Comparing two techniques to estimate energy expenditure on physical activity in group housed animals

Quantification of physical activity in animal energy metabolism studies is important because it may cover up effects experimentors are trying to show, or alternatively, it may be the subject of study. Two different techniques to measure activity of group-housed animals, i.e. radar Doppler and short-term weight variation were compared to evaluate effects on estimations of energy expenditure on physical activity. Compared with radar Doppler, the relationship between weightbased activity parameters and heat production was clearer, but appeared to be non-linear, implying that the energy costs per unit of activity is not constant. The use of different weight-based activity parameters, using non-linear curve fitting to assess the energy costs per unit activity, results in a large variation in estimates of activity related heat production. It may be an artefact of the weighing technique, at some points probably enlarged by the non-linear curve fitting