Peitanika 4(2), 104-108(1981)
The Effect of Water Restriction on the Respiratory
Volumes of the Fowl
H. KASSIM
Department of Animal Sciences, Faculty of Veterinary Medicine and Animal Science,
Universiti Pertanian Malaysia, Serdang, Selangor, Malaysia.
Key words: Fowl; water restriction; heat exposure; respiratory changes.
R1NGKASAN
Isipadu pernafasan telah diukur pada ayam semasa dedahan kepada suhu 35 C dan 40 C. Dua
kumpulan ayam telah digunakan iaitu ayam yang diberi air dan ayam yang tidak diberi air. Keputusan
telah menunjukkan tidak ada perbezaan di dalam isipadu pernafasan di antara ayam yan^ diberi air dengan
ayam yang 24 jam dan 48 jam tidak diberi air semasa dedahan kepada suhu 35°C dan 40 C. Kandungan air
dalam badan tidak mengubah ventilasi pernafasan dan kehilangan air cara pengewapan.
SUMMARY
Respiratory volumes were measured in the fowl during exposures to 35 C and 40 C. Two groups of
birds were used namely normal 'wet* birds and water-restricted 'dry' birds. The results showed that there
were no differences in respiratory volumes between the normal 'wet' birds and the 24 hour and 48 hour
water restricted birds upon exposures to 35°C and 40°C. Total body water content did not affect the
respiratory ventilation and consequently, the respiratory evaporative water loss.
1971; Smith, 1972; and Bouverot et al, 1974).
However the cutaneous evaporative water loss
remains constant after a certain degree of heat
stress while the respiratory evaporative water loss
increases. This total evaporative water loss would
correspond to the total body water content of
the birds.
INTRODUCTION
Many homoeotherms readily resort to
evaporating water in a considerable manner in
response to heat stress. Non-sweating mammals
and birds depend primarily on the respiratory
water loss which is a function of the respiratory
surface area and the vapor pressure differential
between the evaporative surface and the air. Since
birds do not sweat most of the water evaporated
comes from the respiratory tract (Salt 1964).
This study was undertaken to measure the
changes in respiratory volumes of the fowl when
they are supplied with water and when they are
deprived of water for a certain period.
In a hot environment the rate of water loss
(evaporative and excretory) of the birds exceeds
the production of metabolic water (Bartholomew
and Dawson, 1954). Therefore survival, especially
in high temperature, depends on the availability
of water. Several studies have demonstrated the
importance of respiratory evaporative water loss
with increasing ambient temperatures (Dawson,
1958; Bartholomew et al, 1962; Crawford and
Schmidt-Nielsen, 1967 and Menuam and Richards,
1975).
MATERIALS AND METHODS
The experiments were conducted on two
groups of birds: (i) seven one-and-half-year old
medium weight hybrid layers Babcock 390 of
body weights 2.0 to 2.5 kg for the exposures to
35°C and (ii) seven one-and-half-year old light
weight hybrid layers Babcock 305 of body weights
1.5-2.0 kg for exposures to 40°C. Within groups
the birds that were given food and water ad
libitum were termed lwet' birds and those that
were deprived water were termed 'dry' birds. Heat
exposures to 35°C and 40°C were carried out in a
climatic chamber which could maintain the
temperatures within ± 0.5°C. The relative humidity
Most birds are capable of varying their
evaporative water loss as shown by the varying
respiratory volumes (Smith, 1972). Cutaneous
evaporative water loss also contributes to the
total evaporative water loss in birds (Bernstein,
104
H. KASS1M
further test at 35 C for 180 minutes was
carried out.
at 35°C was 25% and at 40°C it was 19% as
measured by a whirling hygrometer. The air velocity
in the chamber was constant at 53m/min as
measured by a katathermometer. After the
experiments, the birds were allowed to recover in a
room at 20°C with R.H. of 35%.
