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

- Summary -
SUMMARY
In the last decade the number of group housed non-lactating sows has been increasing in
Europe. This is mainly caused by elevated public concern of animal welfare with changed
legislation as a consequence. However, among herds with group housed non-lactating sows
there is a huge variation in the reproduction results. The apparently large variation in farrowing
rate and litter size indicates that it will be possible to improve these parameters in
some of these herds. On this background the overall aim of this thesis was to produce
knowledge that managers can implement in their decision-making to improve the reproduction
performance of group housed non-lactating sows. The specific aims were to identify
important causes for impaired reproduction performance in group housed non-lactating
sows and to develop and evaluate indicators suitable for use in decision-making in commercial
sow herds.
First, a review of the literature of reproduction physiology was carried out (Appendix 1). It
was concluded that the endocrine regulation of reproduction might be influenced by energy
intake and stress. Since experimental studies had indicated that group housing might lead
to unequal feed intake and social stress, the hypothesis was put forward that individual
variation in feed intake and social stress might cause impaired reproduction performance in
some group housed non-lactating sows. To illuminate this further, two review papers were
written a) to consider the effect of energy intake (Paper I) as well as social stress and fear
(Paper II) and b) to define indicators of feed intake, stress and fear suitable for use in practice.
A study in 14 herds with different layouts and management routines was carried out to
evaluate the defined indicators (Paper III) and to investigate whether the indicators were
suitable to express variation in the reproduction performance of sows under practical conditions
(Paper IV).
Paper I
The aim of this review was to consider whether the variation in energy intake in a group of
non-lactating sows can influence variation in litter size and pregnancy rate in practice.
Through a review of existing literature with main emphasis on publications after 1980, the
effect of energy supply before mating and in pregnancy on pregnancy rate and litter size
was discussed. Based upon experimental studies, indicating that low ranking sows may
consume considerably less than high ranking sows (e.g. 50-80%) in group housing, it was
suggested that the variation in feed intake in a group of restrictedly fed pregnant female
pigs may be sufficiently severe to influence pregnancy rate and litter size.
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