Meeting Abstract
In the lab, mice are often kept in cages seemingly without any way to exercise, thus restricting their voluntary energy expenditure. Because of this their daily energy expenditure in a cage may grossly underestimate the amount of energy they would expend in the wild. We have been interested in understanding how much energy mice would expend if they could be more active in cages. In recent laboratory experiments we have included wheel access for the deer mice to allow them to have that voluntary component. However, deer mice in cages without wheels often jump up and down and do backflips in their cages. The energy exerted in these behaviors, is non measurable and could be equal to that of wheel running. In order to determine if this is the case, daily oxygen consumption (as a proxy for daily energy expenditure) was measured in mice without and then with wheels. In addition, food intake was measured in each mouse before and after they were given wheels. Measurement without wheel access was always done first because introduction of a wheel could affect future activity. Mass did not differ between treatments and was not a significant covariate for statistical tests. Using age as a covariate, an ANCOVA showed that mice with wheels ate 15% more food that those without wheels (p =0.008; Age was significant at p= 0.025). Likewise mice with wheels expended 34% more energy than those without wheels (p=0.0002). Also, the average maximal 10 minutes of oxygen consumption was higher in mice with wheel access (p=0.006) and the minimal 10 minutes of oxygen consumption was higher in mice with wheels (p=0.020). In conclusion, this study suggests that mice can expend more energy if given access to a wheel. The back flips and jumping that occurs in the cage overall leads to less energy expended. Inclusion of a wheel should be considered in future experiments with the goal of testing the limits of energy expenditure.
