UTILIZATION OF UREA AS A BODY-WATER MARKER IN GROWING PIGS

The urea dilution technique was used to study I the volume of body wat er in 8 crossbred Yorkshire x Duroc x Landrace pigs of 50 +/- 5 kg liv e weight. Urea was infused (2.16 mmols/kg live weight) through a cathe ter in the cava vein. Blood samples were taken 30 and 90 min after the marker infusion. Changes in plasma urea concentration were determined before and after the infusion in each sampling and typical dilution c urves fitting the mathematical model (R-2 varied from 0.76 to 0.98) we re obtained. The equilibrium time varied from 15 to 25 min after urea injection, while the urea exchange ranged from 0.15 to 0.38%/min in th e latter. Urea space (US) was 27.71 and water volume as a percent of e mpty bodyweight (585 +/ -5.2) was positively compared to others estima ted by the same technique(56.5 +/- 3.4) or by the chemical analysis of the body composition (56.5 +/- 3.4 and 54.3 +/- 2.4) in pigs with sim ilar live weight. The results suggest that it is possible to use urea as a marker to estimate body water in growing pigs.