How Are Chicken Eggs Fertilized?

When a rooster and hen mate, the semen is stored inside the oviduct and is used later to fertilize the egg before the shell forms around it. The semen can be used up to a month after storage.

Without a rooster, hens lay unfertilized eggs. Why they continue to lay eggs is unknown, but it is hypothesized that the eggs become too large to remain inside and are expelled. Hens can start laying eggs between 20 to 26 weeks. The egg laying interval varies based on breed and health, though the average is once every 24 hours. There is no chance of a chick hatching from an unfertilized egg, especially if it has been refrigerated.

For good egg production, chickens need approximately 16 percent of their diets to consist of protein. Pasture-fed chickens need more protein to produce eggs of comparable quality and quantity, especially since chickens with plenty of access to grass tend to stop foraging for other kinds of food and need their diets supplemented. However, with optimum pasture, chickens can produce eggs that are higher in vitamin E and omega-3 fatty acids, but it is difficult to create the right kind of environment. The proposed dietary supplements for pasture-fed chickens led to a decrease in nutritional value of the eggs.