Agriculture Reference
In-Depth Information
of the broiler at the end and at the beginning
of the experimental period (g/g), respect-
ively. The coefficient for metabolic body
weight used in the equation is 0.75, but for
data comparison the coefficient 0.67 was
used. From the relationship of N deposition
obtained in the amino acid dilution experi-
ment it was possible to determine an optimum
dietary amino acid pattern. In practice, Roll-
in
et al
. (2003) proposed to calculate the EAA
requirement values (g/kg dry matter) for a
given EAA as follows:
(relative effects on protein quality) are sum-
marized in
Table 21.3.
High N deposition and protein effi-
ciency ratios (
P
< 0.05) were observed in
the BD treatment during the trial. Dilution
of individual EAAs significantly reduced
N deposition, but the extent of reduction
depended on the EAA removed. For each
EAA, a 0.30 reduction was sufficient to set
it in limiting position. The protein effi-
ciency ratio was also significantly reduced
by EAA dilution. The dilution of valine
promoted the greatest reduction in N de-
position (
P
< 0.05) in period I (
6
to 21 days),
followed by leucine in periods II and III
(
22
to 37 days and
38
to 53 days). Based on
the data obtained from the comparative
slaughter technique and assuming a linear
response between N deposition and EAA
intake when a given AA is limiting, the
quantity of each EAA that can be removed
from the BD without affecting N deposition
was determined. From these data, and as-
suming that each EAA is equally limiting,
the ideal dietary EAA profile relative to ly-
sine (=100) is presented in
Fig. 21.1
. Ex-
pressed as g/kg of dry matter, the optimal
balance was estimated and these are pre-
sented in
Table 21.2
.
The effects of dilution of individual
EAAs on protein quality in the experimen-
tal diets are also of fundamental importance
for evaluation of the applied procedure. N
deposition and protein quality were higher
in BD (
P
< 0.05) than in reduced EAA treat-
ments during the trial. However, when com-
paring the N deposition obtained with the
two techniques, the N deposition deter-
mined by the comparative slaughter tech-
nique was lower than that obtained using N
balance. The observed protein quality in
this study declined following dilution of
the crystalline EAA under study. The dilu-
tion of histidine caused a lower protein
quality in period I (
6
to 21 days), followed
by lysine and threonine in periods II and III
(
22
to 37 days and
38
to 53 days), respect-
ively. In each treatment
bc
-
1
,
the efficiency
of the utilization of dietary AAs was calcu-
lated. The ideal ratio between EAAs was de-
rived by dividing efficiency of utilization of
lysine by the efficiency of utilization of the
×
− −
ND
ND
Requirement =(
EAA
)
2
DEL
EAA
BD
BD
Where (
EAA
)
BD
is the concentration of the
considered EAA in the BD (g/kg DM (dry
matter)),
DEL
is the dilution rate of the EAA
in the deficient diet compared with the BD,
ND
EAA
is the N deposition (mg N/BW
kg
0.67
/
day) corresponding to the EAA diet and
ND
BD
is the N deposition observed on the
BD (mg N/BW
kg
0.67
/day). This method is based
on the assumption that N retention is a lin-
ear function of dietary EAA content when a
particular amino acid is limiting. An opti-
mal balance between the EAAs was derived
by dividing the estimated requirement for
each EAA by the estimated requirements for
lysine (base lysine = 100).
Results
All experimental diets were well accepted
by the broilers. No mortality was observed
during the trial but feather abnormalities
were observed in broilers on the treat-
ments in which valine and leucine were
deficient. As the individual feed supply
was controlled and kept constant during the
experimental period, N intake was similar
between dietary treatments (
Tables 21.2
and
21.3)
. The results of the single dietary
EAA dilution for the N deposition and
protein efficiency ratio (PER) obtained in
the comparative slaughter study are pre-
sented in
Table 21.2
and the results of the
N balance studies for each age period