Egg Production and Egg Composition of Parental Lines and F1 and F2 Crosses of White Rock Chickens Selected for 56-Day Body Weight

Egg production and weights of eggs and their components were measured in body weight-selected lines and in reciprocal F1 and F2 crosses. Nonadditive genetic variation was significant for age at onset of lay; percentage of hen-day ovulations, hen-day egg production, and normal eggs produced; egg weight and shell thickness; percentage of dry yolk and total moisture; shell and yolk dry matter; and ratios of albumen to yolk (A:Y) both on a wet and dry weight basis. There was recombination loss for all of these traits except percentage of hen-day ovulations, dry yolk, and total moisture; and shell dry matter, thickness and wet A:Y ratios. Reciprocal effects were negligible except for percentage of dry albumen and A:Y ratios. Greater yolk dry matter in the high BW line was observed than in the low BW line; this was consistent with observations of lipid overproduction in fast growing populations of chickens.