Researchers from Wageningen UR and Hendrix Genetics found heritable variation in uniformity of eggshell colour of brown eggs in laying hens. This means that by breeding, eggs could become more uniform brown. Consumers prefer a certain degree of uniformity of eggs in terms of colour and size. Furthermore, they found that uniformity of eggshell colour in purebred and crossbred laying hens is genetically a similar trait.
There is recent evidence that uniformity is under genetic control. In this recent study published in Genetics Selection Evolution by Han Mulder and co-workers from Hendrix Genetics they found significant heritable variation in uniformity of eggshell colour of brown eggs in purebred and crossbred laying hens. The researchers extended the existing statistical methodology to estimate the genetic correlation between uniformity of eggshell color in purebred and crossbred laying hens. The heritability of uniformity of eggshell color was about 1% for a single egg, but the heritability was about 0.15 when using multiple egg records per hen. Furthermore, the genetic variance was large. Therefore, they concluded that uniformity of eggshell color of brown eggs can be improved by selection. The developed methodology can be used to study the purebred-crossbred correlation for uniformity of other traits and in other species.