METABOLIC ADJUSTMENTS TO LOW TEMPERATURES IN NEW ZEALAND WHITE RABBITS

Abstract

Characteristics of cold acclimation in shaved New Zealand white adult rabbits kept individually at 6 °C for 3–5 weeks were (i) a 40% increase in food consumption, (ii) maintenance of body weight, (iii) a 45% increase in resting metabolism measured at 28 °C, (iv) an almost complete disappearance of shivering, (v) increased cold resistance, (vi) failure to cut off increased heat production when abruptly returned to 28 °C, and (vii) a maximum increase of 41% in oxygen consumption after noradrenaline infusion at 28 °C of doses varying between 1.18 and 9.44 μg/kg per min. Rats acclimated to 6 °C showed a maximum increase of 113% in their oxygen consumption when infused with similar doses of noradrenaline varying between 1.34 and 10.72 μg/kg per min. The conclusion is reached that in rabbits which usually rely on thick fur for protection against cold, the primary metabolic adjustments in these animals when they are shaved are a rise in basal metabolism and an increase of the same order in noradrenaline sensitivity.