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The water economy and food intake of medium-wool Merino, fine-wool Merino, and Border Leicester wethers were compared when water was made available only every 3 or 4 days. The comparisons were made on penned sheep with two diets at both low (max. 12�_C) and high (max. 36�_) temperatures. The Border Leicesters used more water than the two groups of Merinos (20-40%), but they also ate more food per unit of body weight (15-28%). In proportion to food intake, the Border Leicesters and medium-wool Merinos drank 6-20 % more water than the fine-wool Merinos. It was concluded that although economy of water use may assist survival when water is unavailable, it appeared to be inversely related to food intake and therefore of limited value in selecting sheep for arid climates. The Border Leicesters lost more water in their faeces than the Merinos, but similar amounts of water as urine. The volume of urine appeared to be related to the amounts of potassium and sodium excreted, since on the second to fourth day without water the concentration of potassium + sodium was maintained at 600-800 m-equiv./l while the nitrogen concentration varied from 0.9 to 2.4 g/100 ml. Nitrogen and potassium excretion in urine remained relatively constant from day to day, but sodium excretion varied from c. 20 m-equiv./day on the first one or two days without water to 100-120 m-equiv./day on the final one or two days. |
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