Responses in partial, residual and annual egg production expected from selection on part record in synthetic white leghorn flock

Data pertaining to the first generation of a Synthetic White Leghorn flock were used to estimate the heritabilities of and genetic correlation between partial egg production or diversely segmented part records and other traits such as age at sexual maturity, residual and annual egg production, and to compare the expected genetic gain from selection on partial egg number or partial percent production with correlated response in other traits. The estimated heritabilites for six measures of egg production were ranged from .29 to .35, while heritability for age at sexual maturity (SM) was intermediate (.48). Genetic correlations between partial egg number (P) and annual egg number (A), and partial percent production(P’) and annual percent production (A’) were .51 and .72, respectively. Genetic correlation between P and SM was estimated largely negative (-.64), while correlation between P’ and SM was positively intermediate (.34). In comparing direct response from selection on partial production (P or P’) with another response in correlated trait, selection on P would be 25% more efficient than selection on P’ for improving A, while selection on P’ would be 94% more efficient than selection on P for improving A’. For shortening SM selection on P would be 98% more efficient than selection on P’.