2.5.1. Experiment 1
2.5.1.1. Effect of main factors (group size and feed–litter). In order to
study the group size effect, as well as the effect of additional feed
distribution as litter substrate, the number of DB in a cage, number
of PS in a cage and number of hens were expressed for 60 hens in
order to be able to compare the 3 group sizes. Then, the effects of
feed–litter distribution and group size were analysed on:
- number of DBs in the cage, proportion of DB performed in PSA, in
the middle area, and in nest area;
- number of PS in the cage and in the PSA, proportion of PS performed
in PSA, in the middle area, and in nest area;
- number of hens in PSA, in the middle area, and in nest area;
with an ANOVA model where fixed effects were feed–litter
and group size tested (data from scans). Interactions between
feed–litter and group size were systematically tested. A
Shapiro–Wilk test was used to verify the normality and a Levene
test was used to verify the homoscedasticity before using any
ANOVA analysis.
Number of DBs in the PSA and proportion of DBs by the trough in
PSAobserved during continuous observations were analysed with a
stratified Wilcoxon–Mann–Whitney test (litter stratified by group
size and conversely). Non parametric test was used due to low
number of repetitions (data summed at the cage level).