The effect of cold exposure on fluid balance, circulating arginine vasopressin concentration and milk secretion in the goat.

Total body water, water intake, urine output, milk yield, plasma, milk and urine osmolality and plasma arginine vasopressin concentration were measured in goats exposed to thermoneutral (20 degrees C) and cold (0-1.0 degrees C) environments for 24 h. Cold exposure caused the animals to reduce their water intake substantially. This was accompanied by a decrease in total body water and an increase in osmolality of plasma and milk. The output of urine decreased as cold exposure progressed but free water clearance by the kidney was not significantly different in thermoneutral and cold environments and cold exposure had no effect on circulating arginine vasopressin concentration. Milk yield was reduced by cold exposure and it is suggested that the reduced net movement of water from blood to milk is partly a consequence of the dehydration induced by cold exposure and that this, in turn, is due primarily to a decrease in water intake with no effective renal compensation.