2.3.1.2. Main observation. Recording took place from 51st to 61st
weeks of age, before the hens’ laying rate fell below 80%. Recordings
by scan sampling method were from 06:00 h to 23:00 h, with one
scan every hour in each area. Continuous observation from 12:00 h
to 16:00 h was added in PSA to obtain more detailed observations
on DB behaviour, especially on its location relative to the feedertrough. These observations were made on two consecutive days
per cage.
Number and location of DB: For each cage, the number of hens
performing DB, defined as a hen squatting and performing vertical
wing shaking, was counted every hour in each area (36 scans per
cage area over 2 days).
In addition, the total number of DB was recorded continuously
in PSA (total of 8 h) using the “all occurrences sampling” technique
(Altmann, 1974). The location of initiation of these DB in PSA was
specified (by the feeder trough or in the central area) in order to
distinguish DB that could be induced by feed as substrate in the
feeder trough rather than by litter delivered in the PSA.
Number of PS: PS behaviours were recorded every hour in each
area (36 scans per cage area over 2 days). The number of hens performing
ground pecking or ground scratching was defined as the
number of hens standing, pecking repeatedly on the ground, or
scratching repeatedly on the ground with one or two legs. These
behaviours were recorded only when birds were standing, in order
to distinguish them from pre-laying and DB behaviours.
Hen distribution in cage: The number of hens presentin each area
of the cages was counted every hour (36 scans per cage area over 2
days): a hen was considered as being in the area when at least its
head and half of its body were in this given area.