Agriculture Reference
In-Depth Information
255
210
165
120
75
30
0
5
10
15
20
X
(axis)
Fig. 16.3.
Intakes (mg/day) of lysine (Lys), methionine + cystine (Met+Cys) and threonine (Thr) required by
pullets for maintenance and protein deposition over the
20-
week growing period. Model M1, based on
Martin
et al.
(1994), is uncorrected for feather loss and reproductive organ and liver growth, whereas M2
includes these additional features. Lys M1
; Lys M2
...............
; Met+Cys M1
.
; Met+Cys M2 ;
.
.
; and Thr M2
. .
.
Thr M1
because the requirements for the growth of
ovary, oviduct and liver are accounted for in
M1 and not in M2. These differences are il-
The total amount of each amino acid re-
quired, as shown in
Table 16.2
,
was parti-
tioned into maintenance and protein depos-
ition for the different components (the
feather-free body, feathers, ovary, oviduct and
liver). The proportions of the requirement
for each component in relation to the total
required for Lys, Met+Cys and Thr are shown
in
Fig. 16.4a
, b and c, respectively.
During the first week more than 0.88 of
the Lys required was destined for protein de-
position in the feather-free body, 0.08 for pro-
tein deposition in feathers and only 0.04 for
maintenance. With advancing age, the pro-
portion of Lys needed for protein deposition
in the feather-free body was reduced to 0.33
by the 17th week of age. In this week, the total
amount of Lys required for protein deposition
in the ovary (0.21) and oviduct (0.25) and for
maintenance (0.21) was approximately 0.67.
After the sexual maturation phase, the Lys
required for maintenance increased to 0.66 of
the total by the 25th week of age.
Only in the first week of age was the
proportion of Met+Cys required for protein
deposition in the feather-free body (0.50)
higher than the proportion required for that
in feathers (0.45). From the 3rd to the 13th
week, the proportion of Met+Cys required
for deposition in feathers increased from
0.48 to 0.52, while that required for protein
deposition in the feather-free body declined
from 0.46 to 0.30. During the sexual matur-
ation phase the Met+Cys requirement for
protein deposition in the ovary (0.07) and
oviduct (0.14) together equalled 0.21 of the
total required, while that for maintenance
and protein deposition in the feathers
amounted to approximately 0.60 of the total
required.
The proportion of Thr required in the
first week for protein deposition in the
feather-free body, feathers and maintenance
amounted to 0.71, 0.27 and 0.03 of the total,
respectively. As the birds grew, these pro-
portions changed and by the 17th week 0.28
of the protein deposited was in the feath-
er-free body and feathers, whereas mainten-
ance accounted for 0.38, and the ovary and
oviduct accounted for 0.32 of the total.
