I'm wondering how to and how much egg shell to mix into a feed I purchased. The feed is 15-16% protein, a mix of corn, wheat, and fodder. I have laying hens and I know they need 4% calcium. I have been saving eggshells to mix in the feed. I am planning on fermenting this feed. How should I mix in the crushed eggshells? Should I wait until after it is fermented, or should I pour the eggshells into the fermentation bucket? Should I add it by dry weight and have about 10% of the weight be eggshells? Any advice is appreciated.