Agriculture Reference
In-Depth Information
For Met+Cys:
PD
Ova
,
PD
Ovi
and
PD
Liv
are the respective pro-
tein depositions of the feather-free body,
feathers, ovary, oviduct and liver (g/day); and
0.8 is the efficiency of amino acid utilization
for protein deposition.
AAI
= [(93.5 ×
BPm
0.73
×
u
)
+ ( 0.04 ×
FP
× 89.2)]
+ [(33.3 ×
PD
c
)/
0.8
+ (89.2 ×
PD
f
)/
0.8
+ 33.3 × (
PD
Ova
+
PD
Ovi
+
PD
Liv
)/
0.8
]
(16.7)
Models for determining requirements
For Thr:
AAI
= [(44.7 ×
BPm
0.73
×
u
)
+ (0.04 ×
FP
× 44.3)]
+ [(40.4 ×
PD
c
)/
0.8
+ (44.3 ×
PD
f
)/
0.8
+ 40.4
× (
PD
Ova
+
PD
Ovi
+
PD
Liv
)/
0.8
]
The factorial model described estimates the
intake of Lys, Met+Cys and Thr required to
maintain the feather-free body protein, to
meet the requirements for feather loss and
to deposit protein in the feather-free body,
the feathers and the ovary, oviduct and liver
using the value 0.8 for the efficiency of util-
ization of the three amino acids for protein
growth. The weekly requirements through-
out growth are shown in
Table 16.2
.
Differences in the estimates of the daily
intakes required for Lys, Met+Cys and Thr
predicted by models M1 and M2 are illus-
trated in
Fig. 16.3.
The correction for feather
loss is evident to the 13th week of age and
differs for each amino acid. Although the
weekly differences appear to be minimal, the
cumulative differences for Lys, Met+Cys and
Thr to the 13th week of age sum to 6%, 28%
and 18%, respectively.
From the 15th week, the differences
between models M1 and M2 are greater
(16.8)
Where
AAI
is the digestible amino acid
requirement (mg/day);
173,
93.5 and 44.7 are
the respective Lys, Met+Cys and Thr require-
ments for maintaining the feather-free pro-
tein body weight;
BPm
is the protein weight
of the feather-free body at maturity (kg),
u
is
the degree of maturity of the feather-free body
protein (
u
=
BPt
/
BPm
); 0.04 is the protein
loss of the feathers (0.04 g/day);
FP
or
FPc
is
feather protein weight (g/day); 18.7, 89.2 and
44.3 mg/g are the respective Lys, Met+Cys
and Thr contents in the feather protein; 67.8
mg/g, 33.3 mg/g and 40.4 mg/g are the respect-
ive Lys, Met+Cys and Thr contents in the
protein of the feather-free body;
PD
c
,
PD
f
,
Table 16.2.
Predicted lysine (Lys), methionine + cystine (Met+Cys) and threonine (Thr) requirements
(mg/day) of laying-type pullets during the growing period.
Age
Lysine
Methionine + cystine
Threonine
(Week)
M1
a
M2
b
M1
a
M2
b
M1
a
M2
b
1
84
84
71
72
61
61
3
143
144
128
130
106
107
5
193
193
179
182
144
146
7
219
220
209
214
165
167
9
221
222
216
222
166
169
11
207
209
205
211
154
156
13
185
186
182
188
134
136
15
161
165
156
163
112
116
17
139
229
131
179
91
147
19
120
163
108
133
74
101
21
104
116
90
98
59
67
23
93
97
75
79
48
51
25
84
86
63
66
40
42
a
Model
1
based on Martin
et al
. (1994).
b
Model
2
corrected for feather loss and growth of reproductive organs and liver.
