Incubation period of White Leghorn eggs as influenced by lines and pre-incubation storage period

Hatching time of long-term selected strain (PL 2) and an unselected control line (PL 3) were studied under pre-incubation stotage period of 12 days. Chicks of PL 2 had significantly delayed hatching time than the control line (PL 3) by 4 h. Hatching started at 468 h and was completed by 516 h of incubation. Hatching, t)me exhibited normality of distribution. Sex did not effect the hatching time. Pre-incubation storage length of more than 6 days significantly affected hatching time with regression coefficients of hatching time on storage length being 0.92±0.16 and 1.20±0.27 hid in PL 2 and PL 3, respectively during the entire period of 12 days. Linear component of regression of hatching time on a storage length explained 61.7 and 75.3% of the variability. The contribution of quadratic terms was small and non-significant. Interactions among the line, sex and storage length were non-significant.