Eye pigmentation–based in-ovo chicken sexing via precision breeding

) retained normal pigmentation. This clear visual dimorphism enables accurate sexing by routine egg candling. Fertility and reproductive performance of knockouts were comparable to wild-type chickens, and genotyping confirmed 100% prediction accuracy. Unlike many current technologies, our approach requires no complex instrumentation and allows early detection during incubation. This work provides a practical and ethical solution to chick sexing, with significant advantages for commercial hatcheries. More broadly, this study illustrates the potential of precision breeding to address pressing animal welfare concerns in the modern poultry industry.