Agriculture Reference
In-Depth Information
activity). The NRC (2012) gestation model can be used to estimate energy requirements
and utilization for individual sows. According to NRC (2012), priority is given to satisfy
energy requirements for body maintenance functions, growth of conceptus and maternal
body protein deposition. Energy intake over and above requirements for these three
processes is used for body lipid deposition. If energy intake is insufficient to support
maintenance requirements, growth of conceptus and maternal body protein deposition,
then maternal body lipid is mobilized and used as a source of energy. The prioritization in
energy partitioning is consistent with the observation that growth of conceptus is reduced
only at severe energy intake restrictions (Dourmad
et al.
, 1999). Typical partitioning of
daily effective ME intake is presented in Figure 6.2 for a parity 2 sow.
For sows in a relatively stress-free and thermo-neutral environment, maintenance
requirements are estimated at 100 kcal effective ME/d per kg bodyweight
0.75
. However,
the effect of environmental conditions on maintenance energy requirements of gestating
sows should be considered carefully. Because feed intake of gestating sows is usually
restricted, body heat production is relatively low compared with
ad libitum
-fed lactating
sows or growing pigs. As a result the lower critical temperature, e.g. the effective
environmental temperature below which extra feed energy is required to maintain body
temperature, is relatively high. This scenario is especially true in individually housed
sows that are kept on concrete flooring which induces high rates of conductive heat loss
from the sow's body. According to NRC (2012), the lower critical temperature is 20 °C
and 16 °C for individual and group-housed sows, respectively; for group-housed sows
kept on straw the lower critical temperature is 4 °C lower (i.e. 12 °C). Maintenance ME
requirements are increased by 4.30 and 2.39 kcal per kilogram of metabolic body weight
(kg
0.75
) daily for every 1 °C below the lower critical temperature for individually and
group-housed sows, respectively. In pigs, the energy cost of standing and walking are
rather high when compared with other animal species, reflecting the pig's relative large
trunk length. Therefore, increased levels of activity will increase maintenance energy
Heat production @ E retention
Maternal E retention
Conceptus E retention
Maintenance ME requirements
8,000
6,000
4,000
2,000
0
0
10
20
30
40
50
60
70
80
90
100
110
Day of gestation
Figure 6.2. Partitioning of energy (E) intake in a parity 2 gestating sow based on units of metabolizable energy
(ME) and at levels of performance specified in Table 6.2.
