Genetic variation in the time of oviposition in the laying hen.

1. The distribution of oviposition times in modern layers is relatively narrow. Consequently, in management systems where hens have to compete for nestboxes, some eggs will be laid on the floor. 2. The purpose of this study was to investigate the possibility of using genetic methods to change oviposition time while maintaining a high production rate. 3. The mean oviposition times of 464 hens from three selection lines were calculated using time-of-lay records for every egg laid until the hens reached 51 weeks of age. 4. Heritability estimates for mean oviposition time were high for each of the three lines: 0.38, 0.68 and 0.78. 5. The three lines differed in terms of the genetic correlations between mean oviposition time and certain important production traits. It should, however, be possible to shift the mean oviposition time while maintaining a high production rate. 6. It is suggested that the spread in oviposition times be increased by performing divergent selection for mean oviposition time and by mixing the different genotypes in the same commercial flock, kept on the floor or in other non-cage systems.