Whole-animal energy use per unit time, derived from VO₂ and VCO₂, reported per animal and normalized to body or lean mass.
Use energy expenditure when the question is how much energy an animal uses — at rest, across the day, or under exercise. EE is calculated from VO₂ and VCO₂ (for example via the Weir equation), not from oxygen alone, because the caloric value of oxygen depends on the fuel mix. The main analysis pitfall is normalization: EE scales with body and lean mass, so compare with appropriate mass adjustment (ANCOVA) rather than simple ratios.
| Primary value | Energy used per unit time, derived from VO₂ and VCO₂ |
|---|---|
| Common units | kcal/h or kJ/h (whole animal); per body or lean mass when normalized |
| Compatible assays | Home-cage metabolic chamber (RMR, daily EE), graded treadmill exercise (exercise EE) |
| Required boundary | Synchronized VO₂ and VCO₂ and a defined averaging window |
| Do not infer alone | Fat mass, food intake, or fitness without body composition and intake data |
Derive EE from synchronized VO₂ and VCO₂ over a defined window, and record body mass and, where possible, lean mass for normalization. Distinguish resting/basal EE from total daily EE and from exercise EE, and report ambient temperature because EE rises below thermoneutrality.
A difference in raw EE between groups can be an artifact of body size. Adjust for body or lean mass with regression-based methods rather than dividing by mass, and separate the activity state because resting, daily, and exercise EE answer different questions.
Store animal ID, body mass, lean/fat mass, ambient temperature, paired VO₂ and VCO₂, derivation equation, averaging window, activity state, EE value, normalization basis, calibration record, and instrument or software version.
Endpoint pages should cite the method literature behind the scored value and keep high-specificity protocol claims qualified unless the source supports them.
Endpoint articles link to adjacent products, software workflows, and sibling endpoints where the connection is useful and already routable.
