Abstract
Body temperature in homeotherms is maintained
by the thermoregulatory system within 1°C of
its normal temperature under ambient conditions
that do not impose heat stress. A rise in the
core body temperature also increases heat loss
by panting and sweating. These responses are
physiological strategies to transfer heat from
the cow’s body to the environment. In order to
maintain homeothermy, an animal must be in
thermal equilibrium with its environment,
which includes radiation, air temperature,
air movement and humidity. The range of
temperature within which the animal uses
no additional energy to maintain its body
temperature is called the thermoneutral zone
(TNZ), within which the physiological costs
are minimal and productivity is maximum.
Temperature–humidity index (THI) is an index
for assessment of the potential of an environment
to induce heat stress in humans and
farm animals. Heat loss via skin is more in
cows and heat loss by respiration is higher in
buffaloes. This is due to less number of sweat
glands in buffaloes. Exposure of the animal to
high environmental temperature stimulates
the peripheral and core receptors to transmit
nerve impulses to the speci fi c centres in the
hypothalamus, to help in preventing the rise
in body temperature. The speci fi c centres in
the hypothalamus are the defensive evaporative
and non-evaporative cooling systems, appetite
centre and the adaptive mechanisms that cause
such reactions. The suppressive impulses