Number of dams (n), mean (with SD), and minimum and maximum observation (Min—Max) of the production traits of the dams of the studied population of WA leghorn chickens.

The p value indicates significance of the production trait when added as a fixed effects in the model of KLH binding IgM natural antibody titers at 16 weeks of age (not corrected for multiple testing). In case of significance, the estimated regression coefficient (R) is given.a Body weight of the dams was recorded once in the indicated period.b Egg production was recorded as the summed number of eggs laid in the indicated period.c Egg weight was based on the average weight of the eggs laid on 7 subsequent days in the indicated period. Eggs less than 30 g, and eggs over 90 g were excluded, as well as double-yolk eggs.d Egg breaking strength was recorded as the average breaking strength of all eggs laid during a 6 day-period in the indicated period. Egg breaking strength was recorded within one week after collection of the last egg.e Early eggshell whiteness was based on the average of the three first eggs laid. Early eggshell whiteness was recorded as color values on the L*a*b* color space measurement scale. The L* value represents a black (0) to white (100) scale that was used for early eggshell whiteness measurements.f Haugh unit was based on the average of three consecutive eggs laid in the indicated period. Eggs were stored for no more than two days.g Feed conversion ratio was calculated as the feed intake (g) divided by the egg mass produced (g) during a measuring period of three consecutive weeks.Number of dams (n), mean (with SD), and minimum and maximum observation (Min—Max) of the production traits of the dams of the studied population of WA leghorn chickens.