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

- Paper I -
Abstract
The number of group housed non-lactating sows is increasing rapidly in Europe as a consequence
of changed legislation initiated by elevated public concern of animal welfare. Lower
litter size and pregnancy rate in group compared to individual housed non-lactating sows
have been observed in several on-farm experiments. The aim of this review is 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 is discussed. The results indicate that low compared
to high energy intake before mating may impair litter size in gilts and in sows that
experienced severe weight loss during lactation. Furthermore, it seems that moderate compared
to low energy intake the first three days after mating may reduce litter size in the gilt
but not in the sows. However, very low energy intake the first four weeks in pregnancy may
impair litter size in gilts and sows and also pregnancy rate in gilts. Whether the last mentioned
is also the case for sows is not possible to conclude. However, it seems that low energy
intake for several successive parities can increase the risk of being culled as a consequence
of not being pregnant. Based upon studies indicating that low ranking sows may
consume considerably less than high ranking sows (e.g. 50-80%) in group housed systems,
it is suggested that variation in feed intake in a group of restricted fed pregnant female pigs
may be large enough to influence pregnancy rate and litter size.
Keywords: Sow, Gilt, Group housing, Energy intake, Reproduction, Litter size, Pregnancy
rate
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