Agriculture Reference
In-Depth Information
requirements of sows. As reviewed by NRC (2012), sows that spend more than 4 h per
day standing or walking have their maintenance ME requirements increased by 0.0717
kcal/d per kilogram of metabolic body weight (kg
0.75
) for each additional minute spent
standing or walking.
As shown in Figure 6.2, energy retention in the conceptus increases exponentially with
time. For this reason feed allowance may be increased during late gestation to avoid
sows mobilizing body lipid. When daily feed intake is maintained constant throughout
gestation, sows are likely to be in a negative energy balance during late gestation, which
may compound the negative effects of a negative energy balance during lactation on long-
term sow reproductive performance. NRC (2012) estimated that sows typically need 400
g/d extra feed of corn and soybean meal based diets after day 90 of gestation in order
to satisfy increased energy requirements to support the growth of conceptuses. These
levels will vary with anticipated litter size and average piglet birth weight. Increasing feed
intake by more than that required for conceptus growth will increase maternal body lipid
deposition, which may contribute to excess body condition at the time of farrowing and,
as a result, will increase farrowing problems, reduce appetite during lactation, and reduce
sow reproduction and longevity as previously discussed in this chapter.
As described by Dourmad
et al.
(1999, 2008), there are two main components of maternal
body protein deposition in gestating sows, which can be represented as time-dependent
and energy intake-dependent body protein deposition (NRC, 2012). Time-dependent
body protein deposition occurs during early gestation before energy retention is switched
towards fetal growth. Energy intake-dependent body protein deposition reflects the
observed linear increase in body protein deposition with increasing energy intake. This
energy intake-dependent body protein deposition is highest in parity 1 sows. Indeed, as
sows mature the slope of the relationship between energy intake-dependent body protein
deposition and energy intake declines and is estimated to reach 0 in parity 4+ sows
(NRC 2012). The general patterns of time-dependent and energy intake-dependent body
protein deposition have been established, but the actual rates of deposition are likely to
vary among sow genotypes and to be affected by weight losses during lactation. For this
reason, the NRC (2012) model for estimating nutrient requirements of gestating sows
allows model users to adjust maternal body protein deposition, based on observed body
weight and backfat changes during gestation and at defined daily energy intake levels.
Lactation
The single largest determinant of energy requirements of lactating sows is milk production
(NRC, 2012). Given the relatively small contribution of maintenance energy requirements
to total energy requirements, it is not critical to accurately estimate maintenance energy
requirements of lactating sows or to carefully consider environmental factors that
contribute to maintenance energy requirements. Moreover, lactating sows are generally
kept at environmental temperatures that are considerably higher than their lower critical
temperature. A reasonable estimate of maintenance requirements of sows is 100 kcal
effective ME/d per kg bodyweight
0.75
(NRC, 2012).
