Abstract:
The aim of this experiment was to evaluate the use of the ratio of sodium to creatinine (Na�:�Creat) in a spot sample of urine to estimate daily sodium intake. Thirty-six Merino wethers were allocated to 1 of 4 diets with differing levels of sodium addition (0, 0.87, 2.18, 3.48�mol Na/kg DM, equivalent to 0, 20, 50 and 80�g Na/kg DM). Urinary collections began 5 weeks after the sheep had been introduced to the diet. Total urine output was collected daily for 3 days to determine the pattern of sodium and creatinine excretion relative to sodium intake. Also over the 3 days, 4 spot samples of urine were taken at different times of the day. The Na�:�Creat ratio in urine predicted daily sodium intake with an r2 of 0.82. There was significant variation in the estimation of sodium intake depending on the time of spot sample collection. This variation was attributed to diurnal variation in the Na�:�Creat ratio due to differences in renal clearances of sodium and creatinine, possibly caused by the feeding patterns in the experiment. Despite the variation, this technique still provided a good predictor of group sodium intakes. Therefore, under field conditions the technique may be useful in estimating sodium intake.