Exponential relation between sweat rate and skin temperature in hot climates

Abstract

SUMMARYThe sweat rates, skin and rectal temperatures and other components of the heat budgets of cattle were measured in Kenya and in England. Mean sweat rate (Ec) was more closely related to mean skin temperature (T8) than to rectal temperature. The results were described by an exponential relationship between T8, (°C) and Ec (mg/m2.sec) of the form Ee = E0 exp (T8, — T0)/B, where T0 and B are parameters (both with units of °C) which describe the sweating response of the animal, and E0 is 1 mg/m2.sec. T0 was 30·8 °C for a single Bos taurus in England and 33·8 °C for five animals in Kenya suggesting that chronic acclimatization to a hot environment resulted in the cattle being able to tolerate a higher mean skin temperature. The effect of species (Bos indicus cf. B. taurus) was small compared with the effect of acclimatization, although the mean value of B was significantly higher for B. indicus (1·58 cf. 0·94 °C) indicating that the physiological mechanism controlling sweat rate in B. indicus was less sensitive to skin temperature.