When you buy a carton of eggs from a grocery store or local farmer, you may be wondering if they can be hatched into a chick. Are all eggs fertilized? No, the majority of eggs, whether from a chicken, duck, or other bird, are not fertilized.1
Nearly all eggs sold commercially are produced by hens that haven’t mated. The difference between fertilized and unfertilized eggs depends on whether there’s been a rooster in the mix.
Contrary to popular belief, hens do not need a rooster to lay an egg—they do it on their own based on light patterns. Many chicken breeds will produce eggs daily, and none of these eggs contain a potential chick.
If a rooster does mate with a hen, the eggs are fertilized and can be incubated to bear chicks. Without the rooster, there’s no possibility that the eggs will ever become a chick.
Differences Between Unfertilized and Fertilized Eggs
The hen’s genetic material is called a blastodisc, which can be seen on an egg yolk as a light-colored dot with irregular borders.
When an egg is fertilized, this blastodisc becomes a blastoderm, which is the first stage in embryonic development for a chick. This looks like a bullseye on the yolk with concentric circles. The blastoderm will stay as such indefinitely unless it’s warmed to a certain temperature for several hours.
If a fertile egg is incubated correctly with precise temperatures and humidity levels, after 21 days, it may develop into a chick.
Can You Eat Fertilized Eggs?
If fertilized eggs are sold for consumption, there’s no danger in eating a developing embryo. In the US, all eggs sold as food must be refrigerated, which would stop any development of an embryo in the shell.
In addition, eggs are inspected before they hit the supermarket shelves. This is done by shining a bright light through the shell (candling) to find irregularities, such as a developing chick. Eggs with such irregularities are not permitted to be sold.
Only eggs that are incubated and start to develop can be identified as fertilized after three days. Neither the blastoderm nor the blastodisc are visible through the shell with candling. An incubated egg can be fertilized and appear unfertilized, but that’s only if it didn’t develop properly.
Nutritionally, fertilized and unfertilized eggs are around the same—they even taste the same.
What If There’s Blood in an Egg?
If you crack an egg and see blood spots or a small pool of blood, that doesn’t mean it was a potential chick. Blood vessels can rupture during the reproductive cycle for many reasons, including nutritional deficiencies.
There are a lot of misconceptions about eggs, fertilization, and baby chicks, but the short answer is that the eggs you buy in a carton at the store are neither fertilized nor incubated and will never hatch into a chick. Even if a hen mated with a rooster, there’s a complex process that needs to take place for that fertilized egg to become a potential chick.
Featured Image Credit: PhotoSongserm, Shutterstock