If you keep chickens in your backyard, you may be curious about whether the eggs your hens lay are fertilized or not. Knowing how to spot a fertilized egg can be helpful in a number of situations.
Ways to Tell if an Egg is Fertilized
Cracking Open the Egg
The easiest way to tell if an egg is fertilized is to simply crack it open and examine the yolk. All chicken eggs contain a white spot on the yolk known as the germinal disc
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In an unfertilized egg, this spot is small and contains only the hen’s genetic material.
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The germinal disc is bigger and has a bullseye pattern in a fertilized egg. In other words, it has DNA from both the rooster and the hen.
However, this method only works if you don’t intend to hatch the egg!
Candling the Egg
Candling allows you to see inside an intact egg by illuminating it in a dark room. It’s done by holding a bright light source like a flashlight behind the egg.
Candling won’t work on freshly laid eggs – you need to let them incubate for at least a week first. The best time is between days 7-14 of incubation.
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A fertilized egg will show a network of veins and a dark embryonic spot.
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An infertile egg looks empty inside except for the yolk.
It takes some practice, but candling is a useful non-destructive way to identify fertilized eggs.
Reasons for Checking Fertility
Knowing whether your eggs are fertilized can be useful for a few reasons:
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If you plan to eat the eggs, you may want to double check they aren’t developing chicks. Fertilized eggs are safe to eat as long as they’re fresh.
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As you might guess, you need fertilized eggs to hatch chicks. Candling lets you discard any duds.
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Identifying fertile eggs can help troubleshoot incubation issues like low hatch rates.
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It satisfies curiosity about whether your rooster is doing his job!
How Do Eggs Get Fertilized?
To fertilize an egg, a rooster must mate with a hen and move sperm to the hen’s oviduct.
The sperm can survive inside the hen for up to 2-3 weeks. As she releases eggs, some will get fertilized if sperm are present.
Once fertilized, an egg must be properly incubated for the chick embryo to develop.
Simply laying a fertilized egg does not guarantee a chick will hatch. But it provides the potential given the right conditions.
Rooster Requirements for Fertile Eggs
To get fertile eggs, hens need access to an active rooster. However, there are a few factors to consider:
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Rooster to hen ratio – One rooster can mate with 6-10 hens successfully. Too many hens makes it hard for him to reach them all.
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New roosters – It takes 4-6 weeks for a new rooster to start mating with the hens.
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Favoritism – Some roosters only mate with certain hens, leading to low fertility. Separating his “girlfriend” may help.
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Aggression – Overly aggressive roosters should be removed. They can injure hens and prevent mating.
So make sure your rooster has the right flock size and personality to get the job done!
What’s Inside a Fertilized Egg?
Here’s a quick overview of what you may see when candling a fertilized chicken egg:
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Embryo – The developing chick. It starts out very small but grows rapidly.
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Blood vessels – Appear as dark spiderweb-like veins that nourish the embryo.
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Air cell – Found at each end of the egg. Looks like a yellowish illuminated area.
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Yolk – Nutrient source for the embryo. It gets smaller as the chick uses up its contents.
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Eggshell – Contains pores that you may see as tiny white speckles when candling.
Common Myths
There are some misconceptions when it comes to fertilized eggs:
✘ They have different nutritional value – The hen provides the same nutrients whether an egg is fertilized or not.
✘ The shell is harder – Shell quality depends on the hen’s diet and health, not fertility.
✘ They taste different – Fertilized and non-fertilized eggs taste the same.
✘ Blood spots indicate fertility – Blood spots can occur in both fertile and infertile eggs.
Candling Tips
Candling takes some practice at first. Here are some tips:
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Use a bright, narrow beam flashlight. Broad spectrum lights don’t work as well.
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Cup your hand around the end of the flashlight to direct the beam.
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Work in a very dark room or at night. Drape a dark cloth over your hands.
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Let your eyes adjust before candling each egg.
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Don’t keep eggs out of the incubator for long. 15 minutes max for candling.
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Gently wipe eggs clean beforehand since dirt blocks the light.
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Mark eggs with a pencil so you know which ones you’ve checked.
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Candle eggs twice – once at day 7 and again around day 14 if desired.
With some experimentation, you’ll get the hang of identifying fertilized eggs through candling. It’s a useful trick for any backyard chicken keeper to have up their sleeve!
“How Can I Tell If My Chicken Eggs Are Fertilized Without Cracking Them?”
I recently got that question from a reader who wanted to hatch some of his chickens eggs. He has 8 chickens and 1 rooster. He currently has collected about 20 eggs and is wanting to know if they are fertile, so that he can put them in an incubator.
Because of rules in my neighborhood, I can’t have roosters. But I’ve always wondered if I could get a fertilized egg before I got rid of them.
We order chicks and usually get a rooster or two out of the bunch. We get rid of the rooster pretty soon after we know that it is in fact a rooster, though.
How Can I Tell If My Chicken Eggs Are Fertilized Without Cracking Them?
So, first a little talk about the birds and the bees {only, in this case, it really only involves two birds}. In order for an egg to become fertilized, the rooster and the hen have to have mated prior to the formation of the egg. If this happens, the hen will lay a fertilized egg.
This probably goes without saying, but if you don’t have a rooster, you will not have any fertilized eggs. Ever. A hen can lay fertilized eggs from anywhere to 2 days after mating to 3 weeks after mating with the rooster.
The oldest and easiest way to tell if an egg is fertilized is called candling the egg. It is literally holding the egg up to a lit candle {not to warm it, but in order to see inside of the egg}.
How to tell if your chicken eggs are fertile
FAQ
How do farmers know if an egg is fertilised?
You can do this by holding a bright light or candle against the egg in a dark room. A fertilised egg will show some development, such as veins, a dark spot (the embryo), and a shadowy mass. ( I tend to use my Iphone light in a very dark room. This seems to do the trick!).
Can you tell if your egg has been fertilized?
Do you feel anything when the egg is fertilized? This event occurs at a microscopic level, so it is usually impossible to see immediate and obvious changes in the body. In most cases, the woman’s body gives no signs at the moment of fertilization.
How long after fertilization does a chicken lay eggs?
After a rooster has mated with a hen it could take as little as 27 hours for a fertile egg to be laid, or as long as a month since hens can store sperm until ….