9/30/2011
caused by the consumption of feed
Keeping Birds Cool During Hot
Weather
Brian Fairchild
The University of Georgia
The key to keeping bird cool during hot
weather is to realize that…
How does a broiler use this feed energy?

Roughly 35% of the energy is used to power the basic
functions of life:

heat stress is essentially an internal
problem,
Grow, move around, breath, pumping blood, maintain body
temperature, etc.
How does a broiler use this feed energy?
103.0°F
100

The remaining 65% is essentially put off in the form of
heat.

Heat a bird must rid itself in order to maintain a proper body
temperature and survive.
100.0°F
100
95
95
90
90
85
80
85.0°F
75.0°F
1
9/30/2011
Whether it is winter or summer they must
get rid of this heat to survive
Heat loss breakdown

104.0°F
Five pound bird at 70oF – 50% Rh
100

90

80
70
Summer
24 Btu’s/hr is lost to the air surrounding the bird (40%)
36 Btu’s/hr is lost through the evaporation of water off of its
respiratory system (60%)
60
103.0°F
50.0°F
100
Winter
95
90
85.0°F
(23,000 – 8 lb birds)
12:00 PM
6:00 AM
12:00 AM
6:00 PM
12:00 PM
6:00 AM
12:00 PM
6:00 AM
12:00 AM
6:00 PM
to the air
total
12:00 PM
To the air around it
Through the evaporation of moisture off of its respiratory
system
6:00 AM
2)
5,000,000
4,500,000
4,000,000
3,500,000
3,000,000
2,500,000
2,000,000
1,500,000
1,000,000
500,000
0
12:00 AM
1)
12:00 AM
(23,000 – 8 lb birds)
A bird rids itself of this excess heat primarily in two ways:
Heat removal (Btu's/hr)

40’ X 500’ Broiler house
12:00 AM
How does a bird rid itself of this excess
heat?
6:00 PM
12:00 AM
106oF
12:00 PM
70oF
5,000,000
4,500,000
4,000,000
3,500,000
3,000,000
2,500,000
2,000,000
1,500,000
1,000,000
500,000
0
6:00 PM
To the air around it
12:00 PM
1)
6:00 AM
A bird rids itself of this excess heat primarily in two ways:
Heat removal (Btu's/hr)

40’ X 500’ Broiler house
6:00 AM
How does a bird rid itself of this excess
heat?
2
9/30/2011
Seated at rest the average adult male will
produce approximately 340 Btu’s/hr
40’ X 500’ Broiler house
5,000,000
4,500,000
4,000,000
3,500,000
3,000,000
2,500,000
2,000,000
1,500,000
1,000,000
500,000
0


6:00 AM
12:00 PM
6:00 PM
12:00 AM
6:00 AM
12:00 PM
6:00 PM
12:00 AM
6:00 AM
12:00 PM
40’ X 500’ Broiler house
This is a very significant difference
(23,000 – 8 lb birds)
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
Poultry
People
28%
How do we compare?
6:00 AM
60%
40%
air
respiration
72%
12:00 PM
6:00 PM
12:00 AM
6:00 AM
12:00 PM
12:00 AM
6:00 PM
12:00 PM
6:00 AM
evaporation
to the air
12:00 AM
Heat removal percentage
28% is lost due to the evaporation of water from our
respiratory system and skin (perspiration)
72% is lost to the air surrounding us
evaporation
to the air
total
12:00 AM
Heat removal (Btu's/hr)
(23,000 – 8 lb birds)
Poultry

Generate a lot more heat and are MUCH more sensitive
by humidity than we are
103.0°F
100
95
90
85.0°F
3
9/30/2011
Heat loss from a 5 lb broiler
Heat loss from a 5 lb broiler at 77oF
65
60
55
50
45
40
35
30
25
20
15
10
5
0
65
60
55
50
45
40
35
30
25
20
15
10
5
0
respiration
air
70 F - 50%
77 F - 50%
86 F - 50%
respiration
air
50%
Levent, & Portier, 2005
70%
Levent, & Portier, 2005
Heat loss from a 5 lb broiler
Heat loss from a 5 lb broiler at 77oF
65
60
55
50
45
40
35
30
25
20
15
10
5
0
65
60
55
50
45
40
35
30
25
20
15
10
5
0
25% reduction
respiration
air
70 F - 50%
77 F - 50%
86 F - 50%

