When cows are in estrus, sexual desire and external performance are generally obvious, and estrus can be divided into three periods.
Early estrus: The cows are excited, Cleisthenes barks, swims and loses appetite. The labia is swollen and shiny, and the bull below can't climb up. Open examination showed that the cervix was slightly open, with less mucus, and the insertion of the cavity opener was resistant. This period generally lasts 15 hours.
In high estrus, cows swim less and accept bulls to climb. Open cavity examination, mucus increased significantly, vaginal congestion, no resistance when inserting the cavity opener. During rectal examination, one ovary was slightly enlarged and the desire for courtship was strong. This period generally lasts 15 hours.
At the end of estrus, the cows gradually turned calm. When the bull crawled over, the cow turned to avoid, but rarely ran. Incision examination showed that the amount of mucus decreased and the cervix was closed. During rectal examination, follicles are enlarged. This period generally lasts 13 hours.
Breeding practice has proved that the conception rate of cows is only about 5% when they are mated in the early estrus. The mating pregnancy rate at the peak of estrus is about 50%; When mating at the end of estrus, the conception rate is 70%~80%. It can be seen that the end of estrus is the best time for mating.
In order to accurately grasp the best time for breeding, the following methods should be adopted: if the cow is found to be stable in the morning when the bull climbs, don't breed immediately, and postpone breeding until evening or the next morning; If you find that the cows are stable after climbing in the afternoon, you should postpone breeding until the next morning or evening. In the morning and evening, the environment is quiet, and the cerebral cortex of dairy cows is in a state of inhibition, but the excitability of reproductive system is relatively enhanced, ovulation is fast, and the pregnancy rate is high. In order to be more sure, breeding can be repeated at intervals of 10 hour.