It seems like this should be a simple answer, right? Not exactly.
No matter the farm, hens are fed a balanced diet consisting of multiple different nutrient sources. Though the diet on the individual farms may be different, farmers are constantly monitoring and tweaking what the hen is eating to ensure all of the needs of the hen are being met.
Though individual rations may differ, the diet of a hen may include corn, soy and a mineral mixture which provides the necessary amino acids and vitamins. This mineral mixture is specialized to not only the specific farm, but also the barn with the help of feed specialists and nutritionists (yup, chickens can use a nutritionist too!).
On a pound for pound comparison, one hen needs about ten times more protein than the average man! For this reason, soy meal is also a part of their diet, as it is a good source of protein.
Lastly, approximately 10% of their diet is limestone, which is a major source of calcium. Since a hen uses calcium to form the shell, the farmer must supplement the hen’s diet to ensure a strong shell can be formed. A hen will actually take the calcium from their own bones if they don’t receive it in their diet, so it is important for hen health that they are receiving enough through their diet.
Their ration also varies depending on their stage of life. For the first few months, young hens can be fed up to four times a day. As they mature, this moves to twice a day, always with full access to fresh water.
So no matter which eggs you choose to buy at your local grocery store, you are buying eggs from a hen who is healthy, with a complete diet.