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

- Paper III -
1. Introduction
The number of group housed non-lactating sows is increasing rapidly in Europe as a consequence
of changed EU legislation (Council Directive 2001/88/EC amending Directive
91/630/EEC Laying Down Minimum Standards for the Protection of Pigs) combined with
extraordinary national laws (Baustad & Lium, 2002; The welfare of Farmed Animals (England)
(Amendment) Regulations 2003).
However, since individual housing of sows has been the far most common system in commercial
sow herds for many decades, most of the information available about sows’ production
and condition arrives from studies with individual housing. Although the amount of
scientific work related to group housing of sows has increased markedly in the last ten
years, there is still a lot of unanswered questions concerning the function of the sows in
commercial herds with group housed non-lactating sows.
Several experimental studies indicated that group housing of sows might lead to individual
variation in feed intake, social stress, and fear (reviews by Kongsted, 2004ab). This may
constitute a welfare problem and in addition affect the reproduction results negatively (reviews
by Kongsted, 2004ab). Most of the studies referred to in the mentioned reviews were
performed under conditions that did not always reflect those circumstances seen in practice
which are large group sizes (Nielsen et al., 2000), high stocking rates (Svendsen et al.,
1990), constant introduction of new sows into dynamics groups (Svendsen et al., 1990),
slippery floors (Hansen & Kongsted, 2002) and sows with locomotion problems (Gjein &
Larssen, 1995; Nielsen et al., 2000; Hansen & Kongsted, 2002).
In a few Danish on-farm experiments, level and variation of indicators of feed intake expressed
as growth rate (Fisker, 1994; Nielsen, 1995; Fisker, 1999; Hansen, 2000) and stress
expressed as adrenocortical response to additional stressors (Jensen et al., 1995) in group
housed sows has been assessed. However, systematic information of variation in feed intake,
fear and social stress in sows group housed in the entire non-lactating period under
various conditions are lacking. This is most likely, to some extent, because traditional
methods for assessing these factors are expensive and/or time-consuming and therefore
difficult to employ under practical conditions in large scale. First of all, it is therefore necessary
to identify indicators of energy intake, stress and fear suitable for use in practice.
Based upon existing knowledge, a suggestion for such indicators has been put forward in
Kongsted (2004a). However, whether these indicators are suitable for use in group housed
sows under various on-farm conditions is not known.
On this background the aim of this study is 1) to evaluate indicators believed to be suitable
to gain information of variation in feed intake, social stress and fear in non-lactating sows
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