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

- Paper I -
Therefore, the aim of this review is to consider whether the variation in feed intake in a
group of non-lactating female pigs can influence the variation in litter size and pregnancy
rate in practice.
Emphasis will be upon studies made in the eighties and forth. Several studies in the sixties
and seventies have examined the effect of energy intake on pregnancy rate and litter size.
However, intense genetic selection has changed the genotype of breeding sows why some
of the early work may no longer be relevant to commercial sow herds (Ashworth & Antipatis,
1999).
Pope (1994) and Foxcroft (1997) point out that it is important to consider the effect of nutrition
in the different reproductive stages of the sows separately because the effect in the
different phases can vary. Furthermore, from a practical point of view, it is important to
know when the sow’s reproduction is most susceptible to a low or a high energy intake because
only then it is possible to adjust the feeding system in the different stages. This could
be of outmost economical importance for the individual farmer because individual feeding
procedures, like for instance one feeding stall per sow, are much more expensive than
group feeding procedures, like floor feeding. Therefore, in this review, the effect of energy
intake will, whenever possible, be divided into 1) Effect of energy intake before mating (in
the oestrus cycle or after weaning) 2) Effect of energy intake in the early pregnancy (also
called the embryonic phase i.e. the first 35 days after fertilization) and 3) Effect of energy
intake in the mid and late pregnancy.
2. Effect of energy intake before mating
In Table 1, the results from the 12 experiments presented in this chapter are summarized. In
these experiments, the effect of energy intake before mating on ovulation rate; number of
embryos and/or pregnancy rate has been studied.
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