Study at looking at how relative humidity affects heat loss
from a five pound bird at 77oF

respiration
air
50%
Levent, & Portier, 2005
How does changing the humidity affect the
heat loss from a bird?
25% reduction
70%
Levent, & Portier, 2005
Increasing Rh from 50 to 70 % when it is
77oF

Feels the same to the bird as raising the air temperature
from 77 to 86oF when the Rh is 50%
Rh 50%, 70% and 90%
4
9/30/2011
If a bird cannot get rid of all the heat it is
producing…





Body temperature will increase,
Feed consumption will decrease,
Growth rate will decrease,
Feed conversions will increase,
Eventually mortality will increase.
How does changing the humidity affect the
heat loss from a bird?

What happens at high house temperatures
(86oF) with high relative humidity?
Study at looking at how relative humidity affects heat loss
from a 5 lb bird at 77oC

Rh 50%, 70% and 90%
Heat loss from a 5 lb broiler
65
60
55
50
45
40
35
30
25
20
15
10
5
0
respiration
air
70 F - 50% 77 F - 50% 86 F - 50% 86 F - 90%
Levent, & Portier, 2005
Heat loss from a 5 lb broiler at 77oF
65
60
55
50
45
40
35
30
25
20
15
10
5
0
So how do we help remove heat from the
birds?

Lower the air temperature?
32% reduction
respiration
air
50%
70%
90%
Levent, & Portier, 2005
5
9/30/2011
As a result when we use evap. cooling we
tend to get conditions like these…
Evaporative cooling
Pads/fogging nozzles produce cooling through the
evaporation of water into the air which increases relative
humidity of the air
Rh

100
95
90
85
80
75
70
65
60
0:00
12:00
Set Temp
50
40
30
20
10
Relative Humidity (%)
70
0
1:20 PM
1:21 PM
1:22 PM
1:23 PM
1:24 PM
1:25 PM
1:26 PM
1:27 PM
1:28 PM
1:29 PM
1:30 PM
1:31 PM
1:32 PM
1:33 PM
1:34 PM
1:35 PM
1:36 PM
1:37 PM
Temperature (F)
80
60
Temperature
12:00
Outside
0:00
Rh
Heat loss from a 5 lb broiler with and
without evaporative cooling
6” evaporative cooling pad in operation
95
93
91
89
87
85
83
81
79
77
75
0:00
Inside
65
60
55
50
45
40
35
30
25
20
15
10
5
0
Without
respiration
air
86 F - 50 %
Rh
77 F - 70%
86 F - 90%
Levent, & Portier, 2005
For every 1oF cooling produced by the evaporation of
water, the relative humidity will increase
approximately 2.5%
75
70
Rh (%)
65
60
55
50
45
40
78 79 80 81 82 83 84 85 86 87 88 89 90 91 92
Temperature (F)
Heat loss from a 5 lb broiler with and
without evaporative cooling
65
60
55
50
45
40
35
30
25
20
15
10
5
0
Without
With
respiration
air
86 F - 50 %
77 F - 70%
86 F - 90%
Levent, & Portier, 2005
6
9/30/2011
Heat loss from a 5 lb broiler with and
without evaporative cooling
65
60
55
50
45
40
35
30
25
20
15
10
5
0
Broilers
(85oF – 250 ft/min)
95.0°F
With
Without
94
92
respiration
air
With
90
88
Very hot, humid day
86
86 F - 50 %
77 F - 70%
86 F - 90%
84.0°F
Levent, & Portier, 2005
Broilers
(85oF – 550 ft/min)
Evaporative cooling

