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

- Paper I -
seem to impair the number of embryos (Toplis et al., 1983), litter size or farrowing rate
(Sørensen, 1994; Sørensen & Thorup, 2003) in sows.
When looking isolated at energy intake in pregnancy, there is apparently no effect of low
energy intake (21.6, 23.0 MJ ME day -1 ) the first four weeks on the number of embryos
(Kirkwood et al., 1990), litter size or farrowing rate (Sørensen, 1994). However, this is perhaps
only the case when sows are in a good condition at weaning because Kirkwood et al.
(1990) found a lower number of embryos in sows restricted fed during lactation (36.1 MJ
ME day -1 ) and the first 25 days of pregnancy (21.6 MJ ME day -1 ) compared to sows fed
close to ad libitum in lactation and restricted fed the first 25 days of pregnancy.
Very low feed intake (10.6 MJ ME day -1 ) day one to day ten in pregnancy did not affect the
number of piglets born (total or alive) or the farrowing rate (Dyck & Cole, 1986). However,
as found in the study by Dyck & Strain (1983), it seems that low feed intake only has an
effect after day ten of pregnancy, so perhaps a longer period of very low energy intake
would have influenced the farrowing rate in sows. This is confirmed in a study by Sørensen
& Thorup (2003) who found that very low energy intake (13 compared to 49 MJ ME day -1 )
the first 28 days in pregnancy, reduced the litter size significantly.
All in all, there seems to be no evidence that high (≥38.4 MJ ME day -1 ) energy intake in the
first 28 days of pregnancy impair the litter size in sows. It seems that low energy intake
(21.6 MJ ME day -1 ) the first four weeks of pregnancy may impair the litter size only in
sows fed very restricted during lactation. Very low energy intake (10.6 MJ ME day -1 ) the
first ten days in pregnancy does apparently not impair the litter size or the pregnancy rate
but very low energy intake (13 MJ ME day -1 ) for a longer period (28 days) may impair the
litter size.
4. Effect of energy intake in mid-/late pregnancy and in several successive pregnancies
In Table 3, the results from the seven studies presented in this chapter are summarized. In
these experiments, the effect of energy intake in mid- and late pregnancy and in several
successive pregnancies on number of embryos; litter size and/or culling rate has been studied.
34