Agriculture Reference
In-Depth Information
Effect of feed level of fine particles
(+6°C in comparison to Ref. scenario) through-
out (i.e. from
21
to 41 days).
When broilers are reared in hot condi-
tions (+6°C compared to Ref.) with no nutri-
tional changes, growth performances are re-
duced by about 20% for the two periods
corresponding to the two successive diets
(days
21-28,
days
29-41,
respectively), with
average daily gain of 58.9 g/day (vs 71.6 g/day
for Ref.) and 70.3 g/day (vs 87.4 g/day for Ref.)
for these two periods (
Fig. 9.7
). These differ-
ences in average daily gain (
ADG
) can be ex-
plained by a lower feed intake, with average
daily intake (
ADI
) of
106
g/day (vs
118
g/day
for Ref., -10%) and
142
g/day (vs
168
g/day for
Ref., -16%), respectively for the two periods
(
Fig. 9.8)
. This lower feed intake can be
explained by a lower thermolysis capacity
(i.e. the capacity of the animal to evacuate heat)
in the T+6 scenario (-17% on average between
day
21
and day 41). As a consequence, the
animal has to reduce its feed intake in order
to adapt its heat production to its thermolysis
capacity. Thus,
NED
is reduced by about 8%
and, combined with an increase of
Ved
(+15%)
leads to a higher
FCR
(feed conversion
ratio) of about 6% in T+6 compared with
Ref. (1.93 vs 1.81 g/g, respectively)
(Fig. 9.9)
.
This scenario (Fine100%) presents the in-
fluence of physical form of diet (i.e. particle
size) on the performance of a broiler be-
tween
21
and 41 days of age, in comparison
to the Ref. scenario. We simulate a transi-
tion from a full-pelleted diet with no fine
particles (<0.5 mm) to a meal diet with
100% fine particles (e.g. after the delivery of
feed that has not been well processed) from
35 days until 41 days of age.
The transition from a full-pelleted
diet to a meal diet with 100% fine par-
ticles decreased growth performances by
31% over the period days
35-41,
with
ADG
values of 61.9 and 89.9 g/day, respect-
ively, for Fine100% and Ref. scenarios
(
Fig. 9.7
). This can be explained mainly
by the lower
ADI
during this period
(-21%,
142
vs
180
g/day, respectively, for
Fine100% and Ref.), in relation to poor
prehension of diet by the animal (-18%
compared to Ref.,
Fig. 9.8
). At the same
time, the animal uses more energy in
physical activity (
EPA
) to catch the same
amount of feed (+40% compared to Ref.),
which cannot be therefore used for growth.
100.0
90.0
80.0
70.0
60.0
50.0
Ref.
T+6
Fine100%
40.0
20
22
24
26
28
30 32
Age (days)
34
36
38
40
42
Fig. 9.7.
Evolution of daily gain from
21
to 41 days of age in four simulations compared to the reference
scenario (Ref.). T+6: reference indoor temperatures + 6°C compared to Ref. Fine100%: at 35 days, transition
from a diet without fine particles (<0.5 mm) to a diet with 100% fine particles.
