Surprising science behing poultry delicacy

Researchers have revealed that the blue egg first appeared in poultry as a result of an ancient, harmless retrovirus.

The chicken's blue egg, which is reportedly prettier, tastier and cleaner-breaking than the traditional brown one, is becoming more and more popular in supermarkets.

Scientists from the University of Nottingham's School of Biology, set out to find out where, when and why certain poultry began producing these coloured eggs.

Studying over a four-year period, the team found that the first ones were produced by a native South American chicken called the Mapuche fowl and their European descendants, Araucana.

The scientists used unique genetic resources, used by "fancy" poultry breeders, to identify the genetic mutation that first produced the blue chicken egg some 200 to 500 years ago.

Further studies later revealed that the coloured egg shell was the result of a harmless retrovirus in the domestic chicken, which carries its genetic blueprint in the form of ribonucleic acid (RNA).

RNA has the ability to transcribe itself into DNA, allowing it to become genetically incorporated into a species. In this case, the retrovirus produced a green-blue bile pigment that can be seen in eggshells.

"[This study] shows the importance of viruses in shaping evolution and diversity of species," said David Wragg, a doctoral research fellow, who lead the team.

"When appearing in the population, the unusual egg colouration must have attracted the attention of the owners, who must be praised for having selected the trait in subsequent breeding."

The study has been published in the Public Library Of Science (PLOS) ONE journal.