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

- Paper I -
Therefore, low energy supply compared to flushing does not seem to have any effect when
looking isolated at the period from weaning to mating. Whether it has an effect in sows that
experience severe weight loss during lactation is difficult to say because the results are inconsistent.
King & Williams (1984) did not find any significant interactions between feed
intake in lactation (25 MJ ME day -1 or ad libitum) and feed intake from weaning to mating
(19.3 or 50.1 MJ ME day -1 ) on litter size in first litter sows even though the restricted fed
sows had a weight loss of 37 kg during lactation. However, Baidoo et al. (1992) found a
significant interaction between feed intake during lactation and feed intake after weaning in
second parity sows because low feed supply after weaning reduced embryo survival only in
sows fed restricted during lactation.
Nielsen et al. (1981), reported that fasting compared to 44.8 MJ ME on the day of weaning
resulted in a non-significant (P=0.08) smaller litter size. In contrast, Tribble & Orr (1982)
were not able to find any effect of fasting two days after weaning. Perhaps the lacking effect
in Tribble & Orr (1982) is due to a shorter lactation length (18-38 days compared to
28-56 days in Nielsen et al. (1981) since Allrich et al. (1979) only found an effect of starvation
after mating on litter size in sows lactating for 30 days and not in sows lactating for 21
days. Weight loss during lactation is not reported in the mentioned studies but it is however
likely that weight loss is higher, the longer lactation length, why these results confirm that
the effect of low feed intake after mating depends upon the condition of the sow at weaning.
All in all, there seems to be no evidence of an effect of low energy intake (19.3-37.2 MJ
ME day -1 ) compared to flushing (ad lib or close to ad lib) from weaning to mating on ovulation
rate in sows. However, it is possible that low feed intake (37.2 MJ ME day -1 ) has a
negative effect on litter size in sows that experienced severe weight loss (e.g. 39 kg) during
lactation. Pregnancy rate does not seem to be influenced by energy intake before mating.
3. Effect of energy intake in early pregnancy
In Table 2, the results from the 13 experiments presented in this chapter are summarized. In
these experiments, the effect of energy intake in early pregnancy on number of embryos
and/or pregnancy rate has been studied.
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