Agriculture Reference
In-Depth Information
Table 20.3.
Body weight (
BW
, g), feed intake (
FI
, g/day) nitrogen intake (
NI
, mg/BW
k
0.67
/day), nitrogen
excretion (
NEX
, mg/BW
k
0.67
/day) and nitrogen balance (
ND
, mg/BW
k
0.67
/day) of the Dekalb White pullets as
summarized for the individual age periods (I:
14
to 28 days, II:
56
to 70 days and III:
96
to 112 days).
L1
L2
L3
L4
L5
Parameters
14
to 28 days
BW
159
205
216
226
173
FI
18
24
25
23
17
NI
654
1221
1743
2176
2568
NEX
330
516
747
1029
1087
ND
324
705
996
1147
1481
56
to 70 days
BW
492
545
571
585
586
FI
32
34
34
35
34
NI
526
954
1315
1775
2357
NEX
295
431
642
971
1286
ND
231
524
673
803
1072
96
to 112 days
BW
a
805
904
872
940
905
FI
43
51
44
43
40
NI
455
936
1385
1668
2066
NEX
289
477
689
997
1365
ND
166
459
696
671
701
a
BW
= average of the body weights at the beginning and end of each collection period.
NMR
and
NR
max
T
Table 20.4.
Nitrogen maintenance requirements
(
NMR
, mg/kg BW
0.67
/day), theoretical maximum for
daily nitrogen retention (
NR
max
T
, mg/kg BW
0.67
/day)
and theoretical maximum for daily nitrogen
deposition (
ND
max
T
, mg/kg BW
0.67
/day) during each
growth period.
NMR
,
NR
max
T
and
ND
max
T
were calculated
from data in
Table 20.3.
The nitrogen main-
tenance requirements increased with age until
growth began to stabilize, and the retention
and deposition of nitrogen decreased with
increasing age.
In
Fig. 20.1
the exponential function
between
NI
and
NEX
from which
NMR
values are derived is illustrated. Because
there are no observations in which
NI
is equal
to zero,
NMR
values are extrapolations of
the exponential function.
Values for
ND
max
T
obtained from the ex-
ponential function between
NI
and
ND
are
illustrated in
Fig. 20.2.
This figure reveals
that the
ND
data derived by approximation
were higher than the observed values. This
result was expected due to the theoretical
basis of this methodology, which considers
the maximum theoretical potential that
characterizes the genotype, whereas in
practice, the birds cannot achieve this daily
deposition rate.
Period
NMR
a
ND
max
T
a
NR
max
T
b
14
to 28 days
270
2938
3208
56
to 70 days
303
2050
2353
96
to 112 days
348
1391
1739
a
ND
max
T
- theoretical maximum for daily nitrogen
deposition, calculated using the equation
NR
max
T
=
ND
max
T
+
NMR
.
b
ND
=
NR
max
T
(
1
- e
-b·NI
) -
NMR
.
Responses in nitrogen deposition of pul-
lets fed different limiting amino acids (Lys, Met
and Thr) during the periods studied are illus-
Amino acid efficiency and requirements
The daily protein deposition can be con-
