Reproduction performances and conditions of group-housed non ...

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2.2.4 Aggressive interactions, skin lesions and lying solitary
Involvements in aggressive interactions (Barnett et al., 1981; Mendl et al., 1992), skin le-
sions (Barnett et al., 1992) and frequency of lying solitary during resting periods (Barnett et
al., 1984; Bonde, 2004) were used as indicators of stress. For a discussion of why these
parameters are believed to be suitable indicators for stress, see review by Kongsted (2004a).
The first hour after weaning and half an hour at mating and three weeks after mating outside
the resting period, the number of aggressive interactions the individual sow participated
in was recorded. An interaction was defined to have occurred when one sow initiated
a behaviour, which was clearly directed at another sow in the group (Bradshaw et al.,
2000). All interactions were categorised into four different types: 1) a threat, 2) one
bite/knock/push, 3) several bites/knocks/pushes and 4) bites from both sows (Jensen et al.,
1996; Bradshaw et al., 2000; Jensen et al., 2002).
The total number of skin lesions divided into four length categories (10
cm) on head, ears, neck and shoulders (Barnett et al., 1992) were recorded for all F-sows by
a research technician. All lesions (except shoulder wounds because they are not a result of
aggressive interactions) were recorded (also superficial scratches). The recordings were
performed in the home pen of the F-sows, i.e. in a group of sows. Total length was calculated
as total number in the length category 1-4 multiplied with 0.5, 2.5, 7.5 and 10 respectively.
The behaviour of the F-sows was recorded during resting period for 25 minutes. Every five
minute the position of the individual sow (in a feeding stall, in the dung area, in the resting/activity
area) was recorded and the ten F-sows’ behaviour were categorised into the
following: 1) lying/sitting solitary, 2) lying/sitting socially or 3) standing/walking/running
(if a sows position was a feeding stall her behaviour was not recorded). Lying/sitting solitary
was defined as lying/sitting in a distance of 20 cm or more from other sows (Bonde,
2004). If the sow was lying/sitting more frequently than not, the sow was categorised as
lying. If the sow was lying/sitting solitary more frequently than lying/sitting socially, the
sow were categorised as lying solitary.
2.3 Timing and frequency of recordings
The timing of registrations were first of all chosen to give information of the sows’ conditions
from weaning to first mating and from first mating to three weeks in pregnancy because
these phases seems to be the main periods of relevance regarding reproduction performance
(Kongsted, 2004ab). The timing of the above mentioned recordings and measurements
are presented in Table 2. The recordings took place at weaning, at mating, ap-
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