[Use of urea as a marker of body water in Friesian cows]. / Utilisation de l'urée comme marqueur de l'eau corporelle chez des vaches Pie-noires.

Urea was used as a marker body water. Twelve catheterized dairy cows were injected with urea for 3 consecutive days. Equilibrium between injected and endogenous urea was obtained at 35.9 min over the 3 d. Different models to estimate urea space (EU) were compared with body water estimated at slaughter. The standard error was minimum when using the mean of EU on the 3 daily estimates obtained at 20 min. However, repeatability of EU measurement was low.