Egg Laying and Common Egg Abnormalities in Chickens

Learn all about egg laying and common egg abnormalities in chickens. How does a hen produce an egg? What are the most common egg abnormalities and their causes? You’ll find answers to these questions and more!

Anatomy of Egg Laying in Chickens

As sustenance farmers, we raise heritage breeds of chickens that serve as dual purpose birds, birds raised for both meat and eggs.

If you butcher your own birds, as we do, no doubt you have seen eggs-in-waiting in hens of laying age. The laying age for most breeds is 5 to 7 months old.

Each hen is hatched with all of the eggs she will ever lay already there in seed form.

As she matures and begins to prepare for egg production, they begin to gradually increase in size.

In her oviduct system, there is a cluster of little tiny yellow specks that look like grains of sand with small, pebble-like ones around them, graduating in size larger and larger. These are the yolks.

When the yolk for the day is ready, it enters the oviduct where it’s fertilized or not 

Next, the egg white is added. Then it receives two membranes to keep the nutrients in and to keep its shape.

Finally, the shell is put on and the egg moves to just inside her vent.

How long does it take for an egg to develop?

The whole process of development takes about 24 hours.

When the shell is added and the egg moves into her vent, she’s ready to lay! Boy! will she let you know when she’s done it.

My whole flock gets excited and cackles for each and every one laid – every day. That’s almost 50 hens cackling for one another multiple times a day!

You would think they would be used to doing it and not put on such a show, but it’s a production of cackles and crows for every egg!

Just in way of a reminder, a pullet (a hen under a year old) will lay smaller eggs than she will as she grows and matures into a hen.

Does a hen need a rooster to lay an egg?

There are a great many people who have lived in cities all their lives and sincerely don’t know the answer to this question. I get asked this more often than you would think.

The answer is NO. A hen lays eggs all on her own.

However, the eggs will not be fertilized without a rooster, that’s his job. If an egg is not fertilized, it will not become a chick if a hen sets on it.

So, a hen lays eggs whether she has a rooster or not, but the egg will not be fertilized without a rooster.

When does a hen start to lay, how often will she lay, and for how long will she lay eggs?

As a hen matures, the size of her eggs and the frequency of her laying will increase.

Once she begins laying, at around 5 – 7 months depending on her breed, it usually takes her 7 to 10 weeks to work up to full production.

Depending on the breed and the lifestyle of your hen, you can expect her to lay for up to 10 years. The average lifespan of a hen is 14 years.

If your main goal is egg production, then you probably wouldn’t want to keep your hen past 3 to 4 years of age as this is the age range of when she will be most productive.

When I have a hen who is unproductive for more than four months out of the year, we cull her.

That is of course unless she is exceptional in some way. If she has proven to be an excellent mother, has an unusual personality, or some other feature that makes her unique, she gets to live out her days with the flock at large.

This is part of being sustenance farmers. If you are a hobby farmer or backyard chicken keeper who does not eat their birds, you will not have to worry about keeping up with who is productively laying and who is not.

This is a very basic and simple explanation of the egg production process and somewhere in this straightforward, yet complex process, things happen that cause egg abnormalities.

How to tell which hen is laying and which is not?

Judging which hen is laying and which isn’t is not an exact science, but there are some signs to look for.

• Before a hen begins to lay, you will see a yellow color around her vent, eyes, and earlobes.
• After she has been laying for a few months, the yellow in these and her beak will fade slightly.
• After about six months of laying eggs, her feet, toes, claws(toenails), and shanks will also fade in color.
• When she quits laying, you will see the color come back to these.
• This is kind of interesting to me since the sign that she is about to start laying or is actively laying is the bright color of her cone and wattles.
• These will be pink before she is of laying age and will fade to pink after she is finished laying.
• These color changes will also occur when she is molting, sick, or if she is a breed that takes a winter break.
• Although rare, you should acquaint yourself with egg-bound hens.

Common Egg Abnormalities

Egg abnormalities occur with almost every breed of hen at some point in her egg laying career.

Eggs laid by non-commercially bred hens vary considerably in size, shape, and color. In that mix, egg abnormalities will occur.

