How To Tell If Eggs Are Fertile

Since eggs are such a well-loved kind of food, it is no wonder people express some concern about the kind of egg they are eating.

One of these concerns is whether the eggs they got from the supermarket are fertilized eggs or not.

But wait, aren’t all eggs supposed to be fertilized in the first place?

It is a known fact that hens lay eggs.

However, what is not very well known is that hens can lay eggs with or without the presence of a rooster. 

Chicken Biology 101

Like human females, a hen is born with all the eggs she will ever have.

When she reaches maturity, somewhere around the 16th-20th week of life, the egg is released into the oviduct where it will begin it’s journey, along the way adding the egg white, shell membranes, and shell.

Immediately after the yolk is released, it goes into a “holding area” called the infundibulum for about 15 minutes.  If the yolk is to be fertilized, it needs to happen here during this short 15-minute window.

A hen’s bodies can store a rooster’s sperm for up to a week after mating, to be used during this window.  The entire process of forming an egg will take about 24 hours to complete.

If the hen has mated within the past week, as long as the rooster is healthy, it is a good bet the eggs she lays will be fertilized.

For a fertilized egg to begin developing, around 100 degrees with 60% humidity for several hours.

It takes about 3 days of incubating at proper conditions for any visible changes or veining to show. 

It takes 21 days for a chick to fully develop and hatch. During the 21 day development, the temperature and humidity must be constant or the eggs will fail to develop into healthy chicks.

Learn about all you need to get started with baby chicks!

How can I tell if an egg is fertile?

Other than having the potential for developing into a chick, there is no difference in taste or nutritional quality.

When you crack open an egg, in the yolk you will notice a small white dot called a blastodisc. Sometimes it is hard to see but all eggs have a blastodisc.

If the eggs have been fertilized, the small white dot will have a bullseye type ring around it. At this point, it is now called a blastoderm.

Weird But Normal Egg Things

Red spots or blood spots – this does not indicate fertility, it is just a broken blood vessel.  This is safe to eat.

White stringy “things” – some people think this is an umbilical cord, it is not.  It is called a chalaza and is a rope-like structure that helps keep the yolk suspended in the egg so it isn’t banging against the shell.  The chalaza is more prominent in farm fresh eggs.  It is totally safe to eat.

Eat All The Eggs!

One question floating among avid egg-eaters is if fertilized eggs are safe for consumption.

The answer is yes. It is perfectly okay to eat fertilized eggs.

Also, once the fertilized egg is stored in the fridge, the embryo no longer undergoes any change or development. Rest assured that you can eat your fertilized chicken eggs just fine like the unfertilized ones.

As for its nutritional value, the issue whether fertile chicken eggs are healthier than unfertilized eggs remains up to this day a highly debatable one. If you want to get the most of the egg’s nutrients, go for the freshest eggs available.

The longer eggs are kept, the more their protein content gets lost.

Like they say, fresh is often best.

You can learn about the differences between chicken eggs and duck eggs here!

Where do you get your eggs from??