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against the unit of maintenance ( Pm -0.27 × Pt )
for the two chicken strains. Regressions
were significant ( P < 0.05) for EE ( Fig. 14.2 ).
However, EE requirements for maintenance
were not different ( P > 0.05) between chicken
types, resulting in a single equation, applic-
able both to broilers and layers. The esti-
mated EE requirement for maintenance
(1.67 MJ/ Pm -0.27 × Pt ) is similar to that pro-
posed by Emmans (1994).
Amino acid as the most limiting component
When an amino acid is limiting in a feed
the  dFI will be based on the requirement for
that amino acid and its concentration in the
feed.
Amino acid requirements are based on
the sum of the requirement for maintenance
and for protein deposition, divided by their
respective utilization efficiencies. Most stud-
ies relate daily amino acid requirements for
maintenance with fasted body weight (mg/kg)
or with metabolic weight (mg/kg 0.75 ). In this
context, it is difficult to compare mainten-
ance among genotypes with different
mature sizes, among birds of a same geno-
type at different maturity stages or even
among birds with the same body weight
and different body fat content (Emmans and
Oldham, 1988; Burham and Gous, 1992;
Gous, 2007).
In order to consider these aspects the
model adopts the proposal of Emmans and
Fisher (1986). A general equation is applied
to determine body protein maintenance re-
quirements:
MP = 0.008 × ( Pt × Pm -0.27 ) (mg/day)
EE requirement for growth
In the case of poultry, body and feather
protein deposition is combined to pro-
duce DP .
In a feed, effective energy content ( EEC )
of the feed is calculated as:
EEC = ME n  - 3.8 ×  FOM  - 4.67 ×  dCP
+ 12 z  ×  dCL (kJ/day)
Where ME n = metabolizable energy for ni-
trogen retention ( ME n = ME - 8.22 × dCP );
FOM = non-digested feed organic matter;
dCP = feed digestible protein content (g/kg);
z = proportion of dietary fat retained as body
fat (poultry, z = 0.3); and dCL = feed digestible
lipid content (g/kg).
The desired feed intake that will sup-
ply energy requirements in a thermoneutral
environment ( dFI e ) is estimated as:
dFI e  =  EER / EEC  (g/day)
Where MP is maintenance protein require-
ment (g/day); 0.008 is a constant (kilo-
grammes of ideal protein/maintenance unit;
Pm 0.73 × u ), defined on the assumption that
poultry require 8 g of protein with adequate
3500
Broiler and pullet
MEm =1.67. ( PBm 0.27 .PP) - 8.4
R 2 = 0.33
3000
2500
2000
1500
1000
500
0
0
200
400
600
800
Maintenance unit ( PBm - 0.27 . PP, g)
Broiler
Pullet
Broiler and pullet
Fig. 14.2. Regression of energy for maintenance as a function of unit for maintenance ( EEmaintenance =
PBm -0.27 × PP ) for broiler and layer strains.
 
 
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