Use of deuterium oxide for the in vivo prediction of body composition in female rats in various physiological states.

Deuterium oxide (D2O) was used to estimate total body water (TBW) and subsequently to predict the body composition of female rats at breeding, after pregnancy and after lactation as influenced by dietary manipulation. The correlation between D2O space (grams) and body water (grams) was 0.893 (P < 0.01). Deuterium oxide space accounted for 70% of the variance in predicting the weight of TBW. Fixed effects (pregnancy, lactation, feeding levels and two-way interactions) accounted for an additional 10% (P < 0.05) of the variance. The correlation between TBW in grams (predicted from D2O space, grams) and total body protein (grams) was 0.700 (P < 0.01). Total body water accounted for 49% of the variance in total body protein. Fixed effects accounted for an additional 21% (P < 0.05) of the variance in total weight of body protein. The correlations between D2O space (%) and body water (%) and between D20 space (%) and body fat (%) were 0.786 (P < 0.01) and -0.758 (P < 0.01), respectively. The accuracy of estimation of body water (%) and body fat (%) from D2O space was not significantly improved (P > 0.05) when the fixed effects (pregnancy, lactation, feeding levels and two-way interactions) were included in the model.