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

- Paper IV -
1. Introduction
Group housing of non-lactating sows is becoming increasingly widespread in commercial
sow herds in European countries as a result of changed EU-legislations (Council Directive
2001/88/EC amending Directive 91/630/EEC Laying Down Minimum Standards for the
Protection of Pigs) and national extraordinary laws (Baustad & Lium, 2002; The welfare of
Farmed Animals (England) (Amendment) Regulations 2003) initiated by elevated public
concern of animal welfare. Although no legislation yet, similar tendencies are also seen in
other parts of the world (Trezona, 2003).
Impaired reproduction in the shape of reduced litter size or pregnancy rate has been observed
in group compared to individually housed non-lactating sows in several on-farm
studies (Hurtgen et al., 1980; Fisker, 1995; Peltoniemi et al., 1999; Hansen, 2000). Conversely,
in other studies, no difference (England & Spurr, 1969) between grouped and individually
housed sows or even opposite effects (Bates et al., 2003; Hansen, 2003) have been
found. The divergent results are probably a result of differences in the function of the group
housing systems and shows that group housing do not ‘automatically’ lead to poor reproduction
performance.
Results from experimental studies, not necessarily reflecting conditions seen in practice
have indicated that the impaired reproduction performance seen under some circumstances
in group housed non-lactating sows might be a result of social relations causing individual
variation in energy intake (review by Kongsted, 2004b), fear and stress (review by Kongsted,
2004a).
Further, registrations of various indicators of feed intake, stress and fear in sows group
housed under various on-farm conditions suggest a large individual variation in these characteristics
(Kongsted et al., 2004). However, whether these individual variations are severe
enough to impair the reproduction performance in sows group housed in commercial herds
is not known. Therefore, a detailed farm study including 14 commercial sow herds with
different layout and management routines was carried out to investigate the relation between
various indicators of feed intake, stress and fear and the reproduction performance in
practice.
2. Materials and methods
2.1 Design and herds
In 14 herds with group housed non-lactating sows, ten focal sows (F-sows) in each of four
batches were observed from weaning to farrowing. The ten sows were randomly chosen in
the lactation unit just before the sows were moved to the service unit. The F-sows’ back fat,
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