Agriculture Reference
In-Depth Information
Table 14.1.
Growth parameters
in UNESP studies.
Cobb
Ross
Hy-Line
Brown
Hy-Line
White
Hisex
Brown
Hisex
White
Male
Female
Male
Female
B
0.047
0.050
0.037
0.044
0.025
0.028
0.026
0.026
Pm
1042
666
1309
866
364
284
329
248
LRPm
0.80
1.17
1.00
1.00
1.00
0.80
1.10
1.00
Bf
0.040
0.042
0.035
0.036
0.027
0.028
0.029
0.030
Pmf
303
233
483
395
155
144
143
124
a
(water/protein)
1.74
1.74
1.74
1.74
1.82
1.82
1.82
1.82
b
(water/protein)
0.92
0.92
0.92
0.92
0.82
0.82
0.82
0.82
Therefore, live weight (
BWt
) at any age is
estimated by the equation:
BWt
=
BW
(
t
-1)
+
ADG
(g/day)
Similarly to
BWt
, each body component is
determined as the sum of the current status
(protein (
Pt
), lipid (
Lt
), water (
Wt
), ash (
At
)
and feather protein (
FPt
)) with their respect-
ive depositions.
EER
=
M
+
50
×
DP
+
56
×
DL
(KJ/day)
EE requirement for maintenance
Maintenance heat production can be esti-
mated as a function of current protein mass
and protein content at maturity (Emmans
and Fisher, 1986). Based on this proposal
and considering the daily maintenance en-
ergy requirement estimated by Emmans and
Fisher (1986) of 1.63 MJ per maintenance
unit, the following equation is used:
Estimating Voluntary Feed Intake
M
= (1.63 ×
Pt
×
Pm
-0.27
)/1000 (kJ/day)
The maintenance coefficient may present dif-
ferent values for different genotypes. This as-
sumption has been confirmed for pigs by van
Milgen and Noblet (1999), but it has not been
tested in poultry. A meta-analysis was per-
formed by the Group of Study and Research in
Modelling and Nutrition in Monogastric
(Gnutrim) - FCAV, UNESP-Jaboticabal, to
test this hypothesis (Sakomura
et al
., 2011).
In that meta-analysis, a database was built
using data from four PhD theses and contains
information on 1024 chickens of two types
(broilers and layers) and six genetic strains.
Information on EE intake, live weight and
body composition (protein and fat) was col-
lected during the experiments every 7 days.
In place of 1.63 in the above equation
this maintenance coefficient was estimated
from the data collected. In order to evaluate
the effect of chicken strain (broiler and
layer) on EE requirements for maintenance
the EE for maintenance was first calculated
(
EEmaintenance
=
EEintake
-
50
×
DP
-
56
×
DL
) and these were then regressed
The principle used to estimate feed intake
in the model assumes that the bird attempts
to eat sufficient to meet its growth potential,
considering its digestive capacity limita-
tions and the environment. This concept
was first proposed by Emmans (1981).
Desired Feed Intake
This concept assumes that the bird attempts
to ingest the amount of feed that will meet
its energy and amino acid requirements.
Therefore, the desired feed intake is the
amount of feed required to supply the re-
quirement of the most limiting nutrient, be
it energy or amino acids.
Energy as the most limiting component
In order to determine energy requirements
for maintenance (
M
) and growth (
PD
and
LD
)
the EE requirement (
EER
) for chickens
(Emmans, 1994) is calculated as:
