Some physiological responses of yearling sheep placed in a fluctuating low-temperature environment were determined. Four wethers placed in an unheated room, ranging from −2°F. to +56°F., showed significantly higher heart rates, lower rectal temperatures, reduced water consumption, and decreased urine volume than four wethers maintained in a heated room in which ambient temperature was regulated between 55°F. and 65°F. Respiration rates, eosinophil numbers, and jugular blood hematocrits were not significantly different. Correlations of heart rates with rectal temperatures, respiration rates with degree-hours per day, and heart rates with rectal temperatures in the cold were significant.Blood plasma concentrations (m-equiv./1.) of Na+, K+, and Mg+ were not altered significantly by exposure of wethers to the cold, although some transient high concentrations of Na+ were noted. Correlations among plasma Na+, K+, and Mg+ and degree-hours per day were not significant.Urine concentration of Mg+ was not affected by environmental temperature, but the concentrations of urine Na+ and K+ were significantly higher in the cold environment. Correlations among urine K+ and Mg+ and degree-hours per day were not significant, but the correlation between urine Na+ and degree-hours was significant.Observations made during the experiment confirm the necessity of pre-training of animals to be used for environmental studies.
Physiological responses to known intake of ergot alkaloids by steers at environmental temperatures within or greater than their thermoneutral zone
