Body Temperature in Beef Cattle: Its Control and Relevance to Production in the Tropics

Control of body temperature is a consequence of the thermoregulatory mechanism of an animal and the resistances to energy exchanges between it and the environment. To demonstrate the effects of thermoregulation and resistances on body temperature in beef cattle, some of the relevant research on genotypes of Bos indicus and Bos taurus has been reviewed: in particular, resistance of the tissues to transfer of metabolic heat to the skin which is lower in Bos indicus than in Bos taurus; resistance of the coat to solar radiation, which is greater for cattle with coat types similar to Bos indicus; the interaction of coat color and type in resisting environmental heat transfer to the skin; and some differences between Bos taurus and Bos indicus in the ability to increase and sustain evaporative heat-loss from the skin. Food and water availability also affect the control of body temperature in beef cattle. In Bos indicus, curtailing food intake significantly decreases the lower range of the daily body temperature cycle, whereas restricting water intake extends both maximum and minimum body temperatures. These alterations in temperature control promote energy and water conservation during dry seasons or drought; however they also are indicative of a physiological status that is not advantageous to production. The evidence is that a strictly regulated body temperature promotes the greatest productivity in beef cattle. Even small upward shifts in body temperature are deletrious to metabolic processes. As body temperature is a heritable trait, selection within breeds for thermoregulatory characteristics which defend this, such as efficient and sustained sweating rates and low resistances to heat-loss, would be a strategy for lifting productivity in the tropics. However, there is also genetic evidence from within a breed of Bos taurus cattle that changes toward increased capacity for thermoregulation are accompanied by a reduction in inherent energy metabolism. Nevertheless a greater proportion of possible production is realized in cattle with more strictly controlled body temperatures.