Ms. Khatkar et al., EVALUATION OF SELECTION BASED ON SPECIFIC-GRAVITY AND EGG WEIGHT FOR IMPROVEMENT OF SHELL THICKNESS IN LAYER CHICKEN, Indian Journal of Animal Sciences, 67(7), 1997, pp. 599-601
Data collected on 4 568 pullets of 2 strains of White Leghorn were use
d for prediction of shell thickness from egg weight, specific gravity
and shape index. The R-2 values for prediction of shell thickness from
specific gravity ranged from 65.69 to 78.01%, Inclusion of egg weight
improved the prediction significant (R-2 = 69.9 to 80.0%). Shape inde
x did not improve the efficiency of prediction Analysis of relative ef
ficiencies of selection based on specific gravity and an index of spec
ific gravity and egg weight for genetic improvement of shell thickness
was made based on genetic parameter estimates. Selection on specific
gravity was 7.3% less efficient than direct selection for shell thickn
ess. Selection based on index of specific gravity and egg weight was o
nly 1.6% less efficient than direct selection for shell thickness.