TABLE 2.

Estimated genetic parameters in a population of laying hens

Parameter	Classical analysesa	Equations 4 and 5
Phenotypic variance	13,706b	13,725c
Direct genetic variance	917***	960***
Associative genetic variance	—	132**
DA genetic covariance	—	99 NS
Residual correlation	0.12***	0.09***
% heritable variationd	6.7%	20.0%

Significance levels were obtained from likelihood-ratio tests comparing the full model to the model omitting the term of interest. **P < 0.01; *** P < 0.001; NS, not significantly different from zero; DA, direct–associative.

^aIn this analysis, the term Z_Sa_S was omitted from the model (Equation 4).

^bObtained as .

^cObtained as .

^dThe percentage of heritable variation was , in which was obtained from Equation 2 by replacing true values by the corresponding estimates, giving 960 + 2 × 3 × 99 + 3² × 132 = 2742 days². (In the classical analyses ).