Biomedical Engineering Reference
In-Depth Information
basis of the average of hourly THI for accurate
analysis of environmental discomfort. An aver-
age THI is normally calculated on the basis of
maximum and minimum ambient temperature
and is an estimate of the average THI of the day
with 5-7% variations but may be suitable for
determining animal production functions and
impact of environment.
(c) By calculating dry bulb temperature and
relative humidity by using the following
equation:
times the normal, their tongue protruded
and salivary activity increased. In the heif-
ers, the comparison showed that averages of
RT, RR and pulse rate (PR) were lower in
buffaloes than those of the zebu cattle, under
cool, comfortable conditions. The ambient
temperature was 18.5°C, and vapour pres-
sure was 8.5 mmHg, under the cool, com-
fortable conditions. When exposed for 6 h to
hot-humid conditions, the RT and RR of the
buffaloes exceeded those of the zebu heifers
towards the end of the exposure period. The
ambient temperature was 40.5°C, and vapour
pressure was 39.5 mmHg under the hot-
humid conditions. On exposure to hot arid
conditions, the buffalo heifers reacted more
sharply than zebu heifers as evidenced by
increase in RT, RR and respiratory volume.
However, the physiological reactions were
rather mild in case of the zebu heifers and
more severe in the buffalo heifers as com-
pared to the cool comfortable conditions
(Das et al.
1999
) .
Acute heat exposure to 33-43°C and 40-60%
RH of young (aged 6 months) and old Egyptian
buffalo calves (aged 12 months) induced more
significant increases in RT (3.4 and 3.2%) and
RR (495 and 335%, respectively) than in the
control. The chronic heat exposure of 6- and
12-month-old buffalo calves was accompanied
by increases in RT (4.1 and 3.0%), RR (528
and 318%) and evaporative water loss (69.4 and
51.2%, respectively; Nessim
2004
) . In another
study, it was reported that exposure of Egyptian
buffaloes to direct solar radiation for 3 h continu-
ously from 12:00 to 15:00 h caused an increase in
RT (38.5-40.9°C), RR (26.1-124.8 breaths/min)
and PR (64.5-82.2 pulses/min; Ashour
1990
) .
Sha fi e (
1993
) observed the effect of heat, accom-
panied by direct solar radiation for 3 h from 12:00
to 15:00 h, during August in Egypt on the physio-
logical response of buffaloes resulted in an
increase in absolute values of RT (1.7°C), skin
surface temperature (2.3°C), RR (70.0 breaths/
min), PR (18.0 pulses/min) and arterial pressure
(23.0 mmHg). Exposure of Indian buffaloes for
6 h to sun direct radiation in hot and dry season
increased RT and PR by 1.4°C and 11 pulses/
{
}
(
)(
)
THI
=−− −
(Marai et al.
2001
)
db C
°
0.31
0.31 RH
db C
°
14.4
,
where db°C = dry bulb temperature in °C and
RH = relative humidity percentage (RH%)/100.
The values obtained indicate the following:
<22.2 = absence of heat stress
22.2 to <23.3 = moderate heat stress
23.3 to <25.6 = severe heat stress
25.6 and more = extreme severe heat stress
Both equations are applicable in cattle,
sheep, goats and buffaloes.
(d) By observing body temperature and respira-
tory rate to assess heat stress level in cattle:
(Perez
2000
).
Body temperature and respiration rate
have been recommended to be used as para-
meters to determine heat stress in cattle;
altogether with THI values to determine and
evaluate heat stress in cattle, rectal tempera-
ture (RT) and respiration rate (RR) are the
most sensitive indices of assessing heat
stress among the physiological reactions
studied. The increase in ambient temperature
from 29 to 31°C resulted in an increase in
RT from 37.8 to 38.0°C and RR from 20.5 to
22.4 breaths/min in buffalo heifers and from
37.9 to 39.7°C and from 23.4 to 41.0 breaths/
min, respectively, in lactating buffalo cows
(Kamal and Ibrahim
1969a,
b
; Kamal et al.
1978
) . In Murrah male buffalo, 7-9-month-
old calves were not able to maintain RT
within normal range during summer when
ambient temperature and solar radiation were
maximum (44.1°C). Their RR increased 5-6
