Long‐term selection for increased egg production¹

Abstract

1. Results are presented of a closed White Leghorn flock selected for increased egg production over a period of 17 years. 2. During the last 7 years a random breeding sample of the production flock served as a genetic control. 3. Regressions of deviations of the production flock from the control flock on years, were highly significant for age at sexual maturity (‐2.18 d), egg production up to 275 d old (3.04 eggs), egg production to 500 d old (5.04 eggs) and egg weight at 14 months old (October) ( — 0.79 g). 4. The heritability of egg production up to 275 d old declined significantly from 0.35 to 0.19. 5. The realised heritability of egg production up to 275 d old was estimated to be 0.14. 6. The genetic correlation between egg production up to 275 d old and production in the residual part of the year was 0.48. 7. The rate of inbreeding in the production flock was 0.515% per generation and the expected rate of inbreeding in the control flock 0.21% per generation.