See if the sow's breasts are swollen and shiny, because when the sow is in labor, the breasts are swollen and shiny, and the nipples on both sides are splayed outward, and the nipples show signs of dripping milk. Soon, the pig will be born.
Second, look at the tail root; Before delivery, the tail root of sow was sunken, vagina and vulva were slack, and labia were red and swollen. The third is to look at the performance of sow labor behavior; Before delivery, the sow's appetite decreased, which was manifested as fidgeting, walking back and forth in the circle and grabbing grass. After this behavior appears, it is usually about 6 ~ 10 hour before delivery.
There is mucus flowing out of the sow's vulva, and "frequent urination is bound to give birth." One squeeze is to squeeze the nipple; Under normal circumstances, sows can give birth about 20 hours after thick milk appears on the front nipple, about 10 hour when the middle nipple milks, and about 3-6 hours when the rear nipple milks.
But the above time is not absolute, because it is directly related to the management, breeding, variety and physical condition of sows. A more accurate way to judge the farrowing time of sows is to gently press any nipple of sows with your hands, which can express a lot of milk, indicating that sows are about to give birth.