Agriculture Reference
In-Depth Information
oocytes. These differences in maturation of the follicles and oocytes may contribute to
the effects of feed restriction on embryo survival.
In 1992, Morrow
et al.
(1992) found that 40% of 135 US farms had a lower or equal litter
size in second parity compared with that in the first parity. Within farms, it appears that
first litter sows, which have a lower increase in body weight between first insemination
as gilts and first weaning, have an increased risk for reduced litter size in second parity,
known as second litter syndrome (Hoving
et al.
, 2010). This syndrome is both related to
the body weight increase during pregnancy and the body weight loss during lactation.
Moreover, sows suffering from a low litter size in the second litter also have lower litter
sizes in subsequent parities and are culled one parity earlier (Hoving
et al.
, 2011), which
stresses the economic importance of the second litter syndrome.
Body weight losses consist of both protein and fat losses. Clowes
et al.
(2003) noted that
protein losses during first lactation seem to be more related to subsequent reproduction
performance than fat losses, but Schenkel
et al.
(2010) found similar effects of backfat
losses and protein losses on litter size in second lactation. Schenkel
et al.
(2010) further
found that sows harbouring the highest 50% body weights at farrowing (207-245 kg)
had larger effects of fat losses on their subsequent litter size compared with sows of
lower body weights at farrowing. Therefore, the relative importance of lactational protein
losses vs. fat losses for fertility likely depends on many factors, including body weight
and genotype.
The most logical way to prevent post lactational reproductive problems is to prevent
excessive weight loss during lactation. This can be achieved by optimising gilt development,
optimizing feed or nutrient intake during gestation and lactation, or by using strategies
that reduce suckling in late lactation. These will all be discussed below.
Gilt development
Gilt development, more specifically growth rate and age at first insemination can have a
major impact on subsequent fertility, not only in first, but also in second parity (reviewed
by Bortolozzo
et al.
(2009); Hoving
et al.
, 2010). For a review on optimal gilt development,
see Chapter 1 (Rozeboom, 2015).
Feed intake during pregnancy
Over the last 25 years, several studies have shown that excessive feed intake during
pregnancy or high body weight at farrowing decreases the voluntary feed intake during
lactation (e.g. Dourmad, 1991; Mullan and Williams, 1989; Quesnel
et al.
, 2005a; Yang
et
al.
, 1989), which presumably is related with a higher glucose intolerance in these animals
(Quesnel
et al.
, 2005b; Weldon
et al.
, 1994). On the other hand, Yang
et al.
(1989) already
showed that insufficient feed intake during pregnancy (resulting in thin sows) cannot be
compensated for by increased voluntary feed intake during lactation in first litter sows
and resulted in a prolonged weaning-to-oestrus interval. Therefore, gilts should be fed
according to their requirements for maintenance, reproduction and growth but not be