The PRIMARY reason we can use evaporative cooling
pads to keep our birds cool during hot weather is
because of the amount of air movement we have in our
tunnel houses.
95.0°F
94
92
90
88
86
84.0°F
Simmons & Lott 1981
Five pound bird 85oF
(individual bird at 85oF – Drury Siegel, 1968)
Goal
60
Total heat loss
Body temperature vs. Air speed
110.5
55
110
50
109.5
109
45
108.5
40
108
35
107.5
30
100
200
300
400
Air speed (ft/min)
500
600
107
0
50 100 150 200 250 300 350 400 450 500 550
Air speed (ft/min)
7
9/30/2011
(tunnel ventilated without pads)
Outside temperature and Rh
100
200
300
400
500
Air speed (ft/min)
600
Outside T
7:00 PM
0%
6:00 PM
10%
5:00 PM
20%
4:00 PM
30%
3:00 PM
respiration
air
40%
2:00 PM
50%
1:00 PM
60%
90
85
80
75
70
65
60
55
50
45
40
35
30
10:00 AM
70%
Temperature / Rh
80%
12:00 PM
The net result is that air movement lessens
the negative effect of high relative humidity
High density layer house
11:00 AM
More air movement, more heat removal,
panting rate decreases…
Outside Rh
(Simmons & Lott 1981)

The closer the air temperature is to the birds body
temperature the less heat removed from the birds.
Front to rear temperature difference
(22, 52” fans operating at all times)
Front to rear temperature diff (F)
This doesn’t mean that evaporative cooling
is not important
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0
75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90
Average house temperature (F)
8
9/30/2011
Heat prod. (Btu's/hr per bird)
Per bird heat removal by air movement
50 X 560’ broiler house
50
45
40
35
30
25
20
15
10
5
0
75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90
Average house temperature (F)
Heat removal and air temperature
4,500,000
50
45
40
35
30
25
20
15
10
5
0
Heat Removal (Btu’s/hr)
3,500,000
3,000,000
2,500,000
2,000,000
1,500,000
Total per bird heat removal
8:00 AM
7:00 AM
6:00 AM
1,000,000
75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90
Average house temperature (F)
Weekly weight gain
86oF Day – 77oF Night
1.6
50
45
40
35
30
25
20
15
10
5
0
1.4
Weight gain (lbs)
Heat prod. (Btu's/hr per bird)
85
84
83
82
81
80
79
78
77
76
75
4,000,000
5:00 AM
Heat prod. (Btu's/hr per bird)
Per bird heat removal through air movement
AND evaporation
1.2
1
still air
400 ft/min
600 ft/min
0.8
0.6
0.4
0.2
75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90
Average house temperature (F)
0
week 4
week 5
week 6
week 7
9
9/30/2011
Heat removal and air temperature
1.6
4,500,000
1.4
4,000,000
1.2
1
still air
400 ft/min
600 ft/min
0.8
0.6
0.4
Heat Removal (Btu’s/hr)
0.2
85
84
83
82
81
80
79
78
77
76
75
3,500,000
3,000,000
2,500,000
2,000,000
1,500,000
Evaporative cooling keeps air movement
effective
5:00 PM
week 7
3:00 PM
week 6
1:00 PM
week 5
1:00 AM
week 4
9:00 AM
5:00 AM
1,000,000
0
7:00 AM
Weight gain (lbs)
Weekly weight gain
95oF Day – 77oF Night
Growers should not underestimate the
importance of nighttime cooling


