Livestock Production Science 61 (1999) 71–78
Short Communication
Heat stress in Murrah buffalo calves
S.K. Das *,1 , R.C. Upadhyay 1 , M.L. Madan 2
National Dairy Research Institute, Karnal 132 001, India
Received 9 October 1997; accepted 5 February 1999
Abstract
Six young Murrah male buffalo calves, 7 to 9 months old, weighing 165–200 kg, were exposed to solar radiation during
summer (Dbmin. 27.18C, Dbmax. 44.18C) . The surface temperature at forehead, back middle, pinna, neckmiddle, rump,
foreleg and hindlegs were recorded using a non-contact temperature measuring instrument. Respiration rate and rectal
temperature were recorded coincidently at hourly intervals. The difference between mean of minimum and maximum
temperature, at forehead (20.098C), back middle (22.338C), foreleg (lower, 18.508C), pinna (18.218C) were higher than the
temperature gradient of neck middle (13.968C), rump (16.138C), foreleg upper (14.758C), hindleg upper (14.588C), hindleg
lower (15.848C). The surface temperature at all sites increased in relation to the length of radiation exposure. During summer
when ambient temperature and solar radiation was maximum, young buffaloes were not able to maintain their normal rectal
temperature and increased pulmonary frequency by 5–6 times, protruded tongue, and increased salivary activity. Therefore,
young buffaloes should be protected from extreme hot conditions and direct sun exposure be avoided.  1999 Elsevier
Science B.V. All rights reserved.
Keywords: Buffalo calves; Summer; Body surface temperature; Respiration rate; Rectal temperature
1. Introduction
The homeotherms maintain their body temperature
within a relatively narrow range and both physiological and behavioural responses help in thermoregulation. Under thermoneutral environmental conditions
most of the large domestic animals are able to
maintain an equilibrium between the heat production
and heat loss. But in stressful conditions, the number
of physiological and behavioral responses vary in
intensity and duration in relation to the animal
*Corresponding author. Fax: 191-118-425-0042.
E-mail address: [email protected] (S.K. Das)
1
Dairy Cattle Physiology Division, NDRI, Karnal.
2
ICAR, Krishi Bhawan, New Delhi-110 001, India.
genetic make-up and environmental factors. Buffalo
(Bubalus bubalis) are well adapted to hot-humid
conditions and changes that occur during heat exposure has been documented (Ashour and Shafie, 1993;
Hafez et al., 1955; Shafie and Badreldin, 1962, 1963;
Nair and Benzamin, 1963; Cockrill, 1981; Benzamin,
1982; Chikamune, 1986; Chaiyabutr, 1993).
The heat tolerance capacity of buffalo is poor
mainly due to low sweat gland density. Under
excesses thermal loads of heat and work, buffaloes
employ moderate levels of sweating and resort to
open mouth panting. In the past studies on buffaloes
have been oriented to study the magnitude of
changes in physiological reactions. However, information on body surface temperature changes during
summer to solar radiation exposure in young buffalo
0301-6226 / 99 / $ – see front matter  1999 Elsevier Science B.V. All rights reserved.
PII: S0301-6226( 99 )00040-8
S.K. Das et al. / Livestock Production Science 61 (1999) 71 – 78
72
calves is not available. In this paper, therefore, an
attempt has been made to describe changes in body
surface temperature and physiological reactions during a 24-h period. This information is likely to help
in suggesting methods for reducing heat stress in
young buffalo male calves and also in proper shelter
management during summer when outdoor heat load
on the animal could be hatched.
2. Materials and methods
This experiment was conducted during the month
of June at the National Dairy Research Institute,
Karnal. Six Murrah male buffalo calves of 7–9
months, weighing 165–200 kg were maintained in a
loose housing system. On the day of actual experiments all animals were housed in an open paddock
for direct exposure to the sun-light. Feeding con-
sisted of green fodder and drinking water was
available adlibitum. Rectal temperature, respiration
rate and body surface temperature changes were
monitored continuously for 24 h at hourly intervals
beginning at 6.00 h, twice in the month of June.
The weather conditions, as prevailed during the
experiment, were measured on a data logger system
(Solomat, UK). The monthly average air temperature
and relative humidity, as prevailed at Karnal, have
been presented in the form of a climograph (Fig. 1).
On the day of the actual experiment the maximum
ambient temperature (Db) recorded was 44.108C at
15.00 h and the minimum temperature was 27.108C
at 6.00 h. The relative humidity was 64% at 7.30 h
and 19% at 14.22 h. The minimum wind velocity
was 2.7 km / h at 7.00 h while the maximum was
13.2 km / h at 15.00 h and the wind direction was
North-West. Mean changes in climatic variables
during the experiment have been presented in Fig. 2.