People who have a small flock with several different breeds of birds can learn to recognize each hen’s eggs. It’s easier for them to know who’s laying and who isn’t; how often and when; and which hen may be having health issues because of consistent abnormalities.

For people like me who have a larger flock, it’s harder to tell and requires us to separate a suspected hen to determine her laying quality and quantity.

Shelless Eggs

The most bizarre egg abnormality I’ve ever found in my flock is the shelless egg.

As you can see in the photo, it’s perfectly formed down to the protective membrane, but the shell simply didn’t form around the egg.

If you reach into the nest for your eggs without looking, it’s a pretty freaky feeling to grab hold of one of these.

This usually happens in a chicken who is just beginning to lay. I have only had this happen 4-5 times in my 40+ years of chicken keeping.

If you have more than one of these or find them frequently, be sure you are feeding your chickens a balanced diet and add calcium to it.

DO NOT eat this egg. You can give it to your dogs or hogs, but not to humans.

Since the protective shell didn’t form, it’s very probable that bacteria has gotten through the membrane contaminating the egg.

Double-Yolk Eggs

Another common abnormality, which I’ve had less than 10 of these, is the double-yolked egg.

This photo was taken a long time ago. I remember taking it because it was the first one my girls had laid in years and I didn’t know when I would have another one.

The double-yolked egg is just an egg that has developed two yolks. Kinda like it wanted to be twins! This egg is perfectly safe to eat.

Bumps, Swirls, and Cracks

You may get some weirdly shaped ones as well. You may have an outcropping on your eggshell.

This is just a little extra deposit of calcium as you can see in this photo.

Interesting “swirlies” often form in the shell-making process.

Even though I’ve never had one, I’ve heard of having an egg within an egg. This is caused when an egg gets backed up for some reason and goes through the last production stages twice.

I had this egg from one of my younger hens. It was such a puzzle to me. The egg is cracked almost all the way around, yet the protective coating (called the bloom) sealed the egg. It was safe to eat because the bloom sealed and protected it.

Fertilized Eggs and Eggs with Blood in Them

Not a true abnormality, but worth noting, is blood around the yoke.

It’s considered a hereditary characteristic in some chicken breeds. Blood in the egg isn’t an indication of fertilization. This kind of egg is completely edible.

If you have a rooster, you may notice a white or slightly discolored spec in your yolk that has a “bullseye” look to it. Congratulations! You have a fertile egg and given the right opportunity, it would’ve become a chick.

This egg is edible, which is a good thing because almost all my eggs or fertile. Yep, my guys are on the job.

Almost all eggs will have a white or discolored area but that does not mean they are fertilized. Only the ones with the characteristic “bullseye” are fertile. I know it’s hard to see in the photo, some subtilities just don’t translate.

As you can see in this photo, this was the shelless egg – I cooked it for the dogs.

When to Not Eat an Egg

Knowing how to tell if an egg is fresh is important.

If the egg has been compromised in any way such as a crack or no shell, do not eat it.

Of course, if you crack an egg and it smells funny, don’t eat it!

I learned in a very memorable way to crack my eggs into a small bowl one at a time before cooking them.

As a young girl, I was helping my grandmother fix breakfast, and I use the term “helping” loosely.

She had fried the bacon, which came from their smokehouse, and was cooking eggs. She had fried two or three and reached for another.

When she cracked it open and plopped it into the hot skillet, there was a half-developed baby chick! Oh boy did it stink! Needless to say, she rushed it out the back door then cleaned the skillet.

I remember she said, “That’s what I get for not cracking it into a bowl first.” 

She had to explain to me that she had found a nest of eggs and thought she had tested them all for freshness.

She taught me that when you’re not sure, you should crack the egg into a bowl first and then use it. She couldn’t have taught me a more memorable lesson. As you can imagine, neither one of us had eggs for breakfast that day.

Summary

This is a basic overview of the egg laying process and the most common abnormalities. With a proper diet, a healthy living environment, and good coop and yard maintenance, your flock will be productive for several years.

What is the most abnormal egg you’ve had in your flock? I really enjoy that no two eggs are exactly the same.

I can tell which breed laid which egg, but not which hen. Can you tell?

As always, we’re here to help.