In hot conditions, cattle can become unproductive, overheat or die. To asse
ss the effect of a particular set of environmental conditions on an animal,
the thermal balance is modelled and coded into a user-friendly software pa
ckage. Air temperature, humidity, wind speed and radiation, together with m
etabolic heat production, are used to evaluate the thermal balance. Three b
iological cooling mechanisms are included: reduction of thermal resistance
of body tissue, sweating to increase the latent heat loss from the skin and
panting to increase heat loss from the respiratory system. The body temper
ature rises if the cooling mechanisms cannot dissipate sufficient heat. The
model is used to examine the effects of conditions likely to be experience
d by cattle in southern UK. The results show that high yielding animals wou
ld be able to maintain thermal balance in normal conditions but, in hotter
conditions, feed intake would be reduced and production would fall. (C) 200
0 Silsoe Research Institute.