mobilized to observe together. Establish a cow estrus prediction system, predicting the next estrus date based on the previous estrus date (calculated according to the estrus cycle).

It is necessary to determine the ovulation time of some cows through rectal examination or imported cattle using B-ultrasound examination, as they often experience quiet estrus or false heat, malnutrition, decline in reproductive organ function, slow follicular development, delayed or advanced ovulation time.

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