(b) Exposure to 40°C (R.H. 19%)
Normal 'wet' birds were exposed to 40 C
for 120 minutes. Rectal temperature and
respiratory parameters were recorded.
Data collections
48-hour water restriction: Drinking water was
removed from the birds 48 hours before the
experiment.
Food, however, was given
ad libitum. The birds were then retested at
40°C for 120 minutes and the same parameters
were recorded.
(i) Body temperature: Body temperature was
continuously recorded on a potentiometric
recorder by placing a thermocouple 5 cm inside
the cloaca.
(ii) Respiratory frequency
and volumes: The
measurements were made using a whole body
plethysmograph. A metal box measure
33 X 18.5 X 34cm with an air tight cover was
used as a plethysmograph as described by
Kassim (1975). A bird was comfortably
secured to the inside of the box with its head
protruding through a hole made in front of
the box. A rubber cuffling was inserted at the
neck region and tightly secured to the wall of
the box. Changes in the pressure within the
chamber during respiration were measured
with a pressure transducer (type UP1, Ether
Ltd.) and recorded on a Devices M2 pen
recorder. The plethysmograph was precalibrated for volume-pressure linearity at the
tested temperatures. From the recordings,
respiratory frequency (f) and the tidal volume
(V T ) were calculated from the frequency and
amplitude of the recordings. Total ventilation
(V) was derived from the products of
respiratory frequency and tidal volume.
RESULTS AND DISCUSSION
A.
Exposures to 35°C
The results in (Table 1) showed that the
body temperature of birds in both groups
increased during the heat exposures. The
temperature of the normal 'wet' birds increased
by 0.7° C while that of the 'dry' birds increased
by 0.7°C and 1.1°C respectively following the
24-hour and 48-hour water restriction at the
end of the 180 minutes exposure. These
results showed that body temperature was
elevated as the degree of dehydration increased.
Though the body temperature increased at
different rates, the respiratory frequency
increased at a similar rate. However, the
'dry' birds started to pant at a later period than
the 'wet' birds. This could be one of the ways
by which the 'dry1 birds conserved the
respiratory evaporative water loss at the
expense of the body temperature.
The total ventilation, which determines
the respiratory evaporative water loss, however,
increased at the same rate for both the groups.
This indicated that ventilation was temperature
dependent. Since there were no measurements
for the evaporative water loss, any variations
in the total evaporative water loss that occurred
could only be due to the changes in the
cutaneous evaporative water loss.
Measurement of respiratory changes
(a) Exposures to 35°C (R.H. 25%)
Normal 'wet' birds were exposed to 35°C for
180 minutes. Rectal temperature and
respiratory parameters were recorded.
(i) 24-hour water restriction. After the
control experiments were carried out the
birds were allowed to recover. A period
of over 10 days was allowed before the
next experiment was carried out. When
the birds were ready for the tests the
drinking water was withheld for 24 hours
prior to the experiment.
The relation between f, V and VT remained
unchanged for the "wet" and 48-hour water
restricted birds (Figure 1). The relation of f and
V was linear and the birds were only in the
first phase panting.
Food was given ad libitum.
The 'dry' birds were exposed to a
temperature of 35°C for 180 minutes.
B.
Exposures to 40°C
Heat exposure to 40°C was only for
120 minutes because prolonged exposure
usually resulted in death. Under this heat
stress the birds underwent second phase
(ii) 48-hour water restriction. After a 10 days'
recovery period from the previous test,
water was withheld for 48 hours before a
105
WATER RESTRICTION ON RESPIRATORY VOLUMES OF FOWLS
TABLE 1
Comparison of the respiratory responses of normal birds and 24 hour and 48 hour water restricted birds during
exposures to 35°C. Mean ± S.E. of seven birds
1.
3.
4.
48 hour
water restricted
Rectal temperature (°Q
Initial
At panting
At maximum f
At maximum V
Final
2.
