SOME PHYSIOLOGICAL RESPONSES OF SHEEP TO SHORT-TERM COLD EXPOSURE

Abstract

An experiment was conducted with shorn, mature wethers to study the short-term effects of a low ambient temperature on jugular vein temperatures, rectal temperatures, packed cell volumes, eosinophil counts, and the plasma concentrations of sodium, potassium, calcium, magnesium, and glucose. The sheep were placed singly in a chamber in which they were subjected during consecutive 3-day periods to air temperatures of 20.6 ± 1.0, 1.3 ± 1.5, and 19.2 ± 2.0 °C. In the cold period, an immediate and marked downward fluctuation in jugular blood temperature was followed, after 12 hours, by a more gradual decrease in rectal temperature. Eosinophil counts were also markedly decreased. Plasma sodium and glucose concentrations increased in the cold. The plasma potassium concentration fluctuated upward in the first 12 hours of the cold period, while the plasma magnesium and calcium concentrations were not significantly affected. The packed cell volume increased during cold exposure, and it appeared that some of the electrolyte changes observed may have been due to hemoconcentration.