# Metabolic Calculators: Mammals (Interspecific)

Here are some metabolic calculators for mammals, which predict metabolic rates on the basis of body mass. These are interspecific allometries, and are valid only for basal metabolic rates (the animal is post-absorptive, inactive and within its thermal neutral zone). Typical metabolic rates may be somewhat higher. Energy equivalents (Watts, Joules) assume an RQ of 0.83. Like all allometrically-based estimates of metabolic rates, the results are approximate, but should be close enough to real values to act as a reality check.

Flow rate suggestions are for typical flow-through respirometry and are also approximate. The highest usable flow rate is dependent on the quality of the O_{2} analyzer being used, which determines the lowest change in O_{2} concentration that can be reliably resolved. Examples of "superb" and "good" O_{2} analyzers can be found here and here, respectively. In general, a good flow rate to aim for is about 50% of the suggested maximum for the grade of analyzer you are using. The minimum flow rate corresponds to a 1.5% depletion of O_{2} in the excurrent air and should be exceeded by at least twofold if at all possible.

For our biomedical users: Rodents in general and mice in particular are cold-stressed at typical laboratory temperatures. Their thermal neutral zone is about 29 - 32^{o}C. Thus, their metabolic rates at typical lab temperatures of 20 - 25^{o}C are much higher than their predicted BMRs. It follows that most MR data in the biomedical field are amalgams of the variable effects of cold stress on the black-box, non-GLP-compliant measurement of MR, exacerbated by the fact that raw data are not recorded in the systems traditionally used in this field (see Chapter 13). Also, note that "mass independent metabolic rate", derived in such systems by dividing MR by mass raised to the discredited "Kleiber" **interspecific** mass scaling exponent of 0.75, is a meaningless and misleading mismeasure of MR. Systems are available that address these concerns. If you have questions, contact me.

Note that all metabolic calculator JavaScript code on this page is (c) John Lighton 2008. All rights are reserved. You are welcome to link to this page without restrictions, but copying and re-posting of the code is strictly prohibited. Suggestions for additional taxa and citations are welcome.