All About Fertilized Eggs

All About Fertilized Eggs

December 13, 2020

(From left to right: fertilized egg, unfertilized egg.)

One of the most common questions asked in the world of backyard chicken-keeping: "How do I know if my chicken eggs are fertile?" Well, in this week's post, I'm going to explain the mating process, how chicken eggs are fertilized, and how to know whether they are fertilized. By the way, in case you didn't know: You don't need a rooster for a hen to lay eggs, but if you want the eggs to be fertilized, then you want a rooster.

The short answer is, if you have a rooster, then all of the eggs you collect from your chickens are most likely fertile. Breeders will often separate a rooster with just one hen or maybe up to 5 or 6 hens for breeding purposes, but some people have had as many as sixteen hens and only one rooster, and still collected fertilized eggs. Roosters really manage to get around the barnyard quite well! One rooster can easily mate with a dozen or more hens and fertilize all their eggs.

Beginning the second day after you put a rooster and hen together, the hen's eggs should be fertile. And once a hen and rooster "do the deed", that hen will most likely lay fertile eggs for up to two weeks afterwards.

Fertile eggs look just like unfertilized eggs except for the bulls eye on the yolk of a fertile egg. Not fertilized eggs will just have a white spot which is called the germinal disc, which is where the egg is fertilized. 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. 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 constant temperature of 85 degrees or more 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 slightly.

In case you're wondering, you can definitely eat fertilized eggs, as long as you don't overheat them. 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. 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. One last note: 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. Try not to forget that!