Agriculture Reference
In-Depth Information
Table 20.6.
Calculated amino acid requirements and optimal dietary contents of Lys, Met and Thr for pullets
during growth period II (
56
to 70 days, mean BW = 582 g), depending on protein deposition (PD) and
observed amino acid efficiency.
Lys
Met
Thr
Efficiency of AA (
bc
-1
)
a
90
230
160
PD (g/day)
b
4.1
5.1
6.1
4.1
5.1
6.1
4.1
5.1
6.1
AA requirement
c
mg/BW
k
0.67
/day
374
507
671
141
192
253
196
266
351
mg/day (at mean BW)
260
353
467
98
133
176
136
185
245
Optimal dietary content (g/kg)
d
5.78
7.85
10.4
2.18
2.96
3.92
3.03
4.11
5.43
a
Eficiency of amino acid utilization (
bc
-1
) considering that
b
= [ln
NR
max
T
- ln (
NR
max
T
-
NR
)]/
NI
and
c
= protein content of
the feed.
b
Protein deposition values at 40%, 50% and 60% of the theoretical maximum for the daily nitrogen deposition (
ND
max
T
).
c
Amino acid requirements were calculated using the equation
LAAI
= [ln
NR
max
T
- ln (
NR
max
T
-
NR
)]/16
bc
-
1
.
d
For a daily feed intake of
45
g according to the pullet management guide.
Table 20.7.
Calculated amino acid requirements and optimal dietary contents of Lys, Met and Thr for pullets
during growth period III (
96
to 112 days, mean BW = 920 g), depending on protein deposition (PD) and
observed amino acid efficiency.
Lys
Met
Thr
Efficiency of amino acid (
bc
-1
)
a
100
350
180
PD (g/day)
b
4.1
5.1
6.2
4.1
5.1
6.2
4.1
5.1
6.2
Amino acid requirement
c
mg/BW
k
0.67
/day
309
419
554
91
123
162
177
240
318
mg/day (at mean BW)
292
397
524
86
116
154
167
227
300
Optimal dietary content (g/kg)
4=
d
4.00
5.43
7.18
1.51
2.05
2.71
2.10
2.85
3.76
a
Eficiency of amino acid utilization (
bc
-1
) considering that
b
= [ln
NR
max
T
- ln (
NR
max
T
-
NR
)]/
NI
and
c
= protein content of
the feed.
b
Protein deposition values at 40%, 50% and 60% of the theoretical maximum for the daily nitrogen deposition (
ND
max
T
).
c
Amino acid requirements were calculated using the equation
LAAI
= [ln
NR
max
T
- ln (
NR
max
T
-
NR
)]/16
bc
-
1
.
d
Daily feed intake at
65
g according to the pullet management guide.
laying hens determined by Filardi
et al
.
(2000) was
178
mg/BW
k
0.75
/day. Our values
were also higher than the
153
mg/BW
k
0.75
/
day for Passeriformes (Allen and Hume,
2001) and
171
mg/BW
k
0.67
/day for slow-
growing broilers (Samadi and Liebert, 2007b);
however, they were 18% higher than the
values determined for broilers (Samadi and
Liebert, 2006a).
According to Reeds and Lobley (1980),
when nitrogen is absent from the diet (
NI
= 0),
catabolism or degradation of body protein
occurs in order to maintain the pool of free
amino acids for protein synthesis according
to the metabolic priorities; the result of this
degradation process is quantified in the
NMR
, so that differences found in
NMR
values can be associated with protein syn-
thesis and degradation rates of different
genotypes.
According to the traditional method de-
scribed by Sakomura and Rostagno (2007)
NMR
is determined by positive and nega-
tive
NB
responses. The negative balance is
limited by the rate of protein degradation,
which tends to increase endogenous losses
and hence
NMR
. Thus, with this approach,
the positive
NB
is used to determine
NMR
,
