I like the idea of the bio marker, I wonder how early it can be detected…?Here were two other approaches I read about:
https://www.theguardian.com/food/20...ound-waves-eggs-ethical-slaughter-male-chicks
https://www.timesofisrael.com/now-y...ns-before-they-hatch-instead-of-culling-them/
Both seem practical - and I love the sound one - maybe playing Mozart to the broody hens will get them to lay all girls! Of course I hope it isn't some awful noise that upsets the hens. The one with the male marker is clever but I suspect will never be acceptable to consumers so the eggs will get wasted.