Agriculture Reference
In-Depth Information
factors in a single intermediate variable 'in-
forming' the bird and therefore impacting
its behaviour and metabolism. However,
this variable should be improved with new
data from the literature and expertise for the
different impacts it is involved in. As an
example, the influence of this variable on
energy partitioning should be more precisely
taken into account since new knowledge is
now available (Sakomura
et al
., 2009).
phosphorus content on performances has to
be studied simultaneously with dietary cal-
cium and microbial phytase levels. Model-
ling of the combined influence of these fac-
tors is therefore a main future development
to be considered for INAVI.
Conclusions
As stated in the introduction, the audience
for INAVI is both researchers and practi-
tioners. The 'open to change by the user'
approach developed in INAVI induces new
issues that should be investigated in the fu-
ture by experimental trials carried out both
in the laboratory and the field. Since the
start of the INAVI project, new knowledge
has been obtained from the biomolecular up
to batch management scale. Therefore, the
improvement of our model requires the rank-
ing of the mechanisms and laws regulating
growth that should be implemented. This has
to be done through continuous discussion
between stakeholders both on the research
and production sides. To date, this discus-
sion has led to the following improvements:
Amino acid requirements
In INAVI, amino acid requirements were
considered through the use of a synthetic
variable taking into account the level of the
first limiting essential amino acid. However,
the effects on growth of an amino acid defi-
ciency can be different according to the con-
sidered amino acid. Many studies have fo-
cused on lysine and sulphur amino acid
requirements (Mack
et al
., 1999; Conde-
Aguilera
et al
., 2013), but the experiments
carried out to assess those requirements
are mostly based on factorial approaches.
In that sense, the development of new
response laws describing the effect of each
essential amino acid level on growth and
feed intake could be helpful to investigate
further the ideal protein concept proposed
by Mack
et al
. (1999), though a ranking be-
tween amino acids should be proposed,
since the multiplication of response laws
might bias the model behaviour through lack
of consistent data for some amino acids.
1.
Growth prediction connected with body
composition.
2.
Prediction of N and P excretion.
3.
Growth regulation with P-Ca nutrition.
4.
Digestibility of nutrients.
5.
Connection of INAVI with a diet formu-
lation tool (combining nutritional, economic
and environmental constraints).
Influence of phosphorus and
calcium dietary content on growth
performances
Moreover, performances variability is
not taken into account in INAVI, though
this aspect is a key issue for the sustainabil-
ity of poultry production systems. However,
INAVI is a deterministic animal-centred
model, aimed at integrating knowledge at
the animal scale, which does not cope with
variability. Since the development of new
and more sustainable production systems
requires the development of models at the
upper scales (farms, territories), the role of
INAVI in these multi-scale approaches should
be anticipated.
In INAVI, performances are modified by
environmental conditions and feed charac-
teristics. Diet composition is taken into
account, with a specific focus on energy and
protein metabolisms, while several other nu-
trients are known to have a meaningful influ-
ence on broiler performance, such as phos-
phorus. However, the studies of Rousseau
et al
. (2012) and Létourneau-Montminy
et al
.
(2010) showed that the influence of dietary