24 hour
water restricted
Normal
Parameters
Respiratory frequency
Initial
Maximum
At maximum V
Final
Time at onset of
panting (min)
41.6
41.5
41.9
42.1
42.3
±0.14
±0.16
± 0.25
±0.36
± 0.45
41.9
41.9
42.3
42.5
42.6
±
±
±
±
i
0.13
0.20
0.30
0.40
0.37
23
285
257
258
± 0.8
± 4.5
±9
±5
18
287
278
263
+
±
±
±
0.6
15
16
22
41.4 ±0.10
41.3 ±0.17
41.8 ±0.25
42.2 ±0.31
42.5 ± 0.40
f/min)
Tidal volume (ml)
Initial
At panting
At maximum f
At maximum V
Final
25.7 ± 4
48 ± 9
24.1± 2.0
11.2
7.7
9.7
9.2
20.7
10.3
8.1
9.1
9.1
±0.6
± 0.2
± 0.5
± 0.5
± 2.0
± 0.4
± 0.2
± 0.6
±0.7
20
280
262
242
±2
±9
±7
±6
46 ± 5
22.0
9.9
7.6
8.9
9.1
±0.4
i 0.4
i 0.3
± 0.5
±0.4
Total ventilation (L/min)
Initial
At maximum f
Maximum
Final
0.544
2.200
2.560
2.360
0.370
2.314
2.514
2.370
l 0.03
± 0.07
±0.10
±0.10
i
±
±
±
0.04
0.12
0.15
0.19
0.432
2.117
2.327
2.202
1 0.04
+ 0.06
±0.10
±0.10
panting as is clearly shown by the relationship
between f and V and VT in Figure 2.
48 hours had no effect on the maximum respiratory
and total ventilation.
The 'dry' birds were able to maintain a
body temperature lower than the 'wet' birds
such that at the end of the exposure the final
Tre was 43°C compared to 43.5°C for the
latter. This represented an increase of 2°C/h
for the 'wet' birds and 1.2°C/h for the 'dry'
birds.
Evaporative water loss of the birds increases
during thermal polypnoea (Salt, 1964) and the
regions of the respiratory tract from which
evaporation may occur include the buccal mucous
membranes, tongues, nasal passages and trachea
(Schmidt-Nielsen et al., 1970). Menuam and
Richards (1975) had shown that although the fowl
was equipped with voluminous air-sacs, these airsacs were not likely to be involved in the
evaporative water loss.
The wet birds started panting after about
11.7 ± 1.7 minutes exposure but panting was
delayed in the 'dry' birds after about
37 ± 7 minutes when T re had increased from
the normal. However,the maximum respiratory
frequency achieved (f = 285/min) by both
groups were the same with the 'dry' birds
panting at a higher Tre. Since respiratory
changes during this exposure were biphasic,
it could be represented in first-and secondphase breathing (Table 2). This experiment
showed that water-restriction of up to
Water content in the animal's body must be
important in controlling the total evaporative water
loss. When the birds were deprived of water they
exhibited a loss of body weight. As indicated by
Crawford and Schmidt-Nielsen (1967), when the
ostrich was deprived of water the magnitude of
body weight loss increased daily with an increase
in body temperature compared to those of normal
hydrated birds. This increase in body temperature
106
H. KASSIM
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5
2.4
2.4
2.0
2.0
16
a i.2
8
.8
20
.4
20
100
Respiratory
100
Respiratory
200
rate (/min)
Figure 2. 'The relation between the respiratory
rate and total ventilation and tidal
volume of normal 'wet' birds (it)
and 48-hour water-restricted 'dry'
birds (m) during exposures +o 40° C
1 = responses during the first phase
breathing; 2 = responses during second
phase breathing.