Fig. 1. Climograph for Karnal area at the National Dairy Research Institute.
S.K. Das et al. / Livestock Production Science 61 (1999) 71 – 78
73
Fig. 2. Ambient temperature, wind velocity and solar intensity during the experimental period.
The sky was clear without any clouds and the
maximum average solar intensity was 2.64 MJ / M 2 / h
at 12.00 h.
The surface temperature (Tsk) at different sites (a)
forehead, (b) back middle, (c) pinna, (d) neck
middle, (e) rump, (f) forelegs, upper and lower sites,
(g) hindlegs, upper and lower sites were recorded
using a non-contact temperature measurement instrument (RaytekR, model Raynger ST 2L). The surface
temperature was recorded by keeping the instrument
about 6 in. away directed towards the specific site.
The rectal temperature (RT) was recorded with a
mercury in glass clinical thermometer, inserted 3 in.
in the rectum for at least 2 min and the rectal mucosa
was in contact with the bulb of the thermometer. The
respiration rate (RR) of animals was recorded by
counting the flank movement, one inward and one
outward movement as one breath.
An estimate of heat stored (kJ) was made on the
basis of weighted mean changes in rectal (Tre) and
skin (Tsk) temperature in the ratio of 0.8:0.2 (Finch
et al., 1984). The weighted mean change was
multiplied by the specific heat of tissues (3.47 kJ /
kg / 8C) and the weight of the calf (kg).
Heat storage (kJ) 5 D8C (0.8 Tre:0.2 Tsk)
3 B.wt of animal (kg)
3 specific heat of tissues (3.47 kJ)
The statistical analysis of the resulting data related
to physiological reactions and body surface temperatures were performed using two way analysis of
variance. The possible interactions, statistical differences and correlation analysis were tested on the
complete data as per Snedecor and Cochran (1967).
S.K. Das et al. / Livestock Production Science 61 (1999) 71 – 78
74
3. Results and discussion
The mean changes in RT, RR and different body
surface temperatures over a period of 24 h are
presented in Table 1 and Fig. 3.
The mean resting respiration rate (RR) at the
beginning of the experiment (6.00 h) was 14 per
minute. The respiration rate progressively increased
to a peak level at 12.00 h and remained elevated till
17.00 h and declined thereafter. The lowest rate was
observed at 3.00 h. The ANOVA of data revealed
statistical significant (P,0.01) variations in physiological responses and body surface temperatures over
a 24-h period. During the period of exposure to solar
radiation rectal temperature of calves increased as
the ambient temperature and solar radiation increased
during the day (Fig. 2). The highest mean RT
(40.660.18C) was observed at 12.00 h (Db, 42.68C)
and lowest was 38.68C at 17.00 h (Db, 28.88C). The
forehead surface temperature increased from
31.0860.78C at 6.00 h to 48.561.518C at 13.00 h
with a change of 19.48C from minimum temperature
observed. The surface temperature at the back middle site increased from 30.6660.318C to
49.9361.478C at 12.00 h. These variations in surface
temperature(s) were related to the diurnal changes
and to solar cycle. The changes in RT and RR were
observed to be related with discomfort and it was
noticed that their increase was mainly due to exposure to greater intensity of solar radiation. The
pattern of surface temperature changes at neck
middle, pinna, back middle, rump, foreleg, hindleg
and forehead reflected the skin temperature changes
which took place in relation to the environmental
temperature with significant correlation (P,0.05).
The magnitude of changes in body surface temperatures were maximum at the back middle and minimum at the neck middle.
Fig. 3. Rectal temperature (8C) and respiration rate (breath / min) changes in the experimental animals.
Table 1
Mean temperature (8C) (surface & core) aid respiration rate of Murrah buffalo calves during the experimental period
Time of
observation
(h)
Forehead
Middle
Pinna
Middle
Neck
Middle
Back
Rump
Foreleg
(upper)
Foreleg
(lower)
Hindleg
(upper)
Hindleg
(lower)
Rectal
temp.
