Effect of Environmental Temperature on Feed Digestion, Water Metabolism, Body Temperature, and Certain Blood Characteristics of Sheep

In each of four periods, sheep were maintained at 20 °C for 1 week, at −11 °C for the following week, and at 20 °C again for the third week. In one period water intake was voluntary; in the other three periods the sheep received either 1000, 2000, or 3000 g water per day through rumen fistulas. The change from the warm to the cold occasioned no change in feed digestibility but when the sheep were returned to the warm, the apparent digestion of both dry matter and fiber increased. When water intake was voluntary, water consumption, urine water loss, and apparent insensible water loss were lower in the cold than in the warm. During the second week at 20 °C, the apparent insensible water loss was higher than during the first week at 20 °C. When water intake was controlled at the three different levels, urine and fecal water losses tended to reflect the differences in water intake. Temperatures in the rectum and subcutaneous tissues exhibited a decrease when the sheep were transferred from warm to cold and a transient increase on return to the warm. When water intake was voluntary or 1000 g per day, transfer of the sheep to the cold was accompanied by increases of packed cell volume and plasma sodium and phosphate and small increases of potassium and chloride.