TRACER STUDIES OF UREA RECYCLING EN SHEEP

Abstract

The urea transferred from the plasma to the digestive tract of fed sheep was measured employing 14C-urea as a tracer, after establishing metabolic steady state. Plasma urea concentrations were adjusted by intravenous infusion of unlabelled urea. Recycled urea, within the physiological range of plasma urea concentrations, fitted a linear function of plasma concentration. Recycling, in this study, of urea in different animals and for different rations, followed the relationship: [Formula: see text], SE = 2.27, r = 0.85, where [Formula: see text] urea recycled per day and X = plasma urea concentration (up to 45 mg/100 ml).A regression equation, incorporating data from other studies, that could be used for the general prediction of urea recycling in sheep from the plasma urea concentration, was presented. The ration did not appear to influence significantly urea recycling aside from its effects on the plasma urea concentration.