Biomedical Engineering Reference
In-Depth Information
min, respectively, when air temperature was
42.9°C, vapour pressure was 14.3 mmHg and
wind speed was 8.6 km/h. A rise in humidity and
air temperature resulted in an increase in RT
and PR of the same animals, whereas higher wind
speed helped the animals to dissipate heat. The
average sweat gland density in buffalo was 86.94/
cm
2
. Heritability of sweat gland characteristics
(length, diameter, shape, volume and density)
ranged between 0.38 and 0.68 (Nagarcenkar and
Sethi
1981
). It was observed that exposure of
swamp non-pregnant female buffaloes for 2-3 h
to solar radiation at air temperature of 42.1°C
increased RT from 40.1 to 41.1°C, RR from 76.7
to 128.0 breaths/min and PR from 67.0 to
84.7 pulses/min (Zhengkang et al.
1994
) .
The buffalo behaviour changes during direct
heat exposure. Asker and Ragab (
1952
) observed
that the Egyptian buffaloes tied in the sun during
May and June from 10:00 to 12:00 h became
restless and stopped rumination. Other signs of
discomfort observed are kicking, nervous swit-
ching of the tail and stretching of the head, after
half an hour of exposure. Other signs observed
after continued exposure to solar radiations are
panting (64.54-82.16 breaths/min) dribbling of
saliva from their mouth, mucus from the nostrils
and tears from the eyes.
cles that give the skin surface its characteristic
black colour (Shafie
1985
) . The melanin particles
trap the ultraviolet rays preventing them from
penetrating through the dermis of the skin to the
lower tissue. These rays are abundant in solar
radiation in the tropics and subtropics, and
excessive exposure of animal tissue could be
detrimental, even resulting in skin tumours. This
beneficial characteristic is reinforced by well-
developed sebaceous glands, with greater
secretion activity than in cattle (Shafie and Abou
El-Khair
1970
). These glands secrete sebum, a
fatty substance which emerges on the skin's sur-
face and covers it with a lubricant, making it slip-
pery for water and mud. This greasy sebum, along
with the thick hornified top layer of skin, prevents
water and the solutes in it from being absorbed
into the skin. In this way, the animal is protected
from the harmful effects of any deleterious chem-
ical compounds in the water. Moreover, the
sebum layer melts during hot weather and
becomes glossier to reflect many of the heat rays,
thus relieving the animal from the excessive
external heat load.
Particularly, buffaloes suffer in the sun, since
they exhibit signs of great distress when exposed
to direct solar radiation or when working in the
sun during a hot weather due to the fact that their
bodies absorb a great deal of solar radiation
because of their dark skin and sparse coat or hair,
and in addition to that, they possess a less efficient
evaporative cooling system due to their rather
poor sweating ability, although this ability is
more efficient than in cattle. Nagarcenkar and
Sethi (
1981
) indicated that buffaloes possessing
high sweat gland density and sweating volume
coefficient were more heat tolerant, the perfor-
mance was superior among the more heat-tolerant
buffaloes and milk production was higher in more
heat-tolerant buffaloes.
Buffaloes also have different physiological
adaptation to extremes of heat and cold than the
various breeds of cattle. Body temperature of
buffaloes is slightly lower than those of cattle, but
buffalo skin is usually black and heat absorbent
and has only sparsely protection by hair. Buffalo
skin has one-sixth of the density of sweat glands
that cattle skin has, so buffaloes dissipate heat
4
Adaptation to High
Temperature
Morphologically, buffaloes have a good coat of
soft hair like that of cattle at birth and during
early calfhood. The hair on the body becomes
sparser and almost devoid of hair as the animal
grows. The amount of hair coat retained varies
considerably, depending on the breed, season,
housing practices and because of its exposure to
water and mud. The colour of the hair may be
black, dun, creamy yellow, dark, light grey or
white. Series of B (brown), C (albino), D (dilute)
and E (extension) are present in buffaloes, while
only A (agouti), B, C, D, E and P (pink eye) are
found in cattle (Searle
1968
) .
Anatomically, buffalo skin is covered with a
thick epidermis, containing many melanin parti-
