Scientists have demonstrated a non-invasive technique using light to reveal the internal contents of chicken eggs, according to a June 19 study published in the Cell Press journal Newton. The approach may help address the meat industry's practice of killing billions of male chicks at birth by enabling early identification of chick sex and egg quality without breaking the shell.
The research found that when light enters an intact bird eggshell, it bounces back and forth many times, with photons traveling as far as two meters within the four-centimeter interior of a chicken egg. By studying how photons migrate through unbroken eggshells before incubation and during eight days of embryonic development, researchers believe they can determine the sex of developing embryos, assess egg quality, and identify whether intact eggs have been fertilized.
"This previously unobserved phenomenon might help to investigate the content of the egg non-invasively even during embryo development in fertilized and incubated eggs, addressing the ethical dilemma of culling male chicks," said Lennard van den Tweel, a researcher with hatchery technology company HatchTech B.V. in the Netherlands and an author of the study.
Currently, over 300 million male chicks are slaughtered shortly after birth each year in European hatcheries because they cannot lay eggs or grow fast enough for profitability. Animal rights advocates widely oppose this practice, leading many countries to consider laws aimed at ending it.
Optical spectroscopy techniques that use light to reveal physical or chemical properties have traditionally been used in medicine for mammography and monitoring organ function, as well as agriculture for measuring fruit ripeness or wood properties. While such methods have also studied egg characteristics before, "the complex way light migrates through the egg is largely ignored," said van den Tweel.
Further research will be needed to fully understand these "complex and unusual" optical properties so that sensitivity can be improved. The team plans additional studies on how photon behavior changes throughout embryo development and on each component's optical traits within an egg. "The highly scattering nature of the avian eggshell might have evolved to protect the embryo from ultraviolet light or reduce heat dissipation when parents are out foraging," said Damagatla.
