Within-animal variances for flow rates of metabolites in an open-compartment model with continuous isotope infusion in sheep

Abstract

SUMMARYFlow rates of metabolites in an open-compartment model can be calculated from specific activity measurements taken at equilibrium during continuous infusion of an isotope. The within-animal variance gives an estimate of the precision of the flow rate.The Jack-knife method of calculating within-animal variances is described. It was evaluated using simulated data, and shown to be superior to a simpler method, the Single Section method.The increase in experimental accuracy caused by increasing the number of specific activity samples per animal depends on the ratio of between- to within-animal variance components (B/W). For three experiments with sheep, 23 of the 30 values B/W for the different flow rates ranged from 0·25 to 1·5. For this range between six and 12 samples per animal are needed.