Agriculture Reference
In-Depth Information
to the role of body fat reserves. However, re-
cent results in high producing lean animals
suggest that body protein mass may also
play an important role (Quesnel
et al
., 2005;
Solignac
et al
., 2010). Consequently, nutri-
tional supplies to sows have to be modu-
lated to maintain body reserves so that the
sows will be in optimal condition through-
out their productive life, thereby optimizing
reproductive performance. On farm, this re-
quires adjusting the feeding level and feed
composition according to the performance
of individual sows but also to housing con-
ditions, which may affect nutrient utiliza-
tion and voluntary feed intake.
Over the past
20
years reproductive per-
formance of sows has been drastically im-
proved. Maternal lines, most often Landrace
and Large White breeds, have been inten-
sively selected for litter size and, nowadays,
hyperprolific sows are available in most coun-
tries. In some cases, the use of Chinese breeds
has also contributed to that improvement in
prolificacy. Selection for improved growth
performance and carcass quality has also re-
sulted in decreased sow body fatness and in-
creased mature body weight and size. These
changes in sow performance have had major
effects on their nutritional requirements. Dur-
ing pregnancy, the increase in prolificacy
affects nutrient requirements for litter growth,
especially during the last weeks of pregnancy.
During lactation, the drastic improvement in
milk production and litter growth rate results
in a significant increase in nutritional require-
ments, whereas the sow's spontaneous feed
intake remained relatively constant.
At the same time, from the results ob-
tained over the past
20
years on energy, amino
acid and mineral utilization in sows, it has
become possible to improve the determination
of nutrient requirements through the devel-
opment of models and decision support tools,
such as InraPorc
(Dourmad
et al
., 2008), al-
lowing a global approach to better under-
standing of nutrient use by sows, including
the resulting performance.
The purpose of this chapter is to illus-
trate how the use of such a model can help
in optimizing the productivity of sows,
while considering new priorities such as
reducing the environmental impact of pig
production, which can be achieved through
a more precise adjustment of nutrient sup-
ply to requirement. Because the reliability
of the outcome of a simulation depends on
the concepts used in the model, it is essen-
tial that model users have some knowledge
about the model structure and the limita-
tions of its use. For the purpose of this
chapter, we will focus only on the feed and
sow modules of InraPorc (INRA, 2006). The
tool can be downloaded from
http://www.
General Description of the Sow
Module of InraPorc
In InraPorc, the sow is represented as the
sum of different compartments (i.e. body
protein, body lipids, body minerals and
uterus), which change during the repro-
flows are energy, amino acids and minerals.
In gestating sows, priority is given to main-
tenance requirements, requirements for
fetuses, and the development of uterus and
mammary gland. If the nutrient allowance
exceeds these requirements, nutrients in
excess contribute to the constitution of the
sow body reserves. Conversely, body re-
serves can be mobilized when the nutrient
demand is greater than the nutrient intake,
especially in late gestation. In lactating
sows, priority is given to maintenance and
milk production, and body reserves often
contribute to the supply for these priority
functions. The approach for representing
energy supply in sows differs slightly from
that chosen for growing pigs, where en-
ergy originating from each different nutri-
ent is considered separately in the model,
based on the net energy (NE) concept (van
Milgen
et al
., 2008). In the sow model it
was decided to maintain the concept of
metabolizable energy (ME), because the
available information was based on this
concept, and also, the efficiency of energy
use varies according to the physiological
status of the sow. However, a corrected ME
value is calculated to take into account the
effects of diet composition on the utilization
