Variation in Rectal Temperature, Respiration Rate, and Pulse Rate of Cattle as Related to Variation in Four Environmental Variables

Abstract

To determine the relative importance of variations in air temperature, wind velocity, solar radiation, and vapor pressure in producing responses of cattle, a series of four 24-hr. studies in 1953 and five in 1954 were conducted with Brahman, Jersey-Brahman crossbred, Jersey, and Holstein females. Thirteen observations each of the rectal temperature, pulse rate, and respiration rate of each animal were recorded during the 24-hr. period, i.e., at the beginning of the test period and at intervals of 2 hr. Continuous records of solar radiation, air temperature, vapor pressure, and wind velocity were obtained. Though the primary object was not a breed comparison, the data conform to the findings of previous studies with respect to the relative heat tolerance of the groups studied, the order of heat tolerance being Brahman, most heat-tolerant, followed by ½ Jersey-½ Brahman, 34 Jersey- 14 Brahman, Jersey, and Holstein. The data were studied by multiple regression methods, using as independent variables the four environmental variables and as dependent variables those measured on the cattle. The results indicate that under conditions similar to those prevailing during these studies, almost as satisfactory explanation of variation in rectal temperature, respiration rate, and pulse rate can be accomplished with air temperature as the only independent variable as with all four environmental variables included. The percentages of variance due to the regression of the measured physiological responses on all the independent variables did not differ much from those considering air temperature alone. From a practical standpoint, it may be concluded that air temperature is the most important environmental variable with respect to summer weather stress in cattle. Management procedures to combat summer weather stress should emphasize efforts to provide as low air temperatures as economically feasible. This does not mean, however, that no effort should be devoted to the provision of shade for cattle. © 1960, American Dairy Science Association. All rights reserved.