Response to selection for time interval between ovipositions in the hen

Data were collected from seven generations of selection for reduced time interval between oviposition in a line of Single Comb White Leghorns. This study involved 151 sires, 539 dams, and 2100 female progeny. Oviposition time was measured from 174 to 280 days of age. The only deliberate selection practiced was for reduced oviposition time interval. The mating system was random with the restriction of full or half sib matings. The reduction in oviposition time interval has been 73 minutes or 4.8 percent. There were no significant changes for total egg number, body weight or age at first egg. Rate of lay after reaching 50 percent production to 280 days has increased (P less than .07). Egg weight has declined five percent. Heritability estimates for intra-clutch time interval from correlations were .33 +/- .08, .36 +/- .09 and .35 +/- .15 by sire, dam, and combined components, respectively, .36 +/- .15 by regression of offspring on dam and .39 for realized. The magnitude of the selection differential decreased, over time. The genetic correlation of time interval with early production (280 days) was --.43 +/- .13, and with total egg production (500 days) was .20 +/- .27. The genetic correlations of time interval with egg weight and age at first egg were high and positive; and with body weight, it was negative. The increase in clutch size and the days between clutches during the time of this study were both highly significant.