Validation of the tritiated water dilution technique used to estimate fractional turnover rates of body water in sheep.

Daily fractional water turnover rate (i.e. that proportion of total body water which is exchanged daily) was determined in S.A. Mutton Merino sheep (n = 6) under thermoneutral conditions by direct measurement of total water intake and by the tritiated water dilution technique. No significant difference between direct and indirect methods was observed in any of the animals. Tritiated water space estimated from a plasma sample taken at 6 h after tritium administration in general overestimated this compartment when compared with values derived from the zero time intercept of the linear regression analysis obtained for each animal.