ESTIMATION OF ENERGY-EXPENDITURE IN FREE-LIVING RED DEER (CERVUS-ELAPHUS) WITH THE DOUBLY-LABELED WATER METHOD

Energy expenditure was estimated using the doubly-labelled water (DLW) method in summer in five free-living adult, non-pregnant, non-lactati ng, red deer (Cervus elaphus) hinds (weight 107.3 (sE 0.9) kg; age 6 ( sE 1) years) on lowland pasture under typical farming conditions. Clim atic I; conditions were monitored throughout the experiment. Errors du e to H-2 losses in CH4 and faeces were calculated from previous estima tes of stoichiometries. CH4 production, fractionated water loss, urina ry N and O-2 consumption were estimated using an iterative approach. T he water flux (rH(2)O) in these animals consuming only fresh grass was 12 (sE 0.5) kg/d, the CO2 production (rCO(2)) was 1271 (sE 40) litres /d and the mean energy expenditure was 25 (sE 0.8) MJ/d. There were no significant differences in the isotope distribution spaces and flux r ates, rH(2)O, rCO(2) or energy expenditure using the multi-point or tw o-point approaches to calculation. The DLW-derived energy expenditure of 25 MJ/d is approximately 20% higher than the recommended intake of 21 MJ/d for adult hinds kept outdoors (Adam, 1986) and, at 757 kJ/kg(0 .75) per d, one third higher than the value of 570 kJ/kg(0.75) per d f or stags penned indoors (Key er al. 1984).