Interactions between layer age and housing
system Several interactions between layer age and
housing system were found. Egg weight increased
with layer age in both housing systems. The FR
layers had lower egg weight than the BC layers at
the beginning of the experiment, but egg weight
increased faster and was greater at a layer
age of 59 weeks (Figure 1). Eggshell percentage
decreased with layer age in the BC group,
whereas eggshell percentage fluctuated with age
in the FR group (Figure 2).
Overall, albumen height and dry matter
content decreased with age, whereas yolk dry
matter content increased with layer age.
Albumen pH increased slightly until week 41
and thereafter decreased. This increase or
decrease with layer age differed between housing
systems, resulting in an interaction between layer
age and housing system. This was demonstrated
for albumen height (Figure 3a), albumen pH
(Figure 3b), albumen dry matter content (Figure
4a) and yolk dry matter content (Figure 4b). For
all these characteristics, the BC group showed a
more consistent increase or decrease with layer