Agriculture Reference
In-Depth Information
Table 18.1.
Estimates of the three parameters of the Gompertz equation for body weight and empty feather-free
weight of strains of commercial broiler chickens and laying-type pullets.
Broiler chickens
Pullets
Variables
RM
CM
RF
CF
HLB
HSB
HLW
HSW
Empty body weight, EBW
EBWm, kg
6.560
6.544
4.658
4.283
2.060
2.064
1.533
1.598
B
, per day
0.042
0.042
0.047
0.051
0.023
0.023
0.026
0.023
t*
, days
39
39
34
32
59
59
52
55
Empty feather free weight, EFFW
EFFWm, kg
6.239
6.374
4.319
3.977
1.769
1.764
1.261
1.345
B
, per day
0.042
0.041
0.047
0.051
0.024
0.024
0.026
0.024
t*, days
39
39
34
32
60
60
51
55
RM = Ross 308 males; RF = Ross 308 females; CM = Cobb 500 males; CF = Cobb 500 females; HLB = Hy-Line Brown;
HSB = Hisex Brown; HLW = Hy-Line White W-
36;
HSW = Hisex White.
the parameters for early growth (
B
and
t*
) in
EBW and EFFW.
Wm
and
B
. The RM group showed higher
Wm
and lower
B
values, whereas the CF
group showed lower
Wm
and higher
B
values.
The parameters
Wm
,
B
and
t*
fitted to
the chemical components of the laying strains
(
Table 18.2
) indicated that the
Wm
of brown
and white strains differed. The values ob-
tained for
B
reveal similarities between the
strains, with the exception of HLW, which
had the highest rates of maturation for all
body components.
The rates of maturation of water, protein
and ash were similar, whereas body lipid
deposition occurs at a lower rate, and the
other components are relatively delayed.
Mature protein weights of white and
brown strains of laying pullets differed. The
B
and
t*
values indicate that the maximum pro-
tein deposition rates (
PDmax
) for the HLB,
HSB, HLW and HSW strains were 3.36 g/day,
3.15 g/day, 2.93 g/day and 2.37 g/day at 77 days,
57 days, 58 days and 63 days, respectively.
Growth of the chemical components
of the body
The parameters that describe the growth of
the four chemical components are shown
in
Table 18.2.
For the broiler strains, the
parameters
Wm
,
B
and
t*
fitted for protein
weight revealed clear differences in the
growth patterns between strains and sexes.
The results indicate that Ross is the lar-
gest bird, with a protein deposition rate that
is better distributed throughout the rearing
period of 42 days. The Cobb strain, despite
being smaller by approximately 0.250 kg,
presents a more rapid rate of maturing, indi-
cating higher precocity.
The parameters obtained for lipid growth
reveal similarities (
Wm
,
B
and
t*
) between
broiler strains and sexes. The difference in
Wm
between the two strains was less than 0.006,
and between the sexes, CM showed a higher
lipid weight by approximately 0.044 compared
to RM. For the females, Ross showed a diffe-
rence of 0.037 compared to Cobb.
The parameter
Wm
fitted to the compo-
nent body water (BWA) indicates that Cobb
broilers have a higher water content (0.06).
This difference in composition was driven by
a greater water weight in males. For body ash
(BA) content, the greatest differences were ob-
Allometric relationship non-isometric
The ratios of water:protein at maturity
(WPRm), lipid:protein (LPRm) and ash:pro-
tein (APRm) are shown in
Table 18.3.
The
average value for WPRm in strains RM and RF
was 2.63, and for CM and CF 3.47. The aver-
age WPRm for all broiler strains was 3.05,
with the values for Ross and Cobb falling
between -0.137 and +0.137, respectively,
around the overall mean value.
