Analysis of genotype-environment interactions between layer lines and hen housing systems for performance traits, egg quality and bone breaking strength - 2nd communication: Egg quality traits

Egg quality of white lavers (Lohmann Selected Leghorn, LSL) and brown layer s (Lohmann Tradition, LT) was compared between three different housing syst ems battery cages aviary and intensive free range housing. The laying perio d started in April 1999 and ended in March 2000. Each four weeks samples of 10% of all daily produced eggs and each twelve weeks samples of 20% of all daily produced eggs were collected for testing egg quality traits. The LSL -layer line tended to have better egg quality than the LT-layer line. The L SL-hens showed significantly higher values for Haugh Units (91.62), yolk we ight (16.69 g), eggshell thickness (324.22 mum) and eggshell density (75.88 mg/cm(3)), but significantly lower values for yolk colour (12.9) and propo rtions of eggs with meat and blood spots. Comparing egg quality traits betw een housing systems revealed that a consistent advantage for one housing sy stem was not obvious. Both layer lines exhibited higher Haugh Units in the aviary. Eggshell thickness was higher in the intensive free range system fo r both layer lines and eggshell density only for the LT-layer line. The LT- hens layed eggs with a shell thickness of 323.53 mum and a density of 74.09 mg/cm(3) and LSL-hens with a shell thickness of 325.49 mum and a shell den sity of 75.65 mg/cm(3). Yolk weight increased in battery cages for both lay er lines. The highest grade of yolk colour was found in the free range syst em for LSL-hens and in battery cages for LT-hens. The number of meat spots was significantly lower in eggs of the LT-hens kept in the free range syste m. Regarding blood spots of the LT-hens and meat and blood spots of the LSL -hens no significant differences could be shown. The results of this study clearly demonstrate that layer line specific reactions have to be expected in the three tested hen housing systems.