Agriculture Reference
In-Depth Information
Fig. 2.3. Screenshot of InraPorc illustrating the utilization of SID lysine by the growing pig between 30 and
115 kg of body weight.
the efficiency of amino acid utilization dif-
fers from the concept of a fixed ideal amino
acid profile with which most nutritionists
are accustomed to work. The ideal amino
acid profile corresponds to a profile where
all amino acids are equally limiting for per-
formance, independent of their utilization
(i.e. for maintenance or for growth). Because
the maintenance requirements and poten-
tial protein deposition evolve independ-
ently (as a function of BW 0.75 or as a Gom-
pertz function in InraPorc, respectively),
the ideal amino acid profile will change
during growth. InraPorc can display how
the requirement of an amino acid changes
relative to Lys, thereby allowing the user to
evaluate the ideal amino acid supply. As
shown in Fig. 2.4 , these changes are rela-
tively minor during growth. For example, it
is known that Thr is an important contribu-
tor to endogenous secretions (through
mucins), but the change in the relative con-
tribution of basal endogenous secretions
has little impact on the SID Thr:Lys require-
ment ratio during growth.
If an amino acid can be used with the
same maximum efficiency as Lys, the re-
quirement for that amino acid (relative to
Lys) is essentially reflected by the amino
acid composition of whole-body protein.
In InraPorc, the maximum efficiency of Lys
utilization is fixed at 72% ( Table 2.1 ). The
maximum efficiencies of the other amino
acids were determined by reverse-calculation
of an ideal amino acid profile for a standard
situation (van Milgen et al ., 2008). The result
of this calculation was that the maximum ef-
ficiencies are higher for Leu, Phe, His, and
Arg than for Lys (Table 2.1 ). The efficiency
for Arg exceeds 100% because Arg can be
synthesized by the pig, but the synthesis cap-
acity may be insufficient to sustain max-
imum growth. For the other amino acids, the
maximum efficiencies were lower than that
of Lys. As can be seen from Table 2.1 , there is
quite a range in the maximum efficiencies,
although the reasons for these differences are
not fully clear. They are, of course, deter-
mined by the amino acid composition of
whole-body protein, which is assumed to be
 
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