In Part 2 of this series we concluded that in mature non-reproducing ruminants the efficiency
of oxygen utilization for intake of net energy attains a maximum value close to the level of
voluntary feed intake. This level was therefore considered the optimum intake for any feed.
The occurrence of a maximum value is due to the existence of a basal oxygen consumption
and a decreasing partial efficiency of metabolizable energy (ME) utilization when ME intake
increases. In this paper possible causes of a decreasing partial efficiency of ME utilization …

Part I of this thesis contains a critical appraisal of the commonly accepted theory with regard
to feed intake regulation in ruminants and the presentation of a new theory. This new theory
assumes that feed consumption creates both benefits to the animal (in a non-reproducing
animal the intake of net energy for maintenance and gain) and costs (the total oxygen
consumption of the animal). It is hypothesized that, for the animal, the intake level where the
ratio between benefits and costs becomes maximal, is optimal. Predictions of this optimum …