If you eat chicken eggs, at some point, you may have wondered how to tell if a chicken egg is fertilized. If you raise chickens, especially if you plan to mate them to get more chickens, you need to learn how to test whether your eggs are fertile. Therefore, these are a few test methods.
Look at the Yolk’s Germ Spot
There is a tiny white spot, called a germ or germinal spot, on the top of the yolk. This spot tells you whether an egg is fertile or non-fertile. If the spot is small, it is a blastodisc and is not fertile. This spot is small because the egg has no male genetic material. However, if you find that this spot is larger and looks similar to a bullseye, with a white ring around it and a dot in the middle, the egg does have male genetic material and is fertile. This spot is then called a blastoderm and it will grow into an embryo.
Unfortunately, to view this germ spot, you need to crack the egg open. If you plan to breed your chickens, you ruin any embryo formation when you crack open the egg.
Noninvasive Method: Candling
Fortunately, you can also check your eggs for fertilization using candling, which is a noninvasive method. However, you will not know right away if your eggs are fertile. This is the process.
Incubate or Store the Eggs
After you collect your eggs, check them for cracks, odd shapes or other damage. Then, either store them at 53-59 degrees or incubate them. If you store them, turn them every day by 45 degrees. If you incubate them, avoid keeping them out of the heat, either under a chicken or in an incubator, for more than 30 minutes. Unfortunately, you cannot see whether the egg is fertile right after the hen lays it because it can take a few days for the embryo to begin its development.
First Candling Test
After seven days, remove the egg from the incubator and shine a light through it. You should be in a dark room to see into the egg well. In the past, people held the egg up to a candle, but today, you can use a good flashlight. Look for dark lines, which are blood vessels, in the yolk area of the egg. You may also see a dark shape in the center. This darkness indicates fertility, but a clear egg suggests that it was not fertilized. Remove unfertile eggs from the incubator immediately to avoid gas buildup and spoiling.
Second Candling Test
On the 14th day, remove the eggs again. A dark ring around the egg suggests that it was fertile but the embryo did not survive. A clear egg will still look clear, and you may see the yolk but no other lines or development. However, if your egg did get fertilized, you should start to see parts of your chick, such as its beak and toes.
Again, avoid keeping the egg out of the incubator for more than 30 minutes. Also, do not remove them again after the second test because the embryo may not survive it.
You can eat both fertile and infertile eggs before the embryo starts growing, and both have the same taste and nutrition.