Respiration
rate
(breath/min)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
6.00
1.00
8.00
9.00
10.00
11.00
12.00
13.00
14.00
15.00
16.00
17.00
18.00
19.00
20.00
21.00
22.00
23.00
24.00
1.00
2.00
3.00
4.00
5.00
6.00
31.0860.70
37.7560.69
39.8360.92
43.4160.54
47.4160.72
41.4160.15
47.9160.44
48.5061.51
46.6661.20
45.2561.59
42.9160.42
41.0060.43
38.5060.34
35.2560.49
33.8360.31
33.2560.25
30.6660.33
31.2560.71
30.3360.36
29.6660.46
30.7560.33
29.0060.37
28.4160.35
29.1660.17
28.8360.31
29.1260.34
35.9160.22
37.8760.27
39.4160.44
43.1260.43
43.4160.28
43.8760.48
43.5660.17
43.5060.26
42.5460.33
41.6660.12
39.5460.08
37.9560.36
34.2060.82
33.8360.57
33.2560.65
30.6260.11
31.4160.52
30.1660.63
27.9560.59
27.9560.45
28.2960.59
27.7060.51
28.7960.59
25.6660.40
32.5060.42
36.1660.39
31.7060.53
39.6260.60
42.7960.55
41.9160.40
42.7060.58
42.8360.65
42.5060.45
41.7560.42
40.6660.26
39.2560.23
37.3760.19
34.4160.49
34.0060.41
33.6060.27
31.2560.32
32.5860.65
31.9560.25
29.6260.60
29.1266.90
28.8760.18
29.2560.28
29.5460.27
29.9161.00
30.6660.31
28.1661.09
39.9160.61
42.0860.72
48.1660.80
48.7560.73
49.9361.47
48.9161.31
48.6661.30
46.3360.87
44.5860.78
41.1664.31
38.5860.24
34.0860.92
33.0060.50
32.9160.40
30.5860.51
31.0060.68
30.9160.10
30.0861.29
29.0060.58
29.4160.33
28.6660.59
28.5060.45
27.6060.43
31.3760.42
35.8760.69
38.4160.44
40.6260.46
44.2960.25
44.0460.48
44.5460.28
44.5060.31
43.7560.39
43.7560.21
42.6660.28
40.2060.65
37.7560.41
33.2960.55
34.0860.27
32.2560.17
30.3360.52
31.4560.48
30.8760.21
29.6260.31
29.5460.49
29.4560.42
28.5060.42
28.5860.62
28.4160.70
31.6660.78
34.7560.59
36.6660.60
39.6660.78
41.5860.45
42.2560.44
43.5060.53
43.3360.38
43.4160.40
40.8360.33
40.6660.33
39.5860.35
38.2560.56
36.3360.61
34.1660.25
32.4660.40
31.4160.68
32.1660.69
32.1660.59
30.7560.66
31.0060.76
29.1660.46
29.4160.51
28.7560.46
29.3360.49
32.0860.51
33.5860.71
36.1660.28
35.5060.18
43.4160.69
42.5860.78
46.8360.71
44.5860.78
44.5061.01
42.2560.51
40.7560.67
38.5860.30
37.3360.48
34.1660.46
33.1660.56
32.7560.40
30.8360.36
31.4160.33
31.6660.57
30.2560.82
30.8360.70
29.8360.53
29.0060.34
28.6660.36
27.3360.76
31.4160.98
35.0860.27
37.0860.49
38.8360.53
41.6660.38
42.5860.49
42.9160.44
42.4160.47
42.7560.36
41.9160.60
40.4160.77
39.3360.21
37.0860.74
33.6660.56
33.6660.42
33.3360.61
32.0860.58
32.0060.53
31.7560.80
29.7560.53
30.9260.87
29.9160.52
29.1660.61
28.4160.47
28.3361.26
29.5860.65
35.1660.56
36.6660.17
40.0060.54
43.7560.54
43.5860.37
45.5061.08
44.0860.37
45.4160.47
44.2560.38
42.0860.37
39.3360.64
36.9160.61
33.5060.26
33.9160.30
33.8360.33
31.7560.60
32.9160.35
32.5060.45
31.2560.46
31.0860.89
30.3360.96
30.2560.51
29.6660.56
29.6660.56
38.7760.10
38.8360.08
39.0760.08
39.4260.07
39.7260.32
40.3460.01
40.5760.10
40.1760.08
39.9760.12
39.9360.09
39.7460.20
39.4760.07
39.3060.14
38.8660.08
38.8260.05
38.9060.01
38.8660.07
38.7060.05
38.8260.03
38.7660.05
38.5860.10
38.8060.03
38.6860.04
38.5660.09
38.8160.13
14.0060.29
15.0060.56
17.0860.49
28.1660.68
32.3361.30
65.6664.84
72.0063.91
71.3363.58
69.9164.41
70.4162.92
70.7560.77
66.3366.22
34.1663.82
23.0862.81
15.5060.61
14.9160.33
13.9160.45
13.1660.25
12.2560.17
12.5060.18
12.4160.33
11.4160.33
11.5860.24
12.3360.21
12.8360.48
S.K. Das et al. / Livestock Production Science 61 (1999) 71 – 78
SI.
