Doing sow estrus identification work is very helpful for doing a good job of pigs' timely delivery and increasing the conception rate and the number of litters. China's local breed pigs have a strong fertility. In addition to the high strains of the breed, they are also obviously estrusable, easy to observe, and have a close relationship with timely breeding. Intensive farms breed mostly Yorkshire, Landrace and Duroc. Their estrus performance was not as good as that of native breeds. Sows had normal feeding after estrus. They did not jump, didn't squeak, and their pups did not change significantly. They often missed the timing of breeding, resulting in reduced sow fertility or long-term emptying. Identifying initial estrus in gilts is often difficult because they often do not show obvious characteristics. According to the survey statistics, about 36% of gilts have no obvious signs of initial estrus, and about 16% of them show static estrus. The proportion of quill sows standing at 6 o'clock in the morning was 60%, higher than that of noon and afternoon. Identification of exogamous sows should be careful, two to persevere twice a day, but also through the vulva to see the internal color changes or mucus thinness and viscosity, etc. to determine the heat, common estrus identification of the following methods. 1. External observation sows were very sensitive when they were in heat, and they immediately looked up and listened. Usually sows who love to sleep after eating, often walk around in circles after estrus, or often stand in front of the circle. In addition, foreign sows in the non-estrus period, the vulva is not swollen, labia tightly closed, like a straight seam. If the labia is loose, the closure is not strict, the sinus is bent, the color of the labia becomes darker, and the amount of mucus is larger, it can be judged as heat. 2. The method of boar bringing the boar to the sow circle, such as the sow refused to cross the boar, to prove that the sow was not estrus, such as active access to the boar, to accept the boar to cross, to prove that the sow is in heat. 3. The sow test method sends other sows or finishing pigs to the sow house. If the sow climbs across other pigs, it means that it is in heat. If you do not climb other sows or refuse other pigs entering the circle, there will be no heat. 4. The artificial approach often does not show that the sow will escape from the human approach and touch her genitals with her hands or instruments. If the sow does not evade the approach of a person and presses the sow hindquarters with her hand, she will stand still and support it with force. If she is exposed to the vulva with her hands or instruments, she will not hide. This indicates that the sow is in heat and should be bred in time.