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.

Effect of energy intake during pregnancy and lactation on body composition in rats.

A paired feeding experiment involving high (H) and low (L) feeding levels during pregnancy and lactation was conducted using bred and open female rats to determine the effects on body composition. Pregnant rats contained a higher percentage of water in the fat-free body (FFB) than that of non-pregnant rats indicating tissue hydration. Composition of the FFB and fat-free dry matter (FFDM) was not altered by feeding level during pregnancy. During lactation, the feeding levels were either continued H-H and L-L or were changed to H-L or L-H within the lactating or open (non-lactating) pairs. Composition of the FFB and of the FFDM was altered by feeding level during lactation. A high energy intake result in a greater proportional loss of ash than of protein during lactation. In contrast, neither the composition of FFB nor FFDM was altered in the non-lactating rats on similar energy intake regimes. The lactating females had a higher percentage of water in FFB than the non-lactating rats. Although there was variation in water content of FFB and in the composition of FFDM, the correlation between percentage of body water and body fat after the adjustment of effects of pregnancy, lactation, energy and their interaction, was high (r = -0.98).