y = Xb+Z1q+Z2u+Z3m+e (Model 2)
where, y is a vector of the phenotypic values for the hatch
weight; m is a vector of random maternal (dam)
environmental effects; Z3 is incidence matrix for m. The
mean and variance for the maternal (dam) effects can be
defined as: m~N (0, Sm2
), where S is the structuring matrix
for the maternal (dam) environmental effects and m2
is
variance due to dam.
Thresholds for evaluating significance of QTL were
calculated by a numerical method (Piepho, 2001). The
threshold levels established by this method vary as a function
of the trait studied and the chromosome length. A 1%
chromosome-wide threshold for the significant linkage was
employed. A suggestive linkage was employed using a 5%
chromosome-wide threshold. The 1-LOD drop method was
used to estimate the support intervals (SIs) for the identified
QTL (Lander and Botstein, 1989).