No.
75
76
S.K. Das et al. / Livestock Production Science 61 (1999) 71 – 78
These changes were related to the surface area
exposed directly to the sun. The surface temperature
increased in the afternoon as the intensity of solar
radiation increased. The difference between mean of
minimum and maximum temperature at forehead
(20.098C), back middle (22.338C), foreleg (lower,
18.508C), pinna (18.218C) were higher than the
temperature gradient of neck middle (13.968C), rump
(16.138C), foreleg upper (14.758C), hindleg upper
(14.588C), hindleg lower (15.848C).
The blood vessels in the skin vasodilate during
endurable hot weather in summer, primarily, to bring
body heat to the skin for dissipation by radiation and
convection (Bianca, 1968). The structural supply of
buffalo skin with sub epidermis plexus of capillaries
allows readily heat exchange with relatively cooler
air of the environment in buffalo (Shafie, 1985;
Shafie and Badreldin, 1962, 1963; Ashour and
Shafie, 1993).
The mean skin temperature, heat stored has been
presented with changes in ambient temperature in
Fig. 4. The results indicate that a rise in skin
temperature leads to a greater heat storage in the
body of calves due to direct solar radiation exposure
during summer. The average heat stored in buffalo
calves was estimated to be about 1850 kJ with mean
rectal temperature of 40.578C and surface temperature of 42.608C.The heat load on buffalo calves
during the present study as reflected by the results
indicate that young buffalo calves were not able to
maintain their body temperature under sun exposure
and resulted in extra heat load. This rise in heat
stored with increased physiological responses in
young buffalo calves is similar to the mechanisms of
deferred heat dissipation mechanism employed by
other adult mammals (Taylor, 1981). Inability to
eliminate excess heat leads to a rise in body temperature of young buffalo calves and mechanisms associ-
Fig. 4. Heat storage in the experimental animals in relation to ambient temperature and mean rectal and skin temperatures.
S.K. Das et al. / Livestock Production Science 61 (1999) 71 – 78
ated with hyperthermia were observed primarily due
to under developed hypothalamic functions and
lower thermostability in buffaloes (Bianca, 1968).
The sun exposure increased the surface temperature of young buffaloes and these variations in
surface temperature were related to the magnitude of
sun-shine and ambient temperature. Exposure of
calves to solar radiation from 11.00 to 16.00 h
resulted in protruded tongue, frothing and panting. In
the process of thermoregulation, heat loss from the
skin usually occurs by radiation, convection and
evaporation (Chaiyabutr, 1993). The sweat glands of
buffalo skin have a low blood supply (Hafez et al.,
1955; Nair and Benzamin, 1963). The number of
sweat glands per unit area of skin is about one-third
of cattle and the thickness of the corneum layer and
epidermis about double that of cattle (Hafez et al.,
1955; Badreldin and Ghany, 1952). The thickness
and the black pigment of the buffalo skin help in
absorbtion of more heat and leads to disproportionate
convective and radiative heat losses from the extremities during exposure to solar radiation
(Chaiyabutr, 1993).
Air temperature up to around 308C (dry bulb) has
little effect on respiration rate and rectal temperature
(Chaiyabutr et al., 1987; Chikamune, 1986). The
respiratory frequency increase enormously when the
air temperature exceeds 308C and the animal begins
to pant. This panting is thought to be initiated by
thermal stimulation of peripheral receptors and is
unaccompanied by a rise in rectal temperature
(Chikamune, 1986). At higher temperature e.g. 41 /
318C (DB / WB), rectal temperature of the buffalo
has been reported to increase to 0.00338C / min / 340
kg body weight while the respiration rate rises
rapidly to about three to four times the normal values
(Chaiyabutr et al., 1987).
The distress case was manifested in behavioural
symptoms of young buffalo calves during the present
study. These symptoms were similar to the ‘Second
Phase’, panting type, observed in dogs (Hales and
Dampney, 1975), sheep (Hales and Webster, 1967),
taurus cattle (Hales and Findlay, 1968), tarus zebu
crosses (Upadhyay and Madan, 1985) and adult
working buffaloes (Upadhyay and Rao, 1985). The
common observations in young buffaloes were
tongue protrusion and enhanced salivary secretion.
These mechanisms were mainly achieved to facilitate
greater heat dissipation from buccal surfaces.
77
4. Conclusion
Variations in skin surface temperature and physiological responses of Murrah buffaloes revealed that
direct exposure to solar radiation during summer
causes distress to the young animals. During the
summer young animals are not able to maintain their
body heat balance even after employing behavioural
processes of thermoregulation. In order to achieve
greater production the heat alleviation processes
must be aided artificially.
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