How can you tell if a chicken egg is fertelized?

Question

Can you eat a fertelized egg within a day of fertlization?
How can you tell if it is fertilized?

Answer 1

You cannot easily tell if it is only a few days old. Once it has been fertilized for 5 or so days a small patch of red appears where the chick is forming -- it is the embryo's blood supply.

It is perfectly safe to eat a fertilized chicken egg.

Answer 2

You cannot usually tell a fertilised egg from an unfertilised egg until incubation has started. Occasionally you might see a small white dot on the yolk but not normally. A red spot on the yolk is a blood spot that is caused by a broken blood vessel as the egg is forming. This can happen to fertilised or unfertilised eggs and it is safe to eat. If you don't like it, lift it off with the tip of a knife.

Once incubation starts, which could be two or three weeks after the egg has been laid, the fertilised ovum - which is the white dot on the yolk - gets bigger and develops into the chicken. Incubation of the egg is always delayed until the complete clutch has been laid. At one egg a day, this will take two or three weeks. By delaying incubation until all eggs are laid, the hen ensures that they all hatch at the same time.

You can eat fertilised eggs at any time. As long as incubation hasn't started, they keep as long as unfertilised eggs and appear and taste no different.