200
rate (/min)
Figure 1. The relation between the respiratory
rate and total ventilation and tidal
volume of normal 'wet' birds (it) and
48-hour water restricted 'dry' birds (m)
during exposures to 35° C.
through cellular dehydration. Although total
evaporative water loss was not measured in the
current experiment, there was sufficient evidence
to show that respiratory ventilation and respiratory
evaporative water loss were independent of the
total water content of the body. It was assumed
that respiratory ventilation of a bird was not
influenced by the total evaporative water loss and
the respiratory water loss and that they would be
the same for 'wet' and 'dry* birds. Lee and
Schmidt-Nielson (1971), however, found that in
zebra finches the total evaporative water loss during
dehydration was lower in dehydrated birds but
respiratory water loss was the same in both
hydrated and dehydrated birds, thus supporting
the present contention that the decrease in
evaporative water loss could only be due to the
reduction in cutaneous water loss.
was a sequence of reduced evaporative water loss
during heat exposure. The dehydrated birds
expend less water for evaporation than hydrated
ones and permit their body temperature to rise to
hyperthermic levels. During this process, the birds
were able to reduce the circulating fluid for
surface evaporation and thus reduced the cutaneous
evaporation (Smith and Suthers, 1969; Smith,
1972; Bouverot et alt 1974). The increase in
pulmonary ventilation would not be adequate to
remove all the heat and this resulted in slight
increase in body temperature (Table 1).
From Figures 1 and 2, it can be seen that the
relation between total ventilation and respiratory
frequency of 'wet' and *dry' birds remained linear
throughout the first phase breathing. These
observations would lead one to conclude that birds
of different species respond differently when
exposed to heat. This view is supported by Taylor
(1970) who found that dehydrated ungulates
panted at higher air and body temperature; and in
studies in dehydrated rabbit (Turlejska-Stelmasiak,
1974) where panting was found to be blocked
The adaptation to water economy is important
in a hot environment. The role played by the skin
in restricting water loss by evaporation through
cutaneous, sweating, and kidney water economy
form the adaptive process of animals. In birds,
107
WATER RESTRICTION ON RESPIRATORY VOLUMES OF FOWLS
TABLE 2
Changes in the respiratory responses of normal and 48-hour water-restricted birds during exposures to 40°C
Mean i S.E. of seven birds
Control
Parameters
(a)
(b)
Normal birds
f (/min)
V T (ml)
V(L/min)
T re (°C)
(C)
27 ± 1.2
15.91 ± 0.5
0.434 ± 0.01
41 ± 0.09
Water-restricted birds
20 ±2
17.45 ± 3.3
0.344 ± 0.07
41.4 1 0.36
Tre
f
VT
V
Peak of
1st Phase
End of
2nd Phase
Change from
C to 1st
Change from
1st to 2nd
285 ± 32
6.42 ± 0.7
1.787 ± 0.1
41.4 ± 0.1
218 ± 24
11.04 ± 1.4
2.347 ± 0.07
43.2 ±0.24
+ 956%
-60%
+ 312%
+ 0.9%
+ 23.5%
+ 72%
+ 31%
+ 4.5%
283 ± 9
6.67 ± 0.68
1.809 ±0.1
42.2 ± 0.38
268
8.72
2.326
42.8
+ 1315%
-62%
+ 426%
+ 1.9%
water is also reabsorbed from the feces by the
cloaca as observed by the dry feces excreted by
the 'dry' birds. The ability of these birds to
reabsorb water from the feces and the redistribution
of body fluids to reduce the cutaneous water loss,
helps them maintain a body water balance at a
certain level to overcome the severe effect of
dehydration during the short exposures to heat.
+ 31%
+ 29%
+ 1.5%
KASSIM, H. (1975): Studies on the respiratory ventilation
of the fowl in relation to hot climates. Ph.D. Thesis.
University of London.
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MENUAM, B. and RICHARDS, S.A. (1975): Observations
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during thermal panting. Respir. Physiol 25: 39-52.
The author is grateful to Dr. A.H. Sykes, Wye
College (University of London) for providing the
facilities, and Universiti Pertanian Malaysia for
financial support.
SALT, G.W, (1964): Respiratory evaporation in birds.
Biol Rev. 39: 113-136.
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108