Agriculture Reference
In-Depth Information
Table 6.5.
Observed model parameters (
NMR
,
NR
max
T
)
for modern genotype growing barrows depending
on BW. (From Wecke and Liebert, 2009.)
LAAI
= (
NI
·16):
c
(6.5)
Where
LAAI
= daily intake of the
LAA
in mg/
BW
k
0.67
;
c
= concentration of the
LAA
in the
feed protein in g/16g N; and
NI
= according to
Eqn 6.2.
Body
weight (kg)
a
NMR
b
(mg/BW
k
0.67
)
NR
max
T
b,c
(mg/BW
k
0.67
)
31.9
424
4124
NR
=
NR
max
T
(
1
−
e
−LAAI
·
16
·
b
:
c
)
(6.6)
51.6
399
3365
Where
b
:
c
(=
bc
-1
) = observed dietary
efficiency of the
LAA
;
LAAI
= according to
Eqn 6.5;
NR
= according to Eqn 6.2.
Logarithmic transformation of Eqn 6.6,
according to the mathematical treatment of
Eqn 6.1 as earlier described, yields the basic
Eqn 6.7, which is generally applied for as-
sessing quantitative AA requirements. An
important precondition is that experimental
data are available that describe the NR re-
sponse to a defined intake of limiting AA
(
LAAI
) at a defined dietary efficiency of the
LAA
(
bc
-1
):
75.5
368
2732
95.4
342
2352
113.8
318
2067
a
Mean BW of the pigs during experimental periods.
b
NMR
(mg/BW
k
0.67
) = -1.2863 × BW (kg) + 464.78.
c
NR
max
T
(mg/BW
k
0.67
) = -1619.3 × ln BW (kg) + 9733.6.
the animal's response (
ND
,
NR
) generally N
balance or N deposition data from body ana-
lyses are useful. However, factors influen-
cing each of the above procedures may yield
differing results for N balance and N depos-
ition, respectively. This fact is well known
among scientists working in this field, but a
solution to the problem has not as yet been
found. This problem is not specifically re-
lated to the 'Goettingen approach' and con-
sequently it will not be discussed further. To
eliminate possible effects of such discrepan-
cies between procedures when quantifying
ND
, only applications in growing chickens
and fattening pigs utilizing N balance studies
will be presented below.
Equations 6.1-6.4 have demonstrated
earlier model applications where the main
focus was on questions of complex protein
evaluation and where the AA composition
of the feed protein was not of top priority.
When the emphasis of the model changes
to AA-based applications a further import-
ant transformation is required: the func-
tion needs to be adapted because the inde-
pendent variable determining the resultant
dietary protein quality (
b
) is the concen-
tration of the limiting AA in the dietary
protein (
c
). This fundamental connection,
already discussed above, needs to be
'translated' into the traditional model ap-
plications.
The 'key-translator' to provide this pre-
condition is Eqn 6.5, in which the daily in-
take of the
LAA
from
NI
and dietary concen-
tration of the
LAA
in the feed protein is
calculated:
LAAI
= [ln
NR
max
T
− ln(
NR
max
T − NR
)]:
16
bc
−
1
(6.7)
As pointed out with Eqn 6.3 this applica-
tion, which makes use of increasing perform-
ance over a desired range of
NR
, is of great
interest for tabulating individual AA re-
quirements. Consequently, it is crucial to
plot the desired range as a percentage of
NR
max
T
(or
ND
max
T
) and to utilize the abso-
lute daily deposition data for further model
calculation of AA requirements taking into
account the dietary AA efficiency. An ex-
tended example of this application for grow-
ing fattening pigs is summarized in
Table 6.6,
which also shows that the dietary efficiency
of the AA under study can be modulated.
Therefore, an observed value for the dietary
AA efficiency could be increased or lowered
express the implications on derived AA
requirements.
Equation 6.7 makes it possible to derive
requirement data for individual AAs under
the precondition that their efficiency (
bc
-1
)
was measured and validated in a limiting
position of the protein under study. The
question arises as to how this validation
could be achieved. In the case of lysine-,
methionine- or threonine-limiting diets,
based on knowledge of their quantitative and