Though temperatures are at their lowest…
Rh is at its highest
12:00 AM
9:00 PM
6:00 PM
3:00 PM
12:00 PM
9:00 AM
6:00 AM
3:00 AM
12:00 AM
9:00 PM
6:00 PM
3:00 PM
12:00 PM
9:00 AM
1,500,000
1,000,000
500,000
6-Aug
4-Aug
2-Aug
31-Jul
0
29-Jul
9:00 AM
8:00 AM
7:00 AM
6:00 AM
1,000,000
2,000,000
27-Jul
1,500,000
2,500,000
25-Jul
2,000,000
3,000,000
23-Jul
2,500,000
3,500,000
21-Jul
3,000,000
4,000,000
19-Jul
3,500,000
4,500,000
17-Jul
4,000,000
6:00 AM
Bird heat removal in 50’ X 560’ house
85
84
83
82
81
80
79
78
77
76
75
5:00 AM
Heat Removal (Btu’s/hr)
4,500,000
Heat removal (Btu’s/hr)
Heat removal and air temperature
3:00 AM
12:00 AM
100
95
90
85
80
75
70
65
60
55
50
45
10
9/30/2011
But air speed was not a constant…
4,500,000
4,500,000
700
4,000,000
4,000,000
650
3,500,000
600
5-Aug
3-Aug
16-Jul
3-Aug
2-Aug
1-Aug
0
3-Aug
2-Aug
1-Aug
1,000,000
700
3,500,000
600
500
3,000,000
400
2,500,000
300
2,000,000
200
1,500,000
100
1,000,000
0
5-Aug
1,500,000
800
4,000,000
4-Aug
2,000,000
4,500,000
3-Aug
2,500,000
31-Jul
100
1,000,000
2-Aug
3,000,000
30-Jul
200
1,500,000
1-Aug
3,500,000
29-Jul
300
2,000,000
31-Jul
94
92
90
88
86
84
82
80
78
76
74
72
70
4,000,000
Temperature - Rh
4,500,000
28-Jul
400
2,500,000
Which resulted in a 20% decrease in daily
heat removal
But Rh is at its highest
Heat removal (Btu’s/hr)
500
3,000,000
3-Aug
2-Aug
1-Aug
31-Jul
30-Jul
29-Jul
28-Jul
1,000,000
600
31-Jul
1,500,000
700
3,500,000
30-Jul
2,000,000
800
4,000,000
29-Jul
2,500,000
4,500,000
28-Jul
3,000,000
Heat removal (Btu’s/hr)
3,500,000
Heat removal (Btu’s/hr)
Heat removal (Btu’s/hr)
90
88
86
84
82
80
78
76
74
72
70
4,000,000
300
It was significantly lower at night because
fans were shutting off
Temperature (F)
Lowest heat removal occurred when air
temperatures were at their lowest
4,500,000
350
1,000,000
6-Aug
4-Aug
31-Jul
2-Aug
29-Jul
27-Jul
25-Jul
23-Jul
21-Jul
19-Jul
17-Jul
0
400
1,500,000
30-Jul
500,000
450
2,000,000
1-Aug
1,000,000
500
2,500,000
28-Jul
1,500,000
26-Jul
2,000,000
550
3,000,000
24-Jul
2,500,000
22-Jul
3,000,000
20-Jul
3,500,000
18-Jul
Heat removal (Btu’s/hr)
Heat removal (Btu’s/hr)
Bird heat removal in 50’ X 560’ house
11
9/30/2011
Air speed and heat removal
160
140
120
100
80
60
40
20
0
Increasing air speed from 500 to 600 ft/min,
Increases heat removal by 20%
700
650
600
550
500
450
400
350
300
250
200
150
80 F
76 F
84 F
100
Heat removal per square foot
Heat removal chart was developed from data
collected from this particular house
Air speed
Typically during hot weather the house may
only be 4 to 6 degrees cooler at night!
4,500,000
160
140
120
100
80
60
40
20
0
88
Heat removal (Btu’s/hr)
3,000,000
84
82
2,500,000
78
74
1,500,000
72
70
3-Aug
2-Aug
1-Aug
31-Jul
30-Jul
29-Jul
28-Jul
4,500,000
700
4,000,000
650
600
3,500,000
550
3,000,000
500
2,500,000
450
2,000,000
400
31-Jul
29-Jul
27-Jul
300
25-Jul
350
1,000,000
23-Jul
1,500,000
21-Jul
700
650
600
550
500
450
400
350
300
250
200
150
100
80 F
76 F
84 F
Heat removal (Btu’s/hr)
Decreasing house temperature 4oF
Increases heat removal by 6%
Air speed
76
2,000,000
If we decrease our air speed because the air
is “cooler”….
Air temperature and heat removal
160
140
120
100
80
60
40
20
0
80
1,000,000
700
650
600
550
500
450
400
350
300
250
200
150
80 F
76 F
84 F
86
3,500,000
Air speed
Heat removal per square foot
90
4,000,000
100
Heat removal per square foot
Heat removal as a function of air speed and
house temperature
12
9/30/2011
When we don’t run all our fans at night we
are going to have a loss in performance
160
140
120
100
80
60
40
20
0
700
650
600
550
500
450
400
350
300
250
200
150
80 F
76 F
84 F
100
Heat removal per square foot
During the day….
Air speed
86oF day – 77oF night
80 F
76 F
84 F
1.5
1.4
1.3
1.2
1.1
1
0.9
0.8
700
650
600
550
500
450
400
350
300
250
200
150
Heat removal decreased by
40%!
Weekly weight gain (lbs)
1.6
160
140
120
100
80
60
40
20
0
100
Heat removal per square foot
At night…
Day 37 to 44
Air speed
Still air
The net result is 20% decrease in daily heat
removal
550 ft/min
86oF day – 77oF night
1.6
total
air speed
Weekly weight gain (lbs)
180
800
160
700
140
600
120
500
100
400
80
300
60
200
40
100
20
0
0
31-Jul 1-Aug 2-Aug 3-Aug 4-Aug 5-Aug
550/300 ft/min
1.5
1.4
1.3
1.2
1.1
1
0.9
0.8
Day 37 to 44
Still air
550/300 ft/min
Day 44 to 51
550 ft/min
13
12:00 AM
3:00 AM
6:00 AM
9:00 AM
12:00 PM
3:00 PM
6:00 PM
9:00 PM
12:00 AM
3:00 AM
6:00 AM
9:00 AM
12:00 PM
3:00 PM
6:00 PM
9:00 PM
12:00 AM
3:00 AM
6:00 AM
9:00 AM
12:00 PM
3:00 PM
6:00 PM
9:00 PM
12:00 AM


