What happened to the sow calving bow?

6~8 hours before delivery, sows will use grass to make nests and arch their nests, which is a unique symbol of sows before delivery. Observation shows that primiparous sows nest earlier than multiparous sows. Cold weather nests earlier than hot weather; However, imported pig breeds have no obvious grass-hugging performance, but only arch the nest, that is, arch the mat grass or dry soil in the circle to one place. At the same time, loss of appetite or not eating. If the sow is found to be extremely nervous, sometimes walking back and forth, sometimes sitting like a dog, short of breath, its tail swinging back and forth, tears flowing out, frequent defecation and urination, it will give birth within a few hours.