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The pervasive nature of weather and climate and the difficulties in adequately predicting their impact on beef cattle often lead to inadequate management strategies and tactics, resulting in a situation of coping as the need arises. This can lead to "management by crises" rather than rational decisions. The objective of this report is to summarize some of the known responses of cattle to their thermal environment and to address ways by which adverse impacts can be reduced. The discussion is based on results from MARC and other research stations.
General observations: Domestic cattle fall into two main classifications: European Bos taurus breeds (e.g., Herefords, Angus, Shorthorns, and the so-called exotic breeds) which evolved in temperate or cold regions and Bos indicus, or Zebu, breeds which evolved in tropical regions. Bos taurus breeds carry genes for higher production potential in moderate to cold climates when nutrition and other factors are non-limiting. In hot weather, the Bos taurus breeds are more susceptible to reduced performance than Bos indicus cattle, although the latter can also be adversely affected by heat effects on physiological and productive functions. The adaptability of cattle to relatively low temperatures is the result of several factors, including heat produced during roughage digestion, tissue, and a relatively lower surface area to mass ratio than for smaller species, which minimizes the rate of heat loss per unit of mass.
Body temperature represents the integrated response of an animal to various internal and external factors. Body temperature stability is generally considered an essential element for maximum productivity of cattle. However a diurnal cycling of up to 2°F body temperature can occur even in quite moderate thermal conditions. Constancy of body temperature, per se, may be less important to productivity than disruption of the normal cycling of body temperature caused by weather or other potential stressors. The impact of that disruption on physiological factors is presently unknown but may ultimately be expressed in terms of production, reproduction, efficiency and health. Obviously, the impact of cold or hot conditions on beef cattle performance needs to be assessed as a basis for rational management.