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

- Outline of this thesis -
OUTLINE OF THIS THESIS
A basic knowledge of how group housing varies in practice is a prerequisite for identifying
important causes for impaired reproduction performance in group housed non-lactating
sows. A short introduction to group housing in practice is therefore provided in How does
group housing vary in practice.
With the aim to identify, which processes that may go wrong and why, a brief review of the
literature of reproduction physiology was carried out. This review is presented in Appendix
1.
As discussed in Appendix 1, several studies have indicated that group housing may lead to
individual variation in energy intake and increased stress. At the same time there are several
indications that energy intake and stress may influence the reproduction physiology of the
sow. Therefore, two review papers were written to consider whether individual variation in
energy intake (paper I) as well as stress and fear (paper II) could be contributing reasons for
the lower reproduction performance in group housed compared to individually housed sows
found in some on-farm studies.
Based on these two review papers it was concluded that there are indications that group
housing practice may lead to individual variation in energy intake, stress and fear which
may influence reproduction performance negatively. However, traditional methods for assessing
feed intake, stress and fear in sows are not suitable in large-scale on-farm studies or
for the individual farmer, who wants to find out whether level of stress, fear and feed intake
could be contributing reasons for reproduction problems in group housed sows. Therefore,
a need for indicators of stress, fear and energy status suitable for use under practical conditions
was identified. It was possible to define such indicators based upon existing knowledge
and these indicators are presented and discussed in paper II and paper III. However,
whether these indicators are suitable to express variation in sows susceptibility for a good
reproduction performance under practical conditions was not known. Therefore a study in
14 herds with different layouts and management routines was carried out. The level, the
between-farm and within-farm variation in indicators of feed intake, fear and stress from
the 14 herds are presented and discussed in paper III. In paper IV the relation between the
reproduction performance (e.g. litter size and pregnancy rate) and the indicators of feed
intake, stress and fear are presented and discussed.
In the General discussion, the results from the four papers are discussed and put into perspective.
Finally, a general conclusion is put forward in Conclusions.
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