2.2
2.1
2
1.8
Still air
Day 37 to 44
550/300 ft/min
550 ft/min
Day 44 to 51
So Far…
Air speed provides more cooling than temperature
reduction
Birds loose less heat as RH increases
When RH increases, air speed is critical
Nighttime evaporative cooling operation?
12:00 AM
3:00 AM
6:00 AM
9:00 AM
12:00 PM
3:00 PM
6:00 PM
9:00 PM
12:00 AM
3:00 AM
6:00 AM
9:00 AM
12:00 PM
3:00 PM
6:00 PM
9:00 PM
12:00 AM
3:00 AM
6:00 AM
9:00 AM
12:00 PM
3:00 PM
6:00 PM
9:00 PM
12:00 AM
2.3
Temperature - Rh
2.7
2.6
2.5
1.9
12:00 AM
3:00 AM
6:00 AM
9:00 AM
12:00 PM
3:00 PM
6:00 PM
9:00 PM
12:00 AM
3:00 AM
6:00 AM
9:00 AM
12:00 PM
3:00 PM
6:00 PM
9:00 PM
12:00 AM
3:00 AM
6:00 AM
9:00 AM
12:00 PM
3:00 PM
6:00 PM
9:00 PM
12:00 AM

2.4
Temperature - Rh
86oF day – 77oF night
Temperature - Rh
lbs feed/lbs gain
9/30/2011
Typical hot weather
100
95
90
85
80
75
70
65
60
55
50
45
Pads only operating during the day
100
95
90
85
80
75
70
65
60
55
50
45
Pads operating 24 hours a day
100
95
90
85
80
75
70
65
60
55
50
45
14
9/30/2011
Nighttime pad operation can increase heat
stress
9:00 PM
6:00 PM
10:00 PM
12:00 AM
3:00 PM
8:00 PM
9:00 AM
12:00 PM
6:00 AM
3:00 AM
9:00 PM
12:00 AM
6:00 PM
3:00 PM
9:00 AM
12:00 PM
2:00 AM
12:00 AM
6:00 PM
4:00 PM
2:00 PM
12:00 PM
8:00 AM
10:00 AM
6:00 AM
105
100
95
90
85
80
75
70
65
60
55
50
45
40
35
30
12:00 AM
3:00 AM
6:00 AM
9:00 AM
12:00 PM
3:00 PM
6:00 PM
9:00 PM
12:00 AM
3:00 AM
6:00 AM
9:00 AM
12:00 PM
3:00 PM
6:00 PM
9:00 PM
12:00 AM
3:00 AM
6:00 AM
9:00 AM
12:00 PM
3:00 PM
6:00 PM
9:00 PM
12:00 AM
3:00 AM
6:00 AM
9:00 AM
12:00 PM
Temperature - Rh
10:00 PM
12:00 AM
8:00 PM
6:00 PM
4:00 PM
2:00 PM
12:00 PM
10:00 AM
8:00 AM
6:00 AM
4:00 AM
2:00 AM
4:00 AM
12:00 AM
105
100
95
90
85
80
75
70
65
60
55
50
45
40
35
30
Outside temperature and Rh
100
95
90
85
80
75
70
65
60
55
50
12:00 AM
Temperature - Rh
Outside temperature and Rh
6:00 AM
Outside temperature and Rh
Temperature - Rh
But during extremely hot weather old rules
of thumbs may not hold true…
3:00 AM
12:00 AM
105
100
95
90
85
80
75
70
65
60
55
50
45
40
35
30
2:00 AM

Outside temperature and Rh
One way to reduce the possibility of pads operating at
night is to set a pad operating temperature of
approximately 83oF.
Another way is to set a lower pad operating temperature
AND put them on a time clock so they will not operate
between the hours of 10 pm and 9 am.
Temperature - Rh

15
Outside T
pads
center
fans
100
98
96
94
92
90
88
86
84
82
80
78
76
74
72
Temperature - Rh
Normal hot weather
Outside T
Outside T
pads
pads
center
center
2:00 AM
12:00 AM
10:00 PM
8:00 PM
center
6:00 PM
4:00 PM
pads
2:00 PM
Outside T
12:00 PM
10:00 AM
8:00 AM
6:00 AM
4:00 AM
What happens if the pads are not allowed to
operate from 10 pm to 9 am?
12:00 AM
9:00 PM
6:00 PM
3:00 PM
12:00 PM
9:00 AM
6:00 AM
3:00 AM
12:00 AM
9:00 PM
6:00 PM
3:00 PM
12:00 PM
9:00 AM
6:00 AM
3:00 AM
12:00 AM
Temperature - Rh
105
100
95
90
85
80
75
70
65
60
55
50
45
40
35
30
2:00 AM
12:00 AM
Temperature - Rh
12:00 PM
9:00 AM
6:00 AM
3:00 AM
12:00 AM
9:00 PM
6:00 PM
3:00 PM
12:00 PM
9:00 AM
6:00 AM
3:00 AM
12:00 AM
Temperature - Rh
Outside temperature and Rh
12:00 AM
3:00 AM
6:00 AM
9:00 AM
12:00 PM
3:00 PM
6:00 PM
9:00 PM
12:00 AM
3:00 AM
6:00 AM
9:00 AM
12:00 PM
3:00 PM
6:00 PM
9:00 PM
12:00 AM
3:00 AM
6:00 AM
9:00 AM
12:00 PM
3:00 PM
6:00 PM
9:00 PM
12:00 AM
3:00 AM
6:00 AM
9:00 AM
12:00 PM
12:00 AM
10:00 PM
8:00 PM
6:00 PM
4:00 PM
2:00 PM
12:00 PM
10:00 AM
8:00 AM
6:00 AM
4:00 AM
2:00 AM
12:00 AM
Temperature - Rh
9/30/2011
Next day it is hotter…
102
100
98
96
94
92
90
88
86
84
82
80
78
76
74
72
fans
Inside house temperatures
102
100
98
96
94
92
90
88
86
84
82
80
78
76
74
72
fans
The next day hotter yet
102
100
98
96
94
92
90
88
86
84
82
80
78
76
74
72
fans
16
9/30/2011
Inside house temperatures
Outside T
pads
12:00 PM
9:00 AM
6:00 AM
3:00 AM
9:00 PM
center
12:00 AM
6:00 PM
3:00 PM
12:00 PM
9:00 AM
6:00 AM
3:00 AM
12:00 AM
Temperature - Rh
102
100
98
96
94
92
90
88
86
84
82
80
78
76
74
72
fans
Pad operation should be based on house
temperature…not time of day


Set to turn on a 83oF.
If you are going to use a time clock you may have to make
adjustments during very hot weather.
www.poultryventilation.com
17