Genetic improvement of egg number and egg weight (antagonistic traits) in hybrid layers based on restricted selection

Data on performance traits of two purebred strain (H and C) and their reciprocal crosses (HxC, CxH) over nine generation was analysed. The studied traits were body weight at 20 and 40 weeks (BW20, BW40) of age, age at first egg (AFE), egg number (EN) to 40 weeks of age and egg weight (EW) of purebred and crossbred groups. Sire component of variances and co-variances among the trait on the traits were computed after accounting for generation and hatch effects. Considering the levels of restriction from 10–100 percent on the egg number, egg weight independently and combination of restricted traits, 30 selection indexes were computed. Results suggest that 60 percent restriction on egg weight alone is the optimum level to have improvement in egg number with a little decline in egg weight. Restriction on egg number alone was not found desirable. However, simultaneously restriction of 10 or 20 percent on egg weight and 90 or 80 percent on egg number respectively, may be desirable preposition to enhance the egg number more effectively with low or negligible change in egg weight.