Wrinkled Eggs

These eggs appear to have ridges or wrinkled surfaces. Overcrowding, which results in stressed hens, can cause this abnormality. It also can be seen when a hen’s shell gland is defective or if the flock has infectious bronchitis. Wrinkles can result in weakened shells. Based on USDA standards for exterior eggshell quality, a wrinkled egg is downgraded to Grade B.

https://fieldreport.caes.uga.edu/publications/C1255/a-dozen-egg-abnormalities-how-they-affect-egg-quality/