Agriculture Reference
In-Depth Information
6
4
3.5
3
(a)
(b)
5
4
2.5
3
2
1.5
2
1
0.5
0
-
50
1
if stocking rate > 20 kg/m
2
0
0
5
10
Difference of stocking rate (Sim-Ref, kg/m
2
)
15
2
0
2
5
3
0
35
-
40
-
10
Difference of relative humidity (Sim-Ref, %)
-
30
-
20
0
10
20
30
40
50
Airspeed (m/s)
(c)
(d)
1.6
0
0.5
1
1.5
2
2.5
3
3.5
0
1.4
-
1
1.2
-
2
1
0.8
-
3
Ed
=
f(Tp)
Thermolysis capacity =
f
(
Tp
)
MEm
=
f
(
Tp
)
Ved
=
f
(
Tp
)
PA L
=
f
(
Tp
)
0.6
-
4
if Tindoor < 26°C
if Tindoor < 26°C
0.4
-
25
-
20
-
5
Difference of perceived temperature (Sim-Ref, °C)
-
15
-
10
0
5
0 5 0 5
-
5
Fig. 9.5.
Responses of bird-perceived temperature (
Tp
, °C) to various parameters: (a) stocking rate; (b) relative
humidity; (c) air speed (ventilation); and (d) impact of
Tp
on various parameters -
Ed
, Thermolysis capacity,
Ved
,
PAL
and
MEm
(ME for maintenance).
Influence of perceived temperature
on
Ed
,
Ved
, heat production, physical
activity and
MEm
so that the simulated results fitted to the
observations of Geraert
et al
. (1996), which
resulted in a decrease in the
Ed
value with
increasing temperature difference between
the simulation and reference conditions as
shown in
Fig. 9.5d.
Many mechanisms are involved in regulat-
ing broiler metabolism and thus maintaining
homeostasis. In INAVI, we took into account
only five of them. Furthermore, two situ-
ations can be distinguished according to the
value of simulated
Tp
, in comparison with
an 'optimal' temperature that we considered
as the reference (i.e.
Tp
lower or higher than
'optimum').
ved
.
Below 'optimal' temperature, Howlid-
er and Rose (1987) measured an increase in
fattening of 0.8% per supplementary °C as-
sociated with a growth decrease of 0.12%.
From these results, we estimated there to be
a decrease in
Ved
of 0.6% for a decrease of
1°C below the reference temperature. Above
the 'optimal' temperature, the results from
Geraert
et al
. (1996) showed that protein de-
position decreased by 8% when comparing
broilers reared at 22°C and 32°C, which cor-
responds to an increase in
Ved
of 2.5% per
supplementary °C
(
Fig. 9.5d)
.
ed
.
Below 'optimal' temperature, the effi-
ciency of synthesis mechanisms as well as
growth is considered to change little
(Howlider and Rose, 1987). Therefore, in IN-
AVI we considered that
Ed
is decreased by
1% when the temperature is 2°C below the
'optimal' temperature (
Fig. 9.5d
).
To represent the changes in
Ed
above
the 'optimal' temperature,
Ed
was adjusted
heat
production
.
Koh and Macleod (1999)
measured
HP
without physical activity in
