Effect of water restriction and environmental temperatures on metabolic rate and physiological parameters in sheep

Abstract

The hypothesis that water restriction reduces metabolic rate and contributes to energy conservation of sheep, and induces changes in blood parameters was tested. Four of eight adult sheep were housed in either a warm (24.8 ± 1.5 °C) or cold (0.4 ± 1.2 °C) environment and fed a diet of alfalfa pellets at 1.2 × maintenance. Each sheep was fasted with or without water according to a crossover design. Average heat production (HP) and rectal temperature (Tr) were higher (P < 0.05) in the cold than in the warm. Fasting decreased HP and Tr (P < 0.05). Water restriction had no additional effect on HP and Tr. Fasting and fasting plus water restriction influenced plasma osmolality and creatinine concentration. Plasma creatinine concentration was lower (P < 0.01) and haemoglobin (Hb) concentration higher in the cold than in the warm environment. Hb concentration was increased with water restriction (P < 0.01) in the warm environment. Plasma cortisol concentration was altered by fasting. Packed cell volume (PCV) in blood, plasma volume and plasma aldosterone were not affected by treatments. The results suggest that water restriction, per se, for 3 d does not suppress metabolic rate in sheep below that resulting from fasting alone. Key words: Heat production, sheep, temperature, water restriction