There are a lot of facts and myths out there about the nature of fertilized chicken eggs. This list will look at some well-known facts and some that might surprise you. Hopefully, this will leave you more informed and better able to recognize fact from fiction when it comes to fertilized chicken eggs.
1. Supermarket eggs aren’t fertile
This might seem obvious, but the eggs you buy from the supermarket aren’t fertile. Commercial hens are raised without a rooster around. This means there is no way for them to produce a fertile egg. So, there’s no need to worry about eating a commercial egg that could turn into a chick.
If you’re buying eggs from a farmer’s market or local supplier, the story could be different. The presence of a rooster doesn’t guarantee fertilization, but the chances are much higher! There is nothing wrong with eating a fertilized egg. However, if you’re worried, check with your local supplier to see if he keeps a rooster around his hens.
2. It is possible to buy fertilized eggs
It is actually possible to buy a fertilized egg for consumption if you really wanted to. These aren’t normal supermarket eggs though. They’re not even chicken eggs!
There is a popular Filipino dish called balut. This dish is essentially made from an 18-day-old fertilized duck egg. At this stage, a small embryo has started to develop. These eggs are difficult to get ahold of in America, though. While you can order them from specialized sellers, you don’t need to worry about accidentally grabbing them in your grocery store.
3. You don’t need a rooster for a hen to lay eggs
This should be another obvious fact, but you don’t need a rooster around for hens to lay eggs. Roosters are required for fertilized chicken eggs, but hens will lay unfertilized eggs on their own.
Most hens will naturally start laying when they’re around 16-20 weeks old. The breed of your hen will influence when they start laying. The frequency and number of eggs they produce will also vary depending on your hen’s breed.
4. Having a rooster doesn’t guarantee egg fertilization
Not everyone realizes that simply having a rooster around isn’t enough to guarantee fertilized chicken eggs. A rooster has to physically mate with a hen before she has a chance of producing fertile eggs.
This isn’t usually a problem as roosters are known for being quite rowdy when it comes to fathering chicks. In fact, a rooster’s sole purpose is to pass on his bloodline and guard his flock.
There is always a possibility, though, that your rooster won’t mate with all of the hens in a flock. There are also other factors that can contribute to the lack of fertilized chicken eggs, like infertility.
5. Not all roosters are fertile
Rooster infertility is more common than most people realize. In fact, research indicates that 40% of sperm produced by roosters is infertile. This is actually causing a huge problem in the commercial poultry industry.
Since the problem is so widespread, it affects smaller, local flocks as well. It is possible to get a rooster that is completely infertile. It’s also possible to have a rooster that can contribute to fertilized chicken eggs, but not consistently.
If you’re having trouble getting consistently fertilized chicken eggs, your problem might be your rooster. Try introducing a new one to the flock or establish a separate flock with a new rooster.
6. It can take a while after mating for hens to become fertile
Hens don’t become fertile immediately after mating. In fact, it will usually take 7 – 10 days before a hen can lay fertilized chicken eggs. This is the amount of time it takes the sperm to travel to the hen’s oviduct. This is where eggs are produced and semen for fertilization is stored.
7. Hens can stay fertile for a while after mating
Once a hen mates with a rooster, they can actually lay fertilized chicken eggs for up to 3 – 4 weeks. This time period starts after the week it takes for the rooster’s sperm to reach the oviduct.
This prolonged fertilization is possible due to pockets in the hen’s oviduct. These pockets store sperm that is released when hormones related to egg production are present.
This means that a single successful mating can result in fertilized chicken eggs for up to a month. This is assuming, of course, that both parents are healthy and fertile. Also, the frequency of successful egg fertilization starts to decrease after 10 days.
8. Eggs are surprisingly hot
Chicken eggs are 105 degrees Fahrenheit when they are first laid. If this is a fertilized chicken egg, it will need to be kept between 99.5 and 102 degrees Fahrenheit. If it gets any colder, the developing embryo might die. This is why hens are so vigilant about sitting on their eggs. They even pluck out their chest feathers sometimes so the eggs can get closer to their bodies.
ou can also place eggs in an incubator if you want to monitor them more closely. Just remember to rotate the eggs 4 – 5 times a day. Just remember to rotate the eggs 4-5 times a day. This is done naturally by the mother and prevents the embryo from sticking to the side of the shell. You can get an incubator that will rotate eggs automatically if you don’t want to do it yourself.
9. Hens might be able to tell which eggs are healthy
Whether or not this fact is true has been debated a lot. While there is no conclusive evidence either way, hen behavior seems to indicate that they can tell. Hens will often push unfertilized eggs out of their nest, choosing to only warm viable eggs. Hens exhibit this behavior with chicks as well. If some seem too sickly or week to survive, they are often ignored by their mother.
Hens have also been observed cooing to their eggs. Sometimes, the chicks will even coo back if they’re close to hatching!
Hen behavior shouldn’t be taken as a sure sign that eggs are fertilized or unfertilized, though. Many hens will sit on any eggs in their nest out of instinct, while some may have poor maternal instincts and will leave their eggs unattended, even if they’re viable.
10. Eggs contain everything for chick development
Fertilized chicken eggs will usually hatch around 21 days after they’ve been laid. During this time, the embryo in a fertilized chicken egg is slowly growing and developing into a tiny chick. The egg is perfectly designed to provide all the nutrients the chick needs to grow and survive until it hatches.
Chicken eggs typically contain approximately 7 grams of protein, 5 grams of fat, and various vitamins, minerals, and nutrients, though these values can vary depending on the size and type of the egg. This is all absorbed by the embryo for energy as it grows. In the last few hours before a chick hatches, the remaining yolk sack is absorbed into its abdomen. This gives it enough food for 24-36 hours, plenty of time to break free of the shell without starving.
11. Candling can help you see if an egg is fertilized
Candling is a process that lets you see if you have fertilized chicken eggs without damaging them. This is a fairly simple process and only requires a dark room, the eggs you want to check, and a bright light. Start by going into a completely dark room and hold the egg right up against your light source.
This will illuminate the inside of the egg, causing it to glow. If it is fertilized, you should see signs of an embryo. The first signs of life will be a thin network of veins inside the egg. You will often see a small dark spot as well in the center of the veins. This is the developing embryo.
Candling isn’t a sure-fire thing. You won’t be able to see any signs of life till 3 – 4 days after an egg is laid. Sometimes, it can take up to a week to see anything. It’s also possible to misinterpret what you’re seeing. Additionally, dark eggs are notoriously difficult to handle correctly.
12. You can also tell if an egg is fertile by looking for the bullseye
A more precise way of telling if you have fertilized chicken eggs on your hands is to look for the bullseye. Unfortunately, you have to crack the egg open in order to do so. This, of course, means the egg is no longer viable. However, this process can indicate if other eggs in the same clutch may be fertilized.
To look for the bullseye, crack an egg open into a dish. You will be able to see a small white disc called the blastodisc. If this is fertilized, it will have a cohesive, circular shape with concentric circles. This gives it the distinctive bullseye appearance. If it’s not fertilized, the blastodisc will be uneven and lack a center or rings.
13. You should never buy shipped hatching eggs
Fertilized chicken eggs have to be kept at precise humidity and temperature levels for a chick to develop. Because of this, it’s a bad idea to buy eggs that you’re hoping to hatch. It’s possible to safely ship hatching eggs, but there are so many variables that can go wrong. It’s better to buy newly-hatched chicks or hatch chicks from your own flock or local sources.
14. Fertilized and unfertilized eggs taste the same
Some people believe fertilized chicken eggs will taste differently and be more nutritious than unfertilized ones. There has actually been researched conducted in order to scientifically refute this idea. According to scientific study, fertilized chicken eggs will taste the same and have the same nutritional value as unfertilized eggs.
15. The color and shape of the egg have nothing to do with fertility
Another common misconception is that the shape and color of an egg will indicate if it’s fertilized and what sex the chick will be. Some believe that eggs with a point will produce male chicks while rounder eggs will produce female chicks.
There is no scientific evidence to support this. All fertilized chicken eggs have about a 50 – 50 chance either way! Unless, of course, you’re messing with incubator settings as we’ll see in the next section.
Similarly, the color of an egg is determined by the breed of the chicken that laid it. Research shows that there is little difference between eggs of varying colors besides the genetics that went into their making.
16. Adjusting the temperature of the incubator may affect the sex of the chicks
Another commonly held belief is that the incubator temperature can influence the gender of fertilized chicken eggs. It’s believed that setting the temperature half a degree higher than is recommended will result in more male chicks.
Conversely, setting the incubator temperature half a degree lower should result in more female chicks. While this seems like random speculation, it might actually be true. Some research shows that variations in incubator temperature may in fact influence the gender of developing embryos.
17. A blood spot doesn’t indicate fertilization
Cracking open an egg can occasionally reveal a spot of blood in the yolk. Some people believe this only happens in fertilized chicken eggs. The truth is, blood in the yolk isn’t related to fertilization. Instead, it can occur when a blood vessel pops while the egg is developing inside the mother.
A burst blood vessel can be the result of genetic factors or vitamin A deficiency. It can also be a random event. In any case, yolks with blood in them are safe to eat and aren’t more likely to be fertilized.
Fertilized chicken eggs can be surprisingly fascinating. Some information about them is fairly common and obvious, but they can also surprise you! Hopefully, this has cleared up misconceptions about fertilized chicken eggs and leaves you with some interesting facts you didn’t know before.
- Supermarket eggs aren’t fertile
- It is possible to buy fertilized eggs
- You don’t need a rooster for a hen to lay eggs
- Not all roosters are fertile
- It can take a while after mating for hens to lay fertilized eggs
- Hens can stay fertile for a while after mating
- Eggs are surprisingly hot
- Hens might be able to tell which eggs are healthy
- Eggs contain everything for chick development
- Candling can help you see if an egg is fertilized
- You can also tell if an egg is fertile by looking for the bullseye
- You should never buy shipped hatching eggs
- Fertilized and unfertilized eggs taste the same
- The color and shape of the egg have nothing to do with fertility
- Adjusting the temperature of the incubator may affect the sex of the chicks
- A blood spot doesn’t indicate fertilization
Joseph Hudson has been raising chickens for over 15 years. In 2018, he completed the Agriculture & Natural Resources program at Mt. San Antonio College. He currently raises over 1400 chickens on his 7.5-hectare farm. He keeps sharing his experience on raising healthy and happy chickens on Chicken Scratch The Foundry.