You have ever happened to break a egg and discover two yolks Inside? If yes, you’ve probably surprised yourself and you would have thought it was a special event. In fact, there are those who consider double yolk eggs for a sign of luck, while others wonder if it is an anomaly or a defect. In reality, there is nothing strange: it is a natural phenomenon which can occur for different reasons related to biology and the environment in which the hens live. These animals have an incredibly efficient reproductive system, regulated by a delicate hormonal balancejust like many other birds. However, in young hens and in the early stages of their reproductive life, it may happen that their body is not yet perfectly synchronized and that Two eggs are released instead of only one. This leads to egg formation with two yolks. But it is not just a matter of inexperience of the reproductive system: also the geneticsthe diet of the hens and theexposure to light They play a fundamental role in determining the probability that this curious phenomenon will occur. Although they are less common than normal eggs (about one a day in adult hens), understanding the causes of their formation can help optimize poultry production, improving both the economic performance and the quality of the final product.
How an egg is formed with a double yolk
The formation of an egg with two yolks takes place when Two eggs they are released almost simultaneously from the ovary of the hen e incorporated into the same shell. The reproductive system of hens is characterized by a single functional ovary (the left one), which contains a series of follicles in different stages of development. Normally, a single follicle reaches maturity and is released at the moment of ovulation, but in some conditions, two follicles can mature and ovulate together. There are mainly two mechanisms behind this phenomenon.
The first is the retention of a yolk in the oval. In this case, an already ovulated first yolk can undergo a delay in transit through the ovidotto, remaining temporarily trapped while a second yolk is released shortly after. Both, then, are surrounded by the protein that forms the egg white (the albumin), the internal membranes and finally from the shell, resulting in a single egg with two yolks.
The second is thesimultaneous ovulationin which two follicles mature at the same time and are released simultaneously by the ovary. Also in this case, both eggs are then incorporated into the process of formation of the shell and egg, which will be two yolks.
What does it mean when there are two yolks in an egg: the causes
Several factors influence probability That a hen lay eggs with two yolks. First of all there is to be considered theage of the hen. The young hens, at the beginning of the deposition period, have a greater impact of eggs with two yolks. This is because their hormonal and reproductive system have not yet achieved full stabilization. The key hormone in this process is the luteinizing hormone (LH), which regulates the release of the eggs, but it seems that the problem concerns an excessive development of the follicles independent of the hormone itself.
Also the genetics It is a influencing factor, since some breeds and genetic hens lines show a predisposition to the production of double yolk eggs. Studies have shown that this feature is inheritable and can be artificially selected. In addition, exposure to longer cycles of light (photoperiod) stimulates the reproductive activity of hens and can increase the probability of multiple ovulations, especially in the first months of deposition.
Last but not least, also the nutrition influences the formation of a double yolk. In fact, a diet full of protein It can encourage faster growth and early maturation of the reproductive system, increasing the frequency of eggs with two yolks. Finally, also it stress It can influence this phenomenon, making it more or less frequent depending on the management of breeding.
What does it entail for the avicola
The eggs with two yolks have both advantages and disadvantages for the poultry industry. Among the positive aspects There is the fact that these eggs are appreciated by consumers for theirs nutritional valuefor example the very high protein content. For this reason they are sold to higher prices in some markets. In addition, studies have shown that they can have a favorable chemical composition, with a higher content of unsaturated fatty acids. Among the negative aspects There is the fact that they are considered defective in the farms intended for the production of chicks, since the presence of two yolks reduces the probability of hatching. Also, they have thinner and fragile shellswhich can increase losses during manipulation and transport.
