| Abstrakt: |
If we must describe or prescribe the quantity of usable energy needed by or desirable to offer to animals, we must have a workable measurement of it. Whether the term should describe the digestible, or the metabolizable, or the net energy, is still debated by three shcools of thought on this question. The biological accuracy of all terms used to describe the apparently digestible fraction of the energy-yielding components of food suffers by reason of complications introduced by metabolic fecal protein, metabolic fecal fat, and the unrecorded energy losses represented by voided fermentative gases. But from the purely procedural standpoint, the simplest measure of usable energy is that of digestible calories, where a single determination each on the food and on the resulting feces suffices. This in no way interferes with the subsequent calculations of metabolizable or of net energy, should these also be desired.If “digestible calories” gives nutritional information comparable in biological accuracy and general usefulness to the long used TDN scheme, it might well be preferred to it. However, any change from the use of TDN to digestible energy, in feed description or in feeding standards, will make it necessary either to abandon the present extensive TDN data or to find a means of converting these values to acceptably accurate corresponding calorie figures. In 1954 the Committee on Animal Nutrition of the U. S. Research Council appointed a subcommittee to study this problem, having in mind the decision of the Committee on Feed Composition to include caloric |
