Cross performance as influenced by selection in pure lines

Abstract
1. The resultant genetic gains in cross performance due to the individual, dam family and sire family (IDS) method of index selection for increased part‐period egg number in their parent lines are described. 2. A randombred control population of known pedigree was used to measure the environmental trends. 3. Selection in pure lines resulted in concomitant improvement in the crosses for the selected as well as the correlated traits. 4. Cross performance was comparatively more than expected on the basis of mid‐parent values, indicating involvement of non‐additive gene action in the expression of cross performance. 5. Crosses responded better to independent culling level selection for egg weight than their parents. 6. Heterosis appeared to increase in later generations as compared with initial generations of selection.