Agriculture Reference
In-Depth Information
composition (ideal protein) to supply its main-
tenance requirements, and
Pm
is protein
weight at maturity (kg).
In this equation, maintenance require-
ments are related to body protein content,
which is more appropriate to express re-
quirements, because lipid content may be
different even among birds with similar
body weights.
In order to determine maintenance re-
quirements for each amino acid using this
approach, the equation considers body pro-
tein amino acid profile (
AAb
), as shown in
AAm
= [(
Pm
-0.27
) + (0.08 ×
Pt
×
AAb
)]
(mg/day)
feathers daily. Thus, amino acid require-
ments for feather maintenance (
AAmf
) were
calculated as:
AAmf
= 0.01 ×
FPt
×
AAf
(mg/day)
Where
AAf
is amino acid content of feather
protein (
Table 14.2)
.
In order to determine amino acid re-
quirements for growth the factorial equation
takes into account the amino acid profiles
of both body and feather protein and an effi-
ciency of amino acid utilization for body
and feather protein deposition of 0.8. Con-
sidering all the above-mentioned aspects, a
general equation was built to estimate amino
acid requirements:
Where
AAm
is the requirement of a specific
amino acid (AA) for maintenance.
Another important aspect of the model
is that maintenance and body growth com-
ponents were divided into specific ratios to
feather-free body and to feathers, because
feather growth characteristics are different
from the rest of the body and are influenced
by genotype, sex and age, among other factors
(Emmans and Fisher, 1986). Protein require-
ments for feather maintenance are considered
to be proportional to feather losses (Martin
et al
., 1994). According to Emmans (1989)
these losses are equivalent to 0.01g/g of
AA
=
AAm
+
AAmf
+ (
AAb
×
PD
/
k
)
+ (
AAf
×
PDf
/
k
) (mg/day)
Where
AA
is digestible amino acid require-
ment and
k
is the efficiency of the utiliza-
tion of that amino acid for feather-free body
deposition and feather deposition. The model
estimates the requirements for the following
amino acids: lysine, methionine, methio-
nine + cystine, threonine, tryptophan, isoleu-
cine, leucine, valine, phenylalanine, histidine
and arginine.
In order to determine the amount of
feed required for potential growth the di-
gestible amino acid content (
AAd
) must be
known. Therefore, the desired intake to
supply amino acid requirements is calcu-
lated as:
dFI
AA
=
AAd
/
AA (g
/
day)
Table 14.2.
Amino acid composition of the body
and feather for chickens.
a
(From Stilborn
et al
.,
1997, 2010.)
Amino acid
Body
Feather
Arginine
6.51
6.65
Cystine
1.00
7.46
Physical Capacity of the
Digestive Tract
Histidine
2.41
0.71
Isoleucine
3.94
4.60
Leucine
7.19
7.87
Nutrient intake by poultry may be limited
by dietary fibre content due to the physical
limitations of their digestive tract, particu-
larly during early growth stages. To account
for the effect of dietary fibre on feed intake,
a meta-analysis was performed by taking
into account four studies (Nascimento
et al
.,
1998; Bellaver
et al
., 2004; Montazer-Sadegh
et al
., 2008; Sara
et al
., 2009). In those stud-
ies, broilers were fed diets with different
Lysine
6.87
1.97
Methionine
2.16
0.69
Phenylalanine
3.79
4.66
Tyrosine
2.74
2.59
Threonine
4.07
4.80
Tryptophan
0.69
0.74
Valine
4.67
6.14
Alanine
6.26
4.09
Glycine
7.86
7.04
a
Means for male and female.
