How do chicks develop and breathe inside the egg?

In this article, we will discuss a very interesting topic for all poultry lovers. How do chicks breathe inside the egg?

The miracle of life is truly amazing. A baby grows inside its mother’s womb and receives everything it needs to develop within the safe confines of the uterus through an umbilical cord that collects some of the oxygen the mother breathes, along with other forms of nutrition. However, when it comes to animals (like chickens) growing inside an egg, the process obviously can’t be that simple, can it?

At first glance an egg is completely isolated from the outside world, so how can a chick inside the egg get the oxygen it needs to perform its vital biochemical functions? So what exactly happens inside that egg during the short 21 days it takes for a chick to hatch?

Fortunately, chicken embryos are used for scientific research and are frequently studied due to their easy availability. That means there is a lot of information about what goes on inside that egg.

How exactly an egg is formed?

Chickens are born with all the eggs they will have in their ovaries. The whole process begins with a tiny egg in the hen’s ovary. The ovum matures in the yolk of the egg. Once an egg is ready, it will be released into a “holding tank” called an infundibulum for about 15 minutes. If the egg is to be fertilized, it has to happen in this short 15 minute period.


The bodies of the hen can store the sperm of a rooster for up to a week after mating, for use at the right time. So rest assured that if your hen mated with a rooster exactly one week earlier, her eggs will be fertilized, after that time we will need the rooster again.

If you look closely at unfertilized egg yolk, you will see a small white spot. That place is called the germ disc, a female cell. If a rooster has mated with the hen, its sperm will mix with the cell, making embryonic development possible through incubation. Even a fertilized egg will not develop unless it is hatched. Fertilized or not, the yolk will continue through the oviduct where the white is added. Then the chalaza is in charge of keeping the yolk centered in the egg.

By now the egg has reached the hen’s uterus. In the uterus, the shell gland forms the shell of the hard-boiled egg. This process can take more than 20 hours. All egg shells start out as white, but some breeds during the final stages add color to the shell-making process! The final stage before laying the egg is adding a thin protective layer called a flower to the egg. This step helps keep bacteria out of the egg.

Will fertilized eggs begin to develop in the nest?

No, unless they have a hen sitting on them to hatch them. Chicken embryos need a temperature between 55-100 degrees F and a humidity level of 50-65% to develop. In theory, if the temperature and humidity outside were consistently kept in those ranges day and night for 21 days, the eggs could hatch on their own.

Since that is basically impossible, you need a good chicken butt to perform that task or to purchase an automatic incubator! A broody hen will instinctively rotate her eggs to keep her eggs at the proper temperature.

Can the eggs be contaminated by any bacteria from outside?

This is the beauty of flowering added in the last stage of egg development. Bloom is a protective layer that prevents bacteria from spoiling the eggs. This allows a hen to herd over the course of 7-10 days without compromising the health or fertility of the eggs. The eggs will not begin to develop until the hen begins to incubate them.

Once development begins, the eggs must be kept warm or the embryo will die. In a clutch, you will have eggs that were laid a day ago and eggs that were laid a week ago, but they will all develop and hatch at the same time because they all started hatching at the same time.

flowering is the key to keeping the eggs safe. Eggs become “bad” when bacteria enter through microscopic pores in the eggshell. If the bloom is not washed off, the eggs can be safely stored without refrigeration for at least a month. Once the bloom is washed away, refrigeration is needed to keep the eggs fresh. Many backyard farmers keep their eggs fresh on the counter, unwashed.

What do the chicks feed on inside the egg?

Going from a clump of cells to a fully formed fluffy chick in just 21 days takes a lot of energy! Human babies have a placenta to help them get nutrients, and chicks have a yolk. The yolk has everything a growing chicken embryo needs. Once hatched, the chick will have enough yolk stored in its system so that it doesn’t have to eat for the first 24 hours while it waits for all the other chicks to finish hatching and Mom can take them all out.

How does a chick breathe inside the egg?

Beneath the shell is two membranes, between those membranes there is an air sac to provide the chick with a source of oxygen. But as the growing chick breathes in the oxygen, it needs to expel the carbon monoxide.

That carbon monoxide needs to escape from the egg, and the air sac needs to be replenished with fresh oxygen. If you look closely at an eggshell, you will see that it is not a solid surface, but has almost 7000 tiny pores that allow oxygen to enter and carbon monoxide to exit.

Can the chicks hear inside the egg?

The tiny pores in the eggshell can also allow the chick to listen to its mother as soon as its hearing has developed around day 12 of incubation. Chicks have shown that they recognize their mother’s voice at birth. Towards the end of incubation and during hatching, chickens have been observed quietly clucking their eggs, singing lullabies, and cheering them on during hatching.

On the last day before hatching, chicks can be heard poking out of the egg. If you pick up an egg from the nest on day 20, you will be able to feel the chick moving inside the egg. So even though mother hen is not raising her babies inside her, she can still feel them move and begins to bond with them.

How does the chick come out of the egg?

The chick has an egg tooth in its beak that will fall out during the first week of life outside the egg. This egg tooth is an important tool for escaping from the egg. A chick will use the egg tooth to break a small hole in the shell. It will then begin to spin in a circle inside the egg, breaking small holes in it to “unzip” the shell. This is a lot of work for a little baby! They take many breaks and this process can take up to 24 hours. It can be difficult to watch them struggle to hatch knowing how much work it is, but this struggle is really important to the little creature. A chick taken out too early can bleed to death. Fighting also helps strengthen your lungs and legs.

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