Estimating the purebred–crossbred genetic correlation for uniformity of eggshell color in laying hens

Table 6 Genetic variance in environmental variance in multiple-hen cages and the genetic correlations with individual cages for eggshell color

Parameter	Crossbred	Purebred simulations
Parameter	Crossbred	Mean	SD
Genetic variance	0.067	0.14	0.015
Genetic correlation for eggshell color	0.86	0.93	0.018
Genetic correlation for environmental variance different definitions^a	0.70	0.73	0.10
Genetic correlation for environmental variance equal definition^b	0.95	1.00	–

Comparison of 20 replicates (mean and standard deviation) between purebreds and crossbreds
^aFor purebreds, in individual cages, the environmental variance contains only within-individual variance, whereas the environmental variance in multiple-hen cages (also crossbreds) contains within-individual variance and between-individual variance, i.e. different definitions of environmental variance
^bHere the interest lies in the genetic correlation between individual variance in purebred and crossbred laying hens, i.e. equal definition of environmental variance. Therefore, the expected genetic correlation in the purebred simulations is 1.00. Based on this assumption, Eq. 17 can be used to calculate the estimated genetic correlation between within-individual variance in purebred and crossbred laying hens

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