Previously, researchers could determine sex ratio bias only after incubating eggs.

This new method is currently being used to study and understand the mechanisms underlying the primary sex ratio bias in chickens. It might also be possible to apply the methods of affecting the sex ratio in poultry industry. It is interesting from both an economical point of view and an ethical point of view, as it could lead to a decrease in the production of male eggs, thereby reducing the need to kill one-day-old chicks in the layer poultry industry.

In mammals, the sex of the progeny is determined by the male’s sperm cells. In contrast, in birds, the sex of the offspring is determined by the female’s egg. Female birds produce two types of ova; one contains a W-chromosome that results in a female offspring, and the other contains a Z-chromosome that results in a male offspring. Previous studies have found that female birds can change the sex ratio in their eggs by influencing the segregation of the sex-chromosome at the time of meiosis, thereby increasing the likelihood of the preferred sex chromosome to end up in the resulting gamete rather than in the polar body. In birds, the sex ratio when the eggs are fertilised is called the primary sex ratio.

Understanding the mechanisms that govern primary sex ratio bias is important for biologists and animal breeders, and for preserving endangered bird species and the poultry industry. It can help researchers discover ways to induce a sex ratio shift to a desired sex at the industrial level. The study primary sex ratio bias in birds, it is important to identify the sex of the bird embryo in the egg as soon as possible following fertilisation. Determining the sex early is important, as embryonic mortality can affect the apparent primary sex ratio bias if the sex of the egg is determined after incubation, which requires that the egg is laid.

In addition, this method was used to determine whether male or female chicken eggs differ in their yolk metabolites to determine the feasibility of using such differences to identify the sex of the embryo before incubation.