Comparison of three methods for the measurement of the endogenous N-flow at the terminal ileum of pigs, as affected by dietary quebracho extract

Twelve pigs were fed diets based on enzymically hydrolysed casein with or w ithout tannin-rich quebracho extract. Endogenous nitrogen flow was measured using the N-15-isotope dilution method with either oral administration N-1 5-leucine or with continuous infusion, and with the peptide alimentation ul trafiltration method. No differences were found between oral or intravenous administration of the tracer with regard to endogenous N-flow and true ile al N-digestibility. Endogenous N-flow and true ileal N-digestibility measur ed with the N-15 label were higher than those measured by ultrafiltration. Addition of quebracho extract to the diet increased endogenous N-flow (1.7 vs. 5.7 g/kg DMI, P < 0.001) and decreased apparent ileal nitrogen digestib ility (86.1 vs. 70.3 %,P < 0.001) but did not affect true ileal nitrogen di gestibility (92.4 vs. 91.1 %).