Water economy of sheep at fasting

Abstract

To estimate the basal water requirement for sheep, water balance was studied using 12 sheep fasted for 8 days. The balance was determined for the last 3 days at fasting. Mean values for fasting heat production, drinking water intake, metabolic water, water excreted in urine, water lost through respiratory evaporation and water debt were 226±40kJ/kg^0.75, 18.5±21.5g/kg^0.75, 6.1±1.2g/kg^0.75, 30.4±17.2g/kg^0.75, 14.1±3.3g/kg^0.75 and -22.9±20.0 g/kg^0.75, respectively.
Fasting heat production was positively correlated with drinking water intake, metabolic water and water lost through respiratory evaporation (P < 0.01). Drinking water intake was correlated with water excreted in urine and water lost through respiratory evaporation (P < 0.05). Drinking water intake, metabolic water and water lost through respiratory evaporation were estimated to increase 25.6, 2.87 and 6.46 g/kg^0.75 per 100 kJ of fasting heat production, respectively. The basal water requirement for sheep was estimated to be 43 g/kg^0.75. Water drinking was suggested to be insufficient to satisfy this requirement because of inhibition of thirst by some process of the water absorption in the intestine.