The Stoichiometry of Animal Energetics

Models for energy uptake and use by animals implicitly specify all mass transformations, given homeostasis assumptions. This is because mass fluxes can be written as weighted sums of energy fluxes, while the weight coefficients follow from the conservation law of mass. This paper presents mass transformations on the basis of the dynamic energy budget model. A theoretical foundation is given for indirect calorimetry, i.e. empirical rules for heat dissipation in terms of oxygen consumption, carbon dioxide production and nitrogen outflux. The foundation implies a method for obtaining the chemical potentials of structural biomass and reserves. Conditions on the composition of structural biomass, reserves and nitrogen wastes are derived that ensure a constant respiration quotient. An explanation is given for the specific dynamic action, which turns out to be a simple function of the parameters of the energy budget model. A simple model for drinking is presented that takes into account all mass transformations, as implicitly specified by the energy budget model.