USE OF NITROGEN-15 LABELLED UREA TO STUDY UREA UTILIZATION BY PIGS

Abstract

Two experiments were conducted, the first to determine the rate and pattern of nitrogen excretion when weanling pigs were fed a diet containing urea, and the second to study the incorporation and excretion of 15 N-labelled urea in weanling pigs. The 15 N of dietary 15 N-urea was incorporated into the trichloroacetic acid-insoluble fractions of liver, blood plasma, intestinal mucosa, skeletal muscle, and blood cells of 10.3-kg pigs. Blood plasma and liver were enriched to the greatest extent. More 15 N, as a percentage of the administered dose, was used in muscle protein synthesis than in liver protein synthesis. Excretion of 15 N in the urine during 48 h following administration of 15 N-urea in a diet containing 2% urea accounted for 52.2% of the administered dose; excretion during the subsequent 48 h accounted for 1.9% of the administered 15 N. The results indicate that dietary urea is used in protein synthesis by the pig.