Marcio S. Ferreira, Chris M. Wood, Till S. Harter, Giorgi Dal Pont, Adalberto L. Val, and Philip G. D. Matthews
We used respirometric theory and a new respirometry apparatus to assess for the first time the sequential oxidation of the major metabolic fuels during the post-prandial period (10 h) in adult zebrafish fed with commercial pellets (51% protein, 2.12% ration). Compared to a fasted group, fed fish presented peak increases of oxygen consumption (78%), carbon dioxide (80%) and nitrogen excretion rates (338%) at 7-8 h, and rates remained elevated at 10h. Respiratory quotient increased slightly (0.89 to 0.97) whereas nitrogen quotient increased greatly (0.072 to 0.140), representing peak amino acid/protein usage (52%) at this time. After 48-h fasting, endogenous carbohydrate and lipid were the major fuels, but in the first few hours after feeding, carbohydrate oxidation increased greatly, fueling the first part of the post-prandial specific dynamic action (SDA), whereas increased protein/amino acid usage predominated from 6 h onwards. Excess dietary protein/amino acids were preferentially metabolized for energy production.