[Relation between the dilution space of heavy water measured in vivo and body water volume in growing cattle].

Twenty-one Charolais and 21 Friesian bulls were infused with deuteriated water (0.6 g/kg body weight). Blood samples were collected 6,9 and 24 hours after infusion. The dilution space was calculated by either the zero-time extrapolation method (EDC0) or by 6-hour marker concentration in blood water (EDC6). The animals were slaughtered and their empty body water (ECV) and total body water (ECTC) measured. The EDC0 overestimated by 3.2 p. 100 the ECTC and by 17.9 p. 100 the ECV. The standard error of ECTC estimation was lower (2.0 p. 100 of ECTC) than that of ECV (4.3 p. 100 of ECV). The EDC6 overestimated by 4.7 p. 100 the ECTC and was less related to it (SE of estimation = 2.4 p. 100 ECTC). It was concluded that the zero-time extrapolation method of determining the dilution space was preferable. The dilution space of deuteriated water was a fairly good estimate of total body water. Taking into account the close relationship between body water and body lipids, the dilution space measurement could be used to assess the chemical composition of live animals.