Energy equivalents of oxygen consumption in animal energetics

The energy equivalents given in the literature are reviewed and criticised. New equivalents are calculated for protein respiration.The energy equivalent for converting rate of oxygen consumption into rate of heat production (Q _ox cal mg^-1 oxygen consumed) is 3.53 cal mg^-1 for carbohydrate oxidation, 3.28 cal mg^-1 (range 3.22-3.32) for fat oxidation. Q _ox values for the respiration of standard protein are the same at 3.25 cal mg^-1 for ureotelic and uricotelic animals, and about 2% less at 3.20 cal mg^-1 for ammoniotelic animals. The energy equivalent for converting rate of oxygen consumption into rate of energy loss in excreta (Q _ex cal mg^-1) varies considerably with different excretory products. Values for standard protein are 0.62 cal mg^-1 for ammonioteles, 0.58 cal mg^-1 for ureoteles, and 0.94 cal mg^-1 for uricoteles.The various factors affecting both Q _ox and Q _ex are discussed, and examples of the estimation of general energy equivalents are given.