How are Chicken Eggs Fertilized

Bird eggs have been a part of human diet since the prehistoric period. Even though the eggs of various other birds are consumed by people in different parts of the world, chicken eggs are the most common and popular one. According to some studies, there are more than 25 million domesticated chickens in the world. This figure shows the demand for chicken, which is mainly grown for their eggs and meat. Chicken eggs are rich in proteins, vitamins and minerals. Each egg contains enough nutrition for developing a chick, in case, it is fertilized and hatched in the proper manner. So, fertilization is an important factor that determines whether an egg can be hatched to a chick. Is hatching possible with all types of eggs? How to pick out fertilized eggs? How are chicken eggs fertilized? If you have similar doubts, then scroll down to know more about the subject.

Are All Chicken Eggs Fertilized?
Fertilization in animals, is that process which denotes the fusion of the ovum with a sperm, in order to form an embryo, which in turn can develop to a new organism. The same applies to chickens too. The eggs need to be fertilized for developing a new chick. This does not mean that chickens lay only fertilized eggs. A healthy chicken may start laying eggs from the age of four to six months. The natural mating season of chickens starts from spring, when the days start getting longer. But, if the chickens reach sexual maturity before or during cold winter, it will start laying eggs from spring only. The egg laying age for chickens may vary with the breed, climatic conditions and various other factors. Even the number of eggs laid by a chicken may vary with all these factors. An average domestic hen may produce around five eggs a week. In between the egg laying periods, these birds take rest. In other words, they do not produce eggs for a small interval, after an egg laying period. Once a chicken start laying eggs, the productivity is highest during the first year and tends to decline after that.

Now the question is whether all chicken eggs are fertilized? Once the young female chickens (better known as pullets) reach sexual maturity, they will start laying eggs. In other words, chickens that reach the egg laying age will produce eggs, even if there are no roosters. So, mating and fertilization is not necessary for a chicken to produce eggs. In fact, most of the store-bought eggs are not fertilized, as roosters are normally not kept in most of the poultry farms, so as to facilitate mating and fertilization. Only when there is a demand for fertilized chicken eggs, or when they (poultry owners) need a new batch of egg-laying hens, that they search for a rooster. In short, you may not be able to hatch chicks by incubating table eggs, as there is no guarantee that such eggs are fertilized or not. The following paragraph will provide you with some information about how are chicken eggs fertilized.

How are Chicken Eggs Fertilized?
The males, called roosters, have reproductive organs known as testes, which produce sperms that are transferred to the sperm sacs, through tube-like structures called vas deferens. The sperms are released through the cloaca of the bird, while mating. It takes only thirty seconds for the roosters to deposit sperm in the reproductive tract (called the oviduct) of the hens. The sperms that leave the body of the rooster through an opening called cloaca, enter the oviduct of the female and travel through various parts of the reproductive organs to reach the infundibulum, a funnel-shaped organ. In this journey, which takes almost one week to reach the destination, the sperms pass through the shell gland of the hen, then isthmus and magnum, finally to reach infundibulum. Once inside the infundibulum, these sperms can remain live for one week or more, waiting for the eggs, which are not fully formed and lack shells. If there is a yolk in the infundibulum, fertilization takes place instantly.

The eggs are formed as yolk, in the ovaries of the hen. A healthy young hen produces a single yolk in every 24 to 26 hours. This yolk, when released from the ovaries, travels to the infundibulum. If there are sperms in this funnel-shaped organ, the yolk will get fertilized (hens can retain sperms for around 10 to 48 hours). Once fertilized, the yolk passes through the same route, through which the sperm traveled to reach the infundibulum. The only difference is that the yolk travels in the reverse direction and completes its structure to form a proper egg, during the course of this journey. The yolk gets surrounded by the egg white in the magnum, whereas the formation of the shell membrane starts in the isthmus. From there the yolk (covered with egg white) travels to the shell gland, where the shell formation is completed and the shell gets hardened. The egg is ready to be laid, which is usually done in the middle of the day. Once the fertilized egg is laid, the hen is ready to start with the formation of a new egg.

How Long it Takes to Produce Fertile Chicken Eggs?
One of the common questions with regard to chicken egg fertilization is the time period required for production of fertile eggs, from the date of mating. There are various factors that can affect this time period. In case of a flock with less than ten hens, introducing a sexually active rooster can produce fast results. Once the mating is done, the sperms travel to the infundibulum and this takes almost seven days. So, you can expect fertilized eggs only after seven to ten days of mating. The hen may continue to produce fertilized eggs for the following week. Another factor is the number of hens in the flock. If the flock contains less number of hens, there are higher chances of getting fertilized eggs at the earliest. Even the age of the rooster as well as the hens may play a role in forming fertile eggs. The older they get, the longer you have to wait for fertile eggs.

How to Identify Fertilized Chicken Eggs?
A fertilized chicken does not mean that it has a chicken inside it. Such eggs have an embryo inside them and this embryo is capable of producing a chick (within 21 days), if incubated in proper conditions. If refrigerated, fertilized eggs are like the unfertilized ones only and do not develop further. Most of the poultry farms have specialized candling equipment for identifying fertile chicken eggs. Candling eggs can be done at home, with a bright LED flashlight.

As the light passes through the egg, unfertilized eggs will not show any darker part inside it. In case of fertilized ones, you may see a darker yolk on one end. This is mostly seen in one to two-day-old fertilized eggs. If incubated, within two to three days, these eggs will develop a network of veins and you may also see the growing embryo at this stage (seen with LED flashlight only). You may also crack the egg and search for the germinal disc or blastoderm. It will be like a small white spot (like a pin point) in unfertilized eggs and in fertile ones, you can find a more pronounced, bigger (around one eighth inch in width) round white spot. The germinal disc should not be confused with the small white string-like structure (chalazae), which is seen in all eggs. Some people believe that eggs with red spots are fertile ones. This is also incorrect, as red spots can develop in any egg, during its formation.

Are Fertilized Chicken Eggs Edible?
This is one of the common doubts about eggs. While some people detest the idea of consuming fertilized eggs, others consider them more nutritious as compared to unfertilized ones. The fact is that fertilized eggs are same as unfertilized ones in taste, appearance as well as texture. It does not develop a chick without incubation. Apart from that, most of the store-bought chicken eggs are found to be unfertilized. If you are interested more about the various aspects of fertilized vs unfertilized chicken eggs, you may conduct a deeper study about the same.

The above said is only a brief overview about how are chicken eggs fertilized. Now, you know how to identify a fertilized chicken egg. If you want such eggs for hatching, get fresh fertilized chicken eggs. Fresh eggs are preferred for consumption too. Both fertilized and non fertilized chicken eggs can be used for this purpose.