The oral [13C]bicarbonate technique (o13CBT) was assessed for the determination of short-term energy expenditure (EE) under field conditions. A total of eight Alaskan huskies were fed two experimental diets in a cross-over experiment including two periods of 3 weeks. Effects of diets on EE, apparent total tract digestibility (ATTD) and on plasma hormones, blood lactate and glucose were furthermore investigated. The percentages of metabolisable energy derived from protein (P), fat (F) and carbohydrates (C) were 26:58:16 in the PFC diet and 24:75:1 in the PF diet. Measurements of EE were performed in the post-absorptive state during rest. Blood samples were collected during rest and exercise and ATTD was determined after days with rest and with exercise. EE was higher (P < 0·01) in period 2 than in period 1 (68 v. 48 kJ/kg body weight0·75 per h). The ATTD of organic matter, crude protein and crude fat was higher (P < 0·01) in the PF diet compared with the PFC diet, and lower (P < 0·01) for total carbohydrates. Exercise did not affect ATTD. Higher (P < 0·01) insulin-like growth factor 1 and leptin concentrations were measured when fed the PF diet compared with the PFC diet. Concentrations of insulin decreased (P < 0·01), whereas cortisol and ghrelin increased (P < 0·05), after exercise. There was no effect of diet on blood lactate and glucose, but higher (P < 0·001) lactate concentrations were measured in period 1 than in period 2. The results suggest that the o13CBT can be used in the field to estimate short-term EE in dogs during resting conditions. Higher ATTD and energy density of the PF diet may be beneficial when energy requirements are high.