VAILLANCOURT, E; PRUD’HOMME, S; HAMAN, F; GUGLIELMO, CG*; WEBER, J-M; Univ. of Ottawa; Univ. of Ottawa; Univ. of Ottawa; Univ. of Montana; Univ. of Ottawa: Metabolic fuel selection during cold exposure and running in a long-distance migrant shorebird Philomachus pugnax

The extent to which the intensity of energy expenditure affects fuel selection in long-distance migrant birds has not been well characterized. Based on what is known about mammals, we hypothesized that the relative contribution of carbohydrate oxidation to energy demand would increase with increasing energy demand. VO₂, VCO₂ and nitrogen excretion were monitored in adult European ruff sandpipers to measure rates of lipid, carbohydrate, and protein oxidation during cold exposure (15, 10 and 5°C) and treadmill running (15-40 m/min). We found that metabolic rate increments caused by shivering and running are not accompanied by changes in fuel selection. The relative contributions of lipids, carbohydrates and proteins to total metabolism were independent of changes in metabolic rate in response to environmental temperature (70%, 4% and 26%, respectively) or running speed (56%, 22% and 22%, respectively). In mammals, similar stresses are known to stimulate carbohydrate oxidation to a much greater extent. However, in these extreme avian athletes geared for traveling up to 30,000 km/year, lipid oxidation always provided more ATP than all other fuels combined.