Agriculture Reference
In-Depth Information
Table 2.1.
Traits used in InraPorc to determine the protein deposition possible by the amino acid supply.
a
Basal endogenous
losses (g/kg DM
intake)
Maximum efficiency
of amino acid
utilization (%)
Amino acid
composition of
body protein (%)
Maintenance
(mg/kg BW
0.75
/day)
Lysine
0.313
28.4
72
6.96
Methionine
0.087
8.0
64
1.88
Cystine
0.140
9.4
37
1.03
Threonine
0.330
17.1
61
3.70
Tryptophan
0.117
4.4
57
0.95
Isoleucine
0.257
14.9
67
3.46
Leucine
0.427
32.4
76
7.17
Valine
0.357
20.2
71
4.67
Phenylalanine
0.273
16.7
82
3.78
Tyrosine
0.223
10.9
67
2.86
Histidine
0.130
11.5
93
2.79
Arginine
0.280
0
154
6.26
Protein
8.517
465.5
85
−
a
The requirements for basal endogenous losses and maintenance are subtracted from the supply of SID amino acids.
The resulting supply of available amino acids is then multiplied by the maximum efficiency and divided by the amino acid
composition of body protein to determine the protein deposition that would be possible from the amino acid supply.
endogenous losses are accounted for. On an
AID basis, the basal endogenous losses are
part of the feed value. These losses, due to
endogenous secretions and sloughing of in-
testinal cells, are of animal origin and con-
tribute to the ileal amino acid flow. On an
SID basis, the basal endogenous losses are
considered to be part of the requirement of
the animal. Because of the way basal en-
dogenous losses are accounted for, the sup-
ply and the requirement of amino acids are
higher on an SID basis than on an AID basis.
In InraPorc, the basal endogenous losses
(when expressed on an SID basis) are assumed
to be proportional to the dry matter intake
and these losses are directly subtracted from
the SID amino acid supply. Consequently,
the composition of endogenous losses se-
cretions and the efficiency with which the
basal endogenous secretions are synthesized
by the animal are summarized in a single
value for each amino acid. Although this
certainly is an approximation, we felt that
the contribution of basal endogenous losses
is relatively minor (compared to other losses)
and that there is insufficient information to
justify a different approach. We used values
from the INRA and the Association Française
de Zootechnie (AFZ) tables to characterize the
amino acid profile for the basal endogenous
losses (Sauvant
et al
., 2004). These tables
are also the basis for the AID and SID amino
acid digestibility of feed ingredients avail-
able in InraPorc, which warrants a consistent
approach when changing from an AID to an
SID system.
The maintenance amino acid require-
ments used in InraPorc are those proposed
by Moughan (1998), and are expressed rela-
tive to BW
0.75
. These requirements are also
directly subtracted from the digestible
amino acid supply, thereby ignoring that
differences in metabolism (efficiency of
post-absorptive utilization for maintenance)
may exist among amino acids. Again, the
maintenance amino acid requirements are
relatively small and this approximation has
little impact on amino acid utilization.
The available amino acid supply is the
supply of digestible amino acids minus
the basal endogenous losses (for SID) and
the maintenance amino acid requirement. This
supply is then multiplied by maximum effi-
ciency and divided by the amino acid com-
position of whole-body protein to determine
the protein deposition that would be possible
for the supply of each of the amino acids. If
the protein deposition for all of these is greater
than the protein deposition determined by the
Gompertz function or by the energy supply,
