One of the most common questions I get asked is "How do I know if my chicken eggs are fertile?" The short answer is, if you have a rooster, then all of the eggs you collect from your chickens are most likely fertile.
|-a rooster can easily mate with a dozen or more hens and fertilize their eggs-|
Breeders will often separate a rooster with just one hen or maybe up to 5 or 6 hens for optimal breeding purposes, but I've had as many as sixteen hens and only one rooster - and nearly every egg I cracked open was fertile. Roosters really manage to get around the barnyard quite well! Beginning the second day after you put a rooster and hen together, her eggs should be fertile, and once a hen and rooster 'hook up' and do the deed, the sperm from the rooster is stored in the hen's oviduct and that hen will most likely lay fertile eggs for up to two weeks afterwards.
If you are planning on trying to hatch your own chicks, start checking the eggs you crack to eat for the tell-tale 'bullseye' on the yolk. That's the sure sign that egg is fertile. (A common misconception is that a spot of blood or red is indicative of fertility but that's not true. The blood is merely a broken blood vessel.)
|-fertile eggs look just like unfertilized eggs except for the bulls eye on the yolk-|
If you do choose some eggs to incubate, by around day four - if the eggs are fertile - you should be able to see veining and spidering through the shell when you candle it. But rest assured that any fertile eggs you put in the refrigerator won't develop - since the cold temperature will prevent that - nor will fertilized eggs you leave out on the counter unless you keep your house abnormally warm. Fertile eggs need to be maintained at a temperature of 85 degrees for several hours to even begin to develop, and at a temperature of near 100 degrees for 21 days in order to hatch. Even if a broody hen has been sitting for four days on an egg, it will only have developed into this....
|-photo credit of Day 4 of Incubation: The Poultry Help Forum-|
Farm families have been eating fertile eggs for generations upon generations, since every farm flock would always include a rooster for flock protection and to perpetuate the flock as the older hens stop laying. A fertile egg looks and tastes exactly like a non-fertile egg except for the small white bulls eye on the yolk. As the photo below depicts, an unfertilized egg will have a white spot, but it will be without the concentric bulls eye rings. There is no discernible difference in the nutritional content of a fertile egg vs. a non fertile egg.
|-photo credit: University of Kentucky Poultry Extension|
For more information on what is inside an eggs, read my article on Egg Anatomy.
For more information on roosters, read my article entitled Things I Have Learned